Evaluation of sericin/collagen membranes as prospective wound dressing biomaterial

Expanding the boundaries of silk sericin biomaterials in biomedical applications

Silk sericin (SS) has a long history as a by-product of the textile industry. SS has emerged as a sustainable material for biomedical engineering due to its material properties including water solubility, diverse impact on biological activities including antibacterial and antioxidant properties, and ability to promote cell adhesion and proliferation. This review addresses the origin, structure, properties, extraction, and underlying functions of this protein. An overview of the growing research studies and market evolution is presented, along with highlights of the most common fabrication matrices (hydrogels, bioinks, porous and fibrous scaffolds) and tissue engineering applications. Finally, the future trends with this protein as a multifaceted toolbox for bioengineering are explored, along with the challenges with SS. Overall, the present review can serve as a foundation for the creation of innovative biomaterials utilizing SS as a fundamental building block that hold market potential.

Melatonin/Sericin Wound Healing Patches: Implications for Melanoma Therapy

Melatonin and sericin exhibit antioxidant properties and may be useful in topical wound healing patches by maintaining redox balance, cell integrity, and regulating the inflammatory response. In human skin, melatonin suppresses damage caused by ultraviolet radiation (UVR) which involves numerous mechanisms associated with reactive oxygen species/reactive nitrogen species (ROS/RNS) generation and enhancing apoptosis. Sericin is a protein mainly composed of glycine, serine, aspartic acid, and threonine amino acids removed from the silkworm cocoon (particularly Bombyx mori and other species). It is of interest because of its biodegradability, anti-oxidative, and anti-bacterial properties. Sericin inhibits tyrosinase activity and promotes cell proliferation that can be supportive and useful in melanoma treatment. In recent years, wound healing patches containing sericin and melatonin individually have attracted significant attention by the scientific community. In this review, we summarize the state of innovation of such patches during 2021-2023. To date, melatonin/sericin-polymer patches for application in post-operational wound healing treatment has been only sparingly investigated and it is an imperative to consider these materials as a promising approach targeting for skin tissue engineering or regenerative dermatology.

26SCS-Loaded SilMA/Col Composite Sponge with Well-Arranged Layers Promotes Angiogenesis-Based Diabetic Wound Repair by Mediating Macrophage Inflammatory Response

Diabetic wound healing is a significant clinical challenge because abnormal immune cells in the wound cause chronic inflammation and impair tissue regeneration. Therefore, regulating the behavior and function of macrophages may be conducive to improving treatment outcomes in diabetic wounds. Herein, sulfated chitosan (26SCS)-containing composite sponges (26SCS-SilMA/Col-330) with well-arranged layers and high porosity were constructed based on collagen and silk fibroin, aiming to induce an appropriate inflammatory response and promote angiogenesis. The results indicated that the ordered topological structure of composite sponges could trigger the pro-inflammatory response of Mφs in the early stage, and rapid release of 26SCS in the early and middle stages (within the concentration range of 1-3 mg/mL) induced a positive inflammatory response; initiated the pro-inflammatory reaction of Mφs within 3 days; shifted M1 Mφs to the M2 phenotype within 3-7 days; and significantly up-regulated the expression of two typical angiogenic growth factors, namely VEGF and PDGF-BB, on day 7, leading to rapid HUVEC migration and angiogenesis. In vivo data also demonstrated that on the 14th day after surgery, the 26SCS-SilMA/Col-330-implanted areas exhibited less inflammation, faster re-epithelialization, more abundant collagen deposition and a greater number of blood vessels in the skin tissue. The composite sponges with higher 26SCS contents (the (5.0) 26SCS-SilMA/Col-330 and the (7.5) 26SCS-SilMA/Col-330) could better orchestrate the phenotype and function of Mφs and facilitate wound healing. These findings highlight that the 26SCS-SilMA/Col-330 sponges developed in this work might have great potential as a novel dressing for the treatment of diabetic wounds.

Bringing innovative wound care polymer materials to the market: Challenges, developments, and new trends

The development of innovative products for treating acute and chronic wounds has become a significant topic in healthcare, resulting in numerous products and innovations over time. The growing number of patients with comorbidities and chronic diseases, which may significantly alter, delay, or inhibit normal wound healing, has introduced considerable new challenges into the wound management scenario. Researchers in academia have quickly identified promising solutions, and many advanced wound healing materials have recently been designed; however, their successful translation to the market remains highly complex and unlikely without the contribution of industry experts. This review article condenses the main aspects of wound healing applications that will serve as a practical guide for researchers working in academia and industry devoted to designing, evaluating, validating, and translating polymer wound care materials to the market. The article highlights the current challenges in wound management, describes the state-of-the-art products already on the market and trending polymer materials, describes the regulation pathways for approval, discusses current wound healing models, and offers a perspective on new technologies that could soon reach consumers. We envision that this comprehensive review will significantly contribute to highlighting the importance of networking and exchanges between academia and healthcare companies. Only through the joint of these two actors, where innovation, manufacturing, regulatory insights, and financial resources act in harmony, can wound care products be developed efficiently to reach patients quickly and affordably.

Hydrolyzed Collagen Powder Dressing Improves Wound Inflammation, Perfusion, and Breaking Strength of Repaired Tissue

Objective: Hydrolyzed collagen-based matrices are widely used as wound care dressings. Information on the mechanism of action of such dressings is scanty. The objective of this study was to test the effect of a specific hydrolyzed collagen powder (HCP), which is extensively used for wound care management in the United States. Approach: The effects of HCP on resolution of wound inflammation, perfusion, closure, and breaking strength of the repaired skin were studied in an experimental murine model. Results: In early (day 7) inflammatory phase of wound macrophages, HCP treatment boosted phagocytosis and efferocytosis of wound-site macrophages. In these cells, inducible reactive oxygen species were also higher on day (d) 7. HCP treatment potentiated the expression of anti-inflammatory interleukin (IL)-10 cytokine and proangiogenic vascular endothelial growth factor (VEGF) production. Excisional wounds dressed with HCP showed complete closure on day 21, while the control wounds remained open. HCP treatment also demonstrated improved quality of wound healing as marked by the improved breaking strength of the closed wound tissue/repaired skin. Innovation: These data represent first evidence on the mechanism of action of clinically used HCP. Conclusion: HCP dressing favorably influenced both wound inflammation and vascularization. Improved breaking strength of HCP-treated repaired skin lays the rationale for future studies testing the hypothesis that HCP-treated closed wounds would show fewer recurrences.

Advances of regenerated and functionalized silk biomaterials and application in skin wound healing

The cocoon silk of silkworms (Bombyx mori) has multiple potential applications in biomedicine due to its good biocompatibility, mechanical properties, degradability, and plasticity. Numerous studies have confirmed that silk material dressings are more effective than traditional ones in the skin wound healing process. Silk material research has recently moved toward functionalized biomaterials and achieved remarkable results. Herein, we summarize the recent advances in functionalized silk materials and their efficacy in skin wound healing. In particular, transgenic technology has realized the specific expression of human growth factors in the silk glands of the silkworms, which lays the foundation for fabricating novel and low-cost functionalized materials. Without a green and safe preparation process, the best raw silk materials cannot be made into medically safe products. Therefore, we provide an overview of green and gentle approaches for silk degumming and silk sericin (SS) extraction. Moreover, we summarize and discuss the processing methods of silk fibroin (SF) and SS materials and their potential applications, such as burns, diabetic wounds, and other wounds. This review aims to enhance our understanding of new advances and directions in silk materials and guide future biomedical research.

Bilayer wound dressing composed of asymmetric polycaprolactone membrane and chitosan-carrageenan hydrogel incorporating storax balsam

A comprehensive approach is needed to develop multifunctional wound dressing that is simple yet efficient. In this work, Liquidambar orientalis Mill. storax loaded hydroxyethyl chitosan (HECS)-carrageenan (kC) based hydrogel (HECS-kC) and polydopamine coated asymmetric polycaprolactone membrane (PCL-DOP) were used to develop a multifunctional and modular bilayer wound dressing. Asymmetric PCL-DOP membrane was prepared by non-solvent induced phase separation (NIPS) followed by polydopamine coating and demonstrated an excellent barrier against bacteria while allowing permeability for 5.45 ppm dissolved‑oxygen and 2130 g/m2 water vapor transmission in 24 h in addition to 805 kPa tensile strength. Storax loaded HECS-kC hydrogel, on the other hand, demonstrated a pH-responsive degradation and swelling to provide necessary conditions to facilitate wound healing. The hydrogels showed stretchability above 140 %, mild adhesive strength on sheep skin and PCL-DOP membrane, while the storax incorporation enhanced antibacterial and antioxidant activity. Furthermore, rat full-thickness skin defect model showed that the developed bilayer wound dressing could significantly facilitate wound healing compared to Tegaderm™ and control groups. This study shows that the bilayered wound dressing has the potential to be used as a simple and effective wound care system.

A comprehensive review of recent advances in silk sericin: Extraction approaches, structure, biochemical characterization, and biomedical applications

Silks are natural polymers that have been widely used for centuries. Silk consists of a filament core protein, termed fibroin, and a glue-like coating substance formed of sericin (SER) proteins. This protein is extracted from the silkworm cocoons (particularly Bombyx mori) and is mainly composed of amino acids like glycine, serine, aspartic acid, and threonine. Silk SER can be obtained using numerous methods, including enzymatic extraction, high-temperature, autoclaving, ethanol precipitation, cross-linking, and utilizing acidic, alkali, or neutral aqueous solutions. Given the versatility and outstanding properties of SER, it is widely fabricated to produce sponges, films, and hydrogels for further use in diverse biomedical applications. Hence, many authors reported that SER benefits cell proliferation, tissue engineering, and skin tissue restoration thanks to its moisturizing features, antioxidant and anti-inflammatory properties, and mitogenic effect on mammalian cells. Remarkably, SER is used in drug delivery depending on its chemical reactivity and pH-responsiveness. These unique features of SER enhance the bioactivity of drugs, facilitating the fabrication of biomedical materials at nano- and microscales, hydrogels, and conjugated molecules. This review thoroughly outlines the extraction techniques, biological properties, and respective biomedical applications of SER.

Natural Polymer-Based Thin Film Strategies for Skin Regeneration in Lieu of Regenerative Dentistry

Wound healing (WH) is a complex and dynamic process that comprises of a series of molecular and cellular events that occur after tissue injury. The injuries of the maxillofacial and oral region caused by trauma or surgery result in undesirable WH such as delayed wound closure and formation of scar tissue. Skin tissue engineering (TE)/regeneration is an emerging approach toward faster, superior, and more effective resolution of clinically significant wounds effectively. A multitude of TE principles approaches are being put to action for the fabrication of hydrogels, electrospun sheets, 3D scaffolds, and thin films that can be used as wound dressings materials, sutures, or skin substitutes. Thin films are advantageous over other materials owing to their flexibility, ability to provide a barrier against external contamination, easy gaseous exchange, and easy monitoring of wounds. This review focuses on wound-dressing films and their significance and discusses various fabrication techniques. In addition, we explore various natural biopolymers that can be used for fabrication of skin TE materials. Impact Statement In this review article, critical evaluations of natural polymers used in skin regeneration were discussed. Further, the fabrication technology of the 2D and 3D material in wound healing were discussed.

Regenerated silk fibroin loaded with natural additives: a sustainable approach towards health care

According to World Health Organization (WHO), on average, 0.5 Kg of hazardous waste is generated per bed every day in high-income countries. The adverse effects imposed by synthetic materials and chemicals on the environment and humankind have urged researchers to explore greener technologies and materials. Amidst of all the natural fibers, silk fibroin (SF), by virtue of its superior toughness (6 × 10⁴∼16 × 10⁴ J/kg), tensile strength (47.2-67.7 MPa), tunable biodegradability, excellent Young's modulus (1.9-3.9 GPa), presence of functional groups, ease of processing, and biocompatibility has garnered an enormous amount of scientific interests. The use of silk fibroin conjoint with purely natural materials can be an excellent solution for the adverse effects of chemical-based treatment techniques. Considering this noteworthiness, vigorous research is going on in silk-based biomaterials, and it is opening up new vistas of opportunities. This review enswathes the structural aspects of silk fibroin along with its potency to form composites with other natural materials, such as curcumin, keratin, alginate, hydroxyapatite, hyaluronic acid, and cellulose, that can replace the conventionally used synthetic materials, providing a sustainable pathway to biomedical engineering. It was observed that a large amount of polar functional moieties present on the silk fibroin surface enables them to compatibilize easily with the natural additives. The conjunction of silk with natural additives initiates synergistic interactions that mitigate the limitations offered by individual units as well as enhance the applicability of materials. Further the current status and challenges in the commercialization of silk-based biomedical devices are discussed.

Using polyvinyl alcohol-ionic hydrogels containing a wound healing agent to manage wounds in different environments

OBJECTIVE

To explore the effects of pH on properties of polyvinyl alcohol (PVA)-ionic hydrogels containing wound healing promoters.

METHOD

PVA was combined with a natural wound healing promoter (silk sericin (SS)), and an anionic agent (eosin (ES)) or cationic agent (methylene blue (MB)), and made into hydrogels. Properties of the hydrogels and behaviour at different pHs were investigated.

RESULTS

The density and gel fraction of PVA/SS-ES hydrogel and PVA/SS-MB hydrogel were considerably lower compared with hydrogel without SS. The swelling ratio and degradation of the hydrogels increased with increasing SS concentration in all pH solutions. The influence of SS in interrupting long-chain PVA molecules was confirmed based on changes in Fourier-transform infrared spectroscopy (FTIR). The SS released from the gels was found to interact with the ionic agent and influenced the release profile of the ionic agent. Surprisingly, the anionic agent in PVA/SS-ES hydrogel showed 70% release in high pH solution whereas the cationic agent in PVA/SS-MB hydrogel showed 86% release in low pH solution. Moreover, the active agent could accumulate on the skin layer and had a positive effect on a specific wound area.

CONCLUSION

Based on the results obtained in this study, it is suggested to use anionic hydrogels containing wound healing promoter for wounds at high pH and cationic hydrogels containing wound healing promoter for wounds with low pH. Ability to improve wound healing using a natural healing agent combined with ionic agents and controlling the pH of hydrogels will help in developing quick and low-cost treatment for wounds.

Silk sericin-based materials for biomedical applications

Silk sericin, a natural protein extracted from silkworm cocoons, has been extensively studied and utilized in the biomedical field because of its superior biological activities and controllable chemical-physical properties. Sericin is biocompatible and naturally cell adhesive, enabling cell attachment, proliferation, and differentiation in sericin-based materials. Moreover, its abundant functional groups from variable amino acids composition allow sericin to be chemically modified and cross-linked to form versatile constructs serving as alternative matrixes for biomedical applications. Recently, sericin has been constructed into various types of biomaterials for tissue engineering and regenerative medicine, including various bulk constructions (films, hydrogels, scaffolds, conduits, and devices) and micro-nano formulations. In this review, we systemically summarize the properties of silk sericin, introduce its different forms, and demonstrate their newly-developed as well as potential biomedical applications.

Exploring the Mechanical Properties and Performance of Type-I Collagen at Various Length Scales: A Progress Report

Collagen is the basic protein of animal tissues and has a complex hierarchical structure. It plays a crucial role in maintaining the mechanical and structural stability of biological tissues. Over the years, it has become a material of interest in the biomedical industries thanks to its excellent biocompatibility and biodegradability and low antigenicity. Despite its significance, the mechanical properties and performance of pure collagen have been never reviewed. In this work, the emphasis is on the mechanics of collagen at different hierarchical levels and its long-term mechanical performance. In addition, the effect of hydration, important for various applications, was considered throughout the study because of its dramatic influence on the mechanics of collagen. Furthermore, the discrepancies in reports of the mechanical properties of collagenous tissues (basically composed of 20-30% collagen fibres) and those of pure collagen are discussed.

Nonmulberry silk proteins: multipurpose ingredient in bio-functional assembly

The emerging field of tissue engineering and regenerative medicines utilising artificial polymers is facing many problems. Despite having mechanical stability, non-toxicity and biodegradability, most of them lack cytocompatibility and biocompatibility. Natural polymers (such as collagen, hyaluronic acid, fibrin, fibroin, and others), including blends, are introduced to the field to solve some of the relevant issues. Another natural biopolymer: silkworm silk gained special attention primarily due to its specific biophysical, biochemical, and material properties, worldwide availability, and cost-effectiveness. Silk proteins, namely fibroin and sericin extracted from domesticated mulberry silkwormBombyx mori, are studied extensively in the last few decades for tissue engineering. Wild nonmulberry silkworm species, originated from India and other parts of the world, also produce silk proteins with variations in their nature and properties. Among the nonmulberry silkworm species,Antheraea mylitta(Indian Tropical Tasar),A. assamensis/A. assama(Indian Muga), andSamia ricini/Philosamia ricini(Indian Eri), along withA. pernyi(Chinese temperate Oak Tasar/Tussah) andA. yamamai(Japanese Oak Tasar) exhibit inherent tripeptide motifs of arginyl glycyl aspartic acid in their fibroin amino acid sequences, which support their candidacy as the potential biomaterials. Similarly, sericin isolated from such wild species delivers unique properties and is used as anti-apoptotic and growth-inducing factors in regenerative medicines. Other characteristics such as biodegradability, biocompatibility, and non-inflammatory nature make it suitable for tissue engineering and regenerative medicine based applications. A diverse range of matrices, including but not limited to nano-micro scale structures, nanofibres, thin films, hydrogels, and porous scaffolds, are prepared from the silk proteins (fibroins and sericins) for biomedical and tissue engineering research. This review aims to represent the progress made in medical and non-medical applications in the last couple of years and depict the present status of the investigations on Indian nonmulberry silk-based matrices as a particular reference due to its remarkable potentiality of regeneration of different types of tissues. It also discusses the future perspective in tissue engineering and regenerative medicines in the context of developing cutting-edge techniques such as 3D printing/bioprinting, microfluidics, organ-on-a-chip, and other electronics, optical and thermal property-based applications.

Therapeutic potential of Moringa oleifera seed polysaccharide embedded silver nanoparticles in wound healing

Wound healing is a complicated process that influences patient's life quality. Plant-based polysaccharide has recently gained interest in its use in wound dressing materials because of its biological compatibility, natural abundance, and ideal physiochemical properties. The present study reveals the potential of polysaccharide isolated from Moringa oleifera seed (MOS-PS) and its nanocomposite with silver (MOS-PS-AgNPs) as alternative materials for wound dressing. First, MOS-PS was isolated and structurally characterized by TLC, HPLC, FTIR, NMR, and GPC analyses. A green and simple method was used to synthesize AgNPs using MOS-PS as a stabilizing and reducing agent. The size, morphology, and structure of the MOS-PS-AgNPs were characterized by UV-Vis spectroscopy, X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and zeta potential analysis. The results showed that the MOS-PS-AgNPs were spherically shaped, having no cytotoxicity toward mouse fibroblasts cells and promoting their in-vitro migration. Moreover, the MOS-PS-AgNPs displayed strong anti-microbial activity against wound infectious pathogenic bacteria. Finally, the MOS-PS-AgNPs were used for dressing animal wounds and its preliminary mechanism was studied by RT-PCR and histological analysis. The results showed that the MOS-PS-AgNPs can promote wound contraction and internal tissue growth well. Overall, our results indicated that the MOS-PS-AgNPs might be an excellent candidate for use as an optimal wound dressing material.

The Fabrication of Poly(Σ-caprolactone)-Poly(ethylene oxide) Sandwich Type Nanofibers Containing Sericin-Capped Silver Nanoparticles as an Antibacterial Wound Dressing

In this study, antibacterial, synthetic poly(Σ-caprolactone)-poly(ethylene oxide) (PCL-PEO) multilayer nanofibers were produced by an electrospinning method. The material was synthesized in 3 layers. The upper-lower protective layers were produced by PCL nanofibers and the intermediate layer was produced from PEO nanofiber containing sericin-capped silver nanoparticles (S-AgNPs). The electrospinning conditions in which nano-sized, smooth, bead-free fibers were obtained was determined to be an applied voltage of 20 kV, a flow rate of 8 μL/min and a distance between the collector and the needle tip of 22 cm for the PCL layer (dissolved at a 12% g/mL concentration in a chloroform:methanol (3:2) solvent mixture) layer. For the S-AgNPs doped PEO layer (dissolved at a 3.5% g/mL concentration in water), the corresponding conditions were determined to be 20 kV, 15 μL/min and 20 cm. To characterize the three-layer material that consisted of PCL and S-AgNPs doped PEO layers, FTIR and SEM analyses were performed, and the water retention capacity, in situ degradability and antibacterial activity of the material was investigated. According to SEM analysis, the fibers obtained were found to be nano-sized, smooth and bead-free and the average size of the nanofibers forming the PCL layer was 687 nm while the average size of the fibers forming the PEO layer was 98 nm. Antibacterial activity tests were performed using gram-positive (Staphylococcus aureus ATCC 6538) and gram-negative (Escherichia coli ATCC 25922) bacteria and the resulting biomaterial was found to have antimicrobial effect on both gram-negative and gram-positive bacteria. It was determined that the 3-layer material obtained in this study can be used as a wound dressing.

In Situ Forming Silk Sericin-Based Hydrogel: A Novel Wound Healing Biomaterial

In situ cross-linked hydrogels have the advantage of effectively fulfilling the wound in its shape and depth. Amongst the new generation of natural-based biopolymers being proposed for wound care and skin regeneration, silk sericin is particularly interesting due to its exceptional properties such as biocompatibility, biodegradability, and antioxidant behavior, among others. In this study, a new enzyme-mediated cross-linked hydrogel composed of silk sericin is proposed for the first time. The developed hydrogel cross-linking strategy was performed via horseradish peroxidase, under physiological conditions, and presented gelling kinetics under 3 min, as demonstrated by its rheological behavior. The hydrogels presented a high degree of transparency, mainly due to their amorphous conformation. Degradation studies revealed that the hydrogels were stable in phosphate buffer solution (PBS) (pH 7.4) for 17 days, while in the presence of protease XIV (3.5 U/mg) and under acute and chronic physiological pH values, the stability decreased to 7 and 4 days, respectively. During protease degradation, the present sericin hydrogels demonstrated antioxidant activity. In vitro studies using an L929 fibroblast cell line demonstrated that these hydrogels were noncytotoxic, promoting cell adhesion and massive cell colonization after 7 days of culture, demonstrating that cells maintained their viability and proliferation. In addition, the application of sericin-based hydrogel in an in vivo diabetic wound model validated the feasibility of the in situ methodology and demonstrated a local anti-inflammatory effect, promoting the healing process. This study presents a simple, fast, and practical in situ approach to produce a sericin-based hydrogel able to be applied in low exudative chronic wounds. Moreover, the study herein reported fosters the valorization of a textile industrial by-product by its integration in the biomedical field.

Comparative Analysis of Collagen and Chitosan-based Dressing for Haemostatic and Wound Healing Application

Collagen and chitosan have haemostatic, tissue fix and wound healing properties but the poor mechanical property limits their application. Therefore, various concentrations of collagen (1-6%) and chitosan (1-2%) were used to develop biopolymer-coated gauzes, with and without glycerol as plasticiser. Glycerol-treated gauzes showed desired mechanical and adhesive property in comparison to polymer-coated gauzes alone. Developed gauzes were characterized using differential scanning calorimetry, thermal gravimetric analysis and Fourier transform infrared spectrophotometry to confirm the biopolymer coating and stability. Scanning electron microscopy showed multilayer coating of the biopolymer and faster clotting in chitosan gauzes in comparison to collagen. Surface plasmon resonance assay confirmed that chitosan exhibited more binding affinity of 65 RU in comparison to collagen, which showed 55 RU with erythrocytes. Decrease in the value of plateletcrit and mean platelet volume confirmed platelet adhesion and aggregation over the surface of polymer-coated dressings. Gamma scintigraphy studies showed 85 ± 2% formulation retention up to 12 h at the wound site in comparison to 40 ± 3% retention of the radiopharmaceutical alone. Collagen and chitosan-coated gauze showed 226 ± 15 s and 179 ± 12 s haemostasis time, respectively, which was significantly less from 506 ± 15 s in standard gauze. Chitosan gauze showed faster wound healing in comparison to the collagen-coated gauze. Chitosan and collagen-coated gauzes showed 55 ± 4% wound contraction on day seven in comparison to 25 ± 2% in the control group, while chitosan gauzes showed complete wound contraction on day fourteenth, while the collagen-coated gauze showed 90 ± 3% on the same day.

Hydrogel-Based Active Substance Release Systems for Cosmetology and Dermatology Application: A Review

Hydrogels are playing an increasingly important role in medicine and pharmacy. Due to their favorable physicochemical properties, biocompatibility, and designed interaction with living surroundings, they seem to be one of the most promising groups of biomaterials. Hydrogel formulations from natural, semi, or synthetic polymeric materials have gained great attention in recent years for treating various dermatology maladies and for cosmetology procedures. The purpose of this review is to present a brief review on the basic concept of hydrogels, synthesis methods, relevant mechanisms, and applications in dermatology or cosmetology. This review discusses transdermal therapies and the recent advances that have occurred in the field.

Synthesis of sericin-conjugated silver nanoparticles and their potential antimicrobial activity

Nanoparticles (NPs) are being recognized as antibacterial agents due to their rapidly increasing multidrug resistance in bacterial pathogens. Hence, there is an unmet need to identify the natural antibacterial agent. The present study aimed to evaluate the antibacterial activity of sericin-conjugated silver NPs synthesized by using sericin as a reducing and capping agent. Synthesized NPs were characterized by scanning electron microscope, nanolaser particle size analyzer (BT-90), Fourier-transform infrared analysis, and energy-dispersive X-ray. The biogenic NPs significantly inhibited the growth of Escherichia coli (12-15 mm zone of inhibition), Staphylococcus aureus (14.6-15.4 mm zone of inhibition), and Klebsiella pneumoniae (12.5-18 mm zone of inhibition). The stability of naturally synthesized NPs was examined at various temperatures (i.e., 4°C, 37°C, and 55°C) and pH (i.e., 3, 7, and 11). Temperature variability did not significantly affect the efficacy of NPs. However, NPs performed better at higher pH levels. This study suggested that the sericin-based silver NPs are not only effective against bacteria, but they also maintain the stability at different ranges of temperature and pH. We concluded that the sericin-conjugated silver NPs possess the remarkable antibacterial potential, which suggests their large-scale use as a cheap and stable antimicrobial agent in the future.

Silk biomaterials in wound healing and skin regeneration therapeutics: From bench to bedside

Silk biomaterials are known for biomedical and tissue engineering applications including drug delivery and implantable devices owing to their biocompatible and a wide range of ideal physico-chemical properties. Herein, we present a critical overview of the progress of silk-based matrices in skin regeneration therapeutics with an emphasis on recent innovations and scientific findings. Beginning with a brief description of numerous varieties of silks, the review summarizes our current understanding of the biological properties of silk that help in the wound healing process. Various silk varieties such as silkworm silk fibroin, silk sericin, native spider silk and recombinant silk materials have been explored for cutaneous wound healing applications from the past few decades. With an aim to harness the regenerative properties of silk, numerous strategies have been applied to develop functional bioactive wound dressings and viable bio-artificial skin grafts in recent times. The review examines multiple inherent properties of silk that aid in the critical events of the healing process such as cell migration, cell proliferation, angiogenesis, and re-epithelialization. A detailed insight into the progress of silk-based cellular skin grafts is also provided that discusses various co-culture strategies and development of bilayer and tri-layer human skin equivalent under in vitro conditions. In addition, functionalized silk matrices loaded with bioactive molecules and antibacterial compounds are discussed, which have shown great potential in treating hard-to-heal wounds. Finally, clinical studies performed using silk-based translational products are reviewed that validate their regenerative properties and future applications in this area. STATEMENT OF SIGNIFICANCE: The review article discusses the recent advances in silk-based technologies for wound healing applications, covering various types of silk biomaterials and their properties suitable for wound repair and regeneration. The article demonstrates the progress of silk-based matrices with an update on the patented technologies and clinical advancements over the years. The rationale behind this review is to highlight numerous properties of silk biomaterials that aid in all the critical events of the wound healing process towards skin regeneration. Functionalization strategies to fabricate silk dressings containing bioactive molecules and antimicrobial compounds for drug delivery to the wound bed are discussed. In addition, a separate section describes the approaches taken to generate living human skin equivalent that have recently contributed in the field of skin tissue engineering.

A novel bilayer zein/MMT nanocomposite incorporated with H. perforatum oil for wound healing

Recently, layered structures composed of nanofibers have gained attention as a novel material to mimic skin tissue in wound healing applications. The aim of this study is to develop a novel hybrid bilayer material composed of zein based composite film and nanofiber layers as a wound dressing material. The upper layer was composed of H. perforatum oil incorporated zein film including MMT and the bottom layer was comprised of 3D electrospun zein/MMT nanofibers to induce wound healing with the controlled release of H. perforatum oil. The bilayer composites were characterized in terms of mechanical test, WVP, water uptake and surface wettability. Antimicrobial activity of the wound dressings against microorganisms were investigated by disc diffusion method. In vitro cytotoxicity of monolayer film and bilayer structure was performed using WST-1 assay on HS2 keratinocyte and 3T3 cell lines. Results indicated that the prepared monolayer films showed appropriate mechanical and gas barrier properties and surface wettability for wound healing. Controlled release of H. perforatum oil was obtained from fabricated membranes up to 48 h. Bilayer membranes showed antimicrobial activity against E. coli, S. aureus, and C. albicans and did not show any toxic effect on NIH3T3 mouse fibroblast and HS2 keratinocyte cell lines. In vitro scratch assay results indicated that H. perforatum oil had a wound healing effect by inducing fibroblast migration. The proliferation study supported these results by increasing fibroblast proliferation on H. perforatum oil loaded bilayer membranes.

Adipose-Derived Stem Cells (ADSCs) Loaded Gelatin-Sericin-Laminin Cryogels for Tissue Regeneration in Diabetic Wounds

Healing in wounds like pressure ulcers, diabetic ulcers, venous ulcers, and arterial insufficiency ulcers is immensely hampered and causes both an economic burden and morbidity to patients. These wounds face a plethora of hostile conditions like elevated reactive oxygen species (ROS), impaired angiogenesis, senescent fibroblasts, and deficient stem cells that significantly diminish the probability of self-healing in these wounds. Adipose-derived stem cell therapy (ADSC) presents a promising approach to achieve efficient healing in such cases. To address the complex scenario of chronic wounds, we propose a combinatorial approach of delivering ADSCs on antioxidant gelatin-sericin (GS) scaffolds coated with laminin (GSL), an endothelial basement protein to improve angiogenesis. The synthesized GS scaffolds showed values of compression modulus, pore size, porosity, and the swelling ratio in the range of 65 kPa, 158 ± 48.8 μm, 91.1% ± 1.25, and 28 ± 2.5, respectively. A DPPH assay revealed GS scaffolds exhibit around 20% more scavenging as against gelatin (G) scaffolds and better protection against free radical assault, thus enhancing cell viability and the metabolic index of fibroblast cells. Different cells, namely, fibroblasts, keratinocytes, and ADSCs, cultured on GS scaffolds had better metabolic activity as compared with G scaffolds. Laminin coating onto the scaffolds leads to improved attachment and tube formation of endothelial cells as depicted in scanning electron microscopy images. Finally, we validated the applicability of the ADSCs loaded laminin-coated GS scaffolds in a diabetic ulcer rat model. Hematoxylin and eosin, Masson's trichrome, and picrosirius red staining showed better regeneration and collagen remodeling in ADSCs loaded GSL scaffolds. Immunostaining of CD31 staining demonstrates enhanced angiogenesis in GSL-ADSC as compared with other groups.

A Modified Collagen Dressing Induces Transition of Inflammatory to Reparative Phenotype of Wound Macrophages

Collagen containing wound-care dressings are extensively used. However, the mechanism of action of these dressings remain unclear. Earlier studies utilizing a modified collagen gel (MCG) dressing demonstrated improved vascularization of ischemic wounds and better healing outcomes. Wound macrophages are pivotal in facilitating wound angiogenesis and timely healing. The current study was designed to investigate the effect of MCG on wound macrophage phenotype and function. MCG augmented recruitment of macrophage at the wound-site, attenuated pro-inflammatory and promoted anti-inflammatory macrophage polarization. Additionally, MCG increased anti-inflammatory IL-10, IL-4 and pro-angiogenic VEGF production, indicating a direct role of MCG in resolving wound inflammation and improving angiogenesis. At the wound-site, impairment in clearance of apoptotic cell bioburden enables chronic inflammation. Engulfment of apoptotic cells by macrophages (efferocytosis) resolves inflammation via a miR-21-PDCD4-IL-10 pathway. MCG-treated wound macrophages exhibited a significantly bolstered efferocytosis index. Such favorable outcome significantly induced miR-21 expression. MCG-mediated IL-10 production was dampened under conditions of miR-21 knockdown pointing towards miR-21 as a causative factor. Pharmacological inhibition of JNK attenuated IL-10 production by MCG, implicating miR-21-JNK pathway in MCG-mediated IL-10 production by macrophages. This work provides direct evidence demonstrating that a collagen-based wound-care dressing may influence wound macrophage function and therefore modify wound inflammation outcomes.

Overexpression of Gloverin2 in the Bombyx mori silk gland enhances cocoon/silk antimicrobial activity

The Bombyx mori cocoon/silk possesses many immune-related components, including protease inhibitors, seroins, and antimicrobial peptides, which likely help to protect the pupating larva from infection. However, the natural antimicrobial activity of the B. mori cocoon/silk is still too weak for biomedical applications. With the goal of enhancing this natural activity, we constructed a transgenic vector to overexpress the B. mori antimicrobial peptide Gloverin2 (BmGlv2) under control of the silk gland-specific Serion1 promoter. Transgenic silkworms were generated via embryo microinjection. A low level of BmGlv2 was expressed in the non-transgenic silk gland, but BmGlv2 was efficiently overexpressed and proteolytically activated in the transgenic line. Overexpressed BmGlv2 was secreted and incorporated into the silk during spanning without affecting cocoon/silk formation. Moreover, the transgenic cocoon/silk had significantly greater inhibitory activity against bacteria and fungi than the non-transgenic cocoon/silk. This strategy could help enhance the antimicrobial performance and biomedical application of silk.

Preparation and characterization of chitosan/gelatin/nanocrystalline cellulose/calcium peroxide films for potential wound dressing applications

In order to improve mechanical properties and biomedical behavior of chitosan-based polymeric films, the effect of nanocrystalline cellulose (NCC) and calcium peroxide (CP) particles on the properties of polymeric films based on chitosan (CS) and gelatin (GL) were investigated in this study. The films were characterized by Fourier-transform infrared (FTIR), tensile, swelling, water vapor transmission rate (WVTR), antibacterial, oxygen release and cell culture tests. FTIR results indicated that hydrogen bonding has been formed between functional groups of the constituents. The mechanical results showed that the combination of both CP and NCC had better results in improving the mechanical properties of the films. The WVTR and swelling results indicated that CP and NCC particles reduced the amount of WVTR and swelling of the samples. By Adding CP to the film composition, the antibacterial activity of the films against E. coli bacteria increased. The oxygen release for the films containing CP has its maximum value during the first day and it approaches a constant value for 10 days. The MTT assay results revealed that the growth of the human fibroblast cells was increased during 7 days, showing that the chitosan-based films containing CP and NCC had no toxicity and never cause cell death.

Genetically engineered bi-functional silk material with improved cell proliferation and anti-inflammatory activity for medical application

Functional silk is a promising material for future medical applications. These include fabrication of diverse silk fiber and silk protein-regenerated biomaterials such as silk sutures, hydrogel, films, and 3D scaffolds for wound healing and tissue regeneration and reconstruction. Here, a novel bi-functional silk with improved cell proliferation and anti-inflammatory activities was created by co-expressing the human basic fibroblast growth factor (FGF2) and transforming growth factor-β1 (TGF_β1) genes in silkworm. First, both FGF2 and TGF_β1 genes were confirmed to be successfully expressed in silk thread. The characterization of silk properties by SEM, FTIR, and mechanical tests showed that this new silk (FT silk) had a similar diameter, inner molecular composition, and mechanical properties as those of normal silk. Additionally, expressed FGF2 and TGF_β1 proteins were continuously and slowly released from FT silk for one week. Most importantly, the FGF2 and TGF_β1 contained in FT silk not only promoted cell proliferation by activating the ERK pathway but also significantly reduced LPS-induced inflammation responses in macrophages by mediating the Smad pathway. Moreover, this FT silk had no apparent toxicity for cell growth and caused no cell inflammation. These properties suggest that it has a potential for medical applications. STATEMENT OF SIGNIFICANCE: Silk spun by domestic silkworm is a promising material for fabricating various silk protein regenerated biomaterials in medical area, since it owes good biocompatibility, biodegradability and low immunogenicity. Recently, fabricating various functional silk fibers and regenerated silk protein biomaterials which has ability of releasing functional protein factor is the hot point field. This study is a first time to create a novel bi-functional silk material with the improved cell proliferation and anti-inflammatory activity by genetic engineered technology. This novel silk has a great application potential as new and novel medical material, and this study also provides a new strategy to create various functional or multifunctional silk fiber materials in future.

Bioinspired mineralization of a functionalized injectable dense collagen hydrogel through silk sericin incorporation

The incorporation of silk sericin into injectable dense collagen hydrogels represents a powerful approach to mimic the biomineralization process, together with the osteogenic stimulation of seeded mesenchymal stem cells, in vitro.

Three-Dimensionally Printed Silk-Sericin-Based Hydrogel Scaffold: A Promising Visualized Dressing Material for Real-Time Monitoring of Wounds

A wound dressing which can be convenient for real-time monitoring of wounds is particularly attractive and user-friendly. In this study, a nature-originated silk-sericin-based (SS-based) transparent hydrogel scaffold was prepared and evaluated for the visualization of wound care. The scaffold was fabricated from a hybrid interpenetrating-network (IPN) hydrogel composed of SS and methacrylic-anhydride-modified gelatin (GelMA) by 3D printing. The scaffold transformed into a highly transparent hydrogel upon swelling in PBS, and thus, anything underneath could be easily read. The scaffold had a high degree of swelling and presented a regularly macroporous structure with pores around 400 μm × 400 μm, which can help maintain the moist and apinoid environment for wound healing. Meanwhile, the scaffolds were conducive to adhesion and proliferation of L929 cells. A coculture of HaCaT and HSF cells on the scaffold showed centralized proliferation of the two cells in distributed layers, respectively, denoting a promising comfortable environment for re-epithelialization. Moreover, in vivo studies demonstrated that the scaffold showed no excessive inflammatory reaction. In short, this work presented an SS-based transparent hydrogel scaffold with steerable physical properties and excellent biocompatibility through 3D printing, pioneering promising applications in the visualization of wound care and drug delivery.

Biopolymer nanofibrils: structure, modeling, preparation, and applications

Biopolymer nanofibrils exhibit exceptional mechanical properties with a unique combination of strength and toughness, while also presenting biological functions that interact with the surrounding environment. These features of biopolymer nanofibrils profit from their hierarchical structures that spun angstrom to hundreds of nanometer scales. To maintain these unique structural features and to directly utilize these natural supramolecular assemblies, a variety of new methods have been developed to produce biopolymer nanofibrils. In particular, cellulose nanofibrils (CNFs), chitin nanofibrils (ChNFs), silk nanofibrils (SNFs) and collagen nanofibrils (CoNFs), as the four most abundant biopolymer nanofibrils on earth, have been the focus of research in recent years due to their renewable features, wide availability, low-cost, biocompatibility, and biodegradability. A series of top-down and bottom-up strategies have been accessed to exfoliate and regenerate these nanofibrils for versatile advanced applications. In this review, we first summarize the structures of biopolymer nanofibrils in nature and outline their related computational models with the aim of disclosing fundamental structure-property relationships in biological materials. Then, we discuss the underlying methods used for the preparation of CNFs, ChNFs, SNF and CoNFs, and discuss emerging applications for these biopolymer nanofibrils.

Fabrication of the FGF1-functionalized sericin hydrogels with cell proliferation activity for biomedical application using genetically engineered Bombyx mori (B. mori) silk

Sericin, as the major component of Bombyx mori silk, is a useful biomaterial for tissue engineering due to its hydrophilicity, biocompatibility and biodegradability. Here, we report the fabrication of a human acidic fibroblast growth factor (FGF1)-functionalized sericin hydrogel using a transgenic silkworm spun silk with FGF1 incorporated in its sericin layer. Sericin, together with FGF1, were simultaneously extracted from the silk fiber and then exposed to cold-induced hydrogel formation without additional crosslinking. The fabricated FGF1 sericin hydrogels demonstrated injectability, useful mechanical properties and a porous microstructure, which contributed to cell adhesion and survival. In addition, FGF1 achieved long-term storage in the sericin hydrogels over a wide range of temperatures. Further, the sericin-FGF1 demonstrated sustained release to promote cell proliferation and wound healing. Furthermore, cellular inflammatory responses showed that the FGF1 sericin hydrogels exhibited biocompatibility and no immunogenicity. This study revealed the successful exploration of FGF1-functionalized sericin hydrogels as a new protein-based biomaterial to expand applications of FGF1 and sericin in tissue and medical engineering. Further, we demonstrated a strategy for the predesign of exogenous protein-functionalized sericin hydrogels through genetically modifying silk fibers as sources for their cost effective production at a large scale.

STATEMENT OF SIGNIFICANCE

Sericin from the Bombyx mori silk, is regarded as a desirable biomaterial for tissue engineering due to its hydrophilicity, biocompatibility and biodegradability. Genetically engineering the sericin with functional exogenous proteins would enhance its biofunctions and further expand its application in tissue engineering. In this study, we demonstrated a method to fabricate a human acidic fibroblast growth factor (FGF1)-functionalized sericin hydrogel using a transgenic silkworm spun silk with FGF1 incorporated in its sericin layer. The fabricated FGF1 sericin hydrogels demonstrated injectability, porous microstructure, biocompatibility and no immunogenicity which contributed to cell adhesion and survival. Remarkably, FGF1 could achieve a long-term stability in the sericin hydrogels over a wide range of temperatures and sustained release to promote cell proliferation and wound healing. This study revealed the successful exploration of FGF1-functionalized sericin hydrogels as a new protein-based biomaterial in tissue and medical engineering application, and provided a strategy for the predesign of exogenous protein-functionalized sericin hydrogels through genetically modifying silk fibers as sources for their cost effective production at a large scale.

Oligoarginine mediated collagen/chitosan gel composite for cutaneous wound healing

In this study, the collagen/chitosan gel composite supplemented with a cell-penetrating peptide (CPP) (Oligoarginine, R8) was prepared. Then, the physicochemical properties of the new collagen/chitosan/CPPs gel obtained were analyzed and the related characteristics were evaluated by scanning electron microscopy (SEM), fourier transform infrared (FTIR), differential scanning calorimetry (DSC), differential thermal analyzer (DTA). Furthermore, we found that collagen/chitosan/CPPs gel composite was capable of inhibiting Staphylococcus aureus growth and had good ability to heal wounds. The mice test results showed that collagen/chitosan/CPPs gel had the highest healing rate, fastest healing speed in all the treatments. After 14 days, the group treated by collagen/chitosan/CPPs gel showed nearly complete wound surface healing rate of 98 ± 4.71%. In addition, histopathological examination suggested that collagen/chitosan/CPPs could promote cutaneous wound healing through enhancing granulation tissue formation, increasing collagen deposition and promoting angiogenesis in the wound tissue. Meanwhile, no significant cytotoxicity of the gel was observed. In conclusion, the collagen/chitosan/CPPs gel composite which has antibacterial activity renders a high therapeutic efficiency to heal wounds.

Development of a Novel Pre-Vascularized Three-Dimensional Skin Substitute Using Blood Plasma Gel

Skin substitutes with existing vascularization are in great demand for the repair of full-thickness skin defects. In the present study, we hypothesized that a pre-vascularized skin substitute can potentially promote wound healing. Novel three-dimensional (3D) skin substitutes were prepared by seeding a mixture of human endothelial progenitor cells (EPCs) and fibroblasts into a human plasma/calcium chloride formed gel scaffold, and seeding keratinocytes onto the surface of the plasma gel. The capacity of the EPCs to differentiate into a vascular-like tubular structure was evaluated using immunohistochemistry analysis and WST-8 assay. Experimental studies in mouse full-thickness skin wound models showed that the pre-vascularized gel scaffold significantly accelerated wound healing 7 days after surgery, and resembled normal skin structures after 14 days post-surgery. Histological analysis revealed that pre-vascularized gel scaffolds were well integrated in the host skin, resulting in the vascularization of both the epidermis and dermis in the wound area. Moreover, mechanical strength analysis demonstrated that the healed wound following the implantation of the pre-vascularized gel scaffolds exhibited good tensile strength. Taken together, this novel pre-vascularized human plasma gel scaffold has great potential in skin tissue engineering.

Novel sericin-based hepatocyte serum-free medium and sericin’s effect on hepatocyte transcriptome

AIM

To develop a novel hepatocyte serum-free medium based on sericin, and to explore the effect of sericin on the hepatocyte transcriptome.

METHODS

A controlled trial comparing novel serum-free medium and other media: C3A cells were cultured in our novel serum-free medium, HepatoZYME, complete medium (DMEM/F12 with 100 mL/L FBS), and DMEM/F12, and then cell attachment, proliferation, and function as well as the biocompatibility of the media were assessed. A comparative study of serum-free media with or without 2 mg/mL sericin: the effect of sericin on C3A growth was assessed by cell viability and proliferation, the effect of sericin on C3A cell cycle distribution was determined by flow cytometry, and the effect of sericin on the C3A transcriptome was assessed by gene-chip array and RT-qPCR.

RESULTS

More C3A cells attached to the plate containing our serum-free medium than to those containing HepatoZYME and DMEM/F12 at 24 h post-seeding. Both the viability and proliferation rate of C3A cells in sericin-based serum-free medium were superior to those of cells in HepatoZYME and DMEM/F12 (P < 0.001). The content of albumin and urea in our serum-free medium was significantly higher than that in HepatoZYME and DMEM/F12 throughout the whole culture period (P < 0.001) and was similar to that in complete medium at day 3, 4, and 5. In part 2, cell viability and proliferation were greater in the presence of 2 mg/mL sericin (P < 0.001), as was the proportion of cells in S phase (16.21% ± 0.98% vs 12.61% ± 0.90%, P < 0.01). Gene-chip array analysis indicated that the expression of CCR6, EGFR, and FOS were up-regulated by 2 mg/mL sericin, and RT-qPCR revealed that the expression of CCR6, EGFR, FOS, AKT1, JNK1, NFkB1, MMP-9, MEK2, ERK1/2 and MYC was up-regulated by 2 mg/mL sericin (P < 0.05).

CONCLUSION

We developed a novel hepatocyte serum-free medium. Sericin probably enhances cell attachment through the CCR6-Akt-JNK-NF-κB pathway and promotes cell proliferation through CCR6-mediated activation of the ERK1/2-MAPK pathway.

Preparation and Characterization of AgNPs In Situ Synthesis on Polyelectrolyte Membrane Coated Sericin/Agar Film for Antimicrobial Applications

Antibacterial materials are of great importance in preventing bacterial adhesion and reproduction in daily life. Silver nanoparticle (AgNP) is a broad-spectrum antibacterial nanomaterial that has attracted significant attentions for its ability to endow natural materials with antibacterial ability. Silk sericin (SS) has a great advantage for biomaterial application, as it is a natural protein with excellent hydrophilicity and biodegradability. In this study, we prepared AgNPs and polyelectrolyte membrane (PEM) modified SS/Agar films through the layer-by-layer adsorption technique and ultraviolet-assisted AgNPs synthesis method. The film was well characterized by scanning electron microscopy, energy dispersive spectroscopy, X-ray diffraction, fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy. Other properties such as water contact angle, wettability and tensile strength, the release of silver were also studied. The antimicrobial activity of AgNPs-PEM-SS/Agar film was investigated against Escherichia coli and Staphylococcus aureus as the model microorganisms by the inhibition zone and bacterial growth curve assays. The results suggested that the AgNPs-PEM-SS/Agar film had excellent mechanical performance, high hydrophilicity, prominent water absorption ability, as well as outstanding and durable antibacterial activity. Therefore, the prepared novel AgNPs-PEM-SS/Agar composite film is proposed as a potentially favorable antibacterial biomaterial for biomedical applications.