Sericin-carboxymethyl cellulose porous matrices as cellular wound dressing material

Essential oils loaded carboxymethylated Cassia fistula gum-based novel hydrogel films for wound healing

Carboxymethylated Cassia fistula gum (CCFG) and citric acid (CA) based wound healing film, (CCFG-CA) was developed using the solvent casting method. Glycerol was added as a plasticizing agent. The synthesized Carboxymethylated Cassia fistula gum cross-linked citric acid based hydrogel film (CCFG-CA) was evaluated morphologically, thermally, and structurally using FESEM, TGA, XRD and FTIR. Three essential oils (EO), rosemary (Rosmarinus officinalis), turmeric (Curcuma longa) and thuja (Thuja occidentalis L), known for antimicrobial and antioxidant activities, were loaded into the CCFG-CA film to develop essential oils loaded carboxymethylated Cassia fistula gum cross-linked citric acid based hydrogel film (CCFG-CA-EO). In vitro studies (MTT assay, disk diffusion assay, permeability tests and DPPH assay) confirm the biocompatibility, anti-oxidant and anti-microbial properties of the CCFG-CA-EO film. In vivo (wound healing studies on wistar rats and their histology) shows 99 % of wound healing and re-epithelialization in 14 days. Degradability (within 15 days), protein adsorption (12.05 μg/mL) and contact angle determination (69.43°ׄׄ ± 0.48) tests confirmed the potential of CCFG-CA-EO as an effective wound-healing material.

Therapeutic potential of silkworm sericin in wound healing applications

Chronic wounds are characterised by an imbalance between pro and anti-inflammatory signals, which result in permanent inflammation and delayed re-epithelialization, consequently hindering wound healing. They are associated with bacterial infections, tissue hypoxia, local ischemia, reduced vascularization, and MMP-9 upregulation. The global prevalence of chronic wounds has been estimated at 40 million in the adult population, with an alarming annual growth rate of 6.6%, making it an increasingly significant clinical problem. Sericin is a natural hydrophilic protein obtained from the silkworm cocoon. Due to its biocompatibility, biodegradability, non-immunogenicity, and oxidation resistance, coupled with its excellent affinity for target biomolecules, it holds great potential in wound healing applications. The silk industry discards 50,000 tonnes of sericin annually, making it a readily available material. Sericin increases cell union sites and promotes cell proliferation in fibroblasts and keratinocytes, thanks to its cytoprotective and mitogenic effects. Additionally, it stimulates macrophages to release more therapeutic cytokines, thus improving vascularization. This review focuses on the biological properties of sericin that contribute towards enhanced wound healing process and its mechanism of interaction with important biological targets involved in wound healing. Emphasis is placed on diverse wound dressing products that are sericin based and the utilisation of nanotechnology to design sericin nanoparticles that aid in chronic wound management.

Eco-Friendly Production of Polyvinyl Alcohol/Carboxymethyl Cellulose Wound Healing Dressing Containing Sericin

Wound dressing production represents an important segment in the biomedical healthcare field, but finding a simple and eco-friendly method that combines a natural compound and a biocompatible dressing production for biomedical application is still a challenge. Therefore, the aim of this study is to develop wound healing dressings that are environmentally friendly, low cost, and easily produced, using natural agents and a physical crosslinking technique. Hydrogel wound healing dressings were prepared from polyvinyl alcohol/carboxymethyl cellulose and sericin using the freeze-thawing method as a crosslinking method. The morphological characterization was carried out by scanning electron microscopy (SEM), whereas the mechanical analysis was carried out by dynamic mechanical analysis (DMA) to test the tensile strength and compression properties. Then, the healing property of the wound dressing material was tested by in vitro and ex vivo tests. The results show a three-dimensional microporous structure with no cytotoxicity, excellent stretchability with compressive properties similar to those of human skin, and excellent healing properties. The proposed hydrogel dressing was tested in vitro with HaCaT keratinocytes and ex vivo with epidermal tissues, demonstrating an effective advantage on wound healing acceleration. Accordingly, this study was successful in developing wound healing dressings using natural agents and a simple and green crosslinking method.

Development of nanocellulose hydrogels for application in the food and biomedical industries: A review

As the most abundant and renewable natural resource, cellulose has attracted significant attention and research interest for the production of hydrogels (HGs). To address environmental issues and emerging demands, the benefits of naturally produced HGs include excellent mechanical properties and superior biocompatibility. HGs are three-dimensional networks created by chemical or physical cross-linking of linear or branched hydrophilic polymers and have high capacity for absorption of water and biological fluids. Although widely used in the food and biomedical fields, most HGs are not biodegradable. Nanocellulose hydrogels (NC-HGs) have been extensively applied in the food industry for detection of freshness, chemical additives, and substitutes, as well as the biomedical field for use as bioengineering scaffolds and drug delivery systems owing to structural interchangeability and stimuli-responsive properties. In this review article, the sources, structures, and preparation methods of NC-HGs are described, applications in the food and biomedical industries are summarized, and current limitations and future trends are discussed.

Creating and exploring carboxymethyl cellulose aerogels as drug delivery devices

Carboxymethyl cellulose (CMC) is a well-known cellulose derivative used in biomedical applications due to its biocompatibility and biodegradability. In this work, novel porous CMC materials, aerogels, were prepared and tested as a drug delivery device. CMC aerogels were made from CMC solutions, followed by non-solvent induced phase separation and drying with supercritical CO2. The influence of CMC characteristics and of processing conditions on aerogels' density, specific surface area, morphology and drug release properties were investigated. Freeze-drying of CMC solutions was also used as an alternative process to compare the properties of the as-obtained "cryogels" with those of aerogels. Aerogels were nanostructured materials with bulk density below 0.25 g/cm3 and high specific surface area up to 143 m2/g. Freeze drying yields highly macroporous materials with low specific surface areas (around 5-18 m2/g) and very low density, 0.01 - 0.07g/cm3. Swelling and dissolution of aerogels and cryogels in water and in a simulated wound exudate (SWE) were evaluated. The drug was loaded in aerogels and cryogels, and release kinetics in SWE was investigated. Drug diffusion coefficients were correlated with material solubility, morphology, density, degree of substitution and drying methods, demonstrating tuneability of new materials' properties in view of their use as delivery matrices.

Characterization and Evaluation of Silk Sericin-Based Hydrogel: A Promising Biomaterial for Efficient Healing of Acute Wounds

The present study was aimed to prepare the potent silk sericin-based hydrogels in combination with plant extracts (curcumin and banana peel powder) and silver nanoparticles (AgNPs) to accelerate the acute wound healing process. Experimental excision wounds were created in mice by biopsy puncture, and the wound healing potential of silk sericin (2%)-based hydrogel and its combinations with curcumin (2%), banana peel powder (2%), and AgNPs (2%) was estimated by calculating the percent wound contraction, healing time, histology of skin tissues, and different biochemical tests. The results showed that the mice treated with sericin-based hydrogels showed significantly (P < 0.001) high percent wound contraction as compared to negative control, and wounds were healed in 11 days. The histological evaluation also showed that wounds covered with hydrogels were healed more than the uncovered wounds. Furthermore, the results of biochemical tests revealed that the treatment groups showed a significant (P < 0.001) decrease in the serum level of pro-inflammatory cytokines (IL-6). A significant (P < 0.001) increase in anti-inflammatory cytokines (IL-10) and anti-oxidant enzymes was observed in treatment groups. The highest wound healing potential was observed by sericin-based hydrogel containing banana peel powder, leaving behind the commercially available ointment polyfax (positive control). It can be concluded that the silk sericin-based hydrogels in combination with plant extract and AgNPs can be used as natural biomaterials in wound dressing for the rapid healing of acute wounds.

Carboxymethyl Cellulose as a Food Emulsifier: Are Its Days Numbered?

Carboxymethyl cellulose use in industry is ubiquitous. Though it is recognized as safe by the EFSA and FDA, newer works have raised concerns related to its safety, as in vivo studies showed evidence of gut dysbiosis associated with CMC's presence. Herein lies the question, is CMC a gut pro-inflammatory compound? As no work addressed this question, we sought to understand whether CMC was pro-inflammatory through the immunomodulation of GI tract epithelial cells. The results showed that while CMC was not cytotoxic up to 25 mg/mL towards Caco-2, HT29-MTX and Hep G2 cells, it had an overall pro-inflammatory behavior. In a Caco-2 monolayer, CMC by itself increased IL-6, IL-8 and TNF-α secretion, with the latter increasing by 1924%, and with these increases being 9.7 times superior to the one obtained for the IL-1β pro-inflammation control. In co-culture models, an increase in secretion in the apical side, particularly for IL-6 (692% increase), was observed, and when RAW 264.7 was added, data showed a more complex scenario as stimulation of pro-inflammatory (IL-6, MCP-1 and TNF-α) and anti-inflammatory (IL-10 and IFN-β) cytokines in the basal side was observed. Considering these results, CMC may exert a pro-inflammatory effect in the intestinal lumen, and despite more studies being required, the incorporation of CMC in foodstuffs must be carefully considered in the future to minimize potential GI tract dysbiosis.

k-Carrageenan/sericin-based multiparticulate systems: A novel gastro-resistant polymer matrix for indomethacin delivery

This study aimed to develop a natural and multiparticulate carrier of k-carrageenan (k-Car) and sericin (Ser) for encapsulation of indomethacin (IND) in order to minimize gastrointestinal effects caused by immediate-release. Increasing the amount of IND in the formulations subtly reduced the entrapment efficiency (EE) and drug loading (DL) due to matrix saturation. Sericin was essential to improve EE and DL when compared to pure k-Car (EE > 90 % and DL > 47 %) with suitable particle sizes (1.3461 ± 0.1891-1.7213 ± 0.1586 mm). The incorporation and integrity of IND in the particles were confirmed by analytical techniques of HPLC, XRD, FTIR, and SEM. Additionally, the k-Car/Ser matrix was pH-responsive with low IND release at pH 1.2 and extended-release at pH 6.8. The Weibull model had an adequate fit to the experimental data with R²aju 0.950.99 and AIC 82.4-24.9, with curves in parabolic profile (b < 1) and indicative of a controlled drug-release mechanism by diffusion. Besides, k-Car/Ser/IND and placebo were not cytotoxic (cell viability > 85 % at 150-600 μM) for the Caco-2 cell line. Therefore, the polymeric matrix is gastro-resistant, stable, and biocompatible to carry indomethacin and deliver it to the intestinal environment.

Enhanced skin drug delivery using dissolving microneedles: a potential approach for the management of skin disorders

INTRODUCTION

For decades, finding effective long-term or disease-modifying treatments for skin disorders has been a major focus of scientists. The conventional drug delivery systems showed poor efficacy with high doses and are associated with side effects, which lead to challenges in adherence to therapy. Therefore, to overcome the limitations of conventional drug delivery systems, drug delivery research has focused on topical, transdermal, and intradermal drug delivery systems. Among all, the dissolving microneedles have gained attention with a new range of advantages of drug delivery in skin disorders such as breaching skin barriers with minimal discomfort and its simplicity of application to the skin, which allows patients to administer it themselves.

AREAS COVERED

This review highlighted the insights into dissolving microneedles for different skin disorders in detail. Additionally, it also provides evidence for its effective utilization in the treatment of various skin disorders. The clinical trial status and patents for dissolving microneedles for the management of skin disorders are also covered.

EXPERT OPINION

The current review on dissolving microneedles for skin drug delivery is accentuating the breakthroughs achieved so far in the management of skin disorders. The output of the discussed case studies anticipated that dissolving microneedles can be a novel drug delivery strategy for the long-term treatment of skin disorders.

Development of a novel silk sericin-based hydrogel film by mixture design

Sericin has been used in functional and potentially biodegradable materials for cosmetics, biomedical, agricultural, and food applications. It is a natural polymer with applications in absorbent materials, such as hydrogels, because of its hydrophilic character. However, sericin by itself is brittle, and in contact with water has low structural stability, being necessary its blending with other polymers or the application of crosslinking processes. In this work, hydrogel films were prepared from different mixtures containing sericin (SS), carboxymethylcellulose (CMC), and polyvinyl alcohol (PVA), using a simple and environmentally friendly method consisting of a gelling process followed by solvent casting. A mixture design was applied to assess the incidence of each component and its interaction with the output variables of interest. Two response variables were evaluated in each formulation: water absorption capacity (WA) and gel fraction (GF). It was also possible to model the output variables based on the proportions of the sample components. In addition, a set of formulations were used to produce hydrogels with high water absorption rates while maintaining their structural stability. The optimal hydrogel formulation (HF) was structurally and thermally characterized by FTIR and TGA, respectively. Hydrogel morphology was also studied by scanning electron microscopy (SEM). The results of this study constitute an important contribution to the design of novel processing routes to extend the use of silk sericin in the development of new materials.

Turmeric Herb Extract-Incorporated Biopolymer Dressings with Beneficial Antibacterial, Antioxidant and Anti-Inflammatory Properties for Wound Healing

Bacterial infection and inflammation caused by excess oxidative stress are serious challenges in chronic wound healing. The aim of this work is to investigate a wound dressing based on natural- and biowaste-derived biopolymers loaded with an herb extract that demonstrates antibacterial, antioxidant, and anti-inflammatory activities without using additional synthetic drugs. Turmeric extract-loaded carboxymethyl cellulose/silk sericin dressings were produced by esterification crosslinking with citric acid followed by freeze-drying to achieve an interconnected porous structure, sufficient mechanical properties, and hydrogel formation in situ in contact with an aqueous solution. The dressings exhibited inhibitory effects on the growth of bacterial strains that were related to the controlled release of the turmeric extract. The dressings provided antioxidant activity as a result of the radical scavenging effect on DPPH, ABTS, and FRAP radicals. To confirm their anti-inflammatory effects, the inhibition of nitric oxide production in activated RAW 264.7 macrophages was investigated. The findings suggested that the dressings could be a potential candidate for wound healing.

The Potential of Purple Waxy Corn Cob (Zea mays L.) Extract Loaded-Sericin Hydrogel for Anti-Hyperpigmentation, UV Protection and Anti-Aging Properties as Topical Product Applications

Sericin-hydrogel formulations incorporating purple waxy corn (Zea mays L.) cob extract (PWCC) were developed as potential topical skin cosmetic products. Sericin has wound healing properties, protects against ultraviolet (UV) radiation, and exhibits anti-inflammatory, anti-oxidation, and anti-tyrosinase activities. PWCC is a rich source of anthocyanins with antioxidants, UV protective, anti-inflammatory, and collagen-enhancing activities. Six hydrogel formulations (S1-S6) were investigated for anti-melanogenesis on the B16F10 melanoma cell line and UV-protection on human keratinocytes (HaCaT) and anti-aging activities on normal human dermal fibroblasts (NHDFs). The results showed that the hydrogel formulations enhanced the anthocyanin permeation through the skin. The S4 formulation indicated the highest inhibition of tyrosinase activity and reduced the melanin pigment, increased the cell viability of the UV-induced HaCaT cells, the inhibition of collagenase and elastase, and increased the collagen type I production without cytotoxicity. Therefore, the PWCC loaded-sericin hydrogels show a high potential as a novel anti-hyperpigmentation, UV protection, and anti-aging products for topical applications.

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.

Efficient and recyclable sericin-derived carbon aerogel for oils and organic solvents adsorption

Sericin, an industrial waste of the silk industry, is a promising precursor for adsorbent preparation. In this work, an efficient and novel sericin-derived carbon aerogel (SCA) was used to improve the adsorption efficiency of oils and organic solvents. The SCA demonstrated a high-efficiency sorption capacity of not only soybean oil (adsorption capacity reached up to 167.69 times its weight) but also chloroform and methylene chloride (adsorption capacity of 193.67 g/g and 173.25 g/g respectively). It is observed that SCA could be regenerated multiple times through combustion and after five cycles, its adsorbability to ethanol, dimethyl sulfoxide, and soybean oil remained high at 59.08 g/g, 59.34 g/g, and 137.36 g/g, respectively. The physical and chemical characteristics of sericin and SCA were analyzed using Scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET), X-ray diffraction (XRD), Raman spectra and Fourier transform infrared spectroscopy (FTIR) analysis. The results suggest that SCA is an adsorbent with excellent properties and can significantly increase the adsorption capacity of oils and organic solvents. The overall results indicate that SCA is effectively used as an adsorbent for the adsorption of oils and organic solvents, which will contribute to reduce the discharge of sericin-containing wastewater and alleviate pollution caused by oil and organic solvent leakage.

Characterization and Evaluation of Commercial Carboxymethyl Cellulose Potential as an Active Ingredient for Cosmetics

Carboxymethyl cellulose is the most used water-soluble cellulose with applications in industries such as food, cosmetics, and tissue engineering. However, due to a perceived lack of biological activity, carboxymethyl cellulose is mostly used as a structural element. As such, this work sought to investigate whether CMC possesses relevant biological properties that could grant it added value as a cosmeceutical ingredient in future skincare formulations. To that end, CMC samples (Mw between 471 and 322 kDa) skin cell cytotoxicity, impact upon pro-collagen I α I production, and inflammatory response were evaluated. Results showed that samples were not cytotoxic towards HaCat and HDFa up to 10 mg/mL while simultaneously promoting intracellular production of pro-collagen I α I up by 228% relative to the basal metabolism, which appeared to be related to the highest DS and Mw. Additionally, CMC samples modulated HaCat immune response as they decreased by ca. 1.4-fold IL-8 production and increased IL-6 levels by ca. five fold. Despite this increase, only two samples presented IL-6 levels similar to those of the inflammation control. Considering these results, CMC showed potential to be a more natural alternative to traditional bioactive cosmetic ingredients and, as it is capable of being a bioactive and structural ingredient, it may play a key role in future skincare formulations.

Preparation of silane-dispersed graphene crosslinked vinyl carboxymethyl chitosan temperature-responsive hydrogel with antibacterial properties

We synthesized a temperature-sensitive antibacterial hydrogel, defined as NIPAM-CG/GM hydrogel. First, vinyl carboxymethyl chitosan (CG) was synthesized as a crosslinking carrier and silane dispersed graphene (GM) was synthesized as a reinforcer. Then, the N-isopropylacrylamide (NIPAM) monomer was free-radical polymerized with the vinyl groups of CG and GM to form a NIPAM-CG/GM hydrogel without any crosslinking agent. The influences of different hydrogel compositions on the microstructure, compressive properties, swelling, drug loading, and drug release properties of the hydrogels were discussed, and its temperature sensitivity was also demonstrated. The results showed that the lower critical solution temperature (LCST) and mechanical properties of the hydrogel could be adjusted by controlling the amount of CG and GM. Next, its biocompatibility was characterized, and its antibacterial performance was tested against Escherichia coli and Staphylococcus aureus. The antibacterial mechanism was explained by measuring the difference in the ion concentration outside the membrane and changes in the morphology of live/dead bacteria. NIPAM-CG/GM had a high drug loading and nearly complete drug release at a physiological temperature of 37 °C. Its moderate mechanical properties, excellent biocompatibility, and antibacterial effects give NIPAM-CG/GM great potential applications as a wound dressing.

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.

Carboxymethyl cellulose/tetracycline@UiO-66 nanocomposite hydrogel films as a potential antibacterial wound dressing

Designing an antibacterial agent with a suitable water vapor permeability, good mechanical properties, and controlled antibiotic release is a promising method for stopping bacterial infection in wound tissue. In this respect, this work aims to prepare novel flexible polymeric hydrogel films via integrating UiO-66 into the polymeric carboxymethyl cellulose (CMC) hydrogel for improving the mechanical and antibiotic release performances. First, we performed a green hydrothermal synthetic method to synthesis UiO-66 and followed by encapsulating Tetracycline (TC) through immersion in its aqueous solution. Also, the casting technique was utilized to integrate different concentrations of the TC-encapsulated UiO-66 (TC@UiO-66, 5% to 15%) in the polymeric CMC matrix (CMC/TC@UiO-66) cross-linked by citric acid and plasticized by glycerol. The release performance showed a low initial burst release with a controlled release over 72 h in the artificial sweat and simulated wound exudate (PBS, pH 7.4) media. The in vitro cytotoxicity and antibacterial activity results revealed a good cytocompatibility toward Human skin fibroblast (HFF-1) cells and a significant activity against both E. coli and S. aureus with 1.3 and 1.7 cm inhibition zone, respectively. The obtained results recommend CMC/TC@UiO-66 films as a potential antibacterial wound dressing.

Hybrid Bionanocomposite Containing Magnesium Hydroxide Nanoparticles Embedded in a Carboxymethyl Cellulose Hydrogel Plus Silk Fibroin as a Scaffold for Wound Dressing Applications

Based on the promising biomedical developments in wound healing strategies, herein, a new nanobiocomposite scaffold was designed and presented by incorporation of carboxymethyl cellulose hydrogels prepared using epichlorohydrin as a cross-linking agent (CMC hydrogel), a natural silk fibroin (SF) protein, and magnesium hydroxide nanoparticles (Mg(OH)2 NPs). Biological evaluation of the CMC hydrogel/SF/Mg(OH)2 nanobiocomposite scaffold was conducted via in vitro cell viability assays and in vivo assays, red blood cell hemolysis, and antibiofilm assays. Considering the cell viability percentage of Hu02 cells (84.5%) in the presence of the prepared nanobiocomposite after 7 days, it was indicated that this new nanoscaffold was biocompatible. The signs of excellent hemocompatibility and the high antibacterial activity were observed due to the low-point hemolytic effect (8.3%) and high-level potential in constraining the P. aeruginosa biofilm formation with a low OD value (0.13). Moreover, in vivo wound healing assay results indicated that the wound healing method was faster in mice treated with the prepared nanobiocomposite scaffold (82.29%) than the control group (75.63%) in 12 days. Apart from the structural characterization of the CMC hydrogel/SF/Mg(OH)2 nanobiocomposite through FTIR, EDX, FESEM, and TG analyses, compressive mechanical tests, contact angle, porosity, and swelling ratio studies indicated that the combination of the CMC hydrogel structure with SF protein and Mg(OH)2 NPs could significantly impact Young's modulus (from 11.34 to 10.14 MPa), tensile strength (from 299.35 to 250.78 MPa), elongation at break (12.52 to 12.84%), hydrophilicity, and water uptake capacity (92.5%).

Recent Progress on Cellulose-Based Ionic Compounds for Biomaterials

Glycans play important roles in all major kingdoms of organisms, such as archea, bacteria, fungi, plants, and animals. Cellulose, the most abundant polysaccharide on the Earth, plays a predominant role for mechanical stability in plants, and finds a plethora of applications by humans. Beyond traditional use, biomedical application of cellulose becomes feasible with advances of soluble cellulose derivatives with diverse functional moieties along the backbone and modified nanocellulose with versatile functional groups on the surface due to the native features of cellulose as both cellulose chains and supramolecular ordered domains as extractable nanocellulose. With the focus on ionic cellulose-based compounds involving both these groups primarily for biomedical applications, a brief introduction about glycoscience and especially native biologically active glycosaminoglycans with specific biomedical application areas on humans is given, which inspires further development of bioactive compounds from glycans. Then, both polymeric cellulose derivatives and nanocellulose-based compounds synthesized as versatile biomaterials for a large variety of biomedical applications, such as for wound dressings, controlled release, encapsulation of cells and enzymes, and tissue engineering, are separately described, regarding the diverse routes of synthesis and the established and suggested applications for these highly interesting materials.

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.

Quantification of silk protein using phage nanofibers with high binding specificity

Silk sericin (SS) has emerged as an important silk protein for use in medicine and textiles. However, no sensitive method is available for detecting it. Here, we employed phage nanofibers (∼7 nm wide) as a probe to quantify SS from a dilute aqueous solution by exploiting two properties of the bacteria-infecting phage nanofibers, its use as a platform for discovering SS-binding peptide and its ultrasensitive quantification by a simple titering assay (where the number of phage nanofibers displaying the SS-binding peptide is equal to the number of countable millimeter-sized plaques derived from the phage nanofibers by infecting bacteria through plating). We first discovered a SS-binding peptide and the phage nanofibers (SS-phage) displaying this peptide at the tip. We found that this peptide can even differentiate SS from another silk protein (silk fibroin), showing its high specificity. We then employed SS-phage nanofibers as a probe to bind the SS casted from the aqueous solution. Because SS-phage nanofibers bound to the SS and the SS in the original SS solution were numerically correlated and the number of SS-phage nanofibers can be determined by counting the plaques in a Petri dish by the titering assay, determining the number of phage-derived plaques with the naked eye led to the rapid quantification of SS concentration with a detection limit of 19.50 ng ml^-1. This phage-based counting strategy can be potentially applied to the facile detection of other proteins.

Polyurethane/carboxymethylcellulose nanofibers containing Malva sylvestris extract for healing diabetic wounds: Preparation, characterization, in vitro and in vivo studies

In this study, new polyurethane (PU)-based nanofibers wound dressings containing Malva sylvestris extract were prepared and their effect on diabetic wound healing process was evaluated. Different amounts of carboxymethyl cellulose (CMC) were used to improve the absorption ability of wound exudates. The result showed that the usage of 20% w/w CMC in the polymer blend; and producing of nanofibers with an average diameter of 386.5 nm, led to the gradual release of the herbal compound in 85 h and bead-free morphology. Due to the antibacterial activity of wound dressing and wound healing process, the amount of 15% w/w herbal extract was selected as the optimum. For this sample, the fluid absorption was 412.31%. The extract loaded wound dressing samples showed satisfactory effects on Staphylococcus aureus and Escherichia coli bacteria. In vivo wound-healing and histological performance observations indicated that the use of the herbal extract in wound dressing improved wound healing significantly. On day 14, the average healing rate for gauze bandage, PU/CMC, and different amounts of 5, 10, 15 and 20% w/w extract containing wound dressings was 32.1 ± 0.2%, 51.4 ± 0.4%, 71 ± 0.14%, 87.64 ± 1.02%, 95.05 ± 0.24% and 95.11 ± 0.2%, respectively. Compared to the control groups, treatments with extract loaded wound dressings were effective in lowering acute and chronic inflammations. In diabetic rat wounds, collagen deposition and neovascularization were higher in wounds treated with an herbal extract containing wound dressing compared to the wounds treated with a gauze bandage and PU/CMC treated wounds. It can be suggested that this product may be considered as a good dual anti-inflammatory-antimicrobial wound dressing candidate for improving the diabetic wound healing.

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.

Sericin Nerve Guidance Conduit Delivering Therapeutically Repurposed Clobetasol for Functional and Structural Regeneration of Transected Peripheral Nerves

Peripheral nerve injury often causes significant function loss. Autologous nerve grafting as a gold-standard repair strategy for treating such an injury is limited by donor nerve supply. Tissue-engineered nerve guidance conduits (TENGCs) as a promising alternative for autografting are challenged by large nerve gaps. Herein, we fabricate a glutaraldehyde-cross-linked sericin nerve guidance conduit (GSC) incorporated with clobetasol, a glucocorticoid receptor agonist, for repairing a 10 mm long sciatic nerve gap in a rat model. The GSC exhibits biocompatibility and regeneration-favorable physicochemical properties. GSC's degradation products promote the secretion of neurotrophic factors in Schwann cells. By repurposing clobetasol for peripheral nerve regeneration, our work uncovers clobetasol's previously unknown functions in promoting Schwann cell proliferation and upregulating the expression of myelin-related genes. Importantly, the implantation of this clobetasol-loaded GSC in vivo leads to successful regeneration of the transected sciatic nerve. Strikingly, the regeneration outcome is functionally comparable to that of autologous nerve grafting (evidenced by three parameters). Specifically, the static sciatic index (SSI), relative reaction time (RRT) and nerve conduction velocity (NCV) in Clobetasol/GSC group are -74.55, 1.30, and 46.4 mm/s at Week 12, respectively, while these parameters are -64.53, 1.23, and 49.8 mm/s in Autograft group. Thus, this work represents the first report unveiling clobetasol's potential in peripheral nerve regeneration, reveals the feasibility of applying a sericin conduit for repairing a large nerve defect, and demonstrates the effectiveness of the clobetasol-loaded-GSC based strategy in transected nerves' regeneration.

Gelatin-polysaccharide composite scaffolds for 3D cell culture and tissue engineering: Towards natural therapeutics

Gelatin is a promising material as scaffold with therapeutic and regenerative characteristics due to its chemical similarities to the extracellular matrix (ECM) in the native tissues, biocompatibility, biodegradability, low antigenicity, cost-effectiveness, abundance, and accessible functional groups that allow facile chemical modifications with other biomaterials or biomolecules. Despite the advantages of gelatin, poor mechanical properties, sensitivity to enzymatic degradation, high viscosity, and reduced solubility in concentrated aqueous media have limited its applications and encouraged the development of gelatin-based composite hydrogels. The drawbacks of gelatin may be surmounted by synergistically combining it with a wide range of polysaccharides. The addition of polysaccharides to gelatin is advantageous in mimicking the ECM, which largely contains proteoglycans or glycoproteins. Moreover, gelatin-polysaccharide biomaterials benefit from mechanical resilience, high stability, low thermal expansion, improved hydrophilicity, biocompatibility, antimicrobial and anti-inflammatory properties, and wound healing potential. Here, we discuss how combining gelatin and polysaccharides provides a promising approach for developing superior therapeutic biomaterials. We review gelatin-polysaccharides scaffolds and their applications in cell culture and tissue engineering, providing an outlook for the future of this family of biomaterials as advanced natural therapeutics.

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.

Prospects of nonmulberry silk protein sericin-based nanofibrous matrices for wound healing - In vitro and in vivo investigations

Recently, the progress in biomaterials for biomedical applications brings the focus of the research community toward nanomaterials. The nanofibrous matrices offer certain advantages (structural similarity to extracellular matrix, high surface area-to-volume ratio, increased elasticity, biostability, and strength) compared to other prevalent type of materials. This affirms their superiority and flexibility to be used in regenerative medicine. We have fabricated nonmulberry (Antheraea mylitta) silk protein sericin-based nanofibrous matrices (fiber thickness; 80-400 nm) with improved mechanical strength and desired stability (>4 weeks) as required for tissue reconstruction. These matrices support the adhesion, proliferation, and cellular interconnection of human keratinocytes. These are minimally hemolytic, nonimmunogenic, and capable of wound healing in vivo. Antibiotic (cephalexin hydrate [CH])-loaded nanofibrous matrices accelerate the full-thickness wound repair with minimal inflammation and without any signs of infection. The histological analysis authenticates skin restoration with re-epithelialization, generation of associated skin appendages, and synthesis of dense collagen fibrils. In addition, analysis of inflammatory genes and immunohistochemical assays have proved their biocompatibility and wound healing potential. Angiogenesis is also prevalent in the animal tissue treated with nanofibrous matrices. The results of in vitro and in vivo experimentations indicate a clear prospect of the fabricated sericin-based nanofibrous matrices to be used for skin regeneration.

STATEMENT OF SIGNIFICANCE

Nonmulberry silk protein sericin-based nanofibrous matrix is a useful biomaterial for wound healing, collagen production, and skin tissue repair. It has been used in different formulations including hydrogels and nanofibrous membranes with chitosan (CS) and polyvinyl alcohol (PVA). No experiments have been carried out to evaluate sericin-based nanofibrous membranes for skin tissue engineering application. The present study shows that the nanofibrous matrices fabricated by electrospinning nonmulberry silk protein sericin with CS and PVA mimic the architectural environment of the extracellular matrix fibrils. These matrices are minimally hemolytic, are nonimmunogenic, and support better growth of human keratinocytes in vitro and wound healing in vivo with re-epithelialization of the skin tissue and angiogenesis. This work indicates that these nonmulberry sericin-based nanofibrous matrices with CS may be used as an ideal physical environment and biological cues for the promotion of skin tissue reconstruction and repair.

Sodium deoxycholate/TRIS-based hydrogels for multipurpose solute delivery vehicles: Ambient release, drug release, and enantiopreferential release

Herein, we report the investigation of sodium deoxycholate (NaDC)/TRIS-based hydrogels as delivery vehicles for a broad range of applications. Three hydrogel formulations were chosen for unique rheological behaviors that suggest a change in internal hydrogel structure with the application of a shear force. In this work, we compare solute release from sheared and non-sheared hydrogels in order to explore the effect of shear force on structure and release kinetics. It was found that the application of a shear force, in addition to changes in temperature, drug solubility, drug concentration, and hydrogel formulation each affected the amount of solute ultimately released from a hydrogel system. Moreover, the use of the inherent chirality of the hydrogel network for enantio-preferential drug release was also explored. We show significant enantio-preference in the release of model drugs tryptophan and ibuprofen from the hydrogel network. Furthermore, hydrophobic domains within the hydrogel network were exploited to enable ibuprofen loading at ten times the maximum water solubility. Retention of enantio-preference was observed at this higher ibuprofen concentration. Cyclodextrin modification to the hydrogel matrix allowed for enantio-preferential inversion which is an unprecedented observation.

In vivo safety and efficacy of sericin/poly(vinyl alcohol)/glycerin scaffolds fabricated by freeze-drying and salt-leaching techniques for wound dressing applications

In our previous works, two techniques (freeze-drying and salt-leaching) were introduced to fabricate the sericin/poly(vinyl alcohol)/glycerin scaffolds. The freeze-dried and salt-leached sericin/poly(vinyl alcohol)/glycerin scaffolds with the same composition showed distinguished physical and in vitro biological characteristics. In this study, the in vivo safety and efficacy tests of both scaffolds as dressing materials for the healing of full-thickness wounds in rat model were performed in comparison with the clinically used dressing, Allevyn®. In the safety test, the scaffolds were implanted subcutaneously, and the signs of tissue irritation including the extent of inflammatory cells, calcification, vascularization, and fatty infiltration were scored. In the efficacy test, the scaffolds were applied to the full-thickness wound (1.5 cm × 1.5 cm), and the epithelialization and collagen formation in the wound were evaluated. Both freeze-dried and salt-leached scaffolds were characterized as non- to slightly irritant implantable materials. The freeze-dried scaffold minimally causes irritation to the tissue possibly because it was derived from the non-chemical relevant process. Furthermore, the freeze-dried scaffold showed the highest wound healing efficiency as characterized by the fastest epithelialization and highest extent of collagen formation. This might be due to the more sustained release of sericin from the freeze-dried scaffold, compared to that of the salt-leached scaffold. Therefore, fabrication process seemed to directly regulate the properties and applicability of the scaffolds. The safety and efficacy of the dressing materials in wound healing application depended not only on the materials themselves but also on the fabrication process that produces them.

Sustained Local Release of NGF from a Chitosan-Sericin Composite Scaffold for Treating Chronic Nerve Compression

Chronic nerve compression (CNC), a common form of peripheral nerve injury, always leads to chronic peripheral nerve pain and dysfunction. Current available treatments for CNC are ineffective as they usually aim to alleviate symptoms at the acute phase with limited capability toward restoring injured nerve function. New approaches for effective recovery of CNC injury are highly desired. Here we report for the first time a tissue-engineered approach for the repair of CNC. A genipin cross-linked chitosan-sericin 3D scaffold for delivering nerve growth factor (NGF) was designed and fabricated. This scaffold combines the advantages of both chitosan and sericin, such as high porosity, adjustable mechanical properties and swelling ratios, the ability of supporting Schwann cells growth, and improving nerve regeneration. The degradation products of the composite scaffold upregulate the mRNA levels of the genes important for facilitating nerve function recovery, including glial-derived neurotrophic factor (GDNF), early growth response 2 (EGR2), and neural cell adhesion molecule (NCAM) in Schwann cells, while down-regulating two inflammatory genes' mRNA levels in macrophages, tumor necrosis factor alpha (TNF-α), and interleukin-1 beta (IL-1β). Importantly, our tissue-engineered strategy achieves significant nerve functional recovery in a preclinical CNC animal model by decreasing neuralgia, improving nerve conduction velocity (NCV), accelerating microstructure restoration, and attenuating gastrocnemius muscles dystrophy. Together, this work suggests a promising clinical alternative for treating chronic peripheral nerve compression injury.

Sericin/Dextran Injectable Hydrogel as an Optically Trackable Drug Delivery System for Malignant Melanoma Treatment

Severe side effects of cancer chemotherapy prompt developing better drug delivery systems. Injectable hydrogels are an effective site-target system. For most of injectable hydrogels, once delivered in vivo, some properties including drug release and degradation, which are critical to chemotherapeutic effects and safety, are challenging to monitor. Developing a drug delivery system for effective cancer therapy with in vivo real-time noninvasive trackability is highly desired. Although fluorescence dyes are used for imaging hydrogels, the cytotoxicity limits their applications. By using sericin, a natural photoluminescent protein from silk, we successfully synthesized a hydrazone cross-linked sericin/dextran injectable hydrogel. This hydrogel is biodegradable and biocompatible. It achieves efficient drug loading and controlled release of both macromolecular and small molecular drugs. Notably, sericin's photoluminescence from this hydrogel is directly and stably correlated with its degradation, enabling long-term in vivo imaging and real-time monitoring of the remaining drug. The hydrogel loaded with Doxorubicin significantly suppresses tumor growth. Together, the work demonstrates the efficacy of this drug delivery system, and the in vivo effectiveness of this sericin-based optical monitoring strategy, providing a potential approach for improving hydrogel design toward optimal efficiency and safety of chemotherapies, which may be widely applicable to other drug delivery systems.

Multicompartment Microgel Beads for Co-Delivery of Multiple Drugs at Individual Release Rates

Multidrug therapy may yield higher therapeutic effects as compared to monotherapy, yet its wide application has been hampered by the limitations of conventional drug delivery systems, in which not only incompatible drugs cannot be co-delivered but also the release rates of individual co-delivered drugs cannot be tuned separately. Regarding these limitations, we adopt the microfluidic electrospray technology to fabricate alginate-based multicompartment microgel beads. By using cadmium-telluride (CdTe) quantum dots (QDs) and a quenching agent as a model pair, the beads are shown to effectively separate incompatible drugs during co-delivery, and significantly prolong the time of observable fluorescence emission from QDs co-delivered with a quenching agent. Moreover, the drug release rates from different compartments can be tuned using the polymer blending technique to achieve a variety of drug release patterns. This study is one of the first to adopt the microfluidic electrospray technology to generate microgel beads with such versatility for co-delivery of multiple drugs. Our results provide evidence for the promising potential of our beads to be further developed as a carrier for multidrug therapy and other applications that require co-administration of multiple bioactive agents.

A silk sericin/silicone nerve guidance conduit promotes regeneration of a transected sciatic nerve

Peripheral nerve gap defects lead to significant loss of sensory or motor function. Tissue engineering has become an important alternative to nerve repair. Sericin, a major component of silk, is a natural protein whose value in tissue engineering has just begun to be explored. Here, the first time use of sericin in vivo is reported as a long-term implant for peripheral nerve regeneration. A sericin nerve guidance conduit is designed and fabricated. This conduit is highly porous with mechanical strength matching peripheral nerve tissue. It supports Schwann cell proliferation and is capable of up-regulating the transcription of glial cell derived neurotrophic factor and nerve growth factor in Schwann cells. The sericin conduit wrapped with a silicone conduit (sericin/silicone double conduits) is used for bridging repair of a 5 mm gap in a rat sciatic nerve transection model. The sericin/silicone double conduits achieve functional recovery comparable to that of autologous nerve grafting as evidenced by drastically improved nerve function and morphology. Importantly, this improvement is mainly attributed to the sericin conduit as the silicone conduit alone only produces marginal functional recovery. This sericin/silicone-double-conduit strategy offers an efficient and valuable alternative to autologous nerve grafting for repairing damaged peripheral nerve.

Advanced Therapeutic Dressings for Effective Wound Healing--A Review

Advanced therapeutic dressings that take active part in wound healing to achieve rapid and complete healing of chronic wounds is of current research interest. There is a desire for novel strategies to achieve expeditious wound healing because of the enormous financial burden worldwide. This paper reviews the current state of wound healing and wound management products, with emphasis on the demand for more advanced forms of wound therapy and some of the current challenges and driving forces behind this demand. The paper reviews information mainly from peer-reviewed literature and other publicly available sources such as the US FDA. A major focus is the treatment of chronic wounds including amputations, diabetic and leg ulcers, pressure sores, and surgical and traumatic wounds (e.g., accidents and burns) where patient immunity is low and the risk of infections and complications are high. The main dressings include medicated moist dressings, tissue-engineered substitutes, biomaterials-based biological dressings, biological and naturally derived dressings, medicated sutures, and various combinations of the above classes. Finally, the review briefly discusses possible prospects of advanced wound healing including some of the emerging physical approaches such as hyperbaric oxygen, negative pressure wound therapy and laser wound healing, in routine clinical care.

The effect of silk gland sericin protein incorporation into electrospun polycaprolactone nanofibers on in vitro and in vivo characteristics

Silk middle gland extracted sericin protein based electrospun nanofibrous scaffolds with excellent biocompatibility have been developed for tissue engineering applications.

Wound Healing: Biologics, Skin Substitutes, Biomembranes and Scaffolds

This review will explore the latest advancements spanning several facets of wound healing, including biologics, skin substitutes, biomembranes and scaffolds.