Wound dressings for a proteolytic-rich environment

Bridging Nature and Engineering: Protein-Derived Materials for Bio-Inspired Applications

The sophisticated, elegant protein-polymers designed by nature can serve as inspiration to redesign and biomanufacture protein-based materials using synthetic biology. Historically, petro-based polymeric materials have dominated industrial activities, consequently transforming our way of living. While this benefits humans, the fabrication and disposal of these materials causes environmental sustainability challenges. Fortunately, protein-based biopolymers can compete with and potentially surpass the performance of petro-based polymers because they can be biologically produced and degraded in an environmentally friendly fashion. This paper reviews four groups of protein-based polymers, including fibrous proteins (collagen, silk fibroin, fibrillin, and keratin), elastomeric proteins (elastin, resilin, and wheat glutenin), adhesive/matrix proteins (spongin and conchiolin), and cyanophycin. We discuss the connection between protein sequence, structure, function, and biomimetic applications. Protein engineering techniques, such as directed evolution and rational design, can be used to improve the functionality of natural protein-based materials. For example, the inclusion of specific protein domains, particularly those observed in structural proteins, such as silk and collagen, enables the creation of novel biomimetic materials with exceptional mechanical properties and adaptability. This review also discusses recent advancements in the production and application of new protein-based materials through the approach of synthetic biology combined biomimetics, providing insight for future research and development of cutting-edge bio-inspired products. Protein-based polymers that utilize nature's designs as a base, then modified by advancements at the intersection of biology and engineering, may provide mankind with more sustainable products.

Electrospun wound dressings with antibacterial function: a critical review of plant extract and essential oil incorporation

Among the many different types of wound dressings, nanofiber-based materials produced through electrospinning are claimed to be ideal because of their advantageous intrinsic properties and the feasibility of employing several strategies to load bioactive compounds into their structure. Bioactive compounds with antimicrobial properties have been incorporated into different wound dressings to promote healing as well as prevent and treat bacterial infections. Among these, natural products, such as medicinal plant extracts and essential oils (EOs), have proven particularly attractive thanks to their nontoxic nature, minor side effects, desirable bioactive properties, and favorable effects on the healing process. To this end, the present review provides an exhaustive and up-to-date revision of the most prominent medicinal plant extracts and EOs with antimicrobial properties that have been incorporated into nanofiber-based wound dressings. The most common methods used for incorporating bioactive compounds into electrospun nanofibers include: pre-electrospinning (blend, encapsulation, coaxial, and emulsion electrospinning), post-electrospinning (physical adsorption, chemical immobilization, and layer-by-layer assembly), and nanoparticle loading. Furthermore, a general overview of the benefits of EOs and medicinal plant extracts is presented, describing their intrinsic properties and biotechniques for their incorporation into wound dressings. Finally, the current challenges and safety issues that need to be adequately clarified and addressed are discussed.

Biobran-loaded core/shell nanofibrous scaffold: a promising wound dressing candidate

This research examined the effectiveness of Biobran as a bioactive substance that could potentially improve wound healing. It also looked at how Biobran affects the properties of a nanofibrous scaffold made through coaxial electrospinning. This is the first study exploring the use of Biobran in this context and its interaction with nanofibrous scaffolds. The scaffolds were composed of poly(ε-caprolactone) (PCL) in the shell and various concentrations of Biobran blended with polyvinyl alcohol (PVA) in the core. The properties of the scaffolds were characterized by SEM, TEM, FTIR, XRD, TGA, DSC, stress-strain test, WCA, release test, MTT cytotoxicity assay, wound scratching assay, and the dye exclusion method using trypan blue. The scaffolds loaded with Biobran exhibited a more compact and smooth morphology compared with the scaffold without Biobran. The physical interaction and crystallinity of the polymers in the scaffolds were also affected by Biobran in a concentration-dependent manner. This positively influenced their tensile strength, elongation at break, thermal stability, and hydrophilicity. The porosity, water uptake capacity, and WVTR of the nanofibrous scaffolds are within the optimal ranges for wound healing. The release rate of Biobran, which revealed a biphasic release pattern, decreased with increasing Biobran concentration, resulting in controlled and sustained delivery of Biobran from the nanofiber scaffolds. The cell viability assays showed a dose-dependent effect of Biobran on WISH cells, which might be attributed to the positive effect of Biobran on the physicochemical properties of the nanofibrous scaffolds. These findings suggest that Biobran-loaded core/shell nanofiber scaffolds have a potential application in wound healing as an ideal multifunctional wound dressing.

The development of carbohydrate polymer- and protein-based biomaterials and their role in environmental health and hygiene: A review

Biological macromolecules have been significantly used in the medicine due to their certain therapeutic values. Macromolecules have been employed in medical filed in order to enhance, support, and substitute damaged tissues or any other biological function. In the past decade, the biomaterial field has developed considerably because of vast innovations in regenerative medicine, tissue engineering, etc. Different types of biological macromolecules such as natural protein and polysaccharide etc. and synthetic molecules such as metal based, polymer based, and ceramic based etc. have been discussed. These materials can be modified by coatings, fibres, machine parts, films, foams, and fabrics for utilization in biomedical products and other environmental applications. At present, the biological macromolecules can used in different areas like medicine, biology, physics, chemistry, tissue engineering, and materials science. These materials have been used to promote the healing of human tissues, medical implants, bio-sensors and drug delivery, etc. These materials also considered as environmentally sustainable as they are prepared in association with renewable natural resources and living organisms in contrast to non-renewable resources (petrochemicals). In addition, enhanced compatibility, durability and circular economy of biological materials make them highly attractive and innovative for current research.The present review paper summarizes a brief about biological macromolecules, their classification, methods of synthesis, and their role in biomedicine, dyes and herbal products.

Wound Management following Total Knee Arthroplasty: An Updated Review

Optimal wound closure techniques following total knee arthroplasty (TKA) have focused on enhancing healing potential, preventing infection, yielding satisfactory cosmesis, and allowing early ambulation and functionality. An appropriate layered closure and management of the TKA typically involves addressing the (1) deep fascial layer; (2) subdermal layer; (3) intradermal layer, including the subcuticular region; and (4) final application of a specific aseptic dressing, each of which are covered here in detail. This focused critical review of the literature discusses traditional techniques used in all layers of wound closure following TKA while introducing several emerging popular techniques. For example, absorbable barbed skin sutures and occlusive dressings have the potential to reduce operative time, limit the need for early postoperative visits, obviate the need for suture or staple removal, and safely promote patient communication via telemedicine. As novel wound closure techniques continue to emerge and traditional approaches are improved upon, future comparative studies will assist in elucidating the key advantages of various options. In an extremely important field that has tremendous variability, these efforts may enable the reaching of a classically elusive standard of care for these techniques.

Eco-Friendly Keratin-Based Additives in the Polymer Matrix to Enhance the Output of Triboelectric Nanogenerators

A triboelectric nanogenerator (TENG) is an energy generator that converts mechanical energy into electrical energy using triboelectricity at a nanoscale. Given their potential application as power sources in electronic devices, various attempts have been made to improve their output performance. Here, we present an eco-friendly, low-cost, and facile fabrication method to enhance TENG characteristics with keratin protein additives. Keratin sources, human and cat hair, are processed into powder and added to the friction layer, which increases their positive charge affinity, thereby boosting the output performance of the TENG. The output performances of the keratin-added TENG (K-TENG) are measured in the vertical contact-separation mode, with both additives having the highest output values at 5 wt % load. The K-TENG generates more output voltage and current values than the pristine TENG by 90 and 208%, respectively. Hence, we conclude that this method would potentially promote TENG as a strong candidate for a competitive "green" energy harvesting device in future electronics applications.

Dressing Management during Total Knee Arthroplasty: A Systematic Review and Meta-Analysis

Dressings for total knee arthroplasty (TKA) typically focus on promoting optimal healing, while preventing infection, allowing for functionality and immediate ambulation, while providing for excellent cosmesis. We have previously described four aspects of closure after TKA involving the: (1) deep fascial layer; (2) subdermal layer; (3) intradermal layer, including the subcuticular region; and (4) a specific aseptic dressing. In this meta-analysis and systematic review of the literature, we will focus on the dressing. Specifically, we assessed: (1) infection risk of different techniques; (2) re-operation or readmission risk; and (3) length of time until dressing change needed. There were 16 reports on infection risk, re-operation risk, and length of time until change needed. A meta-analysis focused on the qualifying wound complication risk reports was also performed. The meta-analysis including four studies (732 patients) demonstrated overall lower wound complication risk with the use of adhesives and mesh dressings (odds ratio 0.67) versus traditional closures. Additionally, studies demonstrated fewer re-operations and readmissions with the use of adhesives and mesh dressings. Furthermore, one report demonstrated mesh dressings persist longer than silver dressings. Therefore, multiple recent reports suggest superior outcomes when using adhesive and mesh dressings for TKAs.

Alginate as a Promising Biopolymer in Drug Delivery and Wound Healing: A Review of the State-of-the-Art

Biopolymeric nanoparticulate systems hold favorable carrier properties for active delivery. The enhancement in the research interest in alginate formulations in biomedical and pharmaceutical research, owing to its biodegradable, biocompatible, and bioadhesive characteristics, reiterates its future use as an efficient drug delivery matrix. Alginates, obtained from natural sources, are the colloidal polysaccharide group, which are water-soluble, non-toxic, and non-irritant. These are linear copolymeric blocks of α-(1→4)-linked l-guluronic acid (G) and β-(1→4)-linked d-mannuronic acid (M) residues. Owing to the monosaccharide sequencing and the enzymatically governed reactions, alginates are well-known as an essential bio-polymer group for multifarious biomedical implementations. Additionally, alginate’s bio-adhesive property makes it significant in the pharmaceutical industry. Alginate has shown immense potential in wound healing and drug delivery applications to date because its gel-forming ability maintains the structural resemblance to the extracellular matrices in tissues and can be altered to perform numerous crucial functions. The initial section of this review will deliver a perception of the extraction source and alginate’s remarkable properties. Furthermore, we have aspired to discuss the current literature on alginate utilization as a biopolymeric carrier for drug delivery through numerous administration routes. Finally, the latest investigations on alginate composite utilization in wound healing are addressed.

Comparison of silver-embedded occlusive dressings and negative pressure wound therapy following total joint arthroplasty in high BMI patients: a randomized controlled trial

INTRODUCTION

High body mass index (BMI) and wound drainage following total joint arthroplasty (TJA) can lead to wound healing complications and periprosthetic joint infection. Silver-embedded occlusive dressings and negative pressure wound therapy (NPWT) have been shown to reduce these complications. The purpose of this prospective trial was to compare the effect of silver-embedded dressings and NPWT on wound complications in patients with BMI ≥ 35 m/kg2 undergoing TJA.

METHODS

We conducted a randomized control trial of patients who had a BMI > 35 m/kg² and were undergoing primary TJA between October 2017 and February 2020. Patients who underwent revision surgery, or those with an active infection, previous scar, history of wound healing complications, post-traumatic degenerative joint disease with hardware, or inflammatory arthritis were excluded. Patients were randomized to receive either a silver-embedded occlusive dressing (control) or NPWT. Frequency distributions, means, and standard deviations were used to describe patient demographics, postoperative complications, 90-day readmissions, and reoperations. T-test and chi-squared tests were used to test for significant differences between continuous and categorical variables, respectively.

RESULTS

Two hundred-thirty patients with 3-month follow-up were included. One-hundred-fifteen patients received the control and 115 patients received NPWT. There were six patients (5.2%) in the control group with wound complications (drainage: n = 5, non-healing wound: n = 1) and two patients (1.7%) in the NPWT with complications (drainage: n = 2). There were no 90-day readmissions in the control group versus two (1.8%) 90-day readmissions in the NPWT group. Finally, three patients (2.6%) in the control group underwent reoperations (irrigation and debridement [I&D], I&D with modular implant exchange, and implant revision), while none in the NPWT group had undergone reoperation. The two groups showed insignificant differences in wound complications (p = 0.28), 90-day readmissions (p = 0.50), and reoperations (p = 0.25).

CONCLUSION

Patients with BMI ≥ 35 m/kg2 undergoing TJA have no statistical difference in early wound complications, readmissions, or reoperations when treated with either silver-embedded dressings or NPWT.

Biomedical applications of silkworm (Bombyx Mori) proteins in regenerative medicine (a narrative review)

Silk worm (Bombyx Mori) protein, have been considered as potential materials for a variety of advanced engineering and biomedical applications for decades. Recently, silkworm silk has gained significant importance in research attention mainly because of its remarkable and exceptional mechanical properties. Silk has already been shown to have unique interactions with cells in tissues through bio-recognition units. The natural silk contains fibroin and sericin and has been used in various tissues of the human body (skin, bone, nerve, and so on). Besides, silk also still has anti-cancer, anti-tyrosinase, anti-coagulant, anti-oxidant, anti-bacterial, and anti-diabetic properties. This article is supposed to describe the diverse biomedical capabilities of B. Mori silk as the appropriate biomaterial among the assorted natural and artificial polymers that are presently accessible, and ideal for usage in regenerative medicine fields.

Polymer-Based Nanotherapeutics for Burn Wounds

Burn wounds are complex and intricate injuries that have become a common cause of trauma leading to significant mortality and morbidity every year. Dressings are applied to burn wounds with the aim of promoting wound healing, preventing burn infection and restoring skin function. The dressing protects the injury and contributes to recovery of dermal and epidermal tissues. Polymer-based nanotherapeutics are increasingly being exploited as burn wound dressings. Natural polymers such as cellulose, chitin, alginate, collagen, gelatin and synthetic polymers like poly (lactic-co-glycolic acid), polycaprolactone, polyethylene glycol, and polyvinyl alcohol are being obtained as nanofibers by nanotechnological approaches like electrospinning and have shown wound healing and re-epithelialization properties. Their biocompatibility, biodegradability, sound mechanical properties and unique structures provide optimal microenvironment for cell proliferation, differentiation, and migration contributing to burn wound healing. The polymeric nanofibers mimic collagen fibers present in extracellular matrix and their high porosity and surface area to volume ratio enable increased interaction and sustained release of therapeutics at the site of thermal injury. This review is an attempt to compile all recent advances in the use of polymer-based nanotherapeutics for burn wounds. The various natural and synthetic polymers used have been discussed comprehensively and approaches being employed have been reported. With immense research effort that is currently being invested in this field and development of proper characterization and regulatory framework, future progress in burn treatment is expected to occur. Moreover, appropriate preclinical and clinical research will provide evidence for the great potential that polymer-based nanotherapeutics hold in the management of burn wounds.

Evaluation of a novel bioactive wound dressing: an in vitro and in vivo study

OBJECTIVE

Hard-to-heal wounds, such as pressure ulcers and diabetic ulcers, are a major challenge for wound dressings. The aim of this study was to develop a bioactive dressing based on polymers and natural materials with unique biological and therapeutic properties.

METHOD

The dressing was composed of an active layer containing polyvinyl alcohol (PVA), honey, curcumin and keratin, and an upper layer with lower hydrophilicity comprising PVA to induce flexibility. Physicochemical properties of the dressing were characterised by Fourier transform infrared spectroscopy, field emission scanning electron microscopy, swelling behaviour and antibacterial measurements. A wound healing study was performed using an experimental rat model and two different compositions of the bioactive dressing were compared with a commercial wound dressing (Comfeel, Coloplast, Denmark). Histopathological evaluation was conducted for this purpose.

RESULTS

Characterisation results showed that a smooth bilayer film with two homogenous but distinct layers was produced. The dressing also provided adequate moisture to the wound environment without infection and adhesion due to dryness occurring. Our results exhibited significant bactericidal activity against Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus) bacteria and improved the wound healing process without any scarring. Histopathological findings demonstrated a significant higher healing rate in vivo together with well-formed epidermis, granulation tissue formation and tissue contraction, when compared with the commercial wound dressing.

CONCLUSION

Our results demonstrated acceptable physical and healing effects for the novel bioactive wound dressing; however, more investigations are recommended.

Unilateral Silver-Loaded Silk Fibroin Difunctional Membranes as Antibacterial Wound Dressings

Silk fibroin (SF) has been widely used as wound dressings due to its good biocompatibility. To enhance the antibacterial properties of the dressings, silver (Ag) is often added. However, an overdose of Ag may cause cytotoxicity and inhibit wound healing. Therefore, this study aimed to develop a two-layered membrane to reduce cytotoxicity while maintaining the antibacterial properties of Ag through a simplified layer-by-layer technique. The membranes comprised an Ag-rich SF layer (Ag-SF) and a pure SF layer. The unilateral Ag-loaded membranes showed efficient antibacterial properties at doses above 0.06 mg/mL Ag, and the antibacterial properties were comparable on both sides. In contrast, the SF sides of the membranes showed lower cytotoxicity than the Ag-SF sides of the membranes. Further studies on the thickness ratio of Ag-SF/SF layers revealed that Ag0.12-SF/SF membranes with a ratio of 1:3 had high cytocompatibility on the SF sides while holding a strong antibacterial property. Besides, the SF sides of the Ag0.12-SF/SF1:3 membranes promoted the expression levels of collagen I and transforming growth factor-β mRNA in human foreskin fibroblasts. The SF sides of the Ag0.12-SF/SF1:3 membranes significantly promoted the healing of infected wounds in vivo. Therefore, unilateral loading with the simplified layer-by-layer preparation technique provided an effective method to balance the cytotoxicity and the antibacterial property of Ag-loaded materials and thus form a broader therapeutic window for Ag applications. The unilateral Ag-loaded silk fibroin difunctional membranes have the potential to be further preclinically explored as wound dressings.

Preparation of dynamic covalently crosslinking keratin hydrogels based on thiol/disulfide bonds exchange strategy

Dynamic covalently crosslinking (DCC) hydrogels can mimic extracellular matrix and have the functions such as self-healing, self-adapting, and shape memory. The DCC keratin hydrogels based on thiol group-disulfide bonds exchange strategy have no reports so far as we know. Herein, inspired by the rich content of the intramolecular disulfide bonds and free thiol groups in the keratins extracted by reducing agents, we report a simple thiol-disulfide bonds exchange strategy for preparing the DCC keratin hydrogels. While the pH value of the keratin solution extracted by reducing agents was adjusted to 9.5-10.0, the keratin hydrogels showed the characteristic with injectability, self-healing, self-adapting, biocompatibility, and redox-responsive capacity. The extracted type II neutral/alkali keratin plays a critical role in imparting the keratin hydrogels with the reversibility behaviors due to that the keratins could build dynamic covalent bonds through thiol oxidation and disulfide exchange reactions in alkali conditions. This strategy provides an inspiration for forming DCC keratin hydrogel by avoiding the extra introduction of chemical crosslinking agents.

Biomimetic biohybrid nanofibers containing bovine serum albumin as a bioactive moiety for wound dressing

For the first time, a biohybrid nanofibrous wound dressing is developed via green electrospinning of a blend solution of bovine serum albumin (BSA) (1 and 3 wt%) and polycaprolactone (PCL). In such a system, the components are miscible and interact through hydrogen bonding between the carbonyl group of PCL and the amine group of BSA, as verified by ATR-FTIR. As a result, the biohybrid nanofibers show a superior elastic modulus and elongation (300% and 58%, respectively) compared with the neat PCL nanofibers. The included protein induces a hydrophilicity effect to the PCL nanofibers, notably at the higher BSA content (3 wt%). In contrast to the neat nanofibers, the biohybrid ones are bioactive and encourage formation of biominerals (made of amorphous calcium carbonate) on the surface, after immersion in simulated body fluid (SBF). Based on the WST-8 cell viability tests, NIH3T3 fibroblast cells were seen to properly interact with the biohybrid mats and to proliferate in their proximity. SEM images show that the cells largely adhere onto such nanofibers even more than they do on the neat ones and adopt a flattened and stretched shape. In addition, the live/dead assay and phalloidin/DAPI staining assay confirm large cell viability and normal cell morphology on the biohybrid nanofiber mats after 4 days incubation. Taken together, BSA/PCL nanofibers are able to offer optimum mechanical properties (elasticity) as well as mineralization which can potentially stimulate the wound healing process, and can be considered a suitable candidate for wound dressing applications.

An alginate-PHMB-AgNPs based wound dressing polyamide nanocomposite with improved antibacterial and hemostatic properties

Wound dressing should be impenetrable against microorganisms and it should keep the wound wet. Gauze and polyamide (PA) substrate were treated with various concentrations of AgNPs (25, 50, 75, and 100 ppm), PHMB (0.2, 0.4, 0.6, 0.8, and 1% w/v), and constant concentration of alginate (0.5% W/V) using a simple dipping method. Prepared samples were characterized by various techniques including Fourier transform infrared spectroscopy and scanning electron microscopy. The results indicated that the particles were successfully applied onto both substrates with an average diameter of particle size of 78 nm on gauze and 172 nm on the PA substrate surface (based on 50 nanoparticles). Antibacterial activity of the prepared nanocomposite against Staphylococcus aureus (gram-positive) bacteria on PA substrate and gauze were evaluated using the disc diffusion method. The results indicated that the prepared nanocomposites offer favorable antibacterial properties and bacteria would not grow in culture media. The water uptake capacity test of the treated samples was assessed and the data demonstrated that the water absorption rate significantly increases on both treated substrates (gauze and PA substrate) due to the presence of alginate polymer. Also, observing the results of the coagulation test showed that treated samples caused blood clots on the dressing. This is due to the presence of alginate polymer. The present work demonstrates that the prepared samples offer excellent antibacterial properties and good water uptake capacity that capable of being a potential candidate for wound dressings. Due to the results, the produced PA substrate could be an appropriate replacement for the cotton gauze as a wound dressing.

Silk fibroin/poly-(L-lactide-co-caprolactone) nanofiber scaffolds loaded with Huangbai Liniment to accelerate diabetic wound healing

Diabetic infection is a long-term complication difficult to cure. The skin of diabetic patients is prone to damage, the healing is slow after the injury, and the wound occurs repeatedly. Therefore, there is an urgent need to develop an effective method for treating diabetes wounds. In this study, we used the electrospinning technique to load Huangbai Liniment (Compound Phellodendron Liquid, CPL) into Silk fibroin (SF) /poly-(L-lactide-co-caprolactone) (PLCL) to prepare the nanofiber membrane (SP/CPL) to treat the diabetic wound. The morphology and structure of the nanofibers were observed by scanning electron microscope (SEM). The SEM results indicate the smooth and bead free fibers and the diameter of the fiber decreased with increasing drug concentration. The release profile indicates the sustained release of the drug. Moreover, the drug-loaded nanofibers showed inhibitory effects for S.aureus and E.coli. Furthermore, in vitro cell culture studies showed the increased proliferation and adhesion of NIH-3T3 cells on the drug-containing nanofiber membrane. Animal experiments showed that the nanofiber membrane loaded with CPL increases the expression of the TGF-β signaling pathway and collagen during wound healing, inhibits the expression of pro-inflammatory factors, and thus effectively promotes wound healing in diabetic mice. Therefore, the SP/CPL nanofiber scaffold with CPL loading is a potential candidate for diabetic wound dressings and tissue engineering.

Designing Enzyme-responsive Biomaterials

Enzymes are a class of protein that catalyze a wide range of chemical reactions, including the cleavage of specific peptide bonds. They are expressed in all cell types, play vital roles in tissue development and homeostasis, and in many diseases, such as cancer. Enzymatic activity is tightly controlled through the use of inactive pro-enzymes, endogenous inhibitors and spatial localization. Since the presence of specific enzymes is often correlated with biological processes, and these proteins can directly modify biomolecules, they are an ideal biological input for cell-responsive biomaterials. These materials include both natural and synthetic polymers, cross-linked hydrogels and self-assembled peptide nanostructures. Within these systems enzymatic activity has been used to induce biodegradation, release therapeutic agents and for disease diagnosis. As technological advancements increase our ability to quantify the expression and nanoscale organization of proteins in cells and tissues, as well as the synthesis of increasingly complex and well-defined biomaterials, enzyme-responsive biomaterials are poised to play vital roles in the future of biomedicine.

Therapeutic effect of decellularized extracellular matrix-based hydrogel for radiation esophagitis by 3D printed esophageal stent

Radiation esophagitis, the most common acute adverse effect of radiation therapy, leads to unwanted consequences including discomfort, pain, an even death. However, no direct cure exists for patients suffering from this condition, with the harmful effect of ingestion and acid reflux on the damaged esophageal mucosa remaining an unresolved problem. Through the delivery of the hydrogel with stent platform, we aimed to evaluate the regenerative capacity of a tissue-specific decellularized extracellular matrix (dECM) hydrogel on damaged tissues. For this, an esophagus-derived dECM (EdECM) was developed and shown to have superior biofunctionality and rheological properties, as well as physical stability, potentially providing a better microenvironment for tissue development. An EdECM hydrogel-loaded stent was sequentially fabricated using a rotating rod combined 3D printing system that showed structural stability and protected a loaded hydrogel during delivery. Finally, following stent implantation, the therapeutic effect of EdECM was examined in a radiation esophagitis rat model. Our findings demonstrate that EdECM hydrogel delivery via a stent platform can rapidly resolve an inflammatory response, thus promoting a pro-regenerative microenvironment. The results suggest a promising therapeutic strategy for the treatment of radiation esophagitis.

Alginate hydrogel dressings for advanced wound management

Wound healing is a complicated and continuous process affected by several factors, and it needs an appropriate surrounding to achieve accelerated healing. At present, various wound dressings are used for wound management, such as fiber, sponge, hydrogel, foam, hydrocolloid and so on. Hydrogels can provide mechanical support and moist environment for wounds, and are widely used in biomedical field. Alginate is a natural linear polysaccharide derived from brown algae or bacteria, consisting of repeating units of β-1,4-linked D-mannuronic acid (M) and L-guluronic acid (G) in different ratios. It is widely used in biomedical and engineering fields due to its good biocompatibility and liquid absorption capacity. Alginate-based hydrogels have been used in wound dressing, tissue engineering, and drug delivery applications for decades. In this review, we summarize the recent approaches in the chemical and physical preparation and the application of alginate hydrogels in wound dressings.

Crustacean Proteases and Their Application in Debridement

Digestive proteases from marine organisms have been poorly applied to biomedicine. Exceptions are trypsin and other digestive proteases from a few cold-adapted or temperate fish and crustacean species. These enzymes are more efficient than enzymes from microorganism and higher vertebrates that have been used traditionally. However, the biomedical potential of digestive proteases from warm environment species has received less research attention. This review aims to provide an overview of this unrealised biomedical potential, using the debridement application as a paradigm. Debridement is intended to remove nonviable, necrotic and contaminated tissue, as well as fibrin clots, and is a key step in wound treatment. We discuss the physiological role of enzymes in wound healing, the use of exogenous enzymes in debridement, and the limitations of cold-adapted enzymes such as their poor thermal stability. We show that digestive proteases from tropical crustaceans may have advantages over their cold-adapted counterparts for this and similar uses. Differences in thermal stability, auto-proteolytic stability, and susceptibility to proteinase inhibitors are discussed. Furthermore, it is proposed that the feeding behaviour of the source organism may direct the evaluation of enzymes for particular applications, as digestive proteases have evolved to fill a wide variety of feeding habitats, natural substrates, and environmental conditions. We encourage more research on the biomedical application of digestive enzymes from tropical marine crustaceans.

Role of oxygen in wound healing

Not only does oxygen play an essential role in each stage of the wound healing process. It also helps to increases host resistance to infection. Any impairment to the oxygen supply can therefore delay healing. This article explores the affects of oxygen on the wound cells and tissue, and explains how an adequate supply is required for granulation tissue formation and epithelialisation to occur

Keratinous materials: Structures and functions in biomedical applications

Keratins are a family of fibrous proteins anticipated to possess wide-ranging biomedical applications due to their abundance, physicochemical properties and intrinsic biological activity. This review mainly focuses on the biomaterials derived from three major sources of keratins; namely human hair, wool and feather, that have effective applications in tissue engineering, wound healing and drug delivery. This article offers five viewpoints regarding keratin i) an introduction to keratin protein extraction and keratin-based scaffold fabrication methods ii) applications in nerve and bone tissue engineering iii) a review on the keratin dressings applied to different types of wounds to facilitate wound healing and thereby repair the skin iv) the utilization of keratinous materials as a carrier system for therapeutics with a controlled manner v) a discussion regarding the main challenges for using keratin in biomedical applications as well as its future prospects.

Biopolymer-based biomaterials for accelerated diabetic wound healing: A critical review

Non-healing, chronic wounds place a huge burden on healthcare systems as well as individual patients. These chronic wounds especially diabetic wounds will ultimately lead to compromised mobility, amputation of limbs and even death. Currently, wounds and limb ulcers associated with diabetes remain significant health issues; the associated healthcare cost ultimately leads to the increased clinical burden. The presence of diabetes interrupts a highly coordinated cascade of events in the wound closure process. Advances in the understanding of pathophysiological conditions associated with diabetic wounds lead to the development of drug delivery systems which can enhance wound healing by targeting various phases of the impaired processes. Wound environments typically contain degradative enzymes, along with an elevated pH and demonstrate a physiological cascade involved in the regeneration of tissue, which requires the application of an effective delivery system. This article aims to review the pathophysiological conditions associated with chronic and diabetic wounds. The delivery systems, involved in their treatment are described, highlighting potential biomaterials and polymers for establishing drug delivery systems, specifically for the treatment of diabetic wounds and the promotion of the associated mechanisms involved in advanced wound healing. Emerging approaches and engineered devices for effective wound care are reported. The discussion will give insight into the mechanisms relevant to all stages of wound healing.

Naturally-derived electrospun wound dressings for target delivery of bio-active agents

Electrospun nanofibers are known as the advanced means for wound dressing. They have represented remarkable potency to encapsulate and deliver biomolecules promoting the wound healing process. Compared to synthetic polymers, naturally derived polymers (NDP) are more qualified candidates for fabrication of biomedical electrospun scaffolds. Not only nanofibers of NDP illustrate higher biocompatibility and biodegradability rates, but also they mimic the native extracellular matrix more closely, which leads to the wound closure acceleration by enhancing tissue regeneration. Aside, incorporation of bioactive molecules and therapeutic agents into the nanofibers can generate innovative bioactive wound dressings with significantly improved healing potentials. This paper starts with a brief discussion on the steps and factors influencing the wound healing process. Then, the recent applications of electrospun nanofibers as wound dressing with healing accelerating properties are reviewed. Further, the various healing agents and alternative strategies for modification and functionalization of bioactive naturally-derived electrospun nanofibers are discussed.

Highly polydisperse keratin rich nanofibers: Scaffold design and in vitro characterization

The use of bioactive proteins such as keratin has been successfully explored to improve the biological interface of scaffolds with cells during the tissue regeneration. In this work, it is optimized the fabrication of nanofibers combining wool keratin extracted by sulfitolysis, with polycaprolactone (PCL) in order to design bicomponent fibrous matrices able to exert a self-adapting pattern of signals-morphological, chemical, or physical-confined at the single fiber level, to influence cell and bacteria interactions. It is demonstrated that the blending of highly polydisperse keratin with PCL (50:50) improves the stability of the electrospinning process, promoting the formation of nanofibers-144.1 ± 43.9 nm-without the formation of defects (i.e., beads, ribbons) typically recognized in the fabrication of keratin ones. Moreover, keratin drastically increases the fiber hydrophilicity-compared with PCL fiber alone-thus improving the hMSC adhesion and in vitro proliferation until 14 days. Moreover, the growth of bacterial strains (i.e., Escherichia coli and Staphylococcus aureus) seems to be not specifically inhibited by the contribution of keratin, so that the integration of further selected compounds (i.e., metal ions) is suggested to more efficiently fight against bacteria resistance, to make them suitable for the regeneration of different interfaces and soft tissues (i.e., skin and cornea). © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 107A: 1803-1813, 2019.

Control Strategies for Infection Prevention in Total Joint Arthroplasty

Despite the development of newer preventative measures, the rate of infection continues to be approximately 1% for patients undergoing total joint arthroplasty (TJA). The extent of the infection can range from a mild superficial infection to a more serious periprosthetic joint infection (PJI). PJIs not only play a significant role in the clinical well-being of the TJA patient population, but also have substantial economic implications on the health care system. Several approaches are currently being used to mitigate the risk of PJI after TJA. The variety of prophylactic measures to prevent infection after TJA must be thoroughly discussed and evaluated.

Nanopharmaceuticals for wound healing - Lost in translation?

Today, many of the newly developed pharmaceuticals and medical devices take advantage of nanotechnology and with a rising incidence of chronic diseases such as diabetes and cardiovascular disease, the number of patients afflicted globally with non-healing wounds is growing. This has created a requirement for improved therapies and wound care. However, converting the strategies applied in early research into new products is still challenging. Many of them fail to comply with the market requirements. This review discusses the legal and scientific challenges in the design of nanomedicines for wound healing. Are they lost in translation or is there a new generation of therapeutics in the pipeline?

The effect of wound dressings on infection following total joint arthroplasty

Background

The use of perioperative surgical wound dressings is an important factor in the mitigation of infection following total joint arthroplasty (TJA). Few studies have been published comparing wound dressings and infection rates after TJA.

Methods

MEDLINE, PubMed, and EMBASE were searched for studies published between 2006 and 2016 reporting infection rates in patients using various wound dressings after undergoing TJA. All studies comparing Hydrofibre dressings to Standard dressings or Absorbent dressings were included in this meta-analysis. Studies looking at TJA secondary to trauma were excluded. Two individuals independently extracted data, and study results were divided based on type of treatment. The primary outcome was to compare the infection rate of Hydrofibre dressings to that of both Standard Dressings and Absorbent dressings.

Results

Of a total of 3721 participants, 1483 were treated with Standard dressings (non-impregnated gauze), 1911 with Hydrofibre dressings, and 327 with Absorbent dressings. The risk ratio for infection comparing Standard with Hydrofibre was 4.16 (95% confidence interval, 1.71-10.16) as compared to 2.60 (95% confidence interval, 0.66-10.27) when comparing Absorbent with Hydrofibre dressings.

Conclusions

Our analysis suggests that Hydrofibre dressings may be significantly better than Standard and Absorbent dressings with respect to reducing infection. However, given the observed heterogeneity and small number of studies included, more comparative studies are needed to definitively recommend superiority among dressings following TJA.

Level of Evidence

Level 1.

Advances in thermosensitive polymer-grafted platforms for biomedical applications

Studies on "smart" polymeric material performing environmental stimuli such as temperature, pH, magnetic field, enzyme and photo-sensation have recently paid much attention to practical applications. Among of them, thermo-responsive grafted copolymers, amphiphilic steroids as well as polyester molecules have been utilized in the fabrication of several multifunctional platforms. Indeed, they performed a strikingly functional improvement comparing to some original materials and exhibited a holistic approach for biomedical applications. In case of drug delivery systems (DDS), there has been some successful proof of thermal-responsive grafted platforms on clinical trials such as ThermoDox®, BIND-014, Cynviloq IG-001, Genexol-PM, etc. This review would detail the recent progress and highlights of some temperature-responsive polymer-grafted nanomaterials or hydrogels in the 'smart' DDS that covered from synthetic polymers to nature-driven biomaterials and novel generations of some amphiphilic functional platforms. These approaches could produce several types of smart biomaterials for human health care in future.

Preparation of keratin-based microcapsules for encapsulation of hydrophilic molecules

The interest towards microcapsules based on non-toxic, biodegradable and biocompatible polymers, such as proteins, is increasing considerably. In this work, microcapsules were prepared using water soluble keratin, known as keratoses, with the aim of encapsulating hydrophilic molecules. Keratoses were obtained via oxidizing extraction of pristine wool, previously degreased by Soxhlet. In order to better understand the shell part of microcapsules, pristine wool and obtained keratoses were investigated by FT-IR, gel-electrophoresis and HPLC. Production of the microcapsules was carried out by a sonication method. Thermal properties of microcapsules were investigated by DSC. Microencapsulation and dye encapsulation yields were obtained by UV-spectroscopy. Morphological structure of microcapsules was studied by light microscopy, SEM, and AFM. The molecular weights of proteins analyzed using gel-electrophoresis resulted in the range of 38-62kDa. The results confirmed that the hydrophilic dye (Telon Blue) was introduced inside the keratoses shells by sonication and the final microcapsules diameter ranged from 0.5 to 4µm. Light microscope investigation evidenced the presence of the dye inside the keratoses vesicles, confirming their capability of encapsulating hydrophilic molecules. The microcapsule yield and dye encapsulation yield were found to be 28.87±3% and 83.62±5% respectively.

Novel bilayer wound dressing based on electrospun gelatin/keratin nanofibrous mats for skin wound repair

A bilayer membrane (GKU) with a commercial polyurethane wound dressing as an outer layer and electrospun gelatin/keratin nanofibrous mat as an inner layer was fabricated as a novel wound dressing. Scanning electron micrographs showed that gelatin/keratin nanofibers had a uniform morphology and bead-free structure with average fiber diameter of 160.4nm. 3-(4,5-Dimethylthiazolyl)-2,5-diphenyltetrazolium bromide assay using L929 fibroblast cells indicated that the residues released from the gelatin/keratin composite nanofibrous mat accelerated cell proliferation. Cell attachment experiments revealed that adhered cells spread better and migrated deeper into the gelatin/keratin nanofibrous mat than that into the gelatin nanofibrous mat. In animal studies, compared with the bilayer membrane without keratin, gauze and commercial wound dressing, Comfeel®, GKU membrane gave much more number of blood vessels and a greater reduction in wound area at 4days, and better wound repair at 14days with a thicker epidermis and larger number of newly formed hair follicles. GKU membrane, thus, could be a good candidate for wound dressing applications.

Temporary skin grafts based on hybrid graphene oxide-natural biopolymer nanofibers as effective wound healing substitutes: pre-clinical and pathological studies in animal models

In recent years, temporary skin grafts (TSG) based on natural biopolymers modified with carbon nanostructures have received considerable attention for wound healing. Developments are required to improve physico-mechanical properties of these materials to match to natural skins. Additionally, in-deep pre-clinical examinations are necessary to ensure biological performance and toxicity effect in vivo. In the present work, we show superior acute-wound healing effect of graphene oxide nanosheets embedded in ultrafine biopolymer fibers (60 nm) on adult male rats. Nano-fibrous chitosan-based skin grafts crosslinked by Genepin with physico-mechanical properties close to natural skins were prepared by electrospinning of highly concentrated chitosan- polyvinylpyrrolidone solutions containing graphene oxide (GO) nanosheets. No surfactants and organic solvents were utilized to ensure high biocompatibility of the fibrous structure. In vitro evaluations by human skin fibroblast cells including live and dead assay and MTT results show that GO promote cell viability of porous nanofibrous membrane while providing enhanced bactericidal capacity. In vivo studies on rat's skin determine accelerated healing effect, i.e. a large open wound (1.5 × 1.5 cm²) is fully regenerated after 14-day of post operation while healing is observed for sterile gauze sponge (as the control). Pathological studies support thick dermis formation and complete epithelialization in the presence of 1.5 wt% GO nanosheets. Over 99% wound healing occurs after 21 days for the injury covered with TSG containing 1.5 wt% GO while this would takes weeks for the control. Therefore, the developed materials have a high potential to be used as TSG as pre-clinical testing has shown.

Silver-Impregnated Occlusive Dressing Reduces Rates of Acute Periprosthetic Joint Infection After Total Joint Arthroplasty

BACKGROUND

Commercial silver-impregnated occlusive dressings (such as AQUACEL® Ag SURGICAL Cover Dressing) have been touted as antimicrobial dressings to be used following total joint arthroplasty. Given the increased cost of an AQUACEL® Ag SURGICAL Cover Dressing over a standard dressing for total joint arthroplasty, the objective of this study was to determine whether AQUACEL® Ag SURGICAL Cover Dressing is effective in reducing the rates of acute periprosthetic joint infection (PJI) compared to standard sterile dressing.

METHODS

We retrospectively reviewed the charts of 1173 consecutive patients who underwent a total knee or total hip arthroplasty between 2007 and 2015 by 1 surgeon. The surgeon switched from using a standard xeroform/gauze dressing to an AQUACEL® Ag SURGICAL Cover Dressing in June 2011, with no other major changes in antimicrobial management. Charts were reviewed for evidence of acute PJI (within 3 months of surgery).

RESULTS

There were a total of 11 cases of acute PJI in this patient cohort (0.94%). The incidence of acute PJI for patients managed with a sterile xeroform dressing was 1.58% (9 of 568 patients), compared to 0.33% (2 of 605 patients) with the use of AQUACEL® Ag SURGICAL Cover Dressing. Univariate analysis showed this to be statistically significant (P = .03), and a multiple logistic regression model supported AQUACEL® Ag SURGICAL Cover Dressing as a protective factor with an odds ratio of 0.092 (95% confidence interval, 0.017-0.490; P = .005).

CONCLUSION

This 4-fold decrease in acute PJI with the use of AQUACEL® Ag SURGICAL Cover Dressing supports the use of silver-impregnated occlusive dressings for the reduction of acute PJI.

Role of non-mulberry silk fibroin in deposition and regulation of extracellular matrix towards accelerated wound healing

Bombyx mori silk fibroin (BMSF) as biopolymer has been extensively explored in wound healing applications. However, limited study is available on the potential of silk fibroin (SF) from non-mulberry (Antheraea assama and Philosamia ricini) silk variety. Herein, we have developed non-mulberry SF (NMSF) based electrospun mats functionalized with epidermal growth factor (EGF) and ciprofloxacin HCl as potential wound dressing. The NMSF based mats exhibited essential properties of wound dressing like biocompatibility, high water retention capacity (440%), water vapor transmission rate (∼2330gm^-2day^-1), high elasticity (∼2.6MPa), sustained drug release and antibacterial activity. Functionalized NMSF mats enhanced the proliferation of human dermal fibroblasts and HaCaT cells in vitro as compared to non-functionalized mats (p⩽0.01) showing effective delivery of EGF. Extensive in vivo wound healing assesment demonstrated accelerated wound healing, enhanced re-epithelialization, highly vascularized granulation tissue and higher wound maturity as compared to BMSF based mats. NMSF mats treated wounds showed regulated deposition of mature elastin, collagen and reticulin fibers in the extracellular matrix of skin. Presence of skin appendages and isotropic collagen fibers in the regenerated skin also demonstrated scar-less healing and aesthetic wound repair.

STATEMENT OF SIGNIFICANCE

A facile fabrication of a ready-to-use bioactive wound dressing capable of concomitantly accelerating the healing process as well as deposition of the extracellular matrix (ECM) to circumvent further scarring complicacies has become a focal point of research. In this backdrop, our present work is based on non-mulberry silk fibroin (NMSF) electrospun antibiotic loaded semi-occlusive mats, mimicking the ECM of skin in terms of morphology, topology, microporous structure and mechanical stiffness. Regulation of ECM deposition and isotropic orientation evinced the potential of the mat as an instructive platform for skin regeneration. The unique peptide motifs of NMSF assisted the augmented recruitment of fibroblast, keratinocytes and endothelial cells leading to accelerated wound healing. Early progression of mature granulation, faster re-epithelialization and angiogenesis in the wounds in in vivo rabbit model forwarded the blended nanofibrous mats of NMSF and PVA ferrying EGF, apt for scarless healing.