Patent Application
20190381503
It can be useful to monitor drug levels in the blood of a patient. For example, medical conditions such as epilepsy can be managed through administration of drugs, which may only be safe or effective when they are present at predetermined levels in the blood of a patient. Drug level detection and testing can be time consuming and labor intensive.
At least one aspect of this disclosure is directed to a microfluidic device for detecting an analyte in a fluid sample. The microfluidic device can include a substrate defining a flow channel configured to transport the fluid sample from an inlet of the flow channel to an outlet of the flow channel. The microfluidic device can include an organic electrochemical transistor (OECT) including a source, a drain, a transistor channel, and a gate. At least one of the transistor channel or the gate of the OECT can overlap a portion of the flow channel to contact the fluid sample in the flow channel. The microfluidic device can include a coating applied to at least one of the transistor channel or the gate. The coating can include an aptamer or an antibody selected to bind with the analyte to change a conductivity of the transistor channel or a work function of the gate. The microfluidic device can include a sensor configured to receive an electrical output of the OECT and to detect a level of the analyte within the fluid sample based on the electrical output of the OECT.
In some implementations, the microfluidic device can include a first separation region positioned in the flow channel between the inlet and the OECT. The first separation region can be configured to remove cells from the fluid sample before the fluid sample flows to the OECT. In some implementations, the first separation region can include a separation outlet configured to receive a portion of the fluid sample containing the cells and to transport the portion of the fluid sample containing the cells away from the flow channel. In some implementations, the first separation region can further include an acoustic wave generator configured to impart a standing wave across the first separation region to direct the portion of the fluid sample containing the cells toward the separation outlet. In some implementations, the microfluidic device can further include a second separation region positioned in the flow channel between the first separation region and the OECT. The second separation region can be configured to remove bacteria from the fluid sample before the fluid sample flows to the OECT.
In some implementations, the transistor channel of the OECT can include a conductive polymer material. In some implementations, the transistor channel of the OECT can include poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS).
In some implementations, the gate of the OECT can further include a gate electrode including a gold surface positioned within the flow channel of the microfluidic device. In some implementations, a majority of a length of the flow channel can have a first width. A region of the flow channel surrounding the gate of the OECT can have a second width that is at least twice the first width. In some implementations, the transistor channel of the OECT can have a length between 200 microns and 350 microns and a width between 2 millimeters and 6 millimeters. In some implementations, the gate of the OECT can have a rectangular shape with a length between 1 millimeter and 10 millimeters and a width between 3 millimeters and 7 millimeters.
In some implementations, the substrate can include at least one of glass, polydimethylsiloxane (PDMS), and acrylic. In some implementations, the analyte can include a small molecule drug. In some implementations, the small molecule drug can be carbamazepine.
Another aspect of this disclosure is directed to a method of fabricating a device for detecting an analyte in a fluid sample. The method can include forming a first sacrificial layer on a surface of a substrate. The first sacrificial layer can be patterned for the deposition of a source electrode and a drain electrode of a transistor. The method can include depositing a layer of conductive material over the first sacrificial layer. The method can include patterning the layer of conductive material to define the source electrode and the drain electrode of the transistor. The method can include forming a second sacrificial layer over the substrate. The second sacrificial layer can be patterned for the deposition of a transistor channel. The method can include depositing a conductive polymer material over the second sacrificial layer. The method can include patterning the conductive polymer material to define the transistor channel. The method can include functionalizing a gate electrode of the transistor with a coating including an aptamer or an antibody selected to bind with the analyte to change a work function of the gate electrode. The method can include positioning the gate electrode within a microfluidic channel containing the fluid sample with the analyte.
In some implementations, the method can include introducing the fluid sample containing the analyte into an inlet of the microfluidic channel. In some implementations, the method can include receiving an electrical output of the transistor. In some implementations, the method can include detecting or calculating a level of the analyte within the fluid sample based on the electrical output of the transistor.
In some implementations, depositing the layer of conductive material over the first sacrificial layer can include depositing a layer of gold. In some implementations, depositing the conductive polymer material over the second sacrificial layer can include depositing a layer of PEDOT:PSS.
In some implementations, the method can include cleaning a surface of the gate electrode using at least one of oxygen plasma cleaning or electrochemical cleaning. In some implementations, the method can include applying the coating to the surface of the gate electrode after the surface of the gate electrode is cleaned. In some implementations, the method can include removing the first sacrificial layer and removing the second sacrificial layer.
The accompanying drawings are not intended to be drawn to scale. Like reference numbers and designations in the various drawings indicate like elements. For purposes of clarity, not every component may be labeled in every drawing. In the drawings:
The various concepts introduced above and discussed in greater detail below may be implemented in any of numerous ways, as the described concepts are not limited to any particular manner of implementation. Examples of specific implementations and applications are provided primarily for illustrative purposes.
The present disclosure describes systems capable of rapidly detecting a presence or a level of an analyte within a fluid sample. For example, the systems and methods of this disclosure can be capable of determining drug levels in fluid sample, while maintaining a low limit of detection. The systems can include organic electrochemical transistors (OECTs). The OECTs can include a channel material or gate electrode coated with a coating selected for detection of a given analyte. The coating can serve as a drug detection element. Thus, the analyte can be a drug, and the coating can be configured to bind with the drug of interest, such as an anti-epilepsy drug (AED). The coating can include an aptamer or an antibody. Binding of the analyte to the coating can induce a gate voltage change, which can result in a change in the source and drain current of the OECT. The magnitude in the current change can indicate the amount of analyte present in a test sample. The OECTs can be incorporated into microfluidic devices to provide rapid detection of such analytes, which may include small molecule drugs.
Referring now to
The channel material 222 can be coated with a functionalized coating configured to facilitate detection of a small molecule drug. For example, the functionalized coating on the channel material 222 can change the conductivity of the channel material 222 in the presence of the drug of interest. For detecting a biomarker such as small molecule drug, the functionalized coating can include an aptamer or an antibody that selectively binds to the drug of interest. For example, binding of the drug molecules to either an aptamer coating or an antibody coating of the channel material 222 can alter the charge density at the interface between transistor channel 222 and analyte, which can change the conductivity of the channel material 222. In some other implementations, the gate electrode 218 of the OECT 112 may be functionalized with either an aptamer or an antibody, instead of the channel material 222. The change in gate electrode potential due to binding to target analytes will induce a change in conductivity through the channel material 222 can be detected in real-time, via the electrical contact pads 250a and 250b coupled respectively to the drain electrode 214 and the source electrode 216, or the electrical contact pads 256a and 256b coupled to the gate 218. For example, a current meter or voltage meter can probe the current or voltage via these contact pads. The magnitude of the current change indicates the amount of the drug present in a test sample. For example, a relatively large change in the current through the OECT sensor 112 can indicate a relatively large amount of the drug in the test sample. The OECT sensor 112, via the organic electrochemical transistor, can locally amplify an input signal before output and detection by the current meter.
In some implementations, the channel material 222 can have dimensions of about 2.5 mm by about 5.5 mm. The channel material 222 can overlap with each of the drain electrode 214 and the source electrode 215 by a lateral distance of about 100 μm. In some implementations, the channel material 222 may be significantly smaller. For example, the channel material 222 may have a length between 200 microns and 350 microns and a width between 2 microns and 6 microns. In some implementations, the channel material 222 may have a surface area that is smaller than a surface area of the gate electrode 218. For example, the gate electrode may have a surface area of that is two times, three times, four times, five times, six times, seven times, eight times, nine times, or ten times larger than the surface area of the channel material 222. In some implementations, the gate electrode may have a surface area that is 15 times, 20 times, 30 times, 50 times, or 100 times larger than the surface area of the channel material 222. In some implementations, the gate electrode may have a surface area that is 200 times, 300 times, 400 times, 500 times, 600 times, 700 times, 800 times, 900 times, or 1000 times larger than the surface area of the channel material 222.
In some implementations, the gate electrode 218 can be circular. The gate electrode 218 can have a diameter of about 1 mm, about 2 mm, about 3 millimeters. In some implementations, the gate electrode 218 can have a diameter between 1 mm and about 3 millimeters. In some implementations, the gate electrode 218 can have its center positioned about 2.0 mm or about 2.25 mm from the bottom of the channel material 222. In some implementations, the gate electrode 218 can be rectangular. In some implementations, the gate electrode 218 can have a length between 1 millimeter and 10 millimeters and a width between 3 millimeters and 7 millimeters. For example, in some implementations the gate electrode 218 can have dimensions of about 10 millimeters by about 5 millimeters, about 6 millimeters by about 5 millimeters, about 4 millimeters by about 5 millimeters, about 2 millimeters by about 5 millimeters, or about 1 millimeter by about 5 millimeters.
The microfluidic channel 305 can include a region 320 that is substantially wider than a remainder of the microfluidic channel 305. In some implementations, the microfluidic channel 305 can have a width in the range of about 250 μm along a majority of its length. In some other implementations, the microfluidic channel 305 can have a width of about 500 μm along a majority of its length. In contrast, the region 320 may have a width equal to or larger than the width of the gate electrode 218, which may in the range of about 1 mm to about 2 mm.
As shown, the region 320 can be aligned with the gate electrode 218 of the OECT sensor 112. Thus, fluid flowing into the enlarged region 320 can have more surface area over which to contact the gate electrode 218, due to the larger width of the region 320 relative to the rest of the microfluidic channel 305. In this example, the gate electrode 218 can include a functionalized coating configured to interact with a target drug in the fluid sample. The increased surface area of the microfluidic channel 305 in the region 320 aligned with the gate electrode 218 can allow for increased interaction between the target drug within the fluid sample and the functionalized coating, thereby increasing the sensitivity of the system 300 to detection of the target drug.
Unlike the system 100 shown in
Referring again to
To remove particles from fluid flowing through the microfluidic flow channel, the system 100 can be coupled with one or more acoustic wave generators. For example, the system 100 can be coupled with a platform that positions an acoustic wave generator below each of the separation regions 106. The acoustic wave generators can each impart a respective standing wave across the separation regions 106. Particles (e.g., blood cells and bacteria cells) within the fluid sample can be driven towards the nodes or anti-nodes of the standing acoustic wave based the sign of the particles' contrast factor with respect to the fluid sample. For example, formed elements can have a positive contrast factor and can be driven, by the standing acoustic wave, towards the nodes of the standing acoustic wave. Particles with a negative contrast factor can be driven towards the antinode of the standing acoustic wave. The width of the microfluidic flow channel prior to the separation regions 106 and the placement of the acoustic wave generators can be configured such that the standing acoustic wave forms a node or antinode near the central, longitudinal axis of the microfluidic flow channel.
The first separation region 106a can drive the formed elements towards the central, longitudinal axis of the microfluidic flow channel (or other position of the standing acoustic wave's node) such that the formed elements exit the system 100 through a separation outlet in or at the end of the first separation region 106a. The first separation region 106a can drive the other components of the fluid sample, for example, bacteria, plasma, and virus toward the walls of the microfluidic flow channel such the components pass to the second separation region 106b. In some implementations, particles other than the formed elements (e.g., the bacteria, plasma, and virus) can also be driven towards the central, longitudinal axis (and outlet of the first separation region 106a), but at a rate slower than the formed elements. For these particles, the rate of movement towards the central, longitudinal axis may not be great enough to enable the particles to be sufficiently close to the central, longitudinal axis to exit through the first separation outlet and the particles can pass to the second separation region 106b.
The second separation region 106b can drive the remaining undesirable particles (e.g., bacteria) toward the central, longitudinal axis of the microfluidic flow channel such that the remaining particles exit the microfluidic flow channel through a second separation outlet. The remaining components of the fluid sample (e.g., the plasma, virus, and biomarkers) can flow to the OECT sensor, which may be defined within a well of the substrate 104.
The OECT sensor 112 includes the drain electrode 214, the source electrode 216, and the gate electrode 218. The drain electrode 214 and the source electrode 216 can be electrically coupled through the channel material 222. The drain electrode 214, the source electrode 216, the gate electrode 218, and the electrical traces 222 can include an electrically conductive metal such as gold, platinum, silver, or copper.
The channel material 222 can be a conductive polymer. The conductive polymer can include PEDOT:PSS. The channel material 222 can come into contact with both the drain electrode 214 and the source electrode 216 to form an electrochemical transistor. The channel material 222 can have a transconductance between about 2000 μs and about 5000 μs. The relatively high transconductance of the OECT sensor 112 can enable local amplification of an input signal before output and detection by a current or voltage meter.
In some implementations, the channel material 222 can be patterned to fill a void between the drain electrode 214 and the source electrode 216. For example, the drain electrode 214 and the source electrode 216 can first be patterned onto a substrate. Using a mask, the channel material 222 can be patterned into the space between the drain electrode 214 and the source electrode 216. The channel material 222 can be patterned to cover at least a portion of the drain electrode 214 and the source electrode 216. In contact with at least a portion of the drain electrode 214 and the source electrode 216, the channel material 222 can form an electrical connection between the drain electrode 214 and the source electrode 216.
The OECT sensor 112 can include a coating 400 that covers at least a portion of the gate electrode 218. The coating 400 can be a functionalized coating with a drug recognition element that interacts or bind to a drug to be detected in a fluid sample (i.e., the drug 402 shown in
The coating 400 can change the conductivity of the channel material 222 or can change the work function of the gate electrode 218 (depending on the placement of the coating 400) in the presence of the drug 402. The coating 400 can include aptamers or antibodies. The drug 402 can transfer electrons to the coating 400 (or vice versa), which can induce a change in the work function of the gate electrode 218 (or change the conductivity of the channel material 222, if the coating 400 is instead applied to the channel material 222). The change can be detected in real-time by a current meter, for example.
In some implementations, a device may be similar to the device 112 of
The transistor also can include a gate contact 520. In some implementations, the gate contact 520 can be formed on the same substrate as the channel 222, the drain electrode 214, and the source electrode 216. The gate contact 520 can also be electrically coupled with the gate electrode 218. In some implementations, separating the gate contact 520 from the gate electrode 218 can allow the gate electrode 218 to be formed in a separate process from the other components of the transistor. As a result, the gate electrode 218 can be more easily cleaned and functionalized with a coating that can include an aptamer or an antibody without impacting the other components of the transistor. In addition, the gate electrode 218 can be formed to be substantially larger than the gate contact 520. In some implementations, increasing the size of the gate electrode 518 relative to the size of the channel 222 can allow the OECT sensor 500 to have greater sensitivity to the analyte.
The fluid sample can be introduced into the reservoir 550 and can contact the extended gate electrode 560. As described above, an interaction between an analyte in the fluid sample and a functionalized coating on the gate electrode can alter a response of the transistor, which can be detected to determine a presence or concentration of the analyte in the fluid sample. A solderless electrical contact 545 can be inserted through a portion of the electrode fixture 530 to contact the extended gate electrode 560. Thus, electrical equipment can be coupled with the extended gate electrode 560 via the solderless contact pin 545 to eliminate the need to solder the extended gate electrode 560. This can allow for cleaning and functionalization of the extended gate electrode 560 to be performed as a more controlled process, and can help to reduce error in drain current response.
In some implementations, the extended gate electrode 560 can also allow the distance between the gate electrode and the contact pad (e.g., the distance between the extended gate electrode 560 and the solderless contact pin 545) to be increased, relative to the distance between the gate electrode 218 and the contact pad 520 formed on the substrate with the other components of the transistor. For example, in some implementations the distance between the gate electrode 218 and the contact pad 520 can be about 5 millimeters, while the distance between the extended gate electrode 560 and the solderless contact pin 545 can be about 20 millimeters.
The method 600 can include depositing a layer of conductive material over the first sacrificial layer 710 (BLOCK 610). The results of this stage are shown in
In some implementations, the conductive material 715 can include more than one layer of material. For example, a first layer of conductive material, such as chromium, may be deposited first. Then a second layer of another conductive material, such as gold, may be deposited over the first layer of conductive material. In some implementations, the first layer of conductive material may be deposited to a thickness of about 100 nm, while the second layer of conductive material may be deposited to a thickness of about 300 nm.
The method 600 can include patterning the layer of conductive material to define the source electrode and the drain electrode of the transistor (BLOCK 615). The results of this stage are shown in
The method 600 can include forming a second sacrificial layer over the substrate (BLOCK 620). The result of this stage is shown in
The method 600 can include depositing a conductive polymer material over the second sacrificial layer (BLOCK 625). The results of this stage are shown in
The method 600 can include patterning the conductive polymer material to define the transistor channel (BLOCK 630). The results of this stage are shown in
The method 600 can include functionalizing a gate electrode of the transistor with transistor coating (BLOCK 635). In some implementations, the gate electrode can be formed separately from the other components of the transistor, such as the source electrode 216, the drain electrode 214, and the channel 222. For example, the gate electrode may not be formed on the substrate 705. Instead, the gate electrode can be formed separately and later can be electrically coupled with other components of the transistor on the substrate 705. In some implementations, the gate electrode can be functionalized with a coating such as an aptamer or an antibody, which may selected to bind with the analyte (e.g., a target drug molecule) to change a work function of the gate electrode. In some implementations, the gate electrode can be an extended gate electrode such as the extended gate electrode 560 shown in
The method 600 can include positioning the gate electrode within a microfluidic channel containing the fluid sample with the analyte (BLOCK 640). In some implementations, the microfluidic channel may be formed on or defined by the substrate 705. In some other implementations, the microfluidic channel may be formed separately from the substrate 705. For example, the microfluidic channel can be formed from a PDMS, acrylic, or glass material, which may then be bonded or otherwise integrated with the substrate 705. When a fluid sample is introduced into the channel, an output of the transistor may be altered in a manner that corresponds to a presence or level (e.g., concentration) of the analyte of interest within the fluid sample.
In some implementations, the aptamers 805 can be RNA or DNA aptamers. For example, the aptamers 805 can be single stranded DNAs created as specific ligands for the drug of interest. The thiol-functionalized aptamers 805 can be mixed with 6-mercapto-hexanol (MCH) in a phosphate buffer. For example, the ratio aptamers to MCH can be about 1:100 in the buffer. The gold surface can then be immersed in or otherwise exposed to this solution. The gold surface can then be backfilled with a high concentration of MCH and washed and stored in a phosphate buffer.
Thus, the functionalized coating (i.e., the coating 400 shown in
As described above, drug detection can also be achieve through the use of a functionalized coating that includes an antibody selected to interact with the drug of interest.
The gold surface can then be functionalized with a mixture of active groups 905 (which may include alkyl thiols terminated with carboxylic acids), as well as inactive spacer groups 910 (which may include MCH), as shown in
Thus, the functionalized coating (i.e., the coating 400 shown in
While operations are depicted in the drawings in a particular order, such operations are not required to be performed in the particular order shown or in sequential order, and all illustrated operations are not required to be performed. Actions described herein can be performed in a different order.
The separation of various system components does not require separation in all implementations, and the described program components can be included in a single hardware or software product.
Having now described some illustrative implementations, it is apparent that the foregoing is illustrative and not limiting, having been presented by way of example. In particular, although many of the examples presented herein involve specific combinations of method acts or system elements, those acts and those elements may be combined in other ways to accomplish the same objectives. Acts, elements and features discussed in connection with one implementation are not intended to be excluded from a similar role in other implementations or implementations.
The phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including” “comprising” “having” “containing” “involving” “characterized by” “characterized in that” and variations thereof herein, is meant to encompass the items listed thereafter, equivalents thereof, and additional items, as well as alternate implementations consisting of the items listed thereafter exclusively. In one implementation, the systems and methods described herein consist of one, each combination of more than one, or all of the described elements, acts, or components.
As used herein, the term “about” and “substantially” will be understood by persons of ordinary skill in the art and will vary to some extent depending upon the context in which it is used. If there are uses of the term which are not clear to persons of ordinary skill in the art given the context in which it is used, “about” will mean up to plus or minus 10% of the particular term.
Any references to implementations or elements or acts of the systems and methods herein referred to in the singular may also embrace implementations including a plurality of these elements, and any references in plural to any implementation or element or act herein may also embrace implementations including only a single element. References in the singular or plural form are not intended to limit the presently disclosed systems or methods, their components, acts, or elements to single or plural configurations. References to any act or element being based on any information, act or element may include implementations where the act or element is based at least in part on any information, act, or element.
Any implementation disclosed herein may be combined with any other implementation or embodiment, and references to “an implementation,” “some implementations,” “one implementation” or the like are not necessarily mutually exclusive and are intended to indicate that a particular feature, structure, or characteristic described in connection with the implementation may be included in at least one implementation or embodiment. Such terms as used herein are not necessarily all referring to the same implementation. Any implementation may be combined with any other implementation, inclusively or exclusively, in any manner consistent with the aspects and implementations disclosed herein.
The indefinite articles “a” and “an,” as used herein in the specification and in the claims, unless clearly indicated to the contrary, should be understood to mean “at least one.”
References to “or” may be construed as inclusive so that any terms described using “or” may indicate any of a single, more than one, and all of the described terms. For example, a reference to “at least one of ‘A’ and ‘B’” can include only ‘A’, only ‘B’, as well as both ‘A’ and ‘B’. Such references used in conjunction with “comprising” or other open terminology can include additional items.
Where technical features in the drawings, detailed description or any claim are followed by reference signs, the reference signs have been included to increase the intelligibility of the drawings, detailed description, and claims. Accordingly, neither the reference signs nor their absence has any limiting effect on the scope of any claim elements.
The systems and methods described herein may be embodied in other specific forms without departing from the characteristics thereof. The foregoing implementations are illustrative rather than limiting of the described systems and methods. Scope of the systems and methods described herein is thus indicated by the appended claims, rather than the foregoing description, and changes that come within the meaning and range of equivalency of the claims are embraced therein.
This application claims priority to U.S. Provisional Patent Application No. 62/684,895, filed on Jun. 14, 2018 and entitled “INTEGRATED MICROFLUIDIC ORGANIC ELECTROCHEMICAL TRANSISTOR BIO SENSORS FOR DRUG LEVEL DETECTION,” which is hereby incorporated by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 62684895 | Jun 2018 | US |
