Trends in sustainable chitosan-based hydrogel technology for circular biomedical engineering: A review

Eco-friendly materials have emerged in biomedical engineering, driving major advances in chitosan-based hydrogels. These hydrogels offer a promising green alternative to conventional polymers due to their non-toxicity, biodegradability, biocompatibility, environmental friendliness, affordability, and easy accessibility. Known for their remarkable properties such as drug encapsulation, delivery capabilities, biosensing, functional scaffolding, and antimicrobial behavior, chitosan hydrogels are at the forefront of biomedical research. This paper explores the fabrication and modification methods of chitosan hydrogels for diverse applications, highlighting their role in advancing climate-neutral healthcare technologies. It reviews significant scientific advancements and trends chitosan hydrogels focusing on cancer diagnosis, drug delivery, and wound care. Additionally, it addresses current challenges and green synthesis practices that support a circular economy, enhancing biomedical sustainability. By providing an in-depth analysis of the latest evidence on climate-neutral management, this review aims to facilitate informed decision-making and foster the development of sustainable strategies leveraging chitosan hydrogel technology. The insights from this comprehensive examination are pivotal for steering future research and applications in sustainable biomedical solutions.

Adhesivity-tuned bioactive gelatin/gellan hybrid gels drive efficient wound healing

Gelatin-based hydrogels have been widely used for wound healing applications. However, increase in ligand density and reduction in pore size with increasing gelatin concentration may delay wound healing by limiting cell infiltration. In this study, we address this shortcoming by combining gelatin with gellan-which is super hydrophilic and non-adhesive to cells. We show that UV crosslinked hybrid gels composed of methacrylated gelatin (GelMA) and methacrylated gellan gum (mGG), possess considerably larger pores and improved mechanical properties compared to GelMA gels. Reduced spreading and reduced formation of focal adhesions on hybrid gels combined with lower contractility and faster detachment upon trypsin-induced de-adhesion suggests that hybrid gels are less adhesive than GelMA gels. Gradual release of fibroblast growth factor (FGF) and silver nanoparticles (AgNPs) incorporated in hybrid gels not only boosts cell migration, but also confers anti-bacterial activity against gram-positive and gram-negative bacteria at concentrations nontoxic to cells. Full thickness wound healing in Wistar rats revealed increased granulation tissue formation in hybrid gels, fastest epithelialization and highest collagen deposition in rats treated with FGF entrapped hybrid gels. Together, our results demonstrate how adhesive tuning and incorporation of bioactive factors can be synergistically combined for achieving complete wound healing.

A novel multifunctional chitosan-gelatin/carboxymethyl cellulose-alginate bilayer hydrogel containing human placenta extract for accelerating full-thickness wound healing

The replication of skin's dermal and epidermal morphology within a full-thickness wound using a bi-layer hydrogel to cater to their distinct needs is a compelling pursuit. Moreover, human placenta extract (HPE), containing a diverse array of bioactive agents, has proven to be effective in promoting the wound healing process and enhancing epidermal keratinocytes. This study presents a multifunctional bi-layer hydrogel incorporating HPE for accelerating full-thickness wound healing through sustained HPE release, inhibition of bacteria invasion, and promotion of cell proliferation. The upper layer of the scaffold, known as the dressing layer, is composed of carboxymethyl cellulose and sodium alginate, serving as a supportive layer for cell proliferation. The under layer, referred to as the regenerative layer, is composed of chitosan and gelatin, providing an extracellular matrix-like, porous, moist, and antibacterial environment for cell growth. The scaffold was optimized to replicate the morphology of the dermal and epidermal layers, with suitable fibroblast infiltration and a pore size of approximately 283μm. Furthermore, the degradation rate of the samples matched the wound healing rate and persisted throughout this period. The sustained HPE release rate, facilitated by the degradation rate, was optimized to reach ~98% after 28 days, covering the entire healing period. The samples demonstrated robust antibacterial capabilities, with bacterial inhibition zone diameters of and 2.63±0.12cm for S. aureus and E. coli, respectively. The biocompatibility of the samples remained at approximately 68.33±4.5% after 21 days of fibroblast cell culture. The in vivo experiment indicated that the HPE@Bilayer hydrogel promotes the formation of new blood vessels and fibroblasts during the early stages of healing, leading to the appropriate formation of granulation tissue and a wound contraction rate of (79.31±3.1)%. Additionally, it resulted in the formation of a thick epidermal layer (keratinization) that effectively covered all the impaired areas, achieving a wound contraction rate of 95.83±6.3% at the late stage of wound healing. Furthermore, immunohistochemistry staining for CD31 and TGF-β revealed that the HPE@Bilayer group had 22 blood vessels/field and 34%-66% immunoactive cells, respectively, after 14 days of healing. However, by day 21, angiogenesis and TGF-β expression had declined, demonstrating that the wounds had been successfully treated with minimal scarring.

Sodium alginate/Hydroxyapatite/nanocellulose composites: Synthesis and Potentials for bone tissue engineering

Sodium alginate/hydroxyapatite/Nano cellulose (SA/HA/NC) nanocomposite films that possess good biocompatibility for bone tissue engineering are prepared by a simple solution casting. HA is one of the most frequently used bioceramic materials to achieve a high biocompatibility. The bionanocomposite films are analysed by XRD, SEM, EDAX and FTIR studies. XRD confirms the existence of fillers in the polymer. FTIR spectrum shows the different functional modes in the bionanocomposite films. The morphology of fillers and bionanocomposite films are obtained through SEM. The inclusion of NC with different concentrations into the biopolymer film improves the tensile strength. As a result, the loading of 5 wt % of NC and 10 wt% of HA in the SA polymer shows high tensile strength when compared to the pure SA, SA filled with 10 wt% of HA and SA loaded with 10 wt% of HA and inclusion of NC (0.5 and 2.5 wt%). The tensile strength (TS) of bionanocomposite film with 10 wt % of HA is increased by 17%. TS of bionanocomposite film with 0.5 and 2.5 wt% of NC is increased by 177 and 277%, whereas TS of bionanocomposite film loaded 5 wt% of NC is increased by 331%. The swelling, biodegradation and biomineralization tests suggest that this bionanocomposite films are hopeful biomaterials for bone tissue engineering.

Controlled release of protein from gelatin/chitosan hydrogel containing platelet-rich fibrin encapsulated in chitosan nanoparticles for accelerated wound healing in an animal model

The physiological healing process is disrupted in many cases using the current wound healing procedures, resulting in delayed wound healing. Hydrogel wound dressings provide a moist environment to enhance granulation tissue and epithelium formation in the wound area. However, exudate accumulation, bacterial proliferation, and reduced levels of growth factors are difficulties of hydrogel dressings. Here, we loaded platelet-rich fibrin-chitosan (CH-PRF) nanoparticles into the gelatin-chitosan hydrogel (Gel-CH/CH-PRF) by solvent mixing method. Our goal was to evaluate the characteristics of hydrogel dressings, sustained release of proteins from the hydrogel dressing containing PRF, and reduction in the risk of infection by the bacteria in the wound area. The Gel-CH/CH-PRF hydrogel showed excellent swelling behavior, good porosity, proper specific surface area, high absorption of wound exudates, and proper vapor permeability rate (2023 g/m ².day), which provided requisite moisture without dehydration around the wound area. Thermal behavior and the protein release from the hydrogels were investigated using simultaneous thermal analysis and the Bradford test, respectively. Most importantly, an excellent ability to control the release of proteins from the hydrogel dressings was observed. The high antimicrobial activity of hydrogel was confirmed using Gram-positive and Gram-negative bacteria. Due to the presence of chitosan in the hydrogels, the lowest scavenging capacity-50 value (5.82 μgmL^-1) and the highest DPPH radical scavenging activity (83 %) at a concentration 25 μgmL^-1 for Gel-CH/CH-PRF hydrogel were observed. Also, the hydrogels revealed excellent cell viability and proliferation. The wound healing process was studied using an in vivo model of the full-thickness wound. The wound closure was significantly higher on Gel-CH/CH-PRF hydrogel compared to the control group, indicating the highest epidermis thickness, and enhancing the formation of new granulation tissue. Our findings demonstrated that Gel-CH/CH-PRF hydrogel can provide an ideal wound dressing for accelerated wound healing.

Dissolvable wound dressing loaded with silver nanoparticles together with ampicillin and ciprofloxacin

Aim: The current study is focused on the development of water-soluble wound dressings, which are potential dressings for the treatment of burn wounds. Materials & methods: Sodium alginate-based dissolvable wound dressings were prepared and loaded with silver nanoparticles and various antibiotics (ampicillin and ciprofloxacin) followed by characterization and in vitro antibacterial studies. Results & conclusions: The prepared sodium alginate-based dissolvable wound dressing exhibited good porosity, water uptake and moisture content, promising antibacterial activity, high absorption capacity of simulated wound exudates, excellent water vapor transmission rate in the range of 2000 to 5000 g/m² day^-1, sustained drug-release profiles and water solubility. The wound dressings were active against Proteus mirabilis, Staphylococcus aureus, Proteus vulgaris, Escherichia coli and Klebsiella aeruginosa strains of bacteria. The results obtained revealed the wound dressing as potential wound dressings for burn wounds and sensitive skin.

Advances in Fibrin-Based Materials in Wound Repair: A Review

The first bioprocess that occurs in response to wounding is the deterrence of local hemorrhage. This is accomplished by platelet aggregation and initiation of the hemostasis cascade. The resulting blood clot immediately enables the cessation of bleeding and then functions as a provisional matrix for wound healing, which begins a few days after injury. Here, fibrinogen and fibrin fibers are the key players, because they literally serve as scaffolds for tissue regeneration and promote the migration of cells, as well as the ingrowth of tissues. Fibrin is also an important modulator of healing and a host defense system against microbes that effectively maintains incoming leukocytes and acts as reservoir for growth factors. This review presents recent advances in the understanding and applications of fibrin and fibrin-fiber-incorporated biomedical materials applied to wound healing and subsequent tissue repair. It also discusses how fibrin-based materials function through several wound healing stages including physical barrier formation, the entrapment of bacteria, drug and cell delivery, and eventual degradation. Pure fibrin is not mechanically strong and stable enough to act as a singular wound repair material. To alleviate this problem, this paper will demonstrate recent advances in the modification of fibrin with next-generation materials exhibiting enhanced stability and medical efficacy, along with a detailed look at the mechanical properties of fibrin and fibrin-laden materials. Specifically, fibrin-based nanocomposites and their role in wound repair, sustained drug release, cell delivery to wound sites, skin reconstruction, and biomedical applications of drug-loaded fibrin-based materials will be demonstrated and discussed.

Expandable, biodegradable, bioactive quaternized gelatin sponges for rapidly controlling incompressible hemorrhage and promoting wound healing

Designing expandable sponges with biodegradability and effective antibacterial properties are the urgent challenge for incompressible hemorrhage and wound healing. In the present investigation, based on quaternized gelatin (QG) and oxidized dextran (OD), a series of expandable sponges (ODQG) with high-water absorption capacity and robust mechanical properties were prepared. ODQG had good biodegradability in vitro and in vivo, and had inherent antibacterial activity (90% for E. coli and 99.74% for S. aureus). Due to the synergy effect of electrostatic interaction and blood concentration, ODQG could effectively attract and activate red blood cells/platelets and accelerate the coagulation process. Therefore, ODQG showed better hemostatic performance than Kuaikang® gelatin sponges and gauzes in incompressible hemorrhage model. Furthermore, ODQG could regulate inflammatory factor (TNF-α) and cytokines (TGF-β, VEGF), and greatly promote wound healing process. The biodegradable sponges with excellent antibacterial properties might have potential application prospect for incompressible hemostasis and wound healing in the future.

3D Printing Methyl Cellulose Hydrogel Wound Dressings with Parameter Exploration Via Computational Fluid Dynamics Simulation

PURPOSE

To investigate and optimize the use of methyl cellulose in the fabrication of three-dimensional (3D) printed drug-loaded hydrogel wound dressings for the treatment of burns.

METHOD

The effects of incorporating various salts on the properties of methyl cellulose, especially the gelation temperature was investigated for methyl cellulose to undergo gelation at skin temperature (i.e., 31.7°C). The optimized methyl cellulose and salt compositions were then loaded with various drugs beneficial for the treatment of burns. Printability and cumulative release profiles for selected drugs were then obtained, which were then fitted to common release kinetic models. Computational Fluid Dynamics (CFD) simulation was also explored to investigate the relationship between printing parameters and the hydrogel filament produced during extrusion.

RESULTS

The printed hydrogels had moderate dimensional integrity, were found to be stable for up to 2 weeks and demonstrated good swelling properties. In vitro drug release studies of various drugs showed that the hydrogel was able to release various drugs within 6 h and release profiles were fitted to common in vitro drug release models, such as the Korsmeyer Peppas model and the Weibull model. While there were deviations from the actual printing process, CFD simulation was able to predict the shape of the printed structure and showed fair accuracy in determining the mass flow rate and line width of extruded hydrogels.

CONCLUSIONS

Methyl cellulose hydrogels with optimized salt composition demonstrated suitable properties for a wound dressing application, revealing its potential to be used for in situ wound dressing applications.

Fabrication and characterization of scaffolds containing different amounts of allantoin for skin tissue engineering

Using the skin tissue engineering approach is a way to help the body to recover its lost skin in cases that the spontaneous healing process is either impossible or inadequate, such as severe wounds or burns. In the present study, chitosan/gelatin-based scaffolds containing 0.25, 0.5, 0.75, and 1% allantoin were created to improve the wounds' healing process. EDC and NHS were used to cross-link the samples, which were further freeze-dried. Different in-vitro methods were utilized to characterize the specimens, including SEM imaging, PBS absorption and degradation tests, mechanical experiments, allantoin release profile assessment, antibacterial assay, and cell viability and adhesion tests. The results indicated that the scaffolds' average pore sizes were approximately in the range of 390-440 µm, and their PBS uptake amounts were about 1000% to 1250% after being soaked in PBS for 24 h. Around 70% of the specimens were degraded in 6 days, but they were not fully degraded after 21 days. Besides, the samples showed antibacterial activity against S. aureus and E. coli bacteria. In general, the MTT cell viability test indicated that the cells' density increased slightly or remained the same during the experiment. SEM images of cells seeded on the scaffolds indicated appropriate properties of the scaffolds for cell adhesion.

Biocompatibility Study of Electrospun Nanocomposite Membranes Based on Chitosan/Polyvinyl Alcohol/Oxidized Carbon Nano-Onions

In recent decades, the number of patients requiring biocompatible and resistant implants that differ from conventional alternatives dramatically increased. Among the most promising are the nanocomposites of biopolymers and nanomaterials, which pretend to combine the biocompatibility of biopolymers with the resistance of nanomaterials. However, few studies have focused on the in vivo study of the biocompatibility of these materials. The electrospinning process is a technique that produces continuous fibers through the action of an electric field imposed on a polymer solution. However, to date, there are no reports of chitosan (CS) and polyvinyl alcohol (PVA) electrospinning with carbon nano-onions (CNO) for in vivo implantations, which could generate a resistant and biocompatible material. In this work, we describe the synthesis by the electrospinning method of four different nanofibrous membranes of chitosan (CS)/(PVA)/oxidized carbon nano-onions (ox-CNO) and the subdermal implantations after 90 days in Wistar rats. The results of the morphology studies demonstrated that the electrospun nanofibers were continuous with narrow diameters (between 102.1 nm ± 12.9 nm and 147.8 nm ± 29.4 nm). The CS amount added was critical for the diameters used and the successful electrospinning procedure, while the ox-CNO amount did not affect the process. The crystallinity index was increased with the ox-CNO introduction (from 0.85% to 12.5%), demonstrating the reinforcing effect of the nanomaterial. Thermal degradation analysis also exhibited reinforcement effects according to the DSC and TGA analysis, with the higher ox-CNO content. The biocompatibility of the nanofibers was comparable with the porcine collagen, as evidenced by the subdermal implantations in biological models. In summary, all the nanofibers were reabsorbed without a severe immune response, indicating the usefulness of the electrospun nanocomposites in biomedical applications.

Hybrid Gelatin Hydrogels in Nanomedicine Applications

Gelatin based hydrogels are often incorporated with supporting materials such as chitosan, poly(vinyl alcohol), alginate, carbon nanotubes, and hyaluronic acid. These hybrid materials are specifically of interest in diversified nanomedicine fields as they exhibit unique physicochemical properties, antimicrobial activity, biodegradability, and biocompatibility. The applications include drug delivery, wound healing, cell culture, and tissue engineering. This paper reviews the various up-to-date methods to fabricate gelatin-based hydrogels, including UV photo-cross-linking, electrospinning, and 3D bioprinting. This paper also includes physical, chemical, mechanical, and biocompatibility characterization studies of several hybrid gelatin hydrogels and discusses their relevance in nanomedicine based applications. Challenges associated with the fabrication of hybrid materials for nanotechnology implementation, specifically in nanomedicine development, are critically discussed, and some future recommendations are provided.

Development and in vivo evaluation of chitosan-gel containing Mitracarpus frigidus methanolic extract for vulvovaginal candidiasis treatment

Vulvovaginal candidiasis (VVC) is characterized by inflammatory changes in the vaginal mucosa caused by abnormal colonization of Candida species. Traditional topical therapies using reference antifungal drugs usually present several issues and limitations for VVC treatment. Thus, the interest in new vaginal formulations, mainly those based on compounds from natural origin, has been growing over the last years. Methanolic extract from the plant species Mitracarpus frigidus (Willd. Ex Reem Schult.) K. Schum (MFM) has presented potential antifungal activity against C. albicans vaginal infection. Here, we aimed to develop and characterize a gynecological gel formulation based on chitosan containing MFM and to evaluate its anti-C. albicans effectiveness in the treatment of VVC. First, MFM was incorporated into a gel formulation based on chitosan in three final concentrations: 2.5 %, 5.0 %, and 10.0 %. Next, these gel formulations were subjected to stationary and oscillatory rheological tests. Finally, the gel was tested in an experimental VVC model. The rheological tests indicated pseudoplastic fluids, becoming more viscous and elastic with the increase of the extract concentration, indicating intermolecular interactions. Our in vivo analyses demonstrated a great reduction of vulvovaginal fungal burden and infection accompanied with the reduction of mucosal inflammation after MFM chitosan-gel treatment. The present findings open perspectives for the further use of the MFM-chitosan-gel formulation as a therapeutic alternative for VVC treatment.

Effect of varied hair protein fractions on the gel properties of keratin/chitosan hydrogels for the use in tissue engineering

Keratin/chitosan composite is a readily available source for a hybrid hydrogel in tissue engineering. While human hair keratins could provide biological functions, chitosan could further enhance the mechanical strength of the hybrid hydrogels. However, hair keratin is a group of natural proteins, and the uncontrolled hair protein contents in a hydrogel may lead to the batch-to-batch inconsistent gel properties. The purpose of this study was to investigate the role of hair protein composition, including the keratin-associated proteins (KAPs, 6-30 kDa) and keratin intermediate filaments (KIFs, 45-60 kDa) on gel characteristics of the keratin/chitosan hydrogel. The various compressive and tensile modulus of the gel was observed based on the selection of different protein fractions as the significant gel components. These results thus suggest a straightforward method of preparing hair keratin/chitosan hydrogel with much more controllable gel properties by merely modulating the KAPs/KIFs ratios in a gel.

Recent Advances in Hemostasis at the Nanoscale

Rapid and effective hemostatic materials have received wide attention not only in the battlefield but also in hospitals and clinics. Traditional hemostasis relies on materials with little designability which has many limitations. Nanohemostasis has been proposed since the use of peptides in hemostasis. Nanomaterials exhibit excellent adhesion, versatility, and designability compared to traditional materials, laying a good foundation for future hemostatic materials. This review first summarizes current hemostatic methods and materials, and then introduces several cutting-edge designs and applications of nanohemostatic materials such as polypeptide assembly, electrospinning of cyanoacrylate, and nanochitosan. Particularly, their advantages and working mechanisms are introduced. Finally, the challenges and prospects of nanohemostasis are discussed.

The Effect of Matrix Stiffness of Biomimetic Gelatin Nanofibrous Scaffolds on Human Cardiac Pericyte Behavior

Congenital heart disease (CHD) is the most common and deadly congenital anomaly, accounting for up to 7.5% of all infant deaths. Survival in children born with CHD has improved dramatically over the past several decades (this positive trend being counterbalanced by the fact that more patients develop heart failure). Seminal data indicate an alteration of the extracellular matrix occurs with time in these hearts due to diffuse and abundant interstitial fibrosis. This results in an escalation in the stiffness of the local myocardial microenvironment. However, the influence of matrix stiffness in regulating the function of resident human stromal cells has not been reported. The objective of this study was to determine the impact of scaffold stiffness on the antigenic and functional profile of cardiac pericytes (CPs) isolated from patients with CHD. To this end, we have first manufactured gelatin nanofibrous scaffolds with varying degrees of stiffness using an in situ cross-linking electrospinning technique in a pure water solvent system. We assessed Young's modulus and performed a comprehensive physicochemical characterization of the scaffolds employing scanning electron microscopy and Fourier transform infrared spectroscopy. We next evaluated the changes induced by a different scaffold stiffness on CP morphology, antigenic profile, viability, proliferation, angiocrine activity, and induced differentiation. Results indicate that soft matrixes with a fiber diameter of ∼400 nm increase CP proliferation, secretion of angiopoietin 2, and F-actin stress fiber formation, without affecting the antigenic profile, viability, or differentiation. These data indicate for the first time that human CPs can be functionally influenced by slight changes in matrix stiffness. The study elucidates the importance of mechanical/morphological cues in modulating the behavior of stromal cells isolated from patients with CHD.

Comparative long-term study between two dermal regeneration templates for the reconstruction of burn scar contractures in humans: Clinical and histological results

The advent of dermal regeneration templates has fostered major advances in the treatment of acute burns and their sequelae, in the last three decades. Both data on morphological aspects of the newly-formed tissue, and clinical trials comparing different templates, are few. The goal of this study was to prospectively analyze the outcome of randomized patients treated with two of the existing templates, followed by thin skin autograft. They are both 2 mm-thick bovine collagen templates (Matriderm® and Integra®), the latter includes a superficial silicone layer. Surgery was performed on patients with impaired mobility resulting from burn sequelae (n = 12 per template) in a two-step procedure. Negative pressure therapy was applied after surgery; patients were monitored for 12 months. No intra or postoperative complications were observed. Data on scar skin quality (Vancouver scar scale), rate of mobility recovery, and graft contraction were recorded; as well as morphological analyses at light microscopical level. Improvement in mobility and skin quality were demonstrated along with graft contraction, in all patients. The double layer template showed the best performance in retraction rate, skin quality and mobility recovery. The subepidermal newly-formed connective tissue showed no histoarchitectural differences between the templates. The double layer template was not absorbed up to 12 months after placement.

Crosstalk between chitosan and cell signaling pathways

The field of tissue engineering (TE) experiences its most exciting time in the current decade. Recent progresses in TE have made it able to translate into clinical applications. To regenerate damaged tissues, TE uses biomaterial scaffolds to prepare a suitable backbone for tissue regeneration. It is well proven that the cell-biomaterial crosstalk impacts tremendously on cell biological activities such as differentiation, proliferation, migration, and others. Clarification of exact biological effects and mechanisms of a certain material on various cell types promises to have a profound impact on clinical applications of TE. Chitosan (CS) is one of the most commonly used biomaterials with many promising characteristics such as biocompatibility, antibacterial activity, biodegradability, and others. In this review, we discuss crosstalk between CS and various cell types to provide a roadmap for more effective applications of this polymer for future uses in tissue engineering and regenerative medicine.

Recent Advances in Biomaterials Science and Engineering Research in India: A Minireview

Biomedical research in health innovation and product development encompasses convergent technologies that primarily integrate biomaterials science and engineering at its core. Particularly, research in this area is instrumental for the implementation of biomedical devices (BMDs) that offer innovative solutions to help maintain and improve quality of life of patients worldwide. Despite achieving extraordinary success, implantable BMDs are still confronted with complex engineering and biological challenges that need to addressed for augmenting device performance and prolonging lifetime in vivo. Biofabrication of tissue constructs, designing novel biomaterials and employing rational biomaterial design approaches, surface engineering of implants, point of care diagnostics and micro/nano-based biosensors, smart drug delivery systems, and noninvasive imaging methodologies are among strategies exploited for improving clinical performance of implantable BMDs. In India, advances in biomedical technologies have dramatically advanced health care over the last few decades and the country is well-positioned to identify opportunities and translate emerging solutions. In this article, we attempt to capture the recent advances in biomedical research and development progressing across the country and highlight the significant research work accomplished in the areas of biomaterials science and engineering.

A review on recent advances in chitosan based composite for hemostatic dressings

High mortality rate in potentially survivable casualties due to severe hemorrhage is a major challenge in today's battlefield because technological advancements have revolutionized the combat tactics and complicated the type and severity associated with wound grades. Quality of pre-hospital care prior to patient evacuation is crucial in determining the survival rate in injured patients. To deal with this challenge, considerable improvements in the hemostatic dressings have been introduced and pre-hospital care has been upgraded in many tactical combat casually care guidelines. Combat Gauze has been widely used bandage which is now been replaced by different chitosan based hemostatic dressings. It not only exhibits anti-bacterial activity but also induces hemostasis via direct interaction with erythrocytes and platelets. Its hemostasis mechanism is not dependent on host coagulation pathway which makes it an ideal dressing to stop bleeding in coagulopathic patients. Different generations of chitosan bandages have been developed to overcome the limitations of previous ones. This review provides performance analysis of chitosan bandage generations and discusses the progress made in its fabrication methods during the recent years.

Fabrication of asymmetric nanostarch reinforced Chitosan/PVP membrane and its evaluation as an antibacterial patch for in vivo wound healing application

Starch is an abundant, relatively inexpensive and ecofriendly materials which can be easily convert into nanoparticle and also as filler for the preparation of bionanocomposite for wound dressing application. Symmetric and asymmetric Chitosan(C)/PVP(P) films containing porous structure supported with nanostarch (NS) were prepared by salt leaching method for wound dressing application. Symmetric Chitosan/PVP/Nanostarch (CPNS) film with 1% and 3% wt nanostarch was prepared without coating of stearic acid whereas asymmetric Chitosan/PVP/Nanostarch-Stearic acid (CPNS-S) film was prepared by coating of stearic acid. The stearic acid coated surface possesses hydrophobic water repellent, microporous, bacterial anti adhesion property and the stearic acid uncoated hydrophilic surface shows superior antibacterial and noncytotoxicity property with highly porous character. All the symmetric and asymmetric films exhibit almost same mechanical, barrier, swelling and hemolytic property reveals that the stearic acid does not affect the physical and hemolytic property whereas the concentration of nanostarch greatly influence the above property. The reinforcement of nanostarch with chitosan and PVP was proved by TEM and SEM analysis. The CPNS1%-S film shows excellent S. aureus anti adhesion property. Furthermore, the in vivo excision-type wound healing proved that the CPNS1%-S film enhanced the healing effect and increased re-epithelialization and collagen formation.

Biomaterials for Skin Substitutes

Patients with extensive burns rely on the use of tissue engineered skin due to a lack of sufficient donor tissue, but it is a challenge to identify reliable and economical scaffold materials and donor cell sources for the generation of a functional skin substitute. The current review attempts to evaluate the performance of the wide range of biomaterials available for generating skin substitutes, including both natural biopolymers and synthetic polymers, in terms of tissue response and potential for use in the operating room. Natural biopolymers display an improved cell response, while synthetic polymers provide better control over chemical composition and mechanical properties. It is suggested that not one material meets all the requirements for a skin substitute. Rather, a composite scaffold fabricated from both natural and synthetic biomaterials may allow for the generation of skin substitutes that meet all clinical requirements including a tailored wound size and type, the degree of burn, the patient age, and the available preparation technique. This review aims to be a valuable directory for researchers in the field to find the optimal material or combination of materials based on their specific application.

Layer-by-Layer Thin Films for Co-Delivery of TGF-β siRNA and Epidermal Growth Factor to Improve Excisional Wound Healing

The major challenge with treatment of dermal wounds is accelerating healing process, while preventing the scar formation. Herein, we have fabricated layer-by-layer (LbL) polyelectrolyte multilayer films containing epidermal growth factor (EGF) and TGF-β siRNA to improve excisional wound healing and decrease scar formation. The chitosan and sodium alginate LbL thin films showed 13.0 MPa tensile strength and 2.22 N/cm² skin adhesion strength. The LbL thin films were found to be cytocompatible, where A431 epidermal keratinocytes adhered to the film and showed 86.2 ± 0.8% cell growth compared with cells cultured in the absence of LbL thin film. In contrast, LbL thin film did not promote the Escherichia coli and Staphylococcus aureus bacterial colony formation. In a C57BL/6 mouse excisional wound model, application of LbL thin films containing TGF-β siRNA significantly (p < 0.05) reduced the TGF-β protein expression and collagen production. The LbL thin films containing EGF showed improved wound contraction (<9 days post excision). The co-delivery of TGF-β siRNA and EGF using LbL thin films resulted in accelerated wound healing and decreased collagen deposition. Furthermore, the LbL thin films with TGF-β siRNA and EGF combination showed greater reepithelialization. Taken together, we have successfully demonstrated the co-delivery of TGF-β siRNA and EGF peptide using LbL thin films to promote wound healing and decrease scar formation.

Chitosan Oligosaccharide Reduces Propofol Requirements and Propofol-Related Side Effects

Propofol is one of the main sedatives but its negative side effects limit its clinical application. Chitosan oligosaccharide (COS), a kind of natural product with anti-pain and anti-inflammatory activities, may be a potential adjuvant to propofol use. A total of 94 patients receiving surgeries were evenly and randomly assigned to two groups: 10 mg/kg COS oral administration and/or placebo oral administration before being injected with propofol. The target-controlled infusion of propofol was adjusted to maintain the values of the bispectral index at 50. All patients’ pain was evaluated on a four-point scale and side effects were investigated. To explore the molecular mechanism for the functions of COS in propofol use, a mouse pain model was established. The activities of Nav1.7 were analyzed in dorsal root ganglia (DRG) cells. The results showed that the patients receiving COS pretreatment were likely to require less propofol than the patients pretreated with placebo for maintaining an anesthetic situation (p < 0.05). The degrees of injection pain were lower in a COS-pretreated group than in a propofol-pretreated group. The side effects were also more reduced in a COS-treated group than in a placebo-pretreated group. COS reduced the activity of Nav1.7 and its inhibitory function was lost when Nav1.7 was silenced (p > 0.05). COS improved propofol performance by affecting Nav1.7 activity. Thus, COS is a potential adjuvant to propofol use in surgical anesthesia.

Polyurethane foam containing rhEGF as a dressing material for healing diabetic wounds: Synthesis, characterization, in vitro and in vivo studies

Diabetic wounds are a major health issue associated with diabetes mellitus. To surmount this issue, we developed polyurethane foams (PUFs) incorporating varying amounts of recombinant human epidermal growth factor (rhEGF) (rhEGF-PUFs) as a wound dressing for diabetic wounds. From electron microscopy images, it was found that the pore size of the rhEGF-PUFs surface (the wound contact layer) was less than 100μm, regardless of rhEGF content. The release of rhEGF from the PUFs was evaluated using an enzyme-linked immunosorbent assay. The result showed that the release of rhEGF was time and concentration dependent, i.e., the amount of released rhEGF significantly increased as the immersion time and the rhEGF content of the PUFs increased. In vitro cytotoxicity testing showed that rhEGF-PUFs increased the viability of HaCaT human keratinocytes and CCD986-sk human fibroblasts, which indicated that the incorporated rhEGF maintained its biological activity. In an in vitro scratch wound healing assay, the wound closure rate was faster in CCD986-sk human fibroblasts than in HaCaT human keratinocytes. Finally, the rhEGF-PUFs were evaluated as an in vivo treatment in a full-thickness wound model in diabetized Sprague-Dawley rats. The result indicated that compared with PUFs, rhEGF-PUFs accelerated wound healing by promoting wound contraction, re-epithelialization, collagen deposition and the formation of a skin appendage. These findings demonstrate that rhEGF-PUFs are a promising dressing for diabetic wounds.

Bioengineered mussel glue incorporated with a cell recognition motif as an osteostimulating bone adhesive for titanium implants

An engineered mussel glue MAP-RGD can be successfully used as a novel functional osteostimulating bone adhesive for titanium implants through improved osteoblastic cell behaviors, blood responses, and eventually enhanced bone regeneration.