Patent Application
20250224414
Biofilms can include microbial cells enmeshed in an extracellular matrix and firmly attached to a variety of surfaces. It can be challenging to target certain biofilms formed on surfaces with arbitrary orientations and complex topographical features like crevices. Such complex, biofilm-covered surfaces pervade health care and industry, causing chronic infections and costly contaminations.
Sampling biofilm contents can be important, as the sampled biofilm contents can be analyzed for more effective treatment and selection of precision medicine to increase successful clinical outcomes. However, sampling can be challenging due to the heterogeneous distribution of diverse pathogens that are often located within crevices or grooves.
Accordingly, there is a need for improved techniques and sampling systems to access and remove adhesive biofilms and perform sampling for pathogen and/or pathogenic by-products detection as well as composition analysis.
The disclosed subject matter provides techniques for retrieving a target sample. An example system includes a small-scale robot including a plurality of magnetic nanoparticles (MNP) and a magnetic control system including a magnet. In non-limiting embodiments, the small-scale robot can be a magnetically aggregated structure of the MNPs under a magnetic field generated by the magnet. In non-limiting embodiments, the small-scale robot can be configured to disrupt and/or retrieve a target sample from a target area through an automated programmable motion and/or positioning.
In certain embodiments, the magnet can include a permanent magnet, an electromagnet, or a combination thereof. In non-limiting embodiments, the MNPs can include iron oxide nanoparticles (IONPs), nickel, cobalt, iron, or their alloys or oxides.
In certain embodiments, the small-scale robot can be a microscale robot, a milliscale robot, or a centimeter-scale robot. In non-limiting embodiments, the small-scale robot has an extensible and retractable bristle-like configuration. The extensible and retractable bristle-like configuration can be configured to have a topography-adaptive property. The topography-adaptive property can include a stiffness, length, a shape, or a combination thereof.
In certain embodiments, the target area can include grooves, crevices, trenches, space between two or more surfaces, an uneven surface, or combinations thereof. In non-limiting embodiments, the small-scale robot can be configured to reach and conform to the target area. The target area can include any exterior surfaces or enclosed surfaces. In non-limiting embodiments, the IONPs can be configured to be reusable or re-aggregated for an area with different topographies.
The disclosed subject matter also provides methods for retrieving a target sample. An example method includes applying a magnetic field to MNPs, forming a small scale robot by aggregating the MNPs into a predetermined shape, introducing the small scale robot into a target area, and disrupting and/or collecting the target sample from the target area by applying a modified magnetic field that can be configured to induce a motion and positioning of the small scale robot. In non-limiting embodiments, the magnetic field can be configured to induce an automated programmable motion.
In certain embodiments, the method can further include adjusting the mechanical properties of the small-scale robot based on the target area. In non-limiting embodiments, the mechanical properties can include a shape, a length, a stiffness, or combinations thereof.
In certain embodiments, the method can further include analyzing the collected samples for identifying a pathogen, by-products of the pathogen, a composition of the target area, or a combination thereof. The pathogen can include a bacteria, a fungus, a virus, archae, protozoa, algae, and the by-products can include biomolecules and metabolites or combinations thereof.
In certain embodiments, the method can further include reshaping the small-scale robot to reach an area with different topographies. In non-limiting embodiments, the small-scale robot can be configured to reach and conform to the target area. The target area comprises any exterior surfaces or enclosed surfaces.
In certain embodiments, the small-scale robot can be a microscale robot, a milliscale robot, or a centimeter-scale robot. In non-limiting embodiments, the target area can include grooves, crevices, trenches, space between surfaces, an uneven surface, or combinations thereof. In some embodiments, the small-scale robot can have an extended bristle-like configuration.
The disclosed subject matter provides an example system for retrieving a target sample. The example system can include a small-scale robot including a plurality of magnetic nanoparticles (MNP) such as nickel, cobalt, iron or their alloys or oxides. In non-limiting embodiments, the small-scale robot can be a molded structure of the MNPs in a predetermined shape or a 3D printed structure. In some embodiments, the small-scale robot can be configured to disrupt and/or retrieve a target sample from a target area under a magnetic field.
In certain embodiments, the predetermined shape can include a helicoid shape, a vane-like shape, a spherical shape, a spheroid shape, a cylindrical shape, a bullet-like shape, or a spiral-like shape.
In non-limiting embodiments, the small-scale robot can be configured to rotate and translate under the magnetic field. In some embodiments, the small-scale robot is a microscale robot, a milliscale robot, or a centimeter-scale robot.
In certain embodiments, the target area can include smooth surfaces, grooves, crevices, trenches, an uneven surface, or combinations thereof. In non-limiting embodiments, the MNPs can be configured to be reusable or re-aggregated for an area with different topographies.
The method of claim 15, the method further comprising identifying the target sample by detecting components of the sample through an analyzer.
The disclosed subject matter will be further described below, with reference to example embodiments shown in the drawings.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and are intended to provide further explanation of the disclosed subject matter.
The disclosed subject matter provides systems and methods for retrieving a target sample from a multitude of surfaces for diagnostic and compositional analyses.
Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. In case of conflict, the present document, including definitions, will control. Certain methods and materials are described below, although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the presently disclosed subject matter. All publications, patent applications, patents, and other references mentioned herein are incorporated by reference in their entirety. The materials, methods, and examples disclosed herein are illustrative only and not intended to be limiting.
As used in the specification and the appended claims, the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, a reference to “a compound” includes mixtures of compounds.
As used herein, the term “about” or “approximately” means within an acceptable error range for the particular value as determined by one of ordinary skill in the art, which will depend in part on how the value is measured or determined, i.e., the limitations of the measurement system. For example, “about” can mean within 3 or more than 3 standard deviations, per the practice in the art. Alternatively, “about” can mean a range of up to 20%, up to 10%, up to 5%, and up to 1% of a given value. Alternatively, particularly with respect to biological systems or processes, the term can mean within an order of magnitude, within 5-fold, and within 2-fold, of a value.
An “individual” or “subject” herein is a vertebrate, such as a human or non-human animal, for example, a mammal. Mammals include, but are not limited to, humans, primates, farm animals, sport animals, rodents, and pets. Non-limiting examples of non-human animal subjects include rodents such as mice, rats, hamsters, and guinea pigs; rabbits; dogs; cats; sheep; pigs; goats; cattle; horses; and non-human primates such as apes and monkeys.
The disclosed subject matter provides a diagnostic system for retrieving a target sample. In certain embodiments, the system can include a small-scale robot and a magnetic control system (magnet). The disclosed system can utilize the catalytic and magnetic properties of the small-scale robot for retrieving the target sample (e.g., biofilms) from a target area (e.g., complex surface topographies and difficult-to-reach spaces) such as exterior and interior (endodontic) surfaces of teeth. The disclosed system can be used for diagnostic sampling in medicine, medical device/implant contamination, as well as in environmental/industrial biofouling.
In certain embodiments, the small-scale robot can include iron oxide nanoparticles (IONPs). The IONPs can be versatile materials with catalytic and magnetic properties. The IONPs can perform the peroxidase-like activity that efficiently catalyzes hydrogen peroxide for antimicrobial effects, while the applied magnetic field enables control of the positioning of the IONPs. In certain embodiments, the IONPs can be synthesized via a facile a solvothermal method. For example, iron (III) chloride (e.g., 0.82 g) can be dissolved into ethylene glycol (e.g., 40 ml). Then, sodium acetate (e.g., 3.6 g) can be added to the solution under stirring at room temperature (e.g., for 30 min). Subsequently, the mixture can be transferred to an autoclave and heated (e.g., for 12 h). After the autoclave is cooled to room temperature naturally, the IONP precipitate can be collected, rinsed several times with ethanol, and then dried (e.g., at 60° C. for 3 h). In non-limiting embodiments, the small-scale robot can be a magnetically aggregated structure of the IONPs. For example, under a magnetic field generated by the magnets, the IONPs can be aggregated to form a predetermined shape.
In certain embodiments, the disclosed magnet can generate and control a magnetic field. For example, the magnetic field can be controlled with a device combining programmable electromagnets and servo motors. The magnets can be used to shape and/or reconfigure the aggregated structure of IONPs by a plurality of electromagnets (e.g., coaxially arranged at a distance of 8 mm). Between the two electromagnets, an actuation vessel (e.g., with a dimension of 15×6.7×13 mm3 can be added to accommodate IONPs suspension, and a holder can be constructed to maintain an 8 mm gap between the two electromagnets. Both the electromagnets and servo motors can be mounted around the actuation vessel. In non-limiting embodiments, a ferrite core (e.g., with a diameter of 10 mm) can be situated in the center of the rear electromagnet, and an iron core (e.g., with a diameter of 2 mm) can be positioned in the center of the forward electromagnet. The position of the forward iron core can be moved in varying trajectories using servo motors.
In certain embodiments, the disclosed magnet can be configured to move in various directions and motions. For example, for side-to-side motion, a micro servo motor can be programmed to move (e.g., between 65 and 115 degrees) with an arm (e.g., of 14 mm length). In non-limiting embodiments, a symmetrical arc-shaped movement (e.g., approximately 12 mm) can be implemented with various linear velocities (e.g., from 6 to 48 mm s−1). For circular motion, a continuous rotation servo motor can be used and programmed to allow unrestricted movement at angles using a relatively short arm (e.g., 2 mm length). A continuous circular movement can be generated centered with the axis of electromagnets with a linear velocity (e.g., 12 mm s−1) in clockwise or counterclockwise directions.
For multimodal motions with improved repeatability in position and timing, the system can include a sliding vessel. The body of the device can include a holder for the electromagnets and servos and a sliding vessel. One servo can be used to drive a pinion gear attached to the rack of the sliding vessel for left-to-right motion, and the other servo can be used to drive the forward iron core for circular or arc-shaped motions. The sliding vessel can hold the tooth replicas and natural teeth. In non-limiting embodiments, the vessel can be actuated by a programmable micro servo motor. The motion of the sliding vessel can be coupled with the programmable motion of the electromagnet iron core, which can allow combinations of motions to mimic brushing patterns.
In certain embodiments, the magnetic field can be directed by repositioning of the iron core, and the various positions can be implemented by the movement of the servo controlling the iron core within the forward electromagnet (e.g., side to side and circular by regular and continuous micro servo), during which the magnetic field remained constant. In non-limiting embodiments, the actuation can be performed via the application of a magnetic field and servo programmed to achieve the desired motion pattern. In non-limiting embodiments, the movement of the micro servo arm and the magnetic fields of electromagnets can be controlled using a microcontroller independently using a programmable DC power supply and software for system coding (e.g., Arduino integrated development environment (IDE) software). In non-limiting embodiments, the disclosed magnetic field can be produced by any suitable devices and techniques that can create a magnetic field for sampling or diagnostic purposes.
In certain embodiments, the geometries of the actuation vessel and the body of the magnet system can be modified based on the target area. In non-limiting embodiments, the actuation vessel and the body of the device can be fabricated using a 3D printer (e.g., a low-force stereolithography 3D printer).
In certain embodiments, the small-scale robot is a magnetically aggregated structure of the IONPs. For example, under a magnetic field generated by the magnets, the IONPs can be aggregated to form a predetermined shape. The predetermined shape can include various configurations based on the target area. In non-limiting embodiments, the predetermined shape can include an extended bristle-like configuration. The bristle-like superstructures can be assembled using a magnetic field control system. For example, the dispersed IONPs can be collected by magnetic fields from the forward electromagnet (e.g., for 5 s forming a rounded dome shape), and the strength of the magnetic field used for the standardized biofilm removal experiments can be measured (e.g., to be 90 and 25 mT) at the forward and rear regions, respectively. The small-scale robot can then be designed to orthogonally extend from the forward vessel wall to form elongated bristle-like structures (e.g., for 25 s) by energizing the rear electromagnet. At the beginning of the next cycle, IONPs can be recollected in the forward region. In non-limiting embodiments, a cycle (e.g., a cycle of 30 s) can be repeated up to about 20 times for dental biofilm removal.
In certain embodiments, the appearance and physical/mechanical properties of the small-scale robot can be precisely controlled by the concentration of IONPs (e.g., 0.5 to 1 kg ml−1), the sweep velocity of the servo (e.g., 6 to 48 mm s−1), and the strength of magnetic fields (e.g., 13.3 to 96.4 mT) at the center of the actuation vessel. For example, the appearance and physical/mechanical properties of the small-scale robot can include a shape, a length, a stiffness, or combinations thereof.
In certain embodiments, the disclosed small-scale robot can provide improved reconfigurability and adaptability to various hard-to-reach target areas. The target area can include a square groove, a circular groove, a triangular groove, an uneven surface, crevices, trenches, space between two or more surfaces, or combinations thereof. In non-limiting embodiments, the target area can be an interdental space, the exterior surface of teeth, interior spaces of teeth, or combinations thereof. Aggregated IONPs can conform to these variations through their adaptive nature and can reconfigure to reach distant surfaces in confined spaces as it moves from flat to curved (e.g., through interdental spaces).
In certain embodiments, the shape of the small-scale robot can be formed or reconfigured by the magnet system, depending on the target area. In non-limiting embodiments, the IONPs can be configured to be reusable or re-aggregated for an area with different topographies. In non-limiting embodiments, the small-scale robot can be a microscale robot, a milliscale, or a centimeter scale robot.
In certain embodiments, the small-scale robot assembled from IONPs can be administered to the target area. The small-scale robot can be configured to disrupt and retrieve the target sample. For example, biofilms can be treated with the small-scale robot assembled from IONPs (e.g., 0.5 to 2 mg ml−1 final concentration) solution in the actuation vessel. In non-limiting embodiments, the IONPs can be optimized to enhance the catalytic bioactivity with EPS/biofilm-degrading enzymes (e.g., dextranase/mutanase, 25/5 U) and 1% H2O2 (1% v/v). For example, biofilms can be placed in the actuation vessel containing IONP solution for 10 min, followed by the addition of 1% H2O2 and subsequent modulation of the magnetic field, which forms the small-scale robot. The velocity, trajectories, and motion frequencies can be controlled by the system. The biofilm removal and retrieval can be performed via the application of an external magnetic field and servo movement preprogrammed to achieve the desired trajectories, velocities, and motion patterns. In non-limiting embodiments, any enzymes, bioactive molecules and/or biologics can be used with the disclosed devices. The types and/or amount of the enzymes, bioactive molecules and/or biologics can be modified depending on the target area.
In certain embodiments, the small-scale robot can disrupt and collect the target sample through its catalytic and actuation activities. The target sample (e.g., biofilm) can be entrenched among the small-scale robots/IONPs. For example, as aggregated IONPs mechanically disrupt biofilms, mixed-species microbial cells (typical of biofilm infections) can bind to the aggregated IONPs. Once removed from the canal, bacterial samples can be analyzed via various chemical, optical, and/or biological analyses (e.g., fluorescent labeling, colorimetric and qPCR assays, DNA/RNA sequencing, omics-based analyses such as proteomics, metabolomics). For example, the genomic DNA can be extracted and purified from retrieved samples, and qPCR can be performed with specific primers to detect each bacterial species.
In certain embodiments, the disclosed subject matter can provide real-time analysis. The samples retrieved can be analyzed in real-time via facile colorimetric, electrochemical or fluorescence assays that can be detected using readily available sensors integrated into a device. For example, the pathogens captured by the robots can react with specific fluorophores or chromogenic substrates that can be detected via small detectors embedded in a device. This can include combinations of light-emitting diodes (LEDs) and photodetectors to assay optical absorbance, emittance and reflectance. Conversely, IONPs can be functionalized with coatings (e.g., antibodies, polymers, and proteins) that bind to a specific pathogen, allowing in situ detection via colorimetric analysis. Because the outcome provides both qualitative (e.g., yes or no) and quantitative (e.g., levels/amounts) data, simple algorithms can be programmed into apps or integrated into the disclosed device. In non-limiting embodiments, the disclosed subject matter provides improved design flexibility. For example, a small tray- or mouthguard-like device containing colorimetric or fluorescence sensors, which can detect the pathogens or other biofilm components retrieved by the small robots brushing the teeth, can be included.
In certain embodiments, the small-scale robot can be assembled through a 3D mold. For example, the small-scale robot can be a molded structure of the IONPs. The molded robotic system with a predetermined shape can be developed using 3D-printed negative molds using the IONPs as building blocks. In non-limiting embodiments, the predetermined shape can be a helicoid shape. The 3D molded helicoid robots (e.g., two helices wrapped around a central axis) can be formed by embedding IONPs within a thermo-reversible granulated agar gel in a final soft robot composition (e.g., contains 25% glycerol, 3% (w/v) agar gel within which 10% IONPs are embedded). The molding technique can be employed with other hydrogels or polymers. The IONPs-embedded gel can be used to fill the negative molds to create 3D molded soft helicoids (e.g., with a size of ˜700 μm by 1.5 mm). The size can be modified depending on the target area. In non-limiting embodiments, the molded small-scale robot can be 3D printed directly. For example, 3D printers can be used for printing a mixture of photoreactive polymer with nanoparticles, which can provide improved design flexibility.
In certain embodiments, when directed by the magnetic fields, the 3D molded helicoids can be configured to propel and/or rotate. For example, when a magnetic torque is applied, a 3D molded helicoid can rotate around its central axis. This can cause forward locomotion due to the chiral geometry and corkscrew-like action of the helicoid. The helicoid robot can be adapted to access and sample biofilms from other similarly challenging spaces and geometries, such as in the interior of catheters and water lines/pipes.
In certain embodiments, the 3D molded robots can also be used for biofilm diagnostics. For example, for endodontic applications, biofilms can be detected in apical spaces by retrieving samples via physical disruption and adhesion to the 3D molded robot exterior. The collected sample can be analyzed by various chemical and/or biological analyses (e.g., colorimetric, electrochemical, fluorescent labeling and qPCR). The bacteria disrupted by the front end can adhere to the back end of the molded robot via interaction with a dextran coating or other adhesive surface. As with aggregated IONPs, samples are analyzed using fluorescence probes for each species and qPCR with species-specific primers to detect the presence of different bacterial species.
In certain embodiments, the disclosed subject matter provides a method of retrieving a target sample using the disclosed system. The method can include applying a magnetic field to iron oxide nanoparticles (IONPs), forming a small scale robot by aggregating the IONPs into a predetermined shape, introducing the small scale robot into a target area, and disrupting and/or collecting the target sample from the target area by applying a modified magnetic field.
In non-limiting embodiments, the method can further include adjusting the mechanical properties of the small-scale robot based on the target area. In non-limiting embodiments, the mechanical properties comprise a shape, a length, a stiffness, or combinations thereof. The mechanical properties can be modified by controlling the concentration of IONPs, the sweep velocity of the servo, and the strength of magnetic fields.
In non-limiting embodiments, the target area includes any hard-to-reach area with challenging spaces and geometries. For example, the target area can be an interdental space, the exterior surface of teeth, the interior spaces of teeth, the interior of catheters, interior spaces of water lines/pipes, containers/tanks, medical implants, dentures, medical devices, household surfaces, glass surfaces, or combinations thereof.
In certain embodiments, the method can further include analyzing the collected samples for diagnosing a pathogen and/or its by-products. The pathogen can include bacteria, fungi, viruses, archae, protozoa, algae, microial, and the by-products can include biomolecules and metabolites or combinations thereof. The sample can be analyzed via various chemical or biological analyses. For example, the analyses can include a qPCR analysis, a colorimetric assay, a fluorescent labeling analysis, omics-based analysis or a combination thereof.
In certain embodiments, the method can further include reshaping the small-scale robot to reach an area with different topographies. The disclosed small-scale robot can be reusable and configured to be re-assembled through the disclosed magnet system. For example, after collecting the target sample, the small-scale robot can be disassembled and washed. The disassembled IONPs can then be re-assembled for the next target area with different topographies.
The disclosed subject matter provides micro to milliscale robots that can be precisely guided to access difficult-to-reach spaces and complex surface topographies, including angled grooves or narrow crevices. The disclosed system can be used for (1) diagnostics via retrieval and sampling of biofilms associated with infectious diseases, (2) assessment of biofouling of dental/medical devices or implants, (3) compositional analysis of the samples, including microbial composition, by-products and biomolecules, including sugars, proteins, enzymes, polysaccharides, metabolites and (4) analysis of materials for non-medical applications (e.g., industrial application). The disclosed system using the magnetic robotic actuation can allow tether-free controlled motion and enables a wide variety of motility and locomotion strategies. In non-limiting embodiments, the operation of the disclosed robots can be controlled by an automated system.
The disclosed subject matter provides a nanozyme-based microrobotics platform that directs localized catalysis to an infection site with microscale precision to achieve targeted fungal binding. For example, the disclosed subject matter provides a set of structured assemblies composed of iron oxide nanozymes that deliver and localize antifungal activity through dynamic shape transformation and catalysis activation using electromagnetic field frequency modulation and fine-scale spatiotemporal control. The disclosed nanozyme assemblies can display controllable catalysis that varies depending on the location, motion, and velocity, providing tunable and precision-guided reactive oxygen species (ROS) generation.
In certain embodiments, the disclosed nanozyme assemblies can bind avidly to a target (e.g., fungal cells), coating the microbial surface to enable the localized in-situ targeting of biofilms. For example, the structured nanozyme assemblies can be directed to C. albicans-infected sites by programmable robotics and control to perform precisely guided fungal targeting.
The disclosed subject matter also provides microrobots for tetherless biofilm treatment and retrieval using iron oxide nanoparticles (IONPs) with dual catalytic-magnetic functionality as building blocks. For example, an example system can be formed from IONPs that assemble into aggregated microswarms under magnetic fields that can be controlled to disrupt and retrieve biofilm samples for microbial analysis. In non-limiting embodiments, an example platform can be composed of 3-dimensional (3D) micromolded opacifier-infused soft helicoids with embedded catalytic-magnetic IONPs that can be visualized via existing radiographic imaging techniques and controlled magnetically inside the root canal, uninterrupted by the soft and hard tissues surrounding the teeth in an ex vivo model. These microrobots placed inside the root canal can remove biofilms and be efficiently guided with microscale precision.
The disclosed subject matter can be used for various industrial applications. For example, the disclosed robot can be used for any hard-to-reach area with challenging spaces and geometries to retrieve the target sample in the beverage, water, and pipe industries. For example, the target area can be interior spaces of water lines/pipes, household surfaces (swimming pools), glass surfaces, or combinations thereof. For example, industrial applications include food and beverage processing systems and water treatment systems.
In non-limiting embodiments, the amount and/or the size of the disclosed robot can be adjusted for industrial applications. For example, the size of the robot can range from about 1 nm to about 5 m depending on the target sample and/or the industrial application. For example, processing and treatment facilities for food, water, energy and chemical production. The amount of the robot can range from about 1 mg to about 1 kg depending on the target sample and/or the industrial application. For example, sampling of microbes from industrial water treatment or beverage production facilities.
Development of reconfigurable STARS: an automated electromagnetic platform was designed to treat biofilms on vertically oriented surfaces, which requires self-supporting functional elements that withstand gravitational forces. As illustrated in
The components of the control system are arranged around a customized vessel that holds an aqueous IONP solution (
A set of programmable electromagnets positioned on either side of the vessel controls the formation and multimodal action of the magnetic bristles. The magnetic field generated from both electromagnets is coordinated via a programmable microcontroller. Furthermore, the position of the forward iron core can also be controlled while the rear ferrite core is fixed. This design enables flexible positioning and control of bristle-like superstructures that form on a vessel wall and can span the vessel width while moving in multiple directions as directed by the local field. This allows automation of both motions and positioning of the robots.
For example, in one modality, the magnetic field is oriented to drive the superstructure assembly with its base on the vessel wall near the mobile forward electromagnet core in the xz-plane (
Such magneto-catalytic properties combined with magnetic field modulation allow automated, reconfigurable bristles to be formed with multiple programmable functionalities, including extension and retraction, topographical adaptability, and tunable stiffness gradients. These surface topography-adaptive robotic superstructures (STARS) chemically treat and mechanically remove biofilms (
Physical characterization of STARS: The magnetic field generated by the electromagnets enables control over bristle formation, position, and properties. A 3D finite element model was developed to better understand the balance of magnetic fields and forces that control these properties and compare the prediction to the experimental outcome. As shown in
The magnetic fields afford dynamic bristle control. Bristle alignment is controlled using fields from both electromagnets, and the bristle position is tuned using magnetic forces generated by the mobile forward electromagnet core. As these forces sweep laterally across the vessel wall, the bristles follow, allowing brushing motions (
The core of the forward electromagnet is then actuated to move bristles in a lateral motion repeatedly across a vertically oriented surface in a sweeping motion with linear velocities between 6 and 48 mm s−1. Since the forward core is small in diameter (3 mm), the magnetic forces are focused in a small region and bristles closely track its movement. The rear ferrite core is larger in diameter (10 mm) and generates weaker forces that serve primarily to define the direction of bristles' extension. As the forward core translates, the bristle closely follows the highest gradient of the magnetic field, as shown in the finite element model (
Bristle length depends on the IONP suspension concentration and can range from 1 mm in length at 0.5 mg ml−1 to as long as 7 mm at 2 mg ml−1. The bristle shape can be influenced by the movement of the electromagnet core, extending during the first few seconds (
Given the extensibility of the bristles, the bristle interaction with topographically complex surfaces was assessed. Using lithographical methods, surfaces with repeated circular, square, and triangular patterns were generated (
Bristle mechanical properties can be characterized using two complementary methods, both of which are based on force estimates derived from using Euler's beam deflection approximation:
Where δb is deflection, L is beam length, E is Young's modulus, and I is the area moment of inertia. First, the cohesion force of STARS bristles was measured using a PDMS microcantilever to determine the physical strength of the bristle itself (
At the interface of the STARS bristles with the treatment surface, the dominant stresses are the lateral shear stress applied by the bristles, which is opposed by a combination of fluid drag and adhesion between the biofilm and the substrate. Unlike typical monolithic bristles, the IONPs near the bristles end continuously reconfigure and change the bristle structure under high shear near the vertical surface. To verify that these dynamic structures can produce significant stresses, a micropillar composed of PDMS with 50 μm diameter and 240 μm height (aspect ratio=4.8) was used. This single micropillar interacts with the small-scale features at the ends of the bristles allowing characterization of the local force generated by these structures (
The micropillar is vertically placed at the position of the target surface and imaged during bristle contact to measure the deflection. Based on its deflection, the shear stress applied at the 2.2 mm distance to be as high as 83.3 N m−2 was measured depending on the magnetic field strength (
STARS bristle movement is opposed by viscous drag, which increases with actuation speed. This contact force was measured as a drag on a cylindrical body at constant velocity. The Reynolds number,
is on the order of 10 during movement, well within the laminar flow regime, where ρ and μ are the density and dynamic viscosity of the fluid, u is the flow speed, and L is the characteristic linear dimension. The viscous drag force on the translating bristle can be estimated as
where the drag coefficient CD is ˜5, u0 is the velocity of the bristle, and A is the area of the bristles facing the fluid. This yields an estimated maximum drag force on the bristle of 0.8 μN at 12 mm s−1, which is an order of magnitude below the applied shear force at the vertical target surface/bristle interface.
These complementary analyses reveal four essential properties of STARS bristles. (i) The support structure varies along the length of the superstructures, with a highly cohesive base that supports the extended bristles with decreasing yet strong cohesion along the length of the structure. (ii) The cohesion and associated capability of the bristle to mechanically remove strongly adhesive biofilms is retained at the distal end, where stresses exceed the values necessary for biofilm removal. (iii) Even as the STARS bristles reconfigure and adapt to fine-scale surface topography, applied shear stress remains sufficient to remove biofilm, as evidenced by shear stress measurements of the smallest bristles. (iv) This shear stress can be dynamically adjusted by modulating the magnitude of the magnetic field, enabling fine-tuning of the maximum shear for controlled biofilm removal. Hence, the ‘stiffness gradient’ provides strong cohesion at the base of the bristle to withstand gravity and extend horizontally, while flexibility at the tip provides enough shear force to dislodge biofilms while continuously adapting to the topography.
Antibiofilm functionality of STARS: The process of STARS bristle assembly and the physical properties establish the fundamentals for targeted magneto-catalytic action for biofilm treatment and sampling. An oral pathogen (Streptococcus mutans) was used to form one of the stickiest biofilms with matrix-enmeshed bacteria, which is remarkably difficult to remove. Next, the removal of biofilms on vertically oriented surfaces was assessed. To mimic the anatomical positioning of teeth in the upper arch, slabs are 3D-printed and placed in a vertical position similar to the upper incisors (
To characterize biofilm scrubbing on the surface, an automated, standardized process was developed to ensure consistency and repeatability. During forward surface biofilm removal, the geometry was fixed, and the magnetic field strength was held constant at 69 mT for focusing on two parameters, specifically, IONP concentration and scrubbing velocity. The distance between the vessel wall and the biofilm specimen during all experiments was fixed at 2.2 mm. IONP suspensions at concentrations ranging from 0.5 to 2.0 mg ml−1 were added to the vessel. A uniform 10 mm lateral sweeping motion is used to quantify biofilm removal at all IONP concentrations and sweeping velocities. This focused motion was intended to provide a quantifiable metric for efficacy rather than to remove the biofilm from the entire surface. As such, biofilm removal was measured in terms of pre- and post-treatment based on binarized before/after images using a threshold value (
Given that IONPs display peroxidase-like activity, STARS bristles can provide an on-site source of free radicals for catalytic reaction-generated antimicrobial effects. A colorimetric assay using 3,3′,5,5′-tetramethylbenzidine (TMB) was used to demonstrate the generation of reactive oxygen species from H2O2 by the catalytically active STARS bristles. The hydroxyl radicals produced from H2O2 oxidize colorless TMB to blue-colored reaction products, which can be visualized and assayed by measuring the absorbance at 652 nm. The catalytic activity of the STARS bristles is determined in the same conditions as the biofilm removal assay. The assay indicates the rapid generation of reactive oxygen species during the first two minutes of cleaning (
Biofilm removal efficacy is first evaluated as a function of magnetic field strength (
Altogether, STARS bristles operate through multiple complementary mechanisms that are capable of catalysis, physical intelligence (surface conforming, shape-adapting reconfiguration, and adjustable shear strength) and generation of tunable lateral forces and antimicrobial reagents in situ, which can explain the efficacy of biofilm disruption at multiple spatial and length scales, while entrenching biofilm components. This provides multimodal features for designing autonomous motion routines for precise biofilm treatment and sampling by combining controlled mechanical and chemical activation occurring simultaneously with topography-adaptive functionality in real-time.
Automated biofilm removal and retrieval on tooth surface: 3D-printed tooth replicas and ex vivo human teeth were employed to closely mimic the clinical conditions (
A set of fundamental STARS motion patterns, including circular, linear, and arced motions, which mimic toothbrushing and test their cleaning efficacy on 3D-printed human tooth mimics, was developed (
As STARS continually reconfigure during biofilm cleaning at targeted areas, they incorporate biofilm contents into the bristle. This feature enables precise retrieval of biofilm contents with high spatial precision at the submillimeter level (
The directed assembly of reconfigurable, cantilevered bristle-like superstructures, which are composed of packed nanoparticles by spatially and temporally modulating magnetic fields, is disclosed. These STARS, surface topography-adaptive robotic superstructures, have tunable strengths, shapes, and reactivity that are effective for removing biofilms. A spatially ordered bristle superstructure was observed with controllable stiffness that provides strong cohesion at the base where support is required and remains reconfigurable at the distal end where surface conformality is desirable. This gradient in properties allows STARS to self-support, reach, and adapt to variations in surface topography in arbitrary orientations while generating sufficient shear stress to dislodge biofilms. Furthermore, by introducing scalable and reversible architectures, the STARS length can be extended or retracted while conforming to crevices and other complex features, enabling the treatment and retrieval of distinct microbes from within biofilm on hard-to-reach surfaces with microscale precision. Notably, the catalytic property is preserved throughout reconfiguration, providing mechanochemical function afforded by the assembled superstructures.
The findings on the interdependence of superstructure conformability, topography adaptation, physical force adjustment, and spatiotemporal magnetic field control can lead to further investigations at the intersection of reconfigurable soft-matter, functional nanomaterials, and micro robotics. In addition, these dynamic structures can be actuated remotely and precisely with translational and circular motions using automated, programmable control algorithms. An automated, tetherless multi-tasking platform that integrates ‘toothbrushing-like’ and ‘flossing-like’ action simultaneously with antimicrobial activity in real-time and sample retrieval for pathogen detection was created. The disclosed feedback-guided STARS for on-demand motion patterns, control, and functional assembly can lead to highly configurable structures able to adjust to different 3D surface geometries and adhesion strengths to achieve autonomous biofilm disruption, removal, and diagnostics.
Synthesis and characterization of iron oxide nanoparticles (IONPs): The IONPs were synthesized via a facile solvothermal method. 0.82 g of iron (III) chloride was dissolved into 40 ml of ethylene glycol. Then, 3.6 g of sodium acetate was added to the solution under vigorous stirring at room temperature for 30 min. Subsequently, the mixture was transferred to a custom-built 50 ml Teflon-lined stainless-steel autoclave and heated for 12 h. After the autoclave was cooled to room temperature naturally, the IONP precipitate was collected, rinsed several times with ethanol, and then dried at 60° C. for 3 h. The synthesized IONPs were characterized using scanning electron microscopy (SEM, FEI Quanta 600, FEI, Portland, OR, USA). For IONPs size distribution, the region of IONPs was automatically detected and characterized by the size invariant circle detection method implemented in MATLAB built-in function “imfindcircles.”
Magnetic field control device: The magnetic fields are controlled with a device combining programmable electromagnets and servo motors. The magnetic field for the reconfigurable STARS bristle was formed by two coaxially arranged electromagnets at a distance of 8 mm. Between the two electromagnets, an actuation vessel with the dimension of 15×6.7×13 mm3 (width×depth×height, about 1.3 ml) was designed to accommodate IONPs suspension, and a holder was constructed to maintain an 8 mm gap between the two electromagnets. Both the electromagnets and servo motors were mounted around the actuation vessel and remained fixed in the same position for all experiments. A ferrite core with a diameter of 10 mm was situated in the center of the rear electromagnet. An iron core with a diameter of 2 mm was positioned in the center of the forward electromagnet. The position of the forward iron core is moved in varying trajectories using servo motors.
For side-to-side motion, a micro servo motor (SG90) was programmed to move 50 degrees (between 65 and 115 degrees) with an arm of 14 mm in length. A symmetrical arc-shaped movement of approximately 12 mm was implemented with various linear velocities from 6 to 48 mm s−1. For circular motion, a continuous rotation servo motor (FS90R) was used and programmed to allow unrestricted movement at angles using a relatively short arm of 2 mm in length. A continuous circular movement was generated centered with the axis of electromagnets with a linear velocity 12 mm s−1 in clockwise or counterclockwise directions.
To create multimodal motions with a high degree of repeatability in position and timing, a sliding vessel was created. The body of the device consisted of two different parts, a holder for the electromagnets and servos and a sliding vessel. One servo drives a pinion gear attached to the rack of the sliding vessel for left-to-right motion, and the other servo drives the forward iron core for circular or arc-shaped motions. The sliding vessel held the tooth replicas and natural teeth and was actuated by a programmable micro servo motor. The motion of the sliding vessel was coupled with the programmable motion of the electromagnet iron core, which allowed a combination of motions to mimic brushing patterns.
The high-gradient magnetic field was directed by the repositioning of the iron core, and the various positions were mainly implemented by the movement of the servo controlling the iron core within the forward electromagnet (side to side and circular by regular and continuous micro servo), during which the magnetic field remained constant. Actuation in all experiments was performed via the application of a magnetic field and servo programmed to achieve the desired motion pattern. The movement of the micro servo arm and the magnetic fields of electromagnets were controlled using a microcontroller (Arduino Nano, Arduino, Somerville, MA, USA). Each electromagnet was energized independently using a programmable DC power supply (Sorensen XTR60-14, AMETEK Programmable Power, San Diego, USA) and Arduino integrated development environment (IDE) software for system coding.
The geometries of the actuation vessel and the body of the device were developed and designed with Onshape Computer-Aided Design (CAD) software (Onshape Inc, Cambridge, USA). The actuation vessel and the body of the device were fabricated using low force stereolithography (SLA) 3D printer (Form 3B, Formlabs Inc., MA, USA) with 25×25 μm2 lateral resolution and 50 μm layer thickness with a biocompatible photopolymer resin (Dental SG V1 resin, Formlabs Inc., MA, USA). For 3D printed parts, rinsing was performed for 20 min in fresh 99% isopropanol (IPA), air drying for 30 min and 60 min post-print ultraviolet light curing (405 nm light at 60° C.) (FormCure, Formlabs Inc., MA, USA).
Bristle-like STARS formation: The bristle-like superstructures were assembled using a magnetic field control system as described above. The dispersed IONPs were collected by magnetic fields from the forward electromagnet for 5 sec forming a rounded dome shape, and the strength of the magnetic field used for the standardized biofilm removal experiments was measured to be 90 and 25 mT (MF100; Extech Instruments, Boston, MA, USA) at the forward and rear regions, respectively. The STARS were then designed to orthogonally extend from the forward vessel wall to form elongated bristle-like structures for 25 sec by energizing the rear electromagnet. When moving the bristles from the front to the rear, the strength of the magnetic field was measured to be 35 and 70 mT at the forward and rear regions, respectively. At the beginning of the next cycle, IONPs were recollected in the forward region. A cycle of 30 seconds was repeated up to 20 times during dental biofilm removal experiments. The appearance and physical/mechanical properties of STARS bristles can be precisely controlled by the concentration of IONPs (0.5 to 2.0 mg ml−1), the sweep velocity of the servo (6 to 48 mm s−1), and the strength of magnetic fields (13.3 to 96.4 mT) at the center of the actuation vessel.
The STARS bristle formation and movement videos in the actuation vessel were captured using a Zeiss Axio Zoom.V16 fluorescence upright stereo zoom microscope system (Carl Zeiss Microscopy GmbH, Jena, Germany) with a 1× objective (numerical aperture, 0.25) at a video frame rate of up to 100 fps. The videos were processed using Zeiss Zen Blue software to determine the position, velocity, and length of STARS bristle.
Surface conforming property of STARS bristle: To evaluate the reconfigurability and adaptation of STARS bristles, surfaces with various topographies, including repeated circular, square, and triangular patterns, were designed with Onshape. All patterned surfaces repeat the unit structure four times within an 8.5 mm width, and the depth of each unit structure is 0.9 mm. The patterned surfaces were 3D printed using a Formlabs 3B printer with Dental SG V1 resin, as described above. The patterned surfaces were suspended in the vessel at 2.2 mm distance from the forward vessel wall, and a STARS bristle (2 mg ml−1) was formed and moved using the field control methods described above.
Force measurements of STARS bristle: Molds for force-sensing microcantilevers with a square cross-section were created using the Formlabs 3B printer with Dental SG V1 resin as described above. After washing and curing, the molds were coated with a separator (Gingifast Separator, Zhermack, Italy). Molds were filled with polydimethylsiloxane (PDMS, Sylgard 184, Dow Corning Corporation, Midland, MI, USA) elastomers and degassed. The excess PDMS was removed from the surface by scraping. After oven curing at 70° C. for 2 h, cantilevers were individually removed and connected to the arm of a 4-axis nano manipulator (MX7600, Siskiyou Corporation, Grants Pass, OR) to control the position of the PDMS microcantilever. The cohesion force and shear stress of STARS bristle were measured based on the relationship between the elastic deflection of the end-loaded cantilever beam and the applied force by the STARS bristle.
To estimate the shear stress exerted by STARS bristles, PDMS micropillars with a high aspect ratio were fabricated out of a silicon hard master. Briefly, 4 μm S1805 positive photoresist (Microposit, Philadelphia, USA) was spray-coated onto a silicon wafer and patterned through standard photolithography processes. The wafer was then etched in deep reactive ion etching (DRIE, SPTS Rapier Si DRIE) to create microwells with desired heights for PDMS molding. The etching depth was 240 μm, while the diameter was maintained to be the same. The wafer was then cleaned sequentially in nanostrip, deionized water, acetone, isopropyl alcohol (IPA) and deionized water again. PDMS monomer and crosslinker were mixed with a ratio of 10:1 and poured on top of the dried silicon wafer. The mixture was degassed and cured at 70° C. in an oven for 2 h. To facilitate the demolding process, Trichloro (1H,1H,2H,2H-perfluorooctyl) silane (97%, Sigma-Aldrich) was vapor coated in a vacuum chamber for 15 min, prior to PDMS pouring. The cured PDMS micropillars were peeled off from the silicon hard master. The micropillars were cut-off individually under the fluorescence upright stereo zoom microscope (Zeiss Axio Zoom.V16, Carl Zeiss Microscopy GmbH, Jena, Germany) and attached to the 3D printed holder for shear stress measurement. The maximum elastic deflection of the end-loaded micropillars was measured while sweeping STARS bristles laterally across the micropillar tip.
The force measurement videos in the actuation vessel were recorded using a Zeiss Axio Zoom.V16 fluorescence upright stereo zoom microscope system with a 1× objective (numerical aperture, 0.25) at a video frame rate of about 100 fps. The captured frames were analyzed from each video in ImageJ to measure the deflection.
Catalytic activity of STARS bristles: The peroxidase-like activity was tested via an established colorimetric method using 3,3′,5,5′-tetramethylbenzidine (TMB) as a substrate which generates a blue color with specific absorption at 652 nm after reacting with free radicals catalyzed by IONP in the presence of hydrogen peroxide over time. Briefly, the bristles were formed at different concentrations (0.5, 1 and 2 mg ml−1) of IONPs under 12 mm s−1 of sweep velocity and 69 mT of magnetic fields. The reaction mixture of 1 mL sodium acetate (NaOAc) buffer (0.1 M, pH 5.5) containing 0.1% H2O2 and 100 g of TMB was incubated at room temperature during the actuation and assayed spectrophotometrically. The time-lapse reactions were monitored at 652 nm using a Beckman DU800 spectrophotometer (Beckman Coulter, Inc., Fullerton, CA, USA).
Biofilm formation on model surfaces and human teeth: Individual slabs were created as model surfaces with dimensions of 4.0×2.2×4.0 mm3. A T-shaped mechanical locking structure was implemented for secure holding inside the actuation vessel. The 3D structure of the slabs was located where the highest magnetic flux density was controlled inside the actuation vessel. The 3D printed slabs were polished using a muslin wheel (Kerr Dental, USA) and fine pumice (Benco, USA). After polishing, they were bath sonicated for 5 min to wash off the pumice.
Human incisor teeth extracted in the dental clinic (for surgical reasons) at the School of Dental Medicine were collected and repurposed for this study without any identifiers. The teeth were matched into pairs based on morphology and dimensions. Tooth pairs were scanned using CEREC Omnicam Intraoral Scanner and integrated CEREC 5.0 software (Dentsply Sirona, USA) to implement a tooth mimic model. The scanned high-resolution 3D CAD images were used to generate 3D printed teeth replicas and design a custom 3D printed holder to mimic the gingival margins of the natural teeth using 3D CAD software (Blender, version 2.91.0; Blender Foundation, Amsterdam, Netherlands). 3D printing was done using Formlabs 3B printer with a biocompatible Dental SG V1 resin, and the 3D printed teeth replicas were polished as described above. The polished 3D printed tooth pairs and the natural tooth pairs were sterilized in an autoclave for 20 min at 121° C., placed in the custom-fit holder, and subsequently used for biofilm formation. The biofilms formed on teeth were placed in the actuation vessel and subjected to STARS bristle treatment.
Biofilms were formed on saliva-coated 3D printed slabs, 3D printed tooth pairs or ex vivo human tooth pairs. Streptococcus mutans UA159, a biofilm-forming model oral pathogen, was grown in ultrafiltered (10-kDa cut-off; Millipore, MA, USA) tryptone-yeast extract (UFTYE) broth containing 1% (w/v) glucose at 37° C. and 5% CO2 to mid-exponential phase. Both saliva-coated 3D printed slab and tooth pairs were mounted vertically in 24-well plates and inoculated with ˜2×105 colony-forming units (CFU) of actively growing S. mutans cells per milliliter in UFTYE containing 1% (w/v) sucrose at 37° C. with 5% CO2 for 43 h. The culture medium was changed twice daily (at 19 and 29 h) until the end of the experimental period (43 h). In a separate experiment, Candida albicans SC5314 (a well-characterized opportunistic fungal pathogen) was used to generate mixed-species biofilms with S. mutans. For inoculum preparation, C. albicans (yeast form) and S. mutans cells were grown in ultrafiltered UFTYE broth (at pH 5.5 and pH 7.0 for C. albicans and S. mutans, respectively) containing 1% (w/v) glucose at 37° C. and 5% CO2 to mid-exponential phase. Saliva-coated 3D printed slabs were mounted vertically in 24-well plates and inoculated with ˜2×105 colony-forming units (CFU) of actively growing S. mutans cells and ˜2×104 (CFU ml−1) of C. albicans (yeast cells) per milliliter in UFTYE containing 1% (w/v) sucrose at 37° C. with 5% CO2 for 43 h.
Biofilm disruption and removal: Biofilms were treated with STARS bristles assembled from IONPs (0.5, 1, and 2 mg ml−1 final concentration) solution in the actuation vessel as described above. Customized IONP formulation was used to enhance the catalytic bioactivity with EPS-degrading enzymes (dextranase/mutanase, 25/5 U) and 1% H2O2 (1% v/v). Briefly, biofilms were placed in the actuation vessel containing IONP solution for 10 min followed by the addition of 1% H2O2 and subsequent modulation of the magnetic field, which forms STARS bristles. The velocity, trajectories, and motion frequencies were controlled as described in the previous sections. Biofilm removal in all experiments was performed via the application of an external magnetic field and servo movement preprogrammed to achieve the desired trajectories, velocities, and motion patterns.
Standard culturing method (number of viable cells by CFU determination) and stereoscope-based fluorescence imaging were performed to assess the biofilm removal by the STARS bristles. For the culturing method, the total number of CFU per biofilm was determined after biofilm treatment. Briefly, the removed biofilm was collected and homogenized via water bath sonication followed by probe sonication (30 sec pulse at an output of 7 W; Branson Sonifier 150; Branson Ultrasonics, CT, USA). Homogenized biofilm suspensions were serially diluted and subjected to microbiological analysis. The total number of viable cells was determined by CFU counting. For fluorescence imaging, SYTO9 (485/498 nm; Molecular Probes, Carlsbad, CA, USA) fluorescent probe was used for labeling bacterial cells, and Alexa Fluor 647 dextran conjugate (647/668 nm; Molecular Probes, Carlsbad, CA, USA) was used for labeling EPS. Before and after removal, images of the samples were taken with the Zeiss Axio Zoom.V16 fluorescence upright stereo zoom microscope system (Carl Zeiss Microscopy GmbH, Jena, Germany) with 1× objective (numerical aperture, 0.25).
To analyze the area of biofilms on the slab, open-source Fiji software was used. Images were processed for the green channel (SYTO9) due to significant cross-talk from the red channel (Alexa Fluor 647) from stereo microscopy. A standardized and constant rectangular-shaped region of interest (ROI; 4,000×2,000 μm2, width and height) was selected to calculate and compare only the biofilm area on the 4×2 mm2 substrate. A median filter (radius=2) was applied to eliminate noise and reduce false segmentation of background and out-of-focus signals. Otsu's automatic global thresholding algorithm featured in Fiji was used to classify and segment the colonized area of biofilms on the ROIs. The biofilm removal efficacy was calculated as (a-b)/a, where “a” was the segmented area of biofilm before treatment, and “b” was the segmented area of biofilm after treatment for comparing the removal efficacy of biofilms under the various actuating conditions as the normalized area of biofilm.
Biofilm entrenchment by STARS and visualization: Super-resolution confocal microscopy was performed to visualize the biofilm components (bacteria, fungi, and EPS) that become entrenched among the extended STARS bristles. The EPS glucan matrix was labeled with Alexa Fluor 647 dextran conjugate (Molecular Probes). S. mutans and C. albicans (if applicable) were stained with SYTO9 (Molecular Probes) and Concanavalin A-tetramethylrhodamine conjugate (Molecular Probes), respectively. After biofilm removal, STARS bristles were collected and immobilized in 1% agarose for super-resolution imaging using a 40× water immersion objective (numerical aperture=1.2) on an upright confocal microscope (Carl Zeiss LSM 800, Germany) with Airyscan. The STARS bristles were visualized using the reflection mode and a 405 nm laser. In a separate experiment, biofilm components entrenched in STARS bristles were dehydrated through a graded ethanol series, and examined by scanning electron microscope (SEM, FEI Quanta 600, FEI, Portland, OR, USA).
Analysis of the biofilm retrieval components: STARS bristles with entrenched biofilm components were subject to molecular and enzymatic analyses after retrieval. The fungal and bacterial genomic DNA was extracted and purified from the sample using DNeasy PowerLyzer Microbial Kit (Qiagen, Germany), following the manufacturer's instructions. The qPCR reaction was performed using a CFX96 Real-Time PCR Detection System (Bio-Rad Laboratories, Hercules, CA, USA) and PowerTrack SYBR Green Master Mix (ThermoFisher, Waltham, MA, USA). Specific primers were used to detect each microbial species (S. mutans, forward: 5′-ACCAGAAAGGGACGGCTAAC-3′, reverse: 5′-TAGCCTTTTACTCCAGACTTTCCTG-3′; C. albicans, forward: 5′-AGAACGATAATAACGACGATGA-3′, reverse: 5′-AGTCATTGTAGTAATCCATCTCA-3′).
Bacterial glucosyltransferase (Gtf) activity was analyzed using scintillation counting. The Gtf activity in the sample was measured in terms of incorporation of [14C] glucose from radiolabeled sucrose substrate (New England Nuclear Research Products, Boston, MA) into the glucan product for 4 h at 37° C. One unit (U) of Gtf enzyme was defined as the amount of enzyme needed to incorporate 1 mol glucose into glucan over a 4 h reaction period.
Statistical analysis: All statistical analyses were performed with GraphPad Prism 8.0 (GraphPad Software, Inc., La Jolla, CA). All data are represented as mean±s.d. Comparisons between multiple groups were performed using a two-sided one-way analysis of variance (ANOVA) with post-hoc Tukey's test, where P<0.05 was considered significant and P>0.05 was considered not significant. At least three independent experiments were performed unless otherwise stated.
Recent advances in nanotechnology and robotics have enabled the integration of magnetocatalytic nanoparticles with microrobotics principles to target and eradicate biofilms in clinically challenging settings. Here, the catalytic and magnetic properties of iron oxide nanoparticles (NPs) were used to introduce a microrobotics platform designed for biofilm treatment and diagnostics (
Targeting endodontic biofilms. Incomplete root canal disinfection remains the main cause of treatment failure leading to persistent endodontic infections and apical periodontitis in conventional antimicrobial procedures. The anatomical complexities in the root canal system hinder the effective removal of biofilms, while approaches to diagnose or assess disinfection efficacy are limited. New disinfection modalities such as photon-induced, photoacoustic streaming, passive ultrasonic irrigation, antimicrobial nanoparticles and photodynamic therapy have been proposed and or used for endodontic biofilm treatment. However, these approaches lack controlled targeting of the anatomical complexities and are unable to retrieve biofilm samples for diagnostics. New technologies can enable multifunctionality to access difficult-to-reach surfaces and perform biofilm removal, and microbial detection simultaneously for effective and precise endodontic therapy. Such multimodal approaches can be achieved using microrobotics.
Magnetically driven catalytic antibiofilm robots. Iron oxide NPs were used as the fundamental building blocks to create distinctive microrobots to kill, degrade, and retrieve biofilms from confined spaces found in the root canal system, a challenging anatomical space in the oral cavity. The average diameter of the iron oxide nanoparticles is estimated to be 464.9 nm with a standard deviation of 36.08 nm. Iron oxide NPs have catalytic properties that arise from intrinsic enzyme-like (peroxidase-like) activity that activates H2O2 to generate bioactive molecules in situ to disrupt oral biofilms (
The flexibility of ‘NPs building blocks’ allows the formation of reconfigurable aggregated structures, inclusion in 3D molded soft helicoids or even direct 3D printing. Here, two platforms were developed. The first system uses magnetic forces to concentrate NPs and form structured aggregates (
Aggregated structures. Iron oxide NPs can reversibly form aggregated structures by applying and removing the external magnetic fields on-demand. Once the aggregates are formed, collective behavior can be achieved through precise control over the magnetic fields. Functioning as a dynamic collective unit under the magnetic field control, aggregated structures can perform complex tasks and can reconfigure and adapt to the confined space. Using 3D printed teeth replicas generated based on microCT scans of natural human teeth, the data show that the aggregated structures can be moved and directed by the magnetic field and adapt to the variable canal geometry to reach the apical region. The size of the aggregates between the canal walls had a wide range of sizes (from 154.5 μm to 844.4 μm). By measuring the structures' width in a corono-apical direction, the range was between 37.8 μm and 1235.9 μm. (
To test the ability of the structures to disrupt and retrieve samples from the apical regions, 14 day mixed-species biofilms (same bacterial species and inoculum size as described above) were prepared inside vertically positioned 3D printed teeth replicas (media was changed after 24 h, then after every 48 h) (
3D molded helicoids. Given the flexibility of the iron oxide NPs as building blocks, a molded robotic system was developed using 1-mm negative molds designed in SolidWorks and 3D printed using a ProJet 6000 HD stereolithography printer (3D Systems, Rock Hill, SC, USA). Helicoid 3D molded robots (two helices wrapped around a central axis) are formed by embedding NPs within a thermo-reversible granulated agar gel (Difco, BD Biosciences, Sparks, MD, USA) in a final soft robot composition that contains 25% glycerol, 3% (w/v) agar gel within which 10% NPs are embedded. The NP-embedded gel is used to fill the negative molds to create 3D molded soft helicoids with a size of ˜700 μm by 1.5 mm. When directed by the magnetic fields, the 3D molded helicoids can propel with high efficacy (
A practical challenge facing microrobotics is the difficulty of tracking inside the body. Real-time updates of position would aid precise navigation systems, ensure targeting, and confirm that microrobots are performing their desired function. To address the challenge of real-time tracking and locating the microrobots, bismuth oxide opacifiers are incorporated 3% (w/v) within the matrix of 3D molded helicoids to enhance their radiopacity (
The multiple functions demonstrated above can also lead to new methods for biofilm treatment and disinfection in regenerative endodontics, where mechanical instrumentation is not desirable and treatment relies mainly on the chemical effect of antimicrobials. The 3D molded soft helicoids can be precisely controlled and actuated within the root canal space of incompletely formed roots to deliver bioactive on-site to achieve chemical and mechanical disruption of biofilm, while being tracked and located with available radiographic imaging techniques. Notably, 3D molded helicoids can be loaded with microcapsules that contain a clinically used antibiotic mixture (i.e., metronidazole and ciprofloxacin). The cargo (antibiotics) can be released on-demand via the application of rapid oscillation of the magnetic field.
A new technique for precision biofilm treatment using microrobotic platforms with potential for both diagnostics and therapeutics in the root canal system, a clinically challenging anatomical space in the oral cavity is disclosed. The feasibility of tetherless magnetic control uninterrupted by the presence of the intact periodontium surrounding the tooth is shown. Iron oxide nanoparticles were used as fundamental building blocks, which enables significant design flexibility. NPs can form aggregated structures by controlled magnetic fields, which are capable of navigating inside the tooth canal and simultaneously disrupting biofilms and retrieving biological information for pathogen detection using microbiological DNA analysis. Alternatively, NPs can be incorporated into 3D molded soft helicoids that are precisely driven to the apical third of the canal. In addition, the incorporation of opacifiers into the helicoids provides opportunities for real-time tracking using existing radiographic imaging. The inclusion of additional chemicals can provide for drug loading, transport, and on-site released in a controllable manner.
The disclosed micro/nanorobots can be precisely guided to reach the apical area and used to deliver bioactive or drugs in situ to achieve both diagnostics and chemical disinfection with tissue regeneration. The disclosed subject matter can be used in various fields.
The disclosed subject matter provides microrobotic assemblies, including nanozymes using fine-scale spatiotemporal control for localized catalysis and precise targeting of infection sites to achieve in situ fungal capturing. Using electromagnetic field frequency and positioning modulation, morphology-adjustable nanozyme microrobots that can freely extend, retract, roll, vibrate and glide with high spatiotemporal precision were assembled. The catalytic activity of these nanozyme assemblies varies depending on the motion, velocity and shape, providing on-site reactive oxygen species (ROS) generation. The nanozyme assemblies unexpectedly bind avidly to fungal cells (C. albicans) and, more specifically than to human (gingival) cells. This selective binding interaction to fungi can further promote localized nanozyme targeting in situ. The directed targeting of fungal cells through cell-nanozyme binding using cell spheroid and tissue infection models were shown. The nanozyme-based robotics technique resulted in complete C. albicans eradications, providing a uniquely effective and targeted antifungal modality for pathogen control at the infection site.
Preparation and assembly of nanozyme microrobotic assemblies:
The disclosed systems can be based on on-site assembly of individual nanozymes into a set of specific reconfigurable superstructures using custom-built electromagnets array with multi-axis motion. An example setup is shown schematically in
The shape and motion of the nanozyme microrobots are controlled according to the applied magnetic field from electromagnets, which is harmonized via a programmable microcontroller. According to the ratio of the magnetic field strength generated by the electromagnet-1 and electromagnet-2, the nanozyme assemblies can be variably extended along the y-axis from the core side while oscillating components of the magnetic field enable both structural vibrations as well as enhanced controllability of extension. In addition, the x-z position of the nanozyme assemblies is coupled with the position of the iron core, which can also be controlled by the microcontroller. This controllability allows abundant automated multimodal three-dimensional (3D) motions of nanozyme microrobots.
Although catalytic activities of dispersed iron oxide NP have been well assessed, little is known about the catalysis of structured, mesoscale nanozyme assemblies. Therefore, various magnetic field configurations and corresponding motions, as well as the catalytic properties of nanozyme microrobots, were assessed using the custom-built electromagnets device. 4 different dynamic motions, including rolling, vibrating, gliding, and dabbing (
To achieve the vibration motion, electromagnet-2 is energized with a bias current as well as an oscillating component. This causes the structural ‘spikes’ to rapidly oscillate alternately inward and outward relative to the central axis. Lastly, the dabbing motion is characterized by controllable linear extension along the y-axis. This motion is enabled by applying a simultaneous bias field and oscillating field to electromagnet-2 after an initial x-z plane positioning step. The vibration and dabbing motion can be useful for precisely delivering nanozyme catalysis to specific target locations on distal surfaces.
Linear velocities from 0 to 12 mm s−1 with 10 mm path lengths along the x-axis were tested for the rolling and gliding motions, and frequencies from 0 to 16 Hz were considered for the vibrating motion (
It is noteworthy that increasing vibration frequency results only in incremental enhancement catalytic activity despite creating more pronounced structural movements, indicating that sub-millimeter-scaled amplitude of the vibrating motions can be insufficient to generate sufficient mass transport (
Altogether, nanozyme microrobots with shape-tunable and motion-enhanced catalysis were developed. Giving the limited surface area compared to freely dispersed iron oxide nanoparticles, the nanozyme microrobots display reduced catalytic activity when in a static state, suppressing unnecessarily occurring catalytic reactions. On the other hand, nanozyme microrobots can perform localized catalytic reactions when set in motion providing an effective approach to locally generate and directly deliver ROS to targeted spatial locations through the dynamic motions, thereby avoiding off-target effects.
Large amounts of nanozymes bound on C. albicans cells were observed when attempting to achieve closer or direct contact with the fungal surface. The nanozymes adhered with remarkably high affinity to both yeast and hyphal forms of C. albicans coating nearly the entire fungal surface as shown using confocal fluorescence and scanning electron microscopy (SEM) (
Precision targeting using experimental models: Next, directed targeting in a palatal mucosal tissue model with localized C. albicans growth was assessed to mimic clinical characteristics of fungal infection on soft tissues. To effectively use the nanozyme-microrobots for precise targeting, an automated and programmable control system was developed. The disclosed system enables control of nanozyme assemblies with three translational degrees-of-freedom. Two of the directions are controlled by servo motors which reposition the electromagnet cores controlling the center of the nanozyme-microrobot, while the third degree-of-freedom is controlled by modulating the currents to precisely and continuously extend the assemblies along the direction of the central axis of the coils.
To create the precise dabbing motion, a current was applied to the coil opposite the target to collect nanozymes. While holding the nanozymes against the substrate, the center of the electromagnet core was adjusted in the flat, facial plane of the electromagnetic coil. Once centered in a position aligned with the target in the z-direction, current was applied to the coil behind the target, which caused a linear extension of the structured assembly. However, the assembly typically adjusts shape in abrupt, discrete steps as the nanoparticles reorganize during extension, even when the current is adjusted continuously. To overcome this discrete, step-like extension, a continuously modulating sine wave was applied at 15 Hz superimposed on a bias signal to create a smooth, controllable, and repeatable extension. The high frequency modulated wave aids in the smooth morphological rearrangement of the nanoparticle assemblies during the extension and retraction phases and results in higher aspect ratio superstructures. This results in the dabbing motion used to precisely target tissue surfaces (
To automate this system, an algorithm was programmed to convert the servo motor positioning angles into the coordinates of the target. The x-axis is controlled by a rack and pinion gear system, while the y-position is determined by a radially sweeping arm (
In a clinical setting, Candida infection is characterized by localized white plaques (thrush) on the epithelial tissue comprised mostly of hyphal forms. To test the precision and efficacy of the nanozyme-based robotics approach, an experimental model was used to recapitulate the anatomical features of oral mucosa and localized fungal infection. A primary whole-organ culture was created using explant murine oral mucosa with localized infection sites using C. albicans inoculated on predetermined areas on the palatal tissue (
To further assess the antifungal precision and efficacy, a host cell-fungal (human gingival spheroid and C. albicans) model that allows testing fungal cell capturing-transporting to validate nanozyme-binding properties of the microrobots was developed (
In the demonstration, the nanozyme assembly could relocate through magnetically controlled motions to capture the fungal aggregates surrounding the spheroid tissue. Time-lapse images show the nanozyme assembly can bind, capture and engulf fungal aggregates while moving across the surface (
In summary, microrobotics techniques were employed to control the morphology, on-site catalysis and position of nanozyme assemblies and demonstrate targeting efficacy with microscale precision against C. albicans, a widespread opportunistic fungal pathogen associated with many human infections. Nanozymes were directed to fungal surfaces using planktonic cells, biofilms, aggregates, and tissue infection models. Unexpectedly, the nanozyme assemblies bind avidly to the surface of C. albicans and exploit this natural adhesion property to provide localized targeting modalities. The motion routines and enhanced adhesion are combined to demonstrate unique targeted treatments of C. albicans infections on tissue explants with a customized morphologically adaptive dabbing motion for localized targeting of nanozymes as well as capturing and removal of fungal aggregates from in vivo-like cell spheroids. By applying robotic techniques, a potent mechanism was introduced to enhance fungal targeting and capturing.
Altogether, the results demonstrate that microrobotic techniques for assembly and control of nanozyme constructs provide unique targeting approaches for enhancing the precision and capturing of fungi. The disclosed techniques can be broadly applicable to advancing nanozyme-based robotic assemblies for targeting microbial infections.
Synthesis and Characterization of Iron Oxide Nanoparticles: The iron oxide nanoparticles (IONP) were synthesized by a modified solvothermal method via reducing FeCl3 at high temperatures. The reaction mixture was prepared by dissolving 975 mg of FeCl3 in 30 mL of ethylene glycol. 1.5 g of sodium acetate was added as a reductant and solvent. Before the heat treatment, the mixture was stirred for 30 min for homogenization. Subsequently, the obtained homogeneous mixture was transferred to a custom-built 50 mL Teflon-lined stainless-steel autoclave and heated at 200° C. for 14 hours. The final products were washed 3 times with Milli-Q water (MilliporeSigma, Burlington, MA, USA) and ethanol. Transmission electron microscopy (TEM) photographs were taken using a FEI Tecnai T12 microscope (FEI, Hillsboro, OR) at an accelerating voltage of 100 kV. The final concentration of IONP was determined by inductively coupled plasma-optical emission spectrometry (ICP-OES) using a Spectro Genesis ICP (SPECTRO Analytical Instruments GmbH, Boschstr, Germany). ICP-OES was calibrated with calibration standards containing known amounts of elements. The diameters of ions are measured using the “imfindcircles” function in MATLAB, which detects circles of a consistent size. The average diameter is found to be 307.8 nm, with a standard deviation of 79.0 nm.
Magnetic Field Control Device: The magnetic fields for the nanozyme microrobots were generated by two electromagnets coaxially assembled at a distance of 8 mm. Each electromagnet was independently energized using a programmable DC power supply (Sorensen XTR60-14, AMETEK Programmable Power, San Diego, USA). An iron core (2 mm in diameter) was mounted on a servo motor to generate the high-gradient magnetic fields at a focused area. The position of the iron core is controlled using a micro servo motor. Between the two electromagnets, a slidable chamber (15×7.3×19 mm3) was designed to accommodate the IONP dispersion and the position of the chamber was controlled by another servo motor. The electromagnets and servo motors were controlled and harmonized by a microcontroller (Arduino Nano, Arduino, Somerville, MA, USA). The Arduino integrated development environment software was used for system coding. To control the motion of nanozyme microrobots, the micro servo motor connected to the iron core was programmed to move between 65° and 115°, which created an up-and-down arc-shaped iron core movement to control the z-coordinate of the nanozyme microrobot. The second micro servo motor (FS90) was used and programmed to control x-axis coordinates with a pinion gear (5 mm radius) attached to the rack of the slidable container for left-to-right motion. A combination of the micro servo motors with the arm and pinion gear allowed high spatial precision (0.087 mm of x-axis, ˜0.244 mm of y-axis) and repeatability in position and timing with linear velocities ranging from 0 to 12 mm s−1. Actuation in all experiments was performed via the application of a magnetic field and servo programmed to achieve the desired motion pattern. The geometries of the slidable container and the body of the device were developed and designed with Onshape, a computer-aided design software (Onshape Inc., Cambridge, USA). The slidable container and the body of the device were fabricated using a low-force stereolithography (SLA) 3D printer (Form 3B, Formlabs Inc., MA, USA) with a biocompatible resin (Surgical Guide). 3D printed parts were rinsed for 20 min in 99.9% isopropanol and then photopolymerized for 30 min under ultraviolet light (405 nm light at 70° C.) (FormCure, Formlabs Inc., MA, USA).
Dynamic motions of Nanozyme Microrobots: four distinct nanozyme microrobot motions were created: rolling, vibrating, gliding and dabbing, named based on the observed dynamics of the nanozyme superstructures. For each motion, nanozymes were first collected from the solution to the wall of the chamber by applying current to the electromagnet-1 for 1.2 s (50 mT, at the center of the chamber). To generate the rolling motion, a side-to-side motion was activated by moving the iron core (on the same side of the electromagnet-1) with the servo motor while maintaining the current at a constant value. The vibrating motion was activated by applying an oscillating field to the electromagnet-2 after the nanozyme collection step. The static field (50 mT, at the center of the container) from the electromagnet-1 was switched off while an oscillating sine wave (varying from 0 to 16 Hz) was generated by electromagnet-2 to produce the vibrating motion. The strength of the magnetic fields was measured to be 12 to 20 mT, at the center of the container. For the gliding motion, the electromagnet-2 was energized by a constant current to reshape the magnetic field such that the nanozyme superstructure was forced to extend along the central axis of the electromagnets. The strength of the magnetic field was measured to be 50 mT at the center of the container. This extended structure was translated from side-to-side with a servo motor. The velocity of the side-to-side motion varied by controlling the angular velocity of the servo motor. To create the dabbing motion, two servo motors were used to reposition the iron core to the targeted position while maintaining a static current. This positioning step was followed by applying a constant bias field with a superimposed sinusoidal field (15 Hz) to the electromagnet-2. This enables the smooth extension of the superstructure. The strength of the magnetic fields was measured to be 10 to 18 mT, at the center of the container. Once the nanozymes were delivered to the targeted tissue or substrate, the electromagnet-2 was de-energized such that the superstructure was fully retracted.
Catalytic Properties of Nanozyme Microrobots: To measure the catalytic properties of nanozyme microrobots, 952.2 μL of sodium acetate (NaAc) buffer (pH 4.5) was added into the actuation chamber followed by 4 μL of TMB (25 mg mL−1 in dimethylformamide) to reach a final concentration of 0.1 mg mL−1. Then, 40 μL of dispersed IONP was added into the chamber at a final concentration of 1 mg mL−1. Immediately before starting the motions (i.e., rolling, vibrating, or gliding), 3.4 μL of H2O2 (30%, v/v) was added to the mixture (final concentration: 0.1%). At 30, 60, 90 and 120 seconds, the mixture was transferred to a cuvette, and the absorbance at 652 nm was measured using a spectrophotometer (Beckman Coulter, Inc., Fullerton, CA, USA).
C. albicans Biofilm on Model Surfaces and Non-Surface Attached Fungal Aggregates: Individual 3D-printed acrylic sheets were created as model surfaces with dimensions of 18.0×18.0×0.4 mm3. 3D printing was done using a low-force stereolithography (SLA) 3D printer (Form 3B, Formlabs Inc., MA, USA) with a biocompatible Surgical Guide resin. 3D printed parts were rinsed for 20 min in 99.9% isopropanol and then photopolymerized for 30 min under ultraviolet light (405 nm light at 70° C.) (FormCure, Formlabs Inc., MA, USA). The 3D-printed surfaces were sterilized in an autoclave for 15 min at 121° C., and then coated with filter-sterilized, clarified whole human saliva, which was designed to mimic the denture (abiotic) surface in the oral cavity. C. albicans SN250, a biofilm-forming model fungal pathogen, was grown in ultrafiltered (10-kDa cutoff; Millipore, MA, USA) tryptone-yeast extract (UFTYE, pH 5.5) broth containing 1% (w/v) glucose at 37° C. and 5% CO2 to mid-exponential phase. The saliva-coated 3D-printed surfaces were inoculated with ˜105 CFU of actively growing C. albicans cells (yeast form) per milliliter in UFTYE (pH 7.0) containing 1% (w/v) sucrose. Biofilms were grown at 37° C. with 5% CO2 for 12 h. Non-surface attached aggregates of C. albicans were prepared following established protocols. Briefly, planktonic C. albicans cells (105 CFU mL−1, yeast form) were resuspended in filter-sterilized, clarified whole human saliva supplemented with 1% (w/v) sucrose and were incubated at 37° C. for 60 min to form fungal aggregates. C. albicans was stained with concanavalin A (ConA) lectin conjugated with tetramethylrhodamine (555/580 nm; Molecular Probes Inc., Eugene, OR, USA).
Culture of Human Gingival Cells Spheroids and Explant Mucosal Tissue: Human gingival tissue-derived mesenchymal stem cells (GMSCs) were isolated from deidentified gingival tissues obtained during third molar (wisdom tooth) extraction at the University of Pennsylvania under the approved Institutional Review Board (IRB) protocol (IRB #816238). GMSCs were expanded up to passage five in Minimum Essential Medium Alpha (MEM a) media (containing 15% FBS, 2 mM L-glutamine, 100 μM ascorbic acid, 100 U mL−1 penicillin, and 100 μg mL−1 streptomycin). Cells were seeded at a density of 106 mL−1 in ultra-low attachment tubes and grown for 3 days in a humidified tissue culture incubator (37° C., 5% CO2) to form a 3D spheroid. To model a localized C. albicans infection on the oral mucosal tissue, a primary whole-organ explant culture of murine oral mucosa was used. Briefly, mucosal tissue (4 mm×2 mm) was harvested from the palate of C57BL/6 mice and cultivated in MEM a media (15% FBS, 2 mM L-glutamine, 100 μM ascorbic acid, 100 U mL−1 penicillin, and 100 tg mL−1 streptomycin) at 37° C. with 5% CO2 for 24 h. The explant cultures were then used to create focal C. albicans infection, as detailed in the section “Focal Candida Infection on Explant Mucosal Tissue Culture.” Precise Fungal Capturing by Nanozyme Microrobots: To test the precise fungal capturing by nanozyme microrobots, a custom-built dual chamber device and an in vivo host-fungal (human gingival cells and C. albicans) model was developed (diagram in
Focal Candida Infection on Explant Mucosal Tissue Culture: A primary explant culture of murine oral mucosa was used to create a focal Candida infection that mimics localized infection of the oral cavity by C. albicans. The tissue preparation procedure was conducted under the University of Pennsylvania's Institutional Animal Care and Use Committee (IACUC) protocol (IACUC #806682). To establish a localized C. albicans infection on tissue specimens, hydroxyapatite beads (80-μm particle size, Bio-Rad Laboratories, USA) were used as micro-carriers for fungal cells, which allowed inoculating fungal cells onto the mucosal tissue with microscale precision. Briefly, saliva-coated hydroxyapatite beads (sHA) were pre-incubated with ˜106 CFU mL−1 C. albicans (yeast form) in adsorption buffer (50 mM KCl, 1.0 mM KPO4, 1.0 mM CaCl2, 0.1 mM MgCl2, pH 6.5) for 60 min to allow binding of fungal cells. The beads were washed three times with an adsorption buffer to remove unbound fungal cells. Then, the beads were carefully delivered to a predefined site on the mucosal tissue using a microinjection pipette tip under a microscope (Zeiss Axio Zoom V16). Approximately 20 beads were deposited on each tissue specimen. After the inoculation, tissues were incubated in fresh MSC medium at 37° C. with 5% CO2 for 12 h to establish a focal Candida infection.
Qualitative and quantitative imaging analysis: Brightfield and fluorescence images were taken with a Zeiss Axio Zoom.V16 upright stereo zoom microscope system (Carl Zeiss Microscopy GmbH, Jena, Germany) with 1× objective (numerical aperture, 0.25). For fluorescence imaging, Samples were stained with Concanavalin A-tetramethylrhodamine conjugate (Molecular Probes) to visualize C. albicans cells. Additionally, high-resolution confocal microscopy was performed using a Zeiss LSM 800 upright confocal microscope (Zeiss, Germany) equipped with a 40× water immersion objective (numerical aperture=1.2) and a 10× objective (numerical aperture=0.7). Computational image processing and quantitative analysis were conducted. Briefly, fluorescence images were imported using ImageJ Fiji software (https://imagej.net/software/fiji/). After denoising, images were segmented based on the fluorescent intensity using the Otsu algorithm, and particle size-based filtering was applied to only include C. albicans aggregates in the images. Regions of interest were created for each C. albicans aggregate, and the total surface area (in μm2) was calculated. The Removal Index (RI) was calculated to evaluate the effectiveness of C. albicans removal by nanozyme microrobots, which is defined as
Data were presented as not detectable when <2% of fungal cells were detected after the treatment.
Statistical Analysis: Statistical analyses were performed with GraphPad Prism 8.0 (GraphPad Software, CA). Data are represented as mean±standard deviation. Student's t-test was used to compare the mean between two experimental groups. Comparisons of mean between multiple groups were performed using a two-sided one-way analysis of variance (ANOVA) with post hoc Tukey's test. A P value less than 0.05 was considered significant. At least three independent experiments were performed unless otherwise stated.
While microrobots have been developed for specific tasks in the medical field, applications in oral and craniofacial health care remain sparse. The few systems that have been introduced are large-scale haptic robots (e.g., YOMI) to help increase predictability and precision during dental implant surgery. However, there are ample opportunities for implementing microrobots and automation to develop new therapeutic approaches. Potential applications include the automated removal of dental biofilms (plaque) on tooth surfaces, orthodontic appliances, and implants. Microrobotic platforms can also be developed to allow precision-guided therapies to promote soft tissue and bone regeneration. By leveraging the cargo-loading ability of microrobots, therapeutic applications can be tailored for drug, stem cell, or growth factor delivery in different oral-craniofacial sites, from deep periodontal pockets and the apical region of the canal to difficult-to-reach temporomandibular spaces to locally stimulate osteogenic or stem cell differentiation. Recent advances in nanotechnology and robotics have enabled the integration of magnetocatalytic nanoparticles with microrobotics principles to target and eradicate biofilms in clinically challenging settings. Here, the catalytic and magnetic properties of iron oxide nanoparticles (NPs) were exploited to introduce a microro-botics platform designed for biofilm treatment and diagnostics (
Targeting Endodontic Biofilms: Incomplete root canal disinfection remains the main cause of treatment failure, leading to persistent endodontic infections and apical periodontitis in conventional antimicrobial and regenerative procedures. The anatomical complexities in the root canal system hinder the effective removal of biofilms, while approaches to diagnose or assess disinfection efficacy are limited. New disinfection modalities such as photon-induced, photo-acoustic streaming; passive ultrasonic irrigation; antimicrobial nanoparticles; and photodynamic therapy have been proposed and/or used for endodontic biofilm treatment. However, these approaches lack controlled targeting of the anatomical complexities and are unable to retrieve biofilm samples for diagnostics. New technologies could enable multi-functionality to access difficult-to-reach surfaces and perform biofilm removal, and microbial detection simultaneously for effective and precise endodontic therapy. Such multi-modal approaches may be achieved using microrobotics.
Magnetically Driven Catalytic Antibiofilm Robots: IONPs have catalytic properties that arise from intrinsic enzyme-like (peroxidase-like) activity that activates H2O2 to generate bioactive molecules in situ to disrupt oral biofilms (
The flexibility of “NP building blocks” allows the formation of reconfigurable aggregated microswarms, inclusion in 3-dimensional (3D)-molded soft helicoids, or even direct 3D printing. Here, 2 platforms were developed. The first system uses magnetic forces to concentrate NPs and form structured aggregates (
Further development of microrobots can be precisely guided to reach the apical area and used to deliver bioactives or drugs in situ to achieve both chemical disinfection and tissue regeneration. The disclosed subject matter can be used for robotics applications to detect, treat, and remove biofilms associated with other infectious diseases and biofouling of dental/medical devices or implants. The disclosed subject matter can stimulate the utilization of the latest advances in small-scale robotics and nanotechnology that are providing previously unimagined opportunities for new diagnostic and therapeutic approaches with high precision, control, and efficiency.
All patents, patent applications, publications, product descriptions, and protocols, cited in this specification are hereby incorporated by reference in their entireties. In case of a conflict in terminology, the present disclosure controls.
While it will become apparent that the subject matter herein described is well calculated to achieve the benefits and advantages set forth above, the presently disclosed subject matter is not to be limited in scope by the specific embodiments described herein. It will be appreciated that the disclosed subject matter is susceptible to modification, variation, and change without departing from the spirit thereof. Those skilled in the art will recognize or be able to ascertain using no more than routine experimentation, many equivalents to the specific embodiments described herein. Such equivalents are intended to be encompassed by the following claims.
This application is a Continuation of International Patent Application No. Application No. PCT/US2023/021338, filed May 8, 2023, which This application claims priority to U.S. Provisional Patent Application No. 63/339,132, which was filed on May 6, 2022, the entire contents of which are incorporated by reference herein.
This invention was made with government support under DE025848 and DE029985 awarded by the National Institutes of Health. The government has certain rights in the invention.
| Number | Date | Country | |
|---|---|---|---|
| 63339132 | May 2022 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/US2023/021338 | May 2023 | WO |
| Child | 18935777 | US |
