Antimicrobial electrospun nanofibers of cellulose acetate and polyester urethane composite for wound dressing

Electrospinning of natural polymers for the production of nanofibres for wound healing applications

Wound healing is a highly regulated process composed of four overlapping phases: (1) coagulation/haemostasis, (2) inflammation, (3) proliferation and (4) remodelling. Comorbidities such as advanced age, diabetes and obesity can impair natural tissue repair, rendering the wound in a pathological state of inflammation. This results in significant discomfort for patients and considerable financial costs for healthcare systems. Due to the complex nature of wound healing, current treatments are ineffective at dealing with delayed healing. With flexible properties that can be tailored, nanomaterials have emerged as alternative therapeutics for many biomedical applications. A nanofibrous network can be made via electrospinning polymers using a high electric field to create a responsive meshwork that can be used as a medical dressing. A nanofibrous device has properties that can overcome the limitations of traditional dressings, such as: (1) adaptability to wound contour; (2) controlled drug delivery of therapeutics; (3) gaseous exchange; (4) exudate absorption and (5) surface functionalisation to further enhance the biological activity of the dressing. This review details emerging trends in nanotechnology to specifically target wound healing applications. Particular focus is given to the most common natural polymers that could address many unmet healthcare needs.

The biomedical potential of cellulose acetate/polyurethane nanofibrous mats containing reduced graphene oxide/silver nanocomposites and curcumin: Antimicrobial performance and cutaneous wound healing

In this study, nanofibrous scaffolds were prepared from polyurethane and cellulose acetate using electrospinning. Reduced graphene oxide/silver nanocomposites, rGO/Ag, were also used into the mats due to the strong antibacterial activity of rGO/Ag nanocomposites. In order to prevent the agglomeration of silver nanoparticles, AgNPs, the nanoparticles were decorated onto the reduced graphene oxide (rGO) sheets. Initially, Graphene oxide, briefly GO, was synthesized by the improved Hummer method. Then, nanocomposites of reduced graphene oxide were decorated with Ag and were fabricated via a green and facile hydrothermal method. Thereafter, the scaffold containing rGO/Ag nanocomposites, curcumin or both of them were prepared using the electrospinning method. The obtained scaffolds were characterized by scanning electron microscopy (SEM), contact angle, tensile analysis, porosity, and water vapor transmission rate (WVTR). 3-[4,5-Dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide assay, MTT, confirmed the biocompatibility of the composite nanofibers. The scaffolds were able to hinder both of the Gram-negative and Gram-positive bacteria through direct contact with them. In vivo histopathological studies indicated that the scaffold incorporated rGO/Ag nanocomposites and curcumin has the most effect on wound healing and can promote the healing rate of artificial wounds, which indicates the good biomedical potential of nanomaterial in wound healing.

Incorporation of ROS-Responsive Substance P-Loaded Zeolite Imidazolate Framework-8 Nanoparticles into a Ca2+-Cross-Linked Alginate/Pectin Hydrogel for Wound Dressing Applications

PURPOSE

Wound healing, especially of extensive full-thickness wounds, is one of the most difficult problems in clinical studies. In this study, we prepared a novel substance P (SP)-delivery system using zeolite imidazolate framework-8 (ZIF-8) nanoparticles.

METHODS

We synthesized ZIF-8 nanoparticles using a modified biomimetic mineralization method. We then coated SP-loaded ZIF-8 nanoparticles (SP@ZIF-8) with polyethylene glycol-thioketal (PEG-TK) to fabricate SP@ZIF-8-PEG-TK nanoparticles, and encapsulated them in injectable hydrogel composed of sodium alginate and pectin and cross-linked using calcium chloride. The final hydrogel wound dressing containing SP@ZIF-8-PEG-TK nanoparticles was called SP@ZIF-8-PEG-TK@CA.

RESULTS

The fabricated ZIF-8 nanoparticles had high SP-loading efficiency. SP-release assay showed that the SP@ZIF-8-PEG-TK nanoparticles maintained drug activity and showed responsive release under stimulation by reactive oxygen species. The SP@ZIF-8-PEG-TK nanoparticles promoted proliferation of human dermal fibroblasts, up-regulated expression levels of inflammation-related genes in macrophages, and exhibited favorable cytocompatibility in vitro. Full-thickness excision wound models in vivo confirmed that SP@ZIF-8-PEG-TK@CA dressings had excellent wound-healing efficacy by promoting an early inflammatory response and subsequent M2 macrophage polarization in the wound-healing process.

CONCLUSION

In conclusion, these findings indicated that SP@ZIF-8-PEG-TK@CA dressings might be useful for wound dressing applications in the clinic.

Electrophoretic deposition of chitosan/nano silver embedded micro sphere on centrifugal spun fibrous matrices - A facile biofilm resistant biocompatible material

Micro fibrous polycaprolactone (PCL) mat generally used for biomedical application was produced by facile centrifugal spinning system (C-Spin). The produced mat exhibited good structural integrity and good flexibility. The developed mat was used as substrate for electrophoretic deposition (EPD) of chitosan and polyethylene glycol (PEG) along with silver nano particles (AgNPs). During the EPD process, polymeric micro spheres embedded with silver nano particles were formed and deposited on the C-Spun substrates and the size of AgNPs were found to be around 15 nm. Surface topography of all coated samples were analyzed and found that the deposition was neat and uniform. Swelling behavior of the coated substrates were studied and found that CS/HMP/AgNPs coated substrates showed 274% swelling compared to their own dry weight. Release profile of silver nanoparticles confirmed that initial burst release followed by sustained release for CS/HMP/AgNPs coated substrates and this might be attributed to the hydrophilicity and high swellability of HMP. All AgNPs coated samples were completely prevent the bacterial biofilm formation and CS/HMP/AgNPs showed better reduction in bacterial growth on matured biofilm model. Cell proliferation studies confirmed that CS/HMP/AgNPs is biocompatible and can be used as a wound dressing material.

Current status and future outlook of nano-based systems for burn wound management

Wound healing process is a natural and intricate response of the body to its injuries and includes a well-orchestrated sequence of biochemical and cellular phenomena to restore the integrity of skin and injured tissues. Complex nature and associated complications of burn wounds lead to an incomplete and prolonged recovery of these types of wounds. Among different materials and systems which have been used in treating the wounds, nanotechnology driven therapeutic systems showed a great opportunity to improvement and enhancement of the healing process of different type of wounds. The aim of this study is to provide an overview of the recent studies about the various nanotechnology-based management of burn wounds and the future outlook of these systems in this area. Laboratory and animal models for assessing the efficacy of these systems in burn wound management also discussed.

Highly transparent, highly flexible composite membrane with multiple antimicrobial effects used for promoting wound healing

In recent years, bacterial cellulose (BC)-based dressings or patches for skin or soft tissue repair have become investigative emphasis. However, most of the BC-based products used for biomedical applications present limitations due to their low flexibility, poor gas permeability and no inherent antibacterial activity. Herein, we proposed and designed a novel composite composed of natural bacterial cellulose (BC), polyethylene glycol (PEG) and polyhexamethylene biguanidine (PHMB) through new synthetic approaches. The composite membrane exhibited favorable physicochemical performance, especially transparency, water retention ability, flexibility as well as the characteristic of anti-adhesion. In vitro biochemical experiment results indicated that the composite had excellent biocompatibility and exhibited strong and sustained antibacterial effect. In vivo test further demonstrated that the composite could efficiently promote skin wound healing and regeneration in a rat model. This composite membrane possesses multiple mechanisms of promoting cutaneous wound healing and will provide new ideas for future development of wound dressings.

Novel Cellulose-Halloysite Hemostatic Nanocomposite Fibers with a Dramatic Reduction in Human Plasma Coagulation Time

High-performance cellulose-halloysite hemostatic nanocomposite fibers (CHNFs) are fabricated using a one-step wet-wet electrospinning process and evaluated for human plasma coagulation by activated partial thromboplastin time. These novel biocompatible CHNFs exhibit 2.4 times faster plasma coagulation time compared with the industry gold standard QuikClot Combat Gauze (QCG). The CHNFs have superior antileaching property of clay with 3 times higher post-wetting clotting activity compared to QCG. The CHNFs also coagulate whole blood 1.3 times faster than the QCG and retain twice the clotting performance after washing. Halloysite clay is also more effective in plasma coagulation than commercial kaolin clay. The physical and thermal properties of the CHNFs were evaluated using scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, Brunauer-Emmett-Teller surface area analysis, and thermogravimetric analysis. CHNFs show a 7-fold greater clay loading than QCG and their small average diameter of 450 ± 260 nm affords a greater specific surface area (33.6 m² g^-1) compared with the larger average diameter of 12.6 ± 0.9 μm for QCG with a specific surface area of 1.6 m² g^-1. The CHNFs were shown to be noncytotoxic and human primary fibroblasts proliferated on the composite material. The drastic reduction in coagulation time makes this novel nanocomposite a potential lifesaving material for victims of rapid blood loss such as military personnel and patients undergoing major surgical procedures or to aid in the treatment of unexpected bleeding episodes of patients suffering from hereditary blood clotting disorders. Since a person can die within minutes of heavy bleeding, every second counts for stopping traumatic hemorrhaging.

Cellulose Biomaterials for Tissue Engineering

In this review, we highlight the importance of nanostructure of cellulose-based biomaterials to allow cellular adhesion, the contribution of nanostructure to macroscale mechanical properties, and several key applications of these materials for fundamental scientific research and biomedical engineering. Different features on the nanoscale can have macroscale impacts on tissue function. Cellulose is a diverse material with tunable properties and is a promising platform for biomaterial development and tissue engineering. Cellulose-based biomaterials offer some important advantages over conventional synthetic materials. Here we provide an up-to-date summary of the status of the field of cellulose-based biomaterials in the context of bottom-up approaches for tissue engineering. We anticipate that cellulose-based material research will continue to expand because of the diversity and versatility of biochemical and biophysical characteristics highlighted in this review.

Remodeling of inherent antimicrobial nanofiber dressings with melamine-modified fibroin into neoskin

A melamine-modified fibroin was synthesized and fabricated into electrospun nanofiber films with broad-spectrum antimicrobial activity, sustained water retention, and fast reepithelialization and revascularization.

Nanocellulose-Based Antibacterial Materials

In recent years, nanocellulose-based antimicrobial materials have attracted a great deal of attention due to their unique and potentially useful features. In this review, several representative types of nanocellulose and modification methods for antimicrobial applications are mainly focused on. Recent literature related with the preparation and applications of nanocellulose-based antimicrobial materials is reviewed. The fabrication of nanocellulose-based antimicrobial materials for wound dressings, drug carriers, and packaging materials is the focus of the research. The most important additives employed in the preparation of nanocellulose-based antimicrobial materials are presented, such as antibiotics, metal, and metal oxide nanoparticles, as well as chitosan. These nanocellulose-based antimicrobial materials can benefit many applications including wound dressings, drug carriers, and packaging materials. Finally, the challenges of industrial production and potentials for development of nanocellulose-based antimicrobial materials are discussed.

Electrospun cellulose acetate membrane for size separating and antibacterial screening of crude polysaccharides

This study aims to produce electrospun cellulose acetate (CA) membrane as the alternative supporting medium for a separation of crude polysaccharides by electrophoresis and a screening of their antibacterial activity. Among the tested conditions of fabrication, electrospun CA membrane at 57% porosity showed the best separation of each polysaccharide from the standard mixture and the crude extract of Aloe vera via electrophoresis. As compared with the commercial CA membrane, the produced electrospun CA membrane demonstrated more separated spots of polysaccharides. The antibacterial activity of the electrophoretic polysaccharide was also determined against Escherichia coli and Staphylococcus aureus as the inhibition zone after the bacterial culture agar was overlaid on the membrane and incubated for 24 h. The results of this study suggested the potential application of electrospun CA membrane combining with electrophoresis as a simple method for separating crude polysaccharides and screening for their antibacterial activity.

Natural product-based nanomedicines for wound healing purposes: therapeutic targets and drug delivery systems

Wound healing process is an intricate sequence of well-orchestrated biochemical and cellular phenomena to restore the integrity of the skin and subcutaneous tissue. Several plant extracts and their phytoconstituents are known as a promising alternative for wound healing agents due to the presence of diverse active components, ease of access, and their limited side effects. The development of nanotechnological methods can help to improve the efficacy of different therapeutics as well as herbal-based products. Here, we present a review of the efficacy of the plant based-nanomaterials in the management of wounds and discuss the involved therapeutic targets. For this purpose, a profound search has been conducted on in vitro, in vivo, and/or clinical evidences evaluating the efficacy and pharmacological mechanisms of natural product-based nanostructures on different types of wounds. Different pharmacological targets are involved in the wound healing effects of herbal-based nanostructures, including suppressing the production of inflammatory cytokines and inflammatory transduction cascades, reducing oxidative factors and enhancing antioxidative enzymes, and promoting neovascularization and angiogenic pathways through increasing the expression of vascular endothelial growth factor, fibroblast growth factor, and platelet-derived growth factor. Moreover, nanostructure of plant extracts and their phytochemicals can enhance their bioavailability, control their release in the form of sustained delivery systems to the wound site, and enhance the permeability of these therapeutics to the underlying skin layers, which are all necessary for the healing process. Overall, various plant extracts and their natural compounds, used in nanoformulations, have demonstrated high activity in the management of wounds and thus can be assumed as future pharmaceutical drugs.

Functional Nanofibers with Multiscale Structure by Electrospinning

Electrospinning can produce nanofibers with extremely high surface-to-volume ratio and well tunable properties. The technique has been widely used in different disciplines. To fabricate fibers with required properties, parameters of fabrication should be well controlled and adjusted according to specific applications. Modification of electrospinning devices to align fibers in highly ordered architectures could improve their functions. Enhanced efficiency have also been obtained through the upscaling modification of spinnerets. With the outstanding efficiency, electrospinning has exhibited huge potentials to construct various nanostructures, such as artificial vessel, membrane for desalination and so on.

Soy Protein/Cellulose Nanofiber Scaffolds Mimicking Skin Extracellular Matrix for Enhanced Wound Healing

Historically, soy protein and extracts have been used extensively in foods due to their high protein and mineral content. More recently, soy protein has received attention for a variety of its potential health benefits, including enhanced skin regeneration. It has been reported that soy protein possesses bioactive molecules similar to extracellular matrix (ECM) proteins and estrogen. In wound healing, oral and topical soy has been heralded as a safe and cost-effective alternative to animal protein and endogenous estrogen. However, engineering soy protein-based fibrous dressings, while recapitulating ECM microenvironment and maintaining a moist environment, remains a challenge. Here, the development of an entirely plant-based nanofibrous dressing comprised of cellulose acetate (CA) and soy protein hydrolysate (SPH) using rotary jet spinning is described. The spun nanofibers successfully mimic physicochemical properties of the native skin ECM and exhibit a high water retaining capability. In vitro, CA/SPH nanofibers promote fibroblast proliferation, migration, infiltration, and integrin β1 expression. In vivo, CA/SPH scaffolds accelerate re-epithelialization and epidermal thinning as well as reduce scar formation and collagen anisotropy in a similar fashion to other fibrous scaffolds, but without the use of animal proteins or synthetic polymers. These results affirm the potential of CA/SPH nanofibers as a novel wound dressing.

Fabrication of Progesterone-Loaded Nanofibers for the Drug Delivery Applications in Bovine

Progesterone is a potent drug for synchronization of the estrus and ovulation cycles in bovine. At present, the estrus cycle of bovine is controlled by the insertion of progesterone-embedded silicone bands. The disadvantage of nondegradable polymer inserts is to require for disposal of these bands after their use. The study currently focuses on preparation of biodegradable progesterone-incorporated nanofiber for estrus synchronization. Three different concentrations (1.2, 1.9, and 2.5 g) of progesterone-impregnated nanofibers were fabricated using electrospinning. The spun membrane were characterized by scanning electron microscopy, X-ray diffraction, differential scanning calorimetry, thermogravimetric analysis, and Fourier transform infrared spectroscopy. Uniform surface morphology, narrow size distribution, and interaction between progesterone and zein were confirmed by SEM. FTIR spectroscopy indicated miscibility and interaction between zein and progesterone. X-ray analysis indicated that the size of zein crystallites increased with progesterone content in nanofibers. Significant differences in thermal behavior of progesterone-impregnated nanofiber were observed by DSC. Cell viability studies of progesterone-loaded nanofiber were examined using MTT assay. In vitro release experiment is to identify the suitable progesterone concentration for estrus synchronization. This study confirms that progesterone-impregnated nanofibers are an ideal vehicle for progesterone delivery for estrus synchronization of bovines.

Smart Carriers and Nanohealers: A Nanomedical Insight on Natural Polymers

Biodegradable polymers are popularly being used in an increasing number of fields in the past few decades. The popularity and favorability of these materials are due to their remarkable properties, enabling a wide range of applications and market requirements to be met. Polymer biodegradable systems are a promising arena of research for targeted and site-specific controlled drug delivery, for developing artificial limbs, 3D porous scaffolds for cellular regeneration or tissue engineering and biosensing applications. Several natural polymers have been identified, blended, functionalized and applied for designing nanoscaffolds and drug carriers as a prerequisite for enumerable bionano technological applications. Apart from these, natural polymers have been well studied and are widely used in material science and industrial fields. The present review explains the prominent features of commonly used natural polymers (polysaccharides and proteins) in various nanomedical applications and reveals the current status of the polymer research in bionanotechnology and science sectors.

Functional electrospun fibers for the treatment of human skin wounds

Wounds are trauma induced defects of the human skin involving a multitude of endogenous biochemical events and cellular reactions of the immune system. The healing process is extremely complex and affected by the patient's physiological conditions, potential implications like infectious pathogens and inflammation as well as external factors. Due to increasing incidence of chronic wounds and proceeding resistance of infection pathogens, there is a strong need for effective therapeutic wound care. In this context, electrospun fibers with diameters in the nano- to micrometer range gain increasing interest. While resembling the structure of the native human extracellular matrix, such fiber mats provide physical and mechanical protection (including protection against bacterial invasion). At the same time, the fibers allow for gas exchange and prevent occlusion of the wound bed, thus facilitating wound healing. In addition, drugs can be incorporated within such fiber mats and their release can be adjusted by the material and dimensions of the individual fibers. The review gives a comprehensive overview about the current state of electrospun fibers for therapeutic application on skin wounds. Different materials as well as fabrication techniques are introduced including approaches for incorporation of drugs into or drug attachment onto the fiber surface. Against the background of wound pathophysiology and established therapy approaches, the therapeutic potential of electrospun fiber systems is discussed. A specific focus is set on interactions of fibers with skin cells/tissues as well as wound pathogens and strategies to modify and control them as key aspects for developing effective wound therapeutics. Further, advantages and limitations of controlled drug delivery from fiber mats to skin wounds are discussed and a future perspective is provided.

Interpenetrating network hydrogels with high strength and transparency for potential use as external dressings

Interpenetrating polymer network (IPN) hydrogels composed of gelatin and hydroxypropyl cellulose (HPC) were prepared by successive enzymatic and chemical crosslinking approaches. The hydrogels displayed porous structure and the pore size decreased with the increase of HPC content. Due to the entanglement and interpenetrating between the two crosslinked networks, the IPN hydrogels exhibited excellent mechanical strength and light transmittance. The maximum tensile and tear strengths of the IPN hydrogels reached 3.1 and 5.2MPa, respectively. The water vapor permeability of the IPN hydrogels was within the acceptable range to maintain appropriate moisture for wound healing. The cytotoxicity evaluation indicated that the IPN hydrogels exhibited no toxicity to fibroblast cells. In addition, the hydrogels were loaded with chloramphenicol by pre-soaking in drug solutions to evaluate drug-loading capacity and in vitro release behavior. It was found that the drug loaded hydrogels could act as drug delivery devices to create microbe free microenvironment, which was advantageous for wound healing.

Recent advances in electrospun nanofibers for wound healing

Electrospun nanofibers represent a novel class of materials that show great potential in many biomedical applications including biosensing, regenerative medicine, tissue engineering, drug delivery and wound healing. In this work, we review recent advances in electrospun nanofibers for wound healing. This article begins with a brief introduction on the wound, and then discusses the unique features of electrospun nanofibers critical for wound healing. It further highlights recent studies that have used electrospun nanofibers for wound healing applications and devices, including sutures, multifunctional dressings, dermal substitutes, engineered epidermis and full-thickness skin regeneration. Finally, we finish with conclusions and future perspective in this field.

Electrospun nanofibers for wound healing

Electrospinning has been widely used as a nanofiber fabrication technique. Its simple process, cost effectiveness and versatility have appealed to materials scientists globally. Pristine polymeric nanofibers or composite nanofibers with dissimilar morphologies and multidimensional assemblies ranging from one dimension (1D) to three dimensions (3D) can be obtained from electrospinning. Critically, these as-prepared nanofibers possessing high surface area to volume ratio, tunable porosity and facile surface functionalization present numerous possibilities for applications, particularly in biomedical field. This review gives us an overview of some recent advances of electrospinning-based nanomaterials in biomedical applications such as antibacterial mats, patches for rapid hemostasis, wound dressings, drug delivery systems, as well as tissue engineering. We further highlight the current challenges and future perspectives of electrospinning-based nanomaterials in the field of biomedicine.

Electrospun cellulose acetate composites containing supported metal nanoparticles for antifungal membranes

Electrospun cellulose acetate composites containing silver and copper nanoparticles supported in sepiolite and mesoporous silica were prepared and tested as fungistatic membranes against the fungus Aspergillus niger. The nanoparticles were in the 3-50nm range for sepiolite supported materials and limited by the size of mesopores (5-8nm) in the case of mesoporous silica. Sepiolite and silica were well dispersed within the fibers, with larger aggregates in the micrometer range, and allowed a controlled release of metals to create a fungistatic environment. The effect was assessed using digital image analysis to evaluate fungal growth rate and fluorescence readings using a viability stain. The results showed that silver and copper nanomaterials significantly impaired the growth of fungi when the spores were incubated either in direct contact with particles or included in cellulose acetate composite membranes. The fungistatic effect took place on germinating spores before hyphae growth conidiophore formation. After 24h the cultures were separated from fungistatic materials and showed growth impairment only due to the prior exposure. Growth reduction was important for all the particles and membranes with respect to non-exposed controls. The effect of copper and silver loaded materials was not significantly different from each other with average reductions around 70% for bare particles and 50% for membranes. Copper on sepiolite was particularly efficient with a decrease of metabolic activity of up to 80% with respect to controls. Copper materials induced rapid maturation and conidiation with fungi splitting in sets of subcolonies. Metal-loaded nanomaterials acted as reservoirs for the controlled release of metals. The amount of silver or copper released daily by composite membranes represented roughly 1% of their total load of metals. Supported nanomaterials encapsulated in nanofibers allow formulating active membranes with high antifungal performance at the same time minimizing the risk of nanoparticle release into the environment.

Drug loading and delivery using nanofibers scaffolds

In recent times, notable advancement has been made in the field of electrospinning for the fabrication of numerous types of nanofiber scaffolds. Due to the ultrathin fiber diameter, electrospun nanofiber scaffolds are considered to be an operational delivery system for biomolecules, genes, as well as drugs due to the high specific surface area and stereological porous structure. Here, we introduce some of methods for the integration of drugs and biomolecules within electrospun nanofiber scaffolds, such as blending, surface modification, coaxial process, and emulsion methods. Then, we describe some important biomedical applications of nanofibers in drug delivery systems along with their suitable examples in transdermal systems and wound dressings, cancer therapy, growth factor delivery, nucleic acid delivery, and stem cell delivery.

Cellulose reinforced nylon-6 nanofibrous membrane: Fabrication strategies, physicochemical characterizations, wicking properties and biomimetic mineralization

The aim of the present study is to develop a facile, efficient approach to reinforce nylon 6 (N6) nanofibers with cellulose chains as well as to study the effect that cellulose regeneration has on the physicochemical properties of the composite fibers. Here, a cellulose acetate (CA) solution (17wt%) was prepared in formic acid and was blended with N6 solution (20%, prepared in formic acid and acetic acid) in various proportions, and the blended solutions were then electrospun to produce hybrid N6/CA nanofibers. Cellulose was regenerated in-situ in the fiber via alkaline saponification of the CA content of the hybrid fiber, leading to cellulose-reinforced N6 (N6/CL) nanofibers. Electron microscopy studies suggest that the fiber diameter and hence pore size gradually decreases as the mass composition of CA increases in the electrospinning solution. Cellulose regeneration showed noticeable change in the polymorphic behavior of N6, as observed in the XRD and IR spectra. The strong interaction of the hydroxyl group of cellulose with amide group of N6, mainly via hydrogen bonding, has a pronounced effect on the polymorphic behavior of N6. The γ-phase was dominant in pristine N6 and N6/CA fibers while α- phase was dominant in the N6/CL fibers. The surface wettability, wicking properties, and the tensile stress were greatly improved for N6/CL fibers compared to the corresponding N6/CA hybrid fibers. Results of DSC/TGA revealed that N6/CL fibers were more thermally stable than pristine N6 and N6/CA nanofibers. Furthermore, regeneration of cellulose chain improved the ability to nucleate bioactive calcium phosphate crystals in a simulated body fluid solution.

Preparation and Characterization of a Bioartificial Polymeric Material: Bilayer of Cellulose Acetate-PVA

A new bioartificial polymeric material consisting of a bilayer of cellulose acetate and poly(vinyl alcohol) was successfully obtained by casting method. The material was characterized by Fourier transform infrared spectroscopy, contact angle, scanning electron microscopy, differential scanning calorimetry, gas permeability, water vapor permeability, and mechanical properties. The characterization indicates that two distinct and well-differentiated surfaces were achieved without detriment to the bulk properties. The interaction between natural and synthetic polymers indeed enhanced the gas permeability as well as the water vapor permeability in comparison to the original components, although mechanical properties were not substantially boosted by the combination of both. Moreover, beyond the interface, there were no detected interactions between the polymers as can be evidenced by the presence of a uniqueTgin the bilayer. The amalgamation of the relatively good mechanical properties with the two differentiated surfaces and the improvement of the permeability properties could indicate the potential of the material for being used in medicine.

IPN hydrogel nanocomposites based on agarose and ZnO with antifouling and bactericidal properties

Nanocomposite hydrogels with interpenetrating polymer network (IPN) structure based on poly(ethylene glycol) methyl ether methacrylate modified ZnO (ZnO-PEGMA) and 4-azidobenzoic agarose (AG-N3) were prepared by a one-pot strategy under UV irradiation. The hydrogels exhibited a highly macroporous spongelike structure, and the pore size decreased with the increase of the ZnO-PEGMA content. Due to the entanglement and favorable interactions between the two crosslinked networks, the IPN hydrogels exhibited excellent mechanical strength and light transmittance. The maximum compressive and tensile strengths of the IPN hydrogels reached 24.8 and 1.98 MPa respectively. The transparent IPN hydrogels transmitted more than 85% of visible light at all wavelengths (400-800 nm). The IPN hydrogels exhibited anti-adhesive property towards Gram-negative Escherichia coli (E. coli) and Gram-positive Staphylococcus aureus (S. aureus), and the bactericidal activity increased with the ZnO-PEGMA content. The incorporation of ZnO-PEGMA did not reduce the biocompatibility of the IPN hydrogels and all the IPN nanocomposites showed negligible cytotoxicity. The present study not only provided a facile method for preparing hydrogel nanocomposites with IPN structure but also developed a new hydrogel material which might be an excellent candidate for wound dressings.

Polyvinyl alcohol nanofiber formulation of the designer antimicrobial peptide APO sterilizes Acinetobacter baumannii-infected skin wounds in mice

Native and designer cationic antimicrobial peptides are increasingly acknowledged as host defense molecules rather than true antimicrobials. Due to their ability to activate the innate immune system, these structures are used to treat uninfected and bacterially-infected wounds, including those harboring Acinetobacter baumannii. Previously we documented that when administered intramuscularly or topically in liquid formulations, the proline-rich host defense peptide dimer A3-APO accelerates uninfected wound re-epithelization and eliminates systemic and local A. baumannii, methicillin-resistant Staphylococcus aureus and other pathogen load from infected lesions better than conventional antibiotics. In the current study we sought to produce and characterize a novel delivery system, suitable for immediate and convenient application in non-hospital environments. The APO monomer was incorporated into polyvinyl alcohol nanofibers and the complex was polymerized into a solid patch dressing. Mice were subjected to skin abrasion where the wounds were either left uninfected or were inoculated with a near lethal dose of multidrug resistant A. baumannii strain. Analyzed after 3 days, APO monomer-containing patches improved wound appearance significantly better than polymer patches without antibiotics. When compared to colistin, the APO patches accelerated wound healing, and statistically significantly reduced wound size and wound bacterial load. The in vivo antimicrobial effect was more extensive than after intramuscular administration of the peptide drug, by using only one tenth of the active pharmaceutical ingredient. These data suggest that the APO monomer-impregnated nanofiber dressing can be developed as an economical first-line treatment option to skin injuries in general and battlefield burn and blast injuries in particular.

Structural and mechanical characterization of bioresorbable, elastomeric nanocomposites from poly(glycerol sebacate)/nanohydroxyapatite for tissue transport applications

Poly(glycerol sebacate) (PGS)/nanohydroxyapatite (nHA) composites were assessed to develop new materials for closure via tissue transport for nonhealing defects (e.g., cleft palate and large skin wounds). The elastic shape memory polymer, PGS, was reinforced with nHA at 3 and 5% loading to increase the mechanical properties compared with the undoped PGS. Differential scanning calorimetry (DSC) was utilized to identify a glass transition temperature (Tg ) of -25°C. X-ray diffraction demonstrated a reduction in the amorphous nature of the material. The Fourier transform infrared photoacoustic spectral (FTIR-PAS) data showed decreased CO bonding and increased hydrogen bonding with increased nHA incorporation. Composites exhibited Young's moduli in the range of 0.25-0.5 MPa and tensile strength of 1.5-3 N. No significant difference in extension to break (∼50 mm) with addition of nHA was observed. The elastic modulus significantly increased for 5% PGS/nHA compared to 0 and 3% PGS/nHA and tensile strength significantly increased for 3% PGS/nHA compared to 0 and 5% PGS/nHA. Degradation of 5% nHA/PGS significantly increased during the second week compared to PGS 0 and 3% PGS/nHA. The accelerated degradation for 5% PGS/nHA coupled with decreased flexibility and tensile strength implies an interruption in crosslinking. By maintaining flexibility and extension while increasing tensile strength, the 3% PGS/nHA doped satisfied the force range desired for closure of soft tissue defects. Based on this work, PGS with 3% nHA shape memory polymers should serve as a good candidate for closure of nonhealing soft tissues. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 104B: 1366-1373, 2016.