Patent Application
20240165296
The present invention relates to advanced wound care products. In particular, the present invention relates to dressings and associated methods for use of the dressings to treat wounds and burns, and to control bleeding.
Severe burn wounds are the most traumatic and physically debilitating injuries with local and systemic damages to the wound site. Early burn wound excision and autologous split-thickness skin grafts are the current gold standard in clinical practice that have significantly improved the outcomes for severely burned patients by reducing the mortality rate. However, the shortage in donor skin tissue, chronic graft rejection, impaired healing, infection, pain, and scarring are major challenges in burn wound treatment that have fostered the development of alternative approaches such as engineered tissues or synthetic skin substitutes. The majority of the wound healing products currently available do not fully recapitulate native skin, as they cannot replicate the layered structure of skin with regeneration of skin appendages. Due to the severe dehydration, electrolyte imbalance, and damage to the blood vessels, nerves, and underlying tissues, common treatments face many challenges in burn wound healing.
Biosynthetic wound dressings have exhibited positive clinical outcomes. However, these current commercial wound healing products cannot support the regeneration of skin appendages and scarless wound healing. Further, the healing processes associated with these wound healing products often results in a prolonged healing period that may be unacceptably long, as well as other healing conditions that may be less than ideal (e.g., exhibiting no autolytic debridement). Thus, there remains a need for new bioactive materials, wound dressings, and/or methods for preparing the bioactive materials and/or wound dressing products.
The present invention is directed to bioactive borate glass (BBG) wound dressings and processes for preparing the wound dressings. For example, the wound dressings of the present invention may be fabricated by 3D printing technology.
In one aspect, the present invention is directed to a wound dressing comprising a hydrogel matrix and up to 50 w/v % of a bioactive borate glass (BBG) comprising boron.
In another aspect, the present invention is directed to a process for preparing a bioactive borate glass (BBG) loaded hydrogel matrix. The process comprises providing a paste comprising hydrogels and BBG; additive manufacturing of the paste comprising hydrogels and BBG using extrusion-based 3D printing to form 3D printed constructs comprising the BBG and hydrogels; and crosslinking the 3D printed constructs to form a hydrogel matrix comprising up to about 50 w/v % BBG.
The invention is also directed to methods of treating wounds, burns, and/or controlling bleeding in a subject in need thereof. The method comprises applying the wound dressing to a wound, a burn, or a site of bleeding of the subject.
Other objects and features will be in part apparent and in part pointed out hereinafter.
Corresponding reference characters indicate corresponding parts throughout the drawings.
Hydrogels are an essential class of polymers for dermal/epidermal regeneration due to their ability to donate or absorb water depending the wound condition. Wound care products often comprise biodegradable hydrogels to encourage wound healing within a moist environment. A wide variety of hydrogels exist, ranging from single-component hydrogels to complex and functionalized compositions reinforced with nanoparticles and growth factors.
In addition to the use of hydrogels, wound care products have progressed over time to include, for example, advanced skin substitutes containing cells and growth factors. Bioactive glasses are materials that have been shown to have considerable potential in biomedical applications. Bioactive glasses are amorphous solid structures that can be used as a substitute for hard tissue. Bioactive glasses are promising materials for soft tissue regeneration and wound healing applications. Silicate glass has been used in hard and soft tissue engineering. Non-silicate glass compositions for tissue regeneration have also been investigated. For example, biologically active elements such as B, Ag, Ca, Mg, Sr, Cu, and Zn can be incorporated into the glass networks. It is believed that bioactive glasses and corresponding dissolution products have a high potency for inducing anti-inflammatory response, angiogenesis, and antimicrobial activity.
Bioactive borate glass (BBG) is a type of bioactive glass comprising borate (B2O3) as the glass network matrix. Despite generally positive clinical results from utilizing BBG, in the form of a powder or fiber, on wet wounds (e.g., highly discharging wounds such as pressure ulcers), BBG by itself has been found to be unable to effectively treat dehydrated wounds (e.g. burn wounds and necrotic wounds).
Applicant has discovered that the 3D printed BBG-hydrogel mixture of the present invention increases the moisturizing activity of BBG and makes the mixture/matrix suitable for treating burn wounds. A printed BBG-hydrogel mixture has a porous dermal-like structure that is maintained in vivo with controlled vascularization and enhanced wound healing. Applying a 3D printed BBG-hydrogel mixture as a non-stick wound dressing also makes it easier to change the dressing with no pain or secondary trauma to the wound or surrounding tissue.
Recently, bioprinting (e.g., 3D printing) with bioinks consisting of different hydrogels and biocompatible polymers as well as living cells has been investigated to develop various tissue engineering constructs for hard and soft tissue regeneration. Skin bioprinting has also been investigated for artificial skins, synthetic grafts, and wound dressings using hydrogels. The use of 3D bioprinting allows for reproducible fabrication with bioinks, control over the printed structure, and an increased contact surface by adjusting the geometry.
In one embodiment, the present invention is directed to a wound dressing comprising a hydrogel matrix and up to 50 w/v % of a bioactive borate glass (BBG) comprising boron. For example, a wound dressing comprising a hydrogel matrix and 45 w/v % or less, 40 w/v % or less, 35 w/v % or less, 30 w/v % or less, 25 w/v % or less, 20 w/v % or less, 15 w/v % or less, 10 w/v % or less, or 5 w/v % or less of a bioactive borate glass (BBG) comprising boron.
One aspect of the present invention is directed to a method of 3D printing that incorporates BBG into a hydrogel matrix. The method comprises: providing a mixture of BBG-hydrogel paste in a controlled condition, additive manufacturing of the BBG-hydrogel paste using extrusion-based 3D printing, and chemical or physical crosslinking the 3D printed constructs. The 3D printed construction may be further sterilized as required.
In another embodiment, the present invention is directed to a process for preparing a bioactive borate glass (BBG) loaded hydrogel matrix. The process comprises providing a paste comprising hydrogels and BBG; additive manufacturing of the paste comprising hydrogels and BBG using extrusion-based 3D printing to form 3D printed constructs comprising the BBG and hydrogels; and crosslinking the 3D printed constructs to form a hydrogel matrix comprising up to about 50 w/v % a BBG. For example, 45 w/v % or less, 40 w/v % or less, 35 w/v % or less, 30 w/v % or less, 25 w/v % or less, 20 w/v % or less, 15 w/v % or less, 10 w/v % or less, or 5 w/v % or less of a BBG.
In another aspect, the present invention provides a method for applying the 3D printed dressings on different wound types including partial-thickness burn wounds, chronic wounds, etc. For example, the dressing may be applied to a wound, a burn, or a site of bleeding. In certain embodiments, the dressing is capable of autolytic debridement when applied to a wound, a burn, or a site of bleeding. In other embodiments, the dressing is capable of reducing or inhibiting scar tissue formation when applied to a wound, a burn, or a site of bleeding. In certain embodiment, the dressing is capable of inhibiting scar tissue formation when applied to a wound, a burn, or a site of bleeding.
In some embodiments, the wound dressing is capable of commercially acceptable moisture retention for up to 7 days after application to the wound, burn, or site of bleeding. For example, the wound dressing may be capable of commercially acceptable moisture retention for a period of at least about 7 days, at least about 8 days, at least about 9 days, at least about 10 days, at least about 11 days, at least about 12 days, at least about 13 days, at least about 14 days, or at least about 21 days.
In other embodiments, the wound dressing exhibits antibacterial activity for up to 7 days after application to the wound, burn, or site of bleeding. For example, the wound dressing exhibits antibacterial activity for a period of at least about 7 days, at least about 8 days, at least about 9 days, at least about 10 days, at least about 11 days, at least about 12 days, at least about 13 days, at least about 14 days, or at least about 21 days.
In a further aspect of the present invention, a method is provided for using the 3D printed BBG-containing dressing in combination with living cells for therapeutic tissue regeneration, development of tissue models for testing purposes, etc. The living cells are capable of migration, proliferation to the top and/or bottom, and survival within the dressing.
In certain embodiments, the present invention is directed to methods for preparing dressings for burn wounds and other dry wounds comprising BBG mixed with hydrogels. Still further, the dressing may be prepared using a 3D bioprinting technology. Without being bound by the theory, it is believed that the hydrogel acts as a water reservoir and a carrier for the BBG, which aids the printing process when utilizing a 3D bioprinting technology.
3D printed wound dressings of the present invention may comprise a matrix of hydrogels such as alginate, gelatin, GelMa, cellulose, chitosan and other like materials as well as their mixtures, combined with up to 50 w/v % BBG powder consisting of micrometer and/or nanometer sized particles. The mixture results in a BBG powder that is extrudable for 3D printing and a hydrogel that provides moisturizing activity. The ratio of BBG and hydrogel can be adjusted for printability and other functionalities such as degradability, hydration ability, cell viability, etc. The printed BBG-hydrogel mixture has a porous dermal-like structure that can be maintained in vivo for up to 7 days with controlled vascularization and enhanced wound healing.
3D printing technology enables the layer-by-layer deposition of BBG-hydrogel bioink, with numerous positive effects including: (i) allowing the dressings to be fabricated at any desired shapes and dimensions, conforming to the wound geometry if needed, (ii) including pores of any desired pore geometry to increase the available surface area for wound interaction, thus improving hydration and delivering the active ingredients in the BBG more effectively to the wound site for tissue regeneration, and (iii) enabling dressings to be made with multiple materials that vary between and within layers to improve the dressing's functions and performance.
In certain embodiments, a bioink may be formed from a paste made by combining BBG and a hydrogel matrix. The bioink may be used to print a component of a wound dressing. For example, in one embodiment, the bioink is printed by a process comprising additive manufacturing using extrusion-based 3D printing to form 3D printed constructs. The 3D printed constructs may then be crosslinked to form a hydrogel matrix. The hydrogel matrix may be used as a component of the wound dressing. It is believed, without being bound by the theory, that the bioink increases the hydration activity of BBG allowing the resulting dressing to provide a moist environment conducive for burn wound healing. Further, the BBG acts to support increased new tissue formation.
In still a further embodiment, the present invention is directed to a wound dressing as described or prepared above, wherein the BBG-hydrogel mixture of the wound dressing acts as a non-stick wound dressing to ensure that the dressing exchanges painlessly and without secondary trauma to the wound or surrounding tissue.
In a certain embodiment, the BBG of the present invention comprises boron. For example, the BBG of the present invention may comprise at least about 30 wt. %, at least about 35 wt. %, at least about 40 wt. %, at least about 45 wt. %, at least about 50 wt. %, at least about 55 wt. %, at least about 60 wt. %, at least about 65 wt. %, at least about 70 wt. %, at least about 75 wt. %, at least about 80 wt. %, or at least about 85 wt. % of boron. In further embodiments, at least a portion of the boron may be doped. For example, at least a portion of the boron may be doped with an element selected from the group consisting of Ca, Na, P, Cu, Zn, Ag, and combinations thereof. Without being bound by the theory, it is believed that embodiments wherein a portion of the boron is doped with another element result in improved biological performance by stimulating angiogenesis, antimicrobial properties, or other beneficial effects.
The hydrogel or hydrogel matrix of the present invention may comprise at least one component selected from the group consisting of alginate, gelatin, GelMa, cellulose, chitosan and combinations thereof. In further embodiments, the hydrogel or hydrogel matrix of the present invention may comprise one or more of living cells selected from the group consisting of epidermal keratinocytes, dermal fibroblasts, and mesenchymal stem cells. The living cells are capable of migration, proliferation to the top and/or bottom, and survival within the hydrogel, hydrogel matrix, or resulting 3D printed constructs or wound dressings.
In certain embodiments, the 3D printed constructs comprising the BBG and hydrogels are sterilized. In other embodiments, the bioactive borate glass (BBG) loaded hydrogel matrix is sterilized. In still further embodiments, the wound dressing is sterilized.
One particular aspect of the present invention is directed to a novel burn wound dressing product, comprising: a bioink in the form of paste made by adding up to 50 wt./v % bioactive borate glass (BBG) to a hydrogel matrix selected from the group consisting of alginate, gelatin, GelMa, cellulose, chitosan and combinations thereof. The viscosity of the BBG-hydrogel mixture may be adjusted by controlling the temperature, mixing speed, aging time, BBG/hydrogel ratio, and hydrogel compositions. To fabricate the wound dressing product, the BBG-hydrogel paste (i.e. a bioink) is placed in a syringe barrel for extrusion-based 3D printing. The hydrogel matrix is thought to be covalently cross-linked by the ions released from the BBG after mixing with the BBG. The hydrogel matrix may further comprise one or more types of living cells, for example, epidermal keratinocytes, dermal fibroblasts, or mesenchymal stem cells. The bioink and/or resulting wound dressing product is effective for the healing of burn wounds by providing a controlled ion release from the BBG, with the hydrogel serving as a continuous water source.
In addition to 3D printing technology, the novel BBG-hydrogel composite materials, bioinks, and BBG loaded hydrogel matrices can also be used to produce wound dressings using conventional manufacturing methods, such as molding and stamping.
Technical details regarding 3D printing of BBG-hydrogel bioinks to fabricate wound dressings, their mechanical and physical properties, and the results of in vitro and in vivo tests, are described below. All experiments were performed with at least 3 replications in order for the results to be statistically meaningful. Comparisons for statistically significant differences among the groups were performed using one-way ANOVA with significance set at p-value <0.05.
Various BBG-hydrogel compositions (i.e. bioinks) were prepared by mixing natural hydrogels such as gelatin, alginate, GelMa, cellulose, and chitosan with varying amounts of BBG, up to 50 w/v %, under controlled conditions including temperature, mixing speed, and aging time (the incubation time that BBG-hydrogel compositions were subjected to after mixing).
Each BBG-hydrogel composition (i.e. bioink) was loaded into a sterile syringe mounted on the print head of an extrusion-based 3D printer. The printing parameters, including nozzle diameter, extrusion pressure, paste temperature, and printing speed, were modified based on the viscosity of each hydrogel and the desired shape fidelity of the final printed construct.
To control the extrusion-based 3D printing process, the rheological behavior of a hydrogel with and without BBG was measured.
In accordance with the ASTM F2150-8 standard, the tensile strength and Young's modulus of the 3D printed BBG-hydrogel and hydrogel constructs were measured using an Instron 5969 Universal Testing System. The measurements were conducted on samples having dimensions of 40×10×2 mm 3, with the measurements taken in triplicate.
To understand and predict the further interactions between the wound and the dressing, the change in the weight of the 3D printed constructs made of BBG-hydrogel and hydrogel were recorded after soaking the constructs in a phosphate buffered saline (PBS) solution. The 3D printed samples were immersed in PBS at 32° C. and weighed every 24 hours. According to the data shown in
To evaluate the moisturizing activity of the 3D printed constructs, the total water content was measured using thermal analysis. Samples of BBG-hydrogel and hydrogel constructs were weighed and then placed in an oven at 250° C. for 10 minutes. The weight change was recorded based on the total water content within the sample. To understand and predict the hydration activity of the samples to burn wounds, two different absorbent foams composed of ethyl cellulose and polyurethane were used to represent superdehydrated and dry wounds, respectively. The 3D printed constructs were placed on the wound foam surfaces at 32° C., and hydration activity was measured by recording the weight change after 24 h at 32° C.
The total water content and donated water (hydration activity) were measured using the following equations:
where W0 is the initial weight, WH is the weight after heating at 250° C., and W24 is the weight after placing on dry surfaces for 24 hours.
According to the results, presented in
An MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay was used to test and compare the viability and proliferation of skin cells in direct and indirect contact with a 3D printed hydrogel and BBG-hydrogel. Human primary dermal fibroblasts (HDF) were cultured in minimum essential media (MEM) fortified with 10% fetal bovine serum (FBS) and 1% pen/strep antibiotic at 37° C., in accordance with the ISO-10993 standard. 3D printed constructs were immersed in MEM for 1, 3, and 7 days. Indirect cell viability was assessed using an MTT assay and a colorimetric assay was used to assess the cell metabolic activity. Live cells react with MTT to form formazan, which can be measured by an ELISA reader as optical density. The chart set forth in
The ability of the 3D printed skin substitutes for wound healing was evaluated by creating a circular full-thickness wound using a hot metal bar on the lumbar area of 36 Sprague Dawley rats in 6 groups, each group comprising 6 rats. The tested groups were as follows:
After shaving the back area of each rat, the skin was cleaned with iodine and then sterilized with alcohol swaps. The animals were anesthetized using inhaled isoflurane via a nose cone. The full-thickness defect was made by placing a 100° C. metal bar on the lumbar area of the rat for 10 seconds. After implementation, the wounds were disinfected by Dermoplast antiseptic spray. After applying the treatment, wounds were covered with petrolatum gauze, 3M bandage, and Elastikon tape. All animals were monitored daily for post-operative recovery, and the wounds were inspected under isoflurane anesthesia every week to record the wound size, re-epithelialization, and necrotic tissue formation. The necrotic tissue removal (i.e. debridement) was performed using sharp surgical tools. After 4 weeks of treatment, the experiment was terminated, and the animals were euthanized with a lethal dose of CO2. Wound tissues were incised and fixed in formalin solution for 24 hours for further analysis.
Each week after the old dressing removal and prior to rebandaging, wounds were photographed to record the wound size, color, necrotic tissue formation, and traumatic removal. The wound size was quantified by tracing the wound border in each photograph using ImageJ software. The scale was set to a sterile disposable ruler in the wound picture, and wound closure was calculated as follows:
where A0 is the wound area immediately after wound implementation, and At is the wound area at time t (i.e., 1, 2, 3, and 4 weeks). Traumatic removal was evaluated by assessing the presence of traumatic laceration, bleeding, and redness in wound margins and surrounding tissues after the dressing removal.
None of the tested treatment methods resulted in an infection. According to
Overall, the in vivo results appeared to indicate that the positive effect of 3D printed dressings on burn wound healing comes from the increased degradation, hydration, and surface contact, and the combination of BBG and hydrogel exhibits improved results, with BBG providing vital biological effects and the hydrogel serving as a water reservoir for burn wound healing.
When introducing elements of the present invention or the preferred embodiments(s) thereof, the articles “a”, “an”, “the” and “said” are intended to mean that there are one or more of the elements. The terms “comprising”, “including” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements.
In view of the above, it will be seen that the several objects of the invention are achieved and other advantageous results attained.
As various changes could be made in the above compositions, methods and processes without departing from the scope of the invention, it is intended that all matter contained in the above description and shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US2022/020382 | 3/15/2022 | WO |
| Number | Date | Country | |
|---|---|---|---|
| 63161389 | Mar 2021 | US |
