Chitosan based-asymmetric membranes for wound healing: A review

Skin wounds, the healing process, and hydrogel-based wound dressings: a short review

Skin wounds are damage to the epithelial layer and the integrity of living tissue. The healing mechanism is dynamic and complex, and often treatments with wound dressings help in tissue regeneration, reducing the risk of infections. Polymeric hydrogels become good candidates for wet curing process. These materials prevent dehydration of the tissue and avoid discomfort to the patient when changing the dressing. In this short review, we demonstrate the importance of the healing process, the types of skin wounds, and the hydrogels that are potentially attractive as wound dressings.

Chitosan/Hyaluronic acid/Alginate and an assorted polymers loaded with honey, plant, and marine compounds for progressive wound healing-Know-how

Biomaterials are being extensively used in regenerative medicine including tissue engineering applications, as these enhance tissue development, repair, and help in the process of angiogenesis. Wound healing is a crucial biological process of regeneration of ruptured tissue after getting injury to the skin and other soft tissue in humans and animals. Besides, the accumulation of microbial biofilms around the wound surface can increase the risk and physically obstruct the wound healing activity, and may even lead to amputation. Hence, in both acute and chronic wounds, prominent biomaterials are required for wound healing along with antimicrobial agents. This review comprehensively addresses the antimicrobial and wound healing effects of chitosan, chitin, cellulose acetate, hyaluronic acid, pullulan, bacterial cellulose, fibrin, alginate, etc. based wound dressing biomaterials fabricated with natural resources such as honey, plant bioactive compounds, and marine-based polymers. Due to their excellent biocompatibility and biodegradability, bioactive compounds derived from honey, plants, and marine resources are commonly used in biomedical and tissue engineering applications. Different types of polymer-based biomaterials including hydrogel, film, scaffold, nanofiber, and sponge dressings fabricated with bioactive agents including honey, curcumin, tannin, quercetin, andrographolide, gelatin, carrageenan, etc., can exhibit significant wound healing process in, diabetic wounds, diabetic ulcers, and burns, and help in cartilage repair along with good biocompatibility and antimicrobial effects. Among the reviewed biomaterials, carbohydrate polymers such as chitosan-based biomaterials are prominent and widely used for wound healing applications followed by hyaluronic acid and alginate-based biomaterials loaded with honey, plant, and marine compounds. This review first provides an overview of the vast natural resources used to formulate different biomaterials for the treatment of antimicrobial, acute, and chronic wound healing processes.

Electrospun Nanofibers/Nanofibrous Scaffolds Loaded with Silver Nanoparticles as Effective Antibacterial Wound Dressing Materials

The treatment of wounds is expensive and challenging. Most of the available wound dressings are not effective and suffer from limitations such as poor antimicrobial activity, toxicity, inability to provide suitable moisture to the wound and poor mechanical performance. The use of inappropriate wound dressings can result in a delayed wound healing process. Nanosize range scaffolds have triggered great attention because of their attractive properties, which include their capability to deliver bioactive agents, high surface area, improved mechanical properties, mimic the extracellular matrix (ECM), and high porosity. Nanofibrous materials can be further encapsulated/loaded with metal-based nanoparticles to enhance their therapeutic outcomes in wound healing applications. The widely studied metal-based nanoparticles, silver nanoparticles exhibit good properties such as outstanding antibacterial activity, display antioxidant, and anti-inflammatory properties, support cell growth, making it an essential bioactive agent in wound dressings. This review article reports the biological (in vivo and in vitro) and mechanical outcomes of nanofibrous scaffolds loaded with silver nanoparticles on wound healing.

Hyaluronic Acid-Based Scaffolds as Potential Bioactive Wound Dressings

The negative factors that result in delayed and prolonged wound healing process include microbial pathogens, excess wound exudates, underlying conditions, smoking, obesity, etc. Most of the currently used wound dressings demonstrate an inadequate capacity to treat wounds resulting from the factors mentioned above. The commonly used wound dressings include hydrogels, films, hydrocolloids, foams, fibers, sponges, dermal patches, bandages, etc. These wound dressings can be loaded with various types of bioactive agents (e.g., antibiotics, nanoparticles, anti-inflammatory drugs, etc.) to improve their therapeutic outcomes. Biopolymers offer interesting properties suitable for the design of wound dressings. This review article will be based on hyaluronic-acid-based scaffolds loaded with therapeutic agents for the treatment of wounds.

Polysaccharide Matrices for the Encapsulation of Tetrahydrocurcumin-Potential Application as Biopesticide against Fusarium graminearum

Cereals are subject to contamination by pathogenic fungi, which damage grains and threaten public health with their mycotoxins. Fusarium graminearum and its mycotoxins, trichothecenes B (TCTBs), are especially targeted in this study. Recently, the increased public and political awareness concerning environmental issues tends to limit the use of traditional fungicides against these pathogens in favor of eco-friendlier alternatives. This study focuses on the development of biofungicides based on the encapsulation of a curcumin derivative, tetrahydrocurcumin (THC), in polysaccharide matrices. Starch octenylsuccinate (OSA-starch) and chitosan have been chosen since they are generally recognized as safe. THC has been successfully trapped into particles obtained through a spray-drying or freeze-drying processes. The particles present different properties, as revealed by visual observations and scanning electron microscopy. They are also different in terms of the amount and the release of encapsulated THC. Although freeze-dried OSA-starch has better trapped THC, it seems less able to protect the phenolic compound than spray-dried particles. Chitosan particles, both spray-dried and lyophilized, have shown promising antifungal properties. The IC₅₀ of THC-loaded spray-dried chitosan particles is as low as 0.6 ± 0.3 g/L. These particles have also significantly decreased the accumulation of TCTBs by 39%.

Nano- and Micro-Porous Chitosan Membranes for Human Epidermal Stratification and Differentiation

The creation of partial or complete human epidermis represents a critical aspect and the major challenge of skin tissue engineering. This work was aimed at investigating the effect of nano- and micro-structured CHT membranes on human keratinocyte stratification and differentiation. To this end, nanoporous and microporous membranes of chitosan (CHT) were prepared by phase inversion technique tailoring the operational parameters in order to obtain nano- and micro-structured flat membranes with specific surface properties. Microporous structures with different mean pore diameters were created by adding and dissolving, in the polymeric solution, polyethylene glycol (PEG Mw 10,000 Da) as porogen, with a different CHT/PEG ratio. The developed membranes were characterized and assessed for epidermal construction by culturing human keratinocytes on them for up to 21 days. The overall results demonstrated that the membrane surface properties strongly affect the stratification and terminal differentiation of human keratinocytes. In particular, human keratinocytes adhered on nanoporous CHT membranes, developing the structure of the corneum epidermal top layer, characterized by low thickness and low cell proliferation. On the microporous CHT membrane, keratinocytes formed an epidermal basal lamina, with high proliferating cells that stratified and differentiated over time, migrating along the z axis and forming a multilayered epidermis. This strategy represents an attractive tissue engineering approach for the creation of specific human epidermal strata for testing the effects and toxicity of drugs, cosmetics and pollutants.

Antimicrobial and Wound Healing Properties of FeO Fabricated Chitosan/PVA Nanocomposite Sponge

Diabetic and anemia-associated diabetic wounds increase the considerable morbidity and mortality in people, as reported by clinical studies. However, no anemia-associated diabetic wound dressing materials have been developed until now. Hence, this study aimed to develop a nanocomposite scaffold composed of chitosan (CS), poly (vinyl alcohol) (PVA), and phytogenic iron oxide nanoparticles (FeO NPs), for accelerated anemia-associated diabetic wound healing. The aqueous leaves extract of Pinus densiflora (PD) was utilized for the synthesis of iron oxide nanoparticles (FeO NPs). TEM and elemental analysis confirmed smaller size PD-FeO NPs (<50 nm) synthesis with the combination of iron and oxide. In addition, in vitro biological studies displayed the moderate antioxidant, antidiabetic activities, and considerable antibacterial activity of PD-FeO NPs. Further, the different concentrations of PD-FeO NPs (0.01, 0.03, and 0.05%) incorporated CS/PVA nanocomposites sponges were developed by the freeze-drying method. The porous structured morphology and the presence of PD-FeO NPs were observed under FE-SEM. Among nanocomposite sponges, PD-FeO NPs (0.01%) incorporated CS/PVA sponges were further chosen for the in vitro wound-healing assay, based on the porous and water sorption nature. Furthermore, the in vitro wound-healing assay revealed that PD-FeO NPs (0.01%) incorporated CS/PVA has significantly increased the cell proliferation in HEK293 cells. In conclusion, the CS/PVA-PD-FeO NPs (0.01%) sponge would be recommended for diabetic wound dressing after a detailed in vivo evaluation.

Polysaccharide-Based Materials Created by Physical Processes: From Preparation to Biomedical Applications

Polysaccharide-based materials created by physical processes have received considerable attention for biomedical applications. These structures are often made by associating charged polyelectrolytes in aqueous solutions, avoiding toxic chemistries (crosslinking agents). We review the principal polysaccharides (glycosaminoglycans, marine polysaccharides, and derivatives) containing ionizable groups in their structures and cellulose (neutral polysaccharide). Physical materials with high stability in aqueous media can be developed depending on the selected strategy. We review strategies, including coacervation, ionotropic gelation, electrospinning, layer-by-layer coating, gelation of polymer blends, solvent evaporation, and freezing-thawing methods, that create polysaccharide-based assemblies via in situ (one-step) methods for biomedical applications. We focus on materials used for growth factor (GFs) delivery, scaffolds, antimicrobial coatings, and wound dressings.

Asymmetric Wettable, Waterproof, and Breathable Nanofibrous Membranes for Wound Dressings

Despite the progression in wound treatment, the development of wound dressings with considerable skin regeneration capability and improved patient comfort still faces huge challenges. In this study, a type of asymmetric wettable gradient nanofibrous membrane, which is composed of a hydrophobic polyvinyl butyral (PVB)-polydimethylsiloxane (PDMS) upper layer, a PVB-PDMS/gelatin middle layer, and a hydrophilic gelatin lower layer, has been fabricated. The PVB-PDMS upper layer gave dramatically elevated water contact angles from 71.27° to 125.45° as compared with the gelatin membrane, indicating an asymmetric wettability. The composite membrane exhibited outstanding waterproof capability with a hydrostatic pressure of 58.21 kPa, excellent breathability with a water vapor transmission rate of 8.80 kg m^-2 d^-1, improved stretchability and tear resistance, and dramatic improvement in mesenchymal stem cell recruitment with the immobilization of stromal-cell-derived factor-1α for accelerating skin regeneration. The development of asymmetric wettable nanofibrous membranes offers insight into wound-dressing design.

Dual loading of Nigella sativa oil-atorvastatin in chitosan-carboxymethyl cellulose nanogel as a transdermal delivery system

Both Nigella sativa oil and atorvastatin possess anti-inflammatory, immunomodulatory, antioxidant, and antibacterial properties that benefit wound healing. In this work, chitosan-carboxymethyl cellulose was loaded on N. sativa oil to synthesize oil nanogel (ONG) which was later used to load with atorvastatin to obtain atorvastatin-oil nanogel (ATONG). Evaluation of the particle size of ONG and ATONG proved the average of 172 and 193 nm, and their surface charges were found to be 32.2 and 34.7 mV, respectively. Transmission electron microscopy of the sample showed that the particles had homogeneous size distributions with spherical structures. Moreover, drug loading efficiency, drug release, and stability of ATONG were investigated, and their results confirmed the appropriate loading and release of atorvastatin. Cytotoxicity evaluation demonstrated that ATONG can safely release atorvastatin intracellularly in fibroblasts. Results from in vitro skin permeation of ONG and ATONG also revealed that the nanogels (NGs) has proper flux through the skin layers. The in vitro wound closure assay for ATONG verified the proliferation and migration capabilities of fibroblasts, confirming the positive effect on wound-healing applications. In scratch model of fibroblasts, the treatment with ATONG resulted in an increase in the expression of the FGF2, TGF-β1, and VEGF genes involved in fibroblast proliferation and migration aimed at wound healing (p < .001). ATONG, also demonstrated bactericidal effects against Staphylococcus, S. aureus, and S. epidermidis species. Based on the results, ONG and ATONG exhibited great potential to be used as a transdermal drug carrier and skin wound healing NG, respectively.

Biosynthesis and characterization of deuterated chitosan in filamentous fungus and yeast

Deuterated chitosan was produced from the filamentous fungus Rhizopus oryzae, cultivated with deuterated glucose in H₂O medium, without the need for conventional chemical deacetylation. After extraction and purification, the chemical composition and structure were determined by Fourier-transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR), and small-angle neutron scattering (SANS). ¹³C NMR experiments provided additional information about the position of the deuterons in the glucoseamine backbone. The NMR spectra indicated that the deuterium incorporation at the non-exchangeable hydrogen positions of the aminoglucopyranosyl ring in the C3 - C5 positions was at least 60-80 %. However, the C2 position was deuterated at a much lower level (6%). Also, SANS showed that the structure of deuterated chitosan was very similar compared to the non-deuterated counterpart. The most abundant radii of the protiated and deuterated chitosan fibers were 54 Å and 60 Å, respectively, but there is a broader distribution of fiber radii in the protiated chitosan sample. The highly deuterated, soluble fungal chitosan described here can be used as a model material for studying chitosan-enzyme complexes for future neutron scattering studies. Because the physical behavior of non-deuterated fungal chitosan mimicked that of shrimp shell chitosan, the methods presented here represent a new approach to producing a high quality deuterated non-animal-derived aminopolysaccharide for studying the structure-function association of biocomposite materials in drug delivery, tissue engineering and other bioactive chitosan-based composites.

Chitosan/PCL nanoparticles can improve anti-neoplastic activity of 5-fluorouracil in head and neck cancer through autophagy activation

Head and neck squamous cell carcinoma (HNSCC), a prevalent cancer worldwide, has a high incidence of loco-regional dissemination, frequent recurrence, and lower 5-year survival rates. Current gold standard treatments for advanced HNSCC rely primarily on radiotherapy and chemotherapy but with limited efficacy and significant side effects. In this study, we characterized a novel 5-fluorouracil (5-FU) carrier composed of chitosan solution (CS) and polycaprolactone (PCL) microparticles (MPs) in HNSCC preclinical models. The designed MPs were evaluated for their size, morphology, drug entrapment efficiency (EE%) and in vitro drug release profile. The anti-cancer activity of 5-FU-loaded particles was assessed in HNSCC human cell lines (CAL27 and HSC3) and in a preclinical mouse model (AT84) utilizing cell proliferation and survival, cell motility, and autophagy endpoints. The results demonstrated a 38.57 % in 5-FU entrapment efficiency associated with reduced 5-FU in vitro release up to 96 h post-exposure. Furthermore, CS-decorated PCL MPs were able to promote a significant inhibition of cancer cell proliferation based on the metabolic and colony formation assays, in comparison to controls. In contrast, CS-decorated PCL MPs did not influence the pharmacological efficacy of 5-FU to inhibit in vitro cancer cell migration. Last, cell protein analysis revealed a significant increase of autophagy and cell death evaluated by LC3-II expression and PARP1 cleavage, respectively. In summary, these results support the potential utility of CS-decorated PCL MPs as an effective 5-FU-delivery carrier to improve HNSCC therapeutic management.

Recent advances on polymeric hydrogels as wound dressings

Severe hemorrhage is a leading cause of high mortality in critical situations like disaster, accidents, and warfare. The resulting wounds could induce severe physical and psychological trauma to patients and also bring an immense socio-economic burden. Hence, rapid hemostasis and wound healing techniques have become critical initiatives for life-saving treatment. Although traditional methods relying on bandages and gauzes are effective in controlling hemorrhage, they suffer from several limitations: nonbiodegradability, being susceptible to infection, being unsuitable for the irregular wound, secondary tissue damage, and being almost ineffective for wound healing. Owing to the merits of high porosity, good biocompatibility, tunable physicochemical properties, and being beneficial for wound healing, hydrogels with excellent performance have drawn intensive attention and numerous novel effective hydrogel dressings have been widely developed. In this Review, after introducing some commonly used strategies for the synthesis of hydrogels, the most recent progress on polymer-based hydrogels as wound dressings is discussed. Particularly, their hemostasis, antibacterial, and biodegradation properties are introduced. Finally, challenges and future perspectives about the development of hydrogels for wound dressings are outlined.

An asymmetric electrospun membrane for the controlled release of ciprofloxacin and FGF-2: Evaluation of antimicrobial and chemoattractant properties

Here, an asymmetric double-layer membrane has been designed and fabricated by electrospinning as a tool for a potential wound healing application. A hydrophobic layer has been produced by using a polyurethane-polycaprolactone (PU-PCL) copolymer and loaded with the antibacterial ciprofloxacin whereas an ion responsive hydrophilic layer has been produced by using an octyl derivative of gellan gum (GG-C₈) and polyvinyl alcohol (PVA) and loaded with the growth factor FGF-2. This study investigated how the properties of this asymmetric membrane loaded with actives, were influenced by the ionotropic crosslinking of the hydrophilic layer. In particular, the treatment in DPBS and the crosslinking in CaCl₂ 0.1 or 1 M of the hydrophilic layer affected the release profile of the bioactive molecules allowing to modulate both the antimicrobial effect, as assayed by logarithmic reduction of the Staphylococcus aureus viable count, and the chemoattractant properties on NIH 3 T3 cell line, as assayed by scratch test and cell chemoattraction assay.

Semi-interpenetrating chitosan/ionic liquid polymer networks as electro-responsive biomaterials for potential wound dressings and iontophoretic applications

In this work, electro-responsive chitosan/ionic liquid-based hydrogels were synthetized for the first time, envisaging the development of iontophoretic biomaterials for the controlled release/permeation of charged biomolecules. The main goal was to enhance and tune the physicochemical, mechanical, electro-responsive, and haemostatic properties of chitosan-based biomaterials to obtain multi-stimuli responsive (responsive to electrical current, ionic strength, and pH) and mechanically stable hydrogels. To accomplish this objective, polycationic semi-interpenetrating copolymer networks (semi-IPN) were prepared by combining chitosan (CS) and ionic liquid-based polymers and copolymers, namely poly(1-butyl-3-vinylimidazolium chloride) (poly(BVImCl)) and poly(2-hydroxymethyl methacrylate-co-1-butyl-3-vinylimidazolium chloride) (poly(HEMA-co-BVImCl)). Results show that prepared semi-IPNs presented high mechanical stability and were positively charged over a broad pH range, including basic pH. Semi-IPNs also presented faster permeation and release rates of lidocaine hydrochloride (LH), under external electrical stimulus (0.56 mA/cm²) in aqueous media at 32 °C. The kinetic release constants and the LH diffusion coefficients measured under electrical stimulus were ~1.5 and > 2.7 times higher for those measured for passive release. Finally, both semi-IPNs were non-haemolytic (haemolytic index ≤0.2%) and showed strong haemostatic activity (blood clotting index of ~12 ± 1%). Altogether, these results show that the prepared polycationic semi-IPN hydrogels presented advantageous mechanical, responsive and biological properties that enable them to be potentially employed for the design of new, safer, and advanced stimuli-responsive biomaterials for several biomedical applications such as haemostatic and wound healing dressings and iontophoretic patches.

Ag@MOF-loaded chitosan nanoparticle and polyvinyl alcohol/sodium alginate/chitosan bilayer dressing for wound healing applications

In this paper, Ag-Metal-organic framework loaded chitosan nanoparticles (0.1%Ag@MOF/1.5%CSNPs) and polyvinyl alcohol/sodium alginate/chitosan (PACS) were used as the upper and lower layers to successfully prepare a bilayer composite dressing for wound healing. The performance of bilayer dressing was evaluated. The lower layer (PACS) had uniform pore size distribution, good water retention, swelling, water vapor permeability, and biocompatibility while PACS had almost no antibacterial activity. The upper layer (Ag@MOF/CSNPs) possessed excellent antibacterial activity and poor biocompatibility. As the upper layer, it can avoid direct contact with the skin and inhibit microbial invasion. In addition, the bilayer can adhere to a large number of red blood cells and platelets, promoting blood coagulation and cell proliferation. Ag@MOF, CSNPs, Ag@MOF/CSNPs and bilayer showed antibacterial activity in ascending order, due to the synergistic antibacterial action of the upper and lower layer. In vivo evaluation showed that both bilayer and PACS could significantly accelerate the wound healing, and the bilayer dressing showed more complete re-epithelialization with less inflammatory cells. In summary, this new bilayer composite is an ideal dressing for accelerating wound healing.

Electrospun Asymmetric Membranes as Promising Wound Dressings: A Review

Despite all the efforts that have been done up to now, the currently available wound dressings are still unable to fully re-establish all the structural and functional properties of the native skin. To overcome this situation, researchers from the tissue engineering area have been developing new wound dressings (hydrogels, films, sponges, membranes) aiming to mimic all the features of native skin. Among them, asymmetric membranes emerged as a promising solution since they reproduce both epidermal and dermal skin layers. Wet or dry/wet phase inversion, scCO2-assisted phase inversion, and electrospinning have been the most used techniques to produce such a type of membranes. Among them, the electrospinning technique, due to its versatility, allows the development of multifunctional dressings, using natural and/or synthetic polymers, which resemble the extracellular matrix of native skin as well as address the specific requirements of each skin layer. Moreover, various therapeutic or antimicrobial agents have been loaded within nanofibers to further improve the wound healing performance of these membranes. This review article provides an overview of the application of asymmetric electrospun membranes as wound dressings displaying antibacterial activity and as delivery systems of biomolecules that act as wound healing enhancers.

Polymeric Tissue Adhesives

Polymeric tissue adhesives provide versatile materials for wound management and are widely used in a variety of medical settings ranging from minor to life-threatening tissue injuries. Compared to the traditional methods of wound closure (i.e., suturing and stapling), they are relatively easy to use, enable rapid application, and introduce minimal tissue damage. Furthermore, they can act as hemostats to control bleeding and provide a tissue-healing environment at the wound site. Despite their numerous current applications, tissue adhesives still face several limitations and unresolved challenges (e.g., weak adhesion strength and poor mechanical properties) that limit their use, leaving ample room for future improvements. Successful development of next-generation adhesives will likely require a holistic understanding of the chemical and physical properties of the tissue-adhesive interface, fundamental mechanisms of tissue adhesion, and requirements for specific clinical applications. In this review, we discuss a set of rational guidelines for design of adhesives, recent progress in the field along with examples of commercially available adhesives and those under development, tissue-specific considerations, and finally potential functions for future adhesives. Advances in tissue adhesives will open new avenues for wound care and potentially provide potent therapeutics for various medical applications.

Nanocomposite scaffolds for accelerating chronic wound healing by enhancing angiogenesis

Skin is the body's first barrier against external pathogens that maintains the homeostasis of the body. Any serious damage to the skin could have an impact on human health and quality of life. Tissue engineering aims to improve the quality of damaged tissue regeneration. One of the most effective treatments for skin tissue regeneration is to improve angiogenesis during the healing period. Over the last decade, there has been an impressive growth of new potential applications for nanobiomaterials in tissue engineering. Various approaches have been developed to improve the rate and quality of the healing process using angiogenic nanomaterials. In this review, we focused on molecular mechanisms and key factors in angiogenesis, the role of nanobiomaterials in angiogenesis, and scaffold-based tissue engineering approaches for accelerated wound healing based on improved angiogenesis.

Multifunctional hydrogels for wound healing: Special focus on biomacromolecular based hydrogels

Hydrogels are widely used for wound healing applications due to their similarity to the native extracellular matrix (ECM) and ability to provide a moist environment. However, lack of multifunctionality and low mechanical properties of previously developed hydrogels may limit their ability to support skin tissue regeneration. Incorporating various biomaterials and nanostructures into the hydrogels is an emerging approach to develop multifunctional hydrogels with new functions that are beneficial for wound healing. These multifunctional hydrogels can be fabricated with a wide range of functions and properties, including antibacterial, antioxidant, bioadhesive, and appropriate mechanical properties. Two approaches can be used for development of multifunctional hydrogel-based dressings; taking the advantages of the chemical composition of biomaterials and addition of nanomaterials or nanostructures. A large number of synthetic and natural polymers, bioactive molecules, or nanomaterials have been used to obtain hydrogel-based dressings with multifunctionality for wound healing applications. In the present review paper, advances in the development of multifunctional hydrogel-based dressings for wound healing have been highlighted.

Stromal cell-derived factor loaded co-electrospun hydrophilic/hydrophobic bicomponent membranes for wound protection and healing

Chronic wounds are one of the key concerns for people with diabetes, frequently leading to infections and non-healing ulcers, and finally resulting in the amputation of limbs/organs. Stromal cell-derived factor 1 (SDF1) is a major chemokine that plays a significant role in tissue repair, vascularization, and wound healing. However, the long-term sustained delivery of SDF1 in a chronic wound environment is a great challenge. In order to facilitate the sustained release of SDF1 in diabetic wounds, it could be incorporated into wound-healing patches. Herein, we report the fabrication of a hydrophilic/hydrophobic bicomponent fiber-based membrane, where SDF1 was encapsulated inside hydrophilic fibers, and its applicability in wound healing. A co-electrospinning technique was employed for the fabrication of polymeric membranes where PVA and PCL form the hydrophilic and hydrophobic components, respectively. Morphological analysis of the developed membranes was conducted via scanning electron microscopy (SEM). The mechanical strength of the membranes was investigated via uniaxial tensile testing. The water uptake capacity of the membranes was also determined to understand the hydrophilicity and exudate uptake capacity of the membranes. To understand the proliferation, viability, and migration of skin-specific cells in the presence of SDF1-loaded membranes, in vitro cell culture experiments were carried out using fibroblasts, keratinocytes, and endothelial cells. The results showed the excellent porous morphology of the developed membranes with distinguishable differences in fiber diameters for the PVA and PCL fibers. The developed membranes possessed enough mechanical strength for use as wound-healing membranes. The co-electrospun membranes showed good exudate uptake capacity. The controlled and extended delivery of SDF1 from the developed membranes was observed over a prolonged period. The SDF1-loaded membranes showed enhanced cell proliferation, cell viability, and cell migration. These biocompatible and biodegradable SDF1-loaded bicomponent membranes with excellent exudate uptake capacity, and cell proliferation and cell migration properties can be exploited as a novel wound-dressing membrane aimed at chronic diabetic wounds.

Preparation, characterization and wound healing effect of vaccarin-chitosan nanoparticles

Wound healing is a complex, dynamic and difficult process. Much effort and attempt has been made to accelerate this process. The purpose of this study is to prepare nanoparticles loaded with vaccarin (VAC-NPS)hydrogel and evaluate its effect on promoting wound healing. In the present study, the physicochemical properties of VAC-NPS were characterized. Transmission electron microscopy (TEM) was used to observe the morphology of VAC-NPS. Human umbilical vein endothelial cells (HUVEC) was employed to assessment the biocompatibility of VAC-NPS in vitro. The wound healing function of VAC-NPS hydrogels was evaluated in the full-thickness dermal wound in a rat model. The results indicated that VAC-NPS was spherical like particles with uniform particle size distribution and no obvious aggregation with a diameter of (216.6 ± 10.1)nm. The loading capacity and encapsulation efficiency of VAC in the nanoparticles were (14.3 ± 1.2) % and (51.7 ± 1.7) % respectively. MTT assay demonstrated that the VAC-NPS had no cytotoxicity and could promote HUVEC proliferation and migration. In vivo results showed that VAC-NPS promotes wound healing, and the mechanism may be through up-regulating IL-1β and PDGF-BB, promoting angiogenesis. VAC-NPS might have a potential application value for the treatment of the wound healing and a promising performance in bio-medically relevant systems.

Recent Progress of Chitosan and Chitosan Derivatives-Based Nanoparticles: Pharmaceutical Perspectives of Oral Insulin Delivery

Diabetes mellitus is a chronic endocrine disease, affecting more than 400 million people around the world. Patients with poorly controlled blood glucose levels are liable to suffer from life-threatening complications, such as cardiovascular, neuropathy, retinopathy and even premature death. Today, subcutaneous parenteral is still the most common route for insulin therapy. Oral insulin administration is favourable and convenient to the patients. In contrast to injection route, oral insulin delivery mimics the physiological pathway of endogenous insulin secretion. However, oral insulin has poor bioavailability (less than 2%) due to the harsh physiological environment through the gastrointestinal tract (GIT). Over the last few decades, many attempts have been made to achieve an effective oral insulin formulation with high bioavailability using insulin encapsulation into nanoparticles as advanced technology. Various natural polymers have been employed to fabricate nanoparticles as a delivery vehicle for insulin oral administration. Chitosan, a natural polymer, is extensively studied due to the attractive properties, such as biodegradability, biocompatibility, bioactivity, nontoxicity and polycationic nature. Numerous studies were conducted to evaluate chitosan and chitosan derivatives-based nanoparticles capabilities for oral insulin delivery. This review highlights strategies that have been applied in the recent five years to fabricate chitosan/chitosan derivatives-based nanoparticles for oral insulin delivery. A summary of the barriers hurdle insulin absorption rendering its low bioavailability such as physical, chemical and enzymatic barriers are highlighted with an emphasis on the most common methods of chitosan nanoparticles preparation. Nanocarriers are able to improve the absorption of insulin through GIT, deliver insulin to the blood circulation and lower blood glucose levels. In spite of some drawbacks encountered in this technology, chitosan and chitosan derivatives-based nanoparticles are greatly promising entities for oral insulin delivery.

Polymer-Based Materials Loaded with Curcumin for Wound Healing Applications

Some of the currently used wound dressings have interesting features such as excellent porosity, good water-absorbing capacity, moderate water vapor transmission rate, high drug loading efficiency, and good capability to provide a moist environment, but they are limited in terms of antimicrobial properties. Their inability to protect the wound from microbial invasion results in wound exposure to microbial infections, resulting in a delayed wound healing process. Furthermore, some wound dressings are loaded with synthetic antibiotics that can cause adverse side effects on the patients. Natural-based compounds exhibit unique features such as good biocompatibility, reduced toxicity, etc. Curcumin, one such natural-based compound, has demonstrated several biological activities such as anticancer, antibacterial and antioxidant properties. Its good antibacterial and antioxidant activity make it beneficial for the treatment of wounds. Several researchers have developed different types of polymer-based wound dressings which were loaded with curcumin. These wound dressings displayed excellent features such as good biocompatibility, induction of skin regeneration, accelerated wound healing processes and excellent antioxidant and antibacterial activity. This review will be focused on the in vitro and in vivo therapeutic outcomes of wound dressings loaded with curcumin.

Preparation, characterization, and 3D printing verification of chitosan/halloysite nanotubes/tea polyphenol nanocomposite films

In this study, chitosan/halloysite nanotubes/tea polyphenol (CS/HNTs/TP) nanocomposite films were prepared by the solution casting method. The scanning electron microscopy (SEM) result showed that the nanocomposite film with a CS/HNTs ratio of 6:4 and a TP content of 10% (C6H4-TP10) had a relatively smooth surface and a dense internal structure. The water vapor barrier property of the nanocomposite film was improved due to the tortuous channels formed by the HNTs. However, the swelling degree and water solubility of the nanocomposite films were decreased. The nanocomposite films have a good antioxidant capacity. Antibacterial experiments showed that the C6H4-TP10 nanocomposite film had certain inhibitory effects on the growth of both E. coli and S. aureus. In addition, we used 3D printer to verify the printability of the optimal formulation of the film-forming solution. Overall, this strategy provides a simple approach to construct promising natural antioxidants and antibacterial food packaging.

Films of chitosan and natural modified hydroxyapatite as effective UV-protecting, biocompatible and antibacterial wound dressings

Chitosan is a natural polysaccharide widely used in biomedicine, for instance for wound dressing. Hydroxyapatite is a very bioactive calcium phosphate which, if modified with an appropriate element (iron Fe), can also have UV-absorbing properties. In this work, we report the study of films of chitosan incorporated with iron-modified hydroxyapatite of natural origin (from cod fish bones); this combination led to an innovative chitosan-based material with excellent and advanced functional properties. The films showed very high UV absorption (Ultraviolet Protection Factor (UPF) value higher than 50). This is the first time that a chitosan-based material has shown such high UV protection properties. The films also showed to be non-cytotoxic, and possessed antimicrobial activity towards both Gram-positive and negative strains. Their mechanical properties, optimised with an experimental design approach, confirmed their potential use as multifunctional wound dressing, capable of reducing bacterial infections and, at the same time, protecting from UV light.

Chitosan Contribution to Therapeutic and Vaccinal Approaches for the Control of Leishmaniasis

The control of leishmaniases, a complex parasitic disease caused by the protozoan parasite Leishmania, requires continuous innovation at the therapeutic and vaccination levels. Chitosan is a biocompatible polymer administrable via different routes and possessing numerous qualities to be used in the antileishmanial strategies. This review presents recent progress in chitosan research for antileishmanial applications. First data on the mechanism of action of chitosan revealed an optimal in vitro intrinsic activity at acidic pH, high-molecular-weight chitosan being the most efficient form, with an uptake by pinocytosis and an accumulation in the parasitophorous vacuole of Leishmania-infected macrophages. In addition, the immunomodulatory effect of chitosan is an added value both for the treatment of leishmaniasis and the development of innovative vaccines. The advances in chitosan chemistry allows pharmacomodulation on amine groups opening various opportunities for new polymers of different size, and physico-chemical properties adapted to the chosen routes of administration. Different formulations have been studied in experimental leishmaniasis models to cure visceral and cutaneous leishmaniasis, and chitosan can act as a booster through drug combinations with classical drugs, such as amphotericin B. The various architectural possibilities given by chitosan chemistry and pharmaceutical technology pave the way for promising further developments.

Thermosensitive Injectable Chitosan/Collagen/β-Glycerophosphate Composite Hydrogels for Enhancing Wound Healing by Encapsulating Mesenchymal Stem Cell Spheroids

Chronic wounds caused by diabetic or venous diseases remain a social and healthcare burden. In this work, a new strategy is proposed in which injectable thermosensitive chitosan/collagen/β-glycerophosphate (β-GP) hydrogels were combined with three-dimensional mesenchymal stem cell (3D MSC) spheroids to accelerate chronic wound healing by enhanced vascularization and paracrine effects. Chitosan/collagen/β-GP solution mixed with 3D MSC spheroids was rapidly transformed to a gel at body temperature by physical cross-linking, then overlapped the wounds fully and fitted to any shape of the wound. The results showed that the combination therapy exhibited a markedly therapeutic effect than the hydrogel-loaded two-dimensional (2D) MSCs or 2D MSCs alone. The hydrogel could provide an environment conductive to the attachment and proliferation of encapsulated MSCs, especially accelerating the proliferation and paracrine factor secretion of 3D MSC spheroids. These results supplied a novel alternative approach to treat chronic wounds caused by diabetic or venous diseases.

Morphology-controllable cellulose/chitosan sponge for deep wound hemostasis with surfactant and pore-foaming agent

Developing a facile and scalable synthetic route is important to explore the potential application of functional cellulose sponges. Here, a simple and efficient strategy to produce porous and hydrophilic cellulose sponges using surfactant and pore-foaming agent is demonstrated. The obtained cellulose sponges exhibit high water absorption capacity and rapid shape recoverability. The introduction of chitosan endows the chitosan/cellulose composite sponge with good mechanical properties. Inhibitory effects on Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa are particularly proved. Besides, the result of the dynamic whole blood clotting time indicated that the chitosan/cellulose composite sponge has better coagulation ability than those of traditional gauze and gelatin sponge. Animal experiment further showed that rapid hemostasis within 105 s could be reached with the composite sponge. Good biocompatibility of the composite sponge is proved by the results of hemocompatibility and cytotoxicity, indicating an excellent candidate as a rapid hemostatic material.

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.

Asymmetric Cellulosic Membranes: Current and Future Aspects

In this paper, we report our attempt to elaborate on cellulose-based materials and their potential application in membrane science, especially in separation applications. Furthermore, the cellulosic membrane has received attention for potential use as biomaterials such as novel wound-dressings and hemodialysis materials. In this mini-review, we mainly focus on the separation and antimicrobial properties of cellulosic membranes and the advanced synthesis/processing methods for superior functional quality for various potential applications. Finally, we conclude with the market and the impact of developments of future expectations.

Asymmetric Membranes: A Potential Scaffold for Wound Healing Applications

Currently, due to uprising concerns about wound infections, healing agents have been regarded as one of the major solutions in the treatment of different skin lesions. The usage of temporary barriers can be an effective way to protect wounds or ulcers from dangerous agents and, using these carriers can not only improve the healing process but also they can minimize the scarring and the pain suffered by the human. To cope with this demand, researchers struggled to develop wound dressing agents that could mimic the structural and properties of native skin with the capability to inhibit bacterial growth. Hence, asymmetric membranes that can impair bacterial penetration and avoid exudate accumulation as well as wound dehydration have been introduced. In general, synthetic implants and tissue grafts are expensive, hard to handle (due to their fragile nature and poor mechanical properties) and their production process is very time consuming, while the asymmetric membranes are affordable and their production process is easier than previous epidermal substitutes. Motivated by this, here we will cover different topics, first, the comprehensive research developments of asymmetric membranes are reviewed and second, general properties and different preparation methods of asymmetric membranes are summarized. In the two last parts, the role of chitosan based-asymmetric membranes and electrospun asymmetric membranes in hastening the healing process are mentioned respectively. The aforementioned membranes are inexpensive and possess high antibacterial and satisfactory mechanical properties. It is concluded that, despite the promising current investigations, much effort is still required to be done in asymmetric membranes.

A novel bacterial β-N-acetyl glucosaminidase from Chitinolyticbacter meiyuanensis possessing transglycosylation and reverse hydrolysis activities

BACKGROUND

N-Acetyl glucosamine (GlcNAc) and N-Acetyl chitooligosaccharides (N-Acetyl COSs) exhibit many biological activities, and have been widely used in the pharmaceutical, agriculture, food, and chemical industries. Particularly, higher N-Acetyl COSs with degree of polymerization from 4 to 7 ((GlcNAc)₄-(GlcNAc)₇) show good antitumor and antimicrobial activity, as well as possessing strong stimulating activity toward natural killer cells. Thus, it is of great significance to discover a β-N-acetyl glucosaminidase (NAGase) that can not only produce GlcNAc, but also synthesize N-Acetyl COSs.

RESULTS

The gene encoding the novel β-N-acetyl glucosaminidase, designated CmNAGase, was cloned from Chitinolyticbacter meiyuanensis SYBC-H1. The deduced amino acid sequence of CmNAGase contains a glycoside hydrolase family 20 catalytic module that shows low identity (12-35%) with the corresponding domain of most well-characterized NAGases. The CmNAGase gene was highly expressed with an active form in Escherichia coli BL21 (DE3) cells. The specific activity of purified CmNAGase toward p-nitrophenyl-N-acetyl glucosaminide (pNP-GlcNAc) was 4878.6 U/mg of protein. CmNAGase had a molecular mass of 92 kDa, and its optimum activity was at pH 5.4 and 40 °C. The V _max, K _m, K _cat, and K _cat/K _m of CmNAGase for pNP-GlcNAc were 16,666.67 μmol min^-1 mg^-1, 0.50 μmol mL^-1, 25,555.56 s^-1, and 51,111.12 mL μmol^-1 s^-1, respectively. Analysis of the hydrolysis products of N-Acetyl COSs and colloidal chitin revealed that CmNAGase is a typical exo-acting NAGase. Particularly, CmNAGase can synthesize higher N-Acetyl COSs ((GlcNAc)₃-(GlcNAc)₇) from (GlcNAc)₂-(GlcNAc)₆, respectively, showed that it possesses transglycosylation activity. In addition, CmNAGase also has reverse hydrolysis activity toward GlcNAc, synthesizing various linked GlcNAc dimers.

CONCLUSIONS

The observations recorded in this study that CmNAGase is a novel NAGase with exo-acting, transglycosylation, and reverse hydrolysis activities, suggest a possible application in the production of GlcNAc or higher N-Acetyl COSs.

Topical delivery of growth factors and metal/metal oxide nanoparticles to infected wounds by polymeric nanoparticles: an overview

INTRODUCTION

Infected chronic wounds particularly diabetic foot ulcers (DFUs) can result from stable colonization of antibiotic-resistant bacteria and fungi at the wound sites. In this context, the rapid healing of infected wounds has been the main goal in recent investigations. This issue can be solved by improving wound-healing phases including hemostasis, inflammatory, proliferative, and remodeling/maturation, and removal of bacteria and fungi. The applications of growth factors (GFs) and metal/metal oxide nanoparticles (MNPs/MONPs) are two choices for these targets. However, the lack of sustainable release of these agents is an important problem for appropriate wound healing.

AREA COVERED

The present review is focused on recent advances in delivery systems composed of growth factor and MNPs/MONPs for rapid wound healing.

EXPERT OPINION

Synthetic and natural polymeric micro- and nanocarriers including polyvinylpyrrolidone (PVP) and chitosan play a vital role in the healing of infected chronic wounds. Using various derivatives of chitosan as pH-responsive polymer with basic and acidic groups can be the best option to prepare controllable and sequential GF release. However, it warrants further extensive research to solve wound-healing problems.

Dual spinneret electrospun nanofibrous/gel structure of chitosan-gelatin/chitosan-hyaluronic acid as a wound dressing: In-vitro and in-vivo studies

Structural and compositional similarity to the natural extracellular matrix (ECM) is a main characteristic of an ideal scaffold for tissue regeneration. In order to resemble the fibrous/gel structure of skin ECM, a multicomponent scaffold was fabricated using biopolymers with structural similarity to ECM and wound healing properties i.e., chitosan (CS), gelatin (Gel) and hyaluronic acid (HA). The CS-Gel and CS-HA nanofibers were simultaneously electrospun on the collector through dual-electrospinning technique. The presence of polymers, possible interactions, and formation of polyelectrolyte complex were proven by attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy and thermogravimetric analysis (TGA). The noncomplex component of CS-HA fibers formed a gel state when the scaffold was exposed to the aqueous media, while the CS-Gel fibers reserved their fibrous structure, resulting in formation of fibrous/gel structure. The CS-Gel/CS-HA scaffold showed significantly higher cell proliferation (109%) in the first 24 h comparing with CS (90%) and CS-Gel (96%) scaffolds. Additionally, the initial cell adhesion improved by incorporation of HA. The in-vivo wound healing results in rat elucidated more wound healing capability of the CS-Gel/CS-HA scaffold in which new tissue with most similarity to the normal skin was formed.

Chitosan Film Containing Mansoa hirsuta Fraction for Wound Healing

Chitosan films entrapped with the Mansoa hirsuta fraction (CMHF) was developed as a new dressing for wound care. The chromatographic profile of the M. hirsuta fraction (MHF) was evaluated by ultra-high-performance liquid chromatography-quadrupole time-of-flight mass spectrometry, and the results showed that MHF is rich in acid triterpenes. Physicochemical characterization of the films prepared using the solvent casting method was performed by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetry (TGA), differential scanning calorimetry (DCS), scanning electron microscopy (SEM), atomic force microscopy (AFM), and mechanical properties. CMHF exhibited characteristic bands of both chitosan and MHF, revealing a physical mixture of both. CMHF presented an amorphous nature, thermostability, and dispersion of MHF in the chitosan matrix, resulting in a rough structure. Incorporation of M. hirsuta fraction into chitosan matrix favorably enhanced the mechanical performance and films thickness. The in vivo wound treatment with CMHF for seven days showed a characteristic area of advanced healing, re-epithelization, cell proliferation, and collagen formation. Furthermore, wound closure reached 100% contraction after 10 days of treatment with modulation of interleukins. The incorporation of M. hirsuta fraction into chitosan films was advantageous and showed great potential for stimulating wound repair and regeneration.

Synthesis, Characterization, and Histological Evaluation of Chitosan-Ruta Graveolens Essential Oil Films

The development of new biocompatible materials for application in the replacement of deteriorated tissues (due to accidents and diseases) has gained a lot of attention due to the high demand around the world. Tissue engineering offers multiple options from biocompatible materials with easy resorption. Chitosan (CS) is a biopolymer derived from chitin, the second most abundant polysaccharide in nature, which has been highly used for cell regeneration applications. In this work, CS films and Ruta graveolens essential oil (RGEO) were incorporated to obtain porous and resorbable materials, which did not generate allergic reactions. An oil-free formulation (F1: CS) and three different formulations containing R. graveolens essential oil were prepared (F2: CS-RGEO 0.5%; F3: CS+RGEO 1.0%; and F4: CS+RGEO 1.5%) to evaluate the effect of the RGEO incorporation in the mechanical and thermal stability of the films. Infrared spectroscopy (FTIR) analyses demonstrated the presence of RGEO. In contrast, X-ray diffraction (XRD) and differential scanning calorimetry (DSC) analysis showed that the crystalline structure and percentage of CS were slightly affected by the RGEO incorporation. Interesting saturation phenomena were observed for mechanical and water permeability tests when RGEO was incorporated at higher than 0.5% (v/v). The results of subdermal implantation after 30 days in Wistar rats showed that increasing the amount of RGEO resulted in greater resorption of the material, but also more significant inflammation of the tissue surrounding the materials. On the other hand, the thermal analysis showed that the RGEO incorporation almost did not affect thermal degradation. However, mechanical properties demonstrated an understandable loss of tensile strength and Young’s modulus for F3 and F4. However, given the volatility of the RGEO, it was possible to generate a slightly porous structure, as can be seen in the microstructure analysis of the surface and the cross-section of the films. The cytotoxicity analysis of the CS+RGEO compositions by the hemolysis technique agreed with in vivo results of the low toxicity observed. All these results demonstrate that films including crude essential oil have great application potential in the biomedical field.

Preparation of 2,6-diurea-chitosan oligosaccharide derivatives for efficient antifungal and antioxidant activities

In this study, 2-urea-chitosan oligosaccharide derivatives (2-urea-COS derivatives) and 2,6-diurea-chitosan oligosaccharide derivatives (2,6-diurea-COS derivatives) were successfully designed and synthesized via intermediate 2-methoxyformylated chitosan oligosaccharide. All samples were characterized and compared based on FT-IR, ¹H NMR spectroscopy, and elemental analysis. The antifungal effects of COS derivatives were tested against Fusarium oxysporum f. sp. niveum, Phomopsis asparagus, and Botrytis cinereal. Their antioxidant properties, including superoxide radicals' scavenging activity, hydroxyl radicals' scavenging activity, and DPPH radicals' scavenging activity were also explored within different concentrations. COS derivatives bearing urea groups showed improved bioactivity compared with pristine COS and 2,6-diurea-COS derivatives had a higher biological activity than 2-urea-COS derivatives in tested concentrations. Additionally, L929 cells were used to carry out cytotoxicity test of COS and COS derivatives by CCK-8 assay. The results indicated that some of samples showed low cytotoxicity. These findings offered a suggestion that COS derivatives bearing urea groups are promising biological materials.