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

Tailoring Cu2+-loaded electrospun membranes with antibacterial ability for guided bone regeneration

Copper (Cu)-loaded electrospun membranes were tailored for guided bone regeneration (GBR), targeting the stimulation of innate cells active in bone growth and the prevention of bacterial infections. Functional GBR membranes were produced via an electrospinning set-up using a silk-based solution associated with polyethylene oxide (Silk/PEO - control). Experimental groups were loaded with copper oxide using varying weight percentages (0.05 % to 1 % of CuO). The morphological, structural, chemical, and mechanical properties of membranes were evaluated. Direct and indirect in vitro cytocompatibility experiments were performed with primary human bone mesenchymal stem cells and primary human umbilical vein endothelial cells. The antibacterial potential of membranes was tested with Staphylococcus aureus and Fusobacterium nucleatum biofilm. CuO was successfully incorporated into membranes as clusters without compromising their mechanical properties for clinical applicability. Increased Cu concentrations generated membranes with thinner nanofibers, greater pore areas, and stronger antimicrobial effect (p < 0.01). Cu²⁺ ion was released from the nanofiber membranes during 1 week, showing higher release in acidic conditions. CuO 0.1 % and CuO 0.05 % membranes were able to support and stimulate cell adhesion and proliferation (p < 0.05), and favor angiogenic responses of vascular cells. In addition, detailed quantitative and qualitative analysis determined that amount of the attached biofilm was reduced on the tailored functional Cu²⁺-loaded GBR membrane. Importantly, these qualities represent a valuable strategy to improve the bone regeneration process and diminish the risk of bacterial infections.

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.

High-Strength Collagen-Based Composite Films Regulated by Water-Soluble Recombinant Spider Silk Proteins and Water Annealing

Spider silk has attracted extensive attention in the development of high-performance tissue engineering materials because of its excellent physical properties, biocompatibility, and biodegradability. Although high-molecular-weight recombinant spider silk proteins can be obtained through metabolic engineering of host bacteria, the solubility of the recombinant protein products is always poor. Strong denaturants and organic solvents have thus had to be exploited for their dissolution, and this seriously limits the applications of recombinant spider silk protein-based composite biomaterials. Herein, through adjusting the temperature, ionic strength, and denaturation time during the refolding process, we successfully prepared water-soluble recombinant spider major ampullate spidroin 1 (sMaSp1) with different repeat modules (24mer, 48mer, 72mer, and 96mer). Then, MaSp1 was introduced into the collagen matrix for fabricating MaSp1-collagen composite films. The introduction of spider silk proteins was demonstrated to clearly alter the internal structure of the composite films and improve the mechanical properties of the collagen-based films and turn the opaque protein films into transparency ones. More interestingly, the composite film prepared with sMaSp1 exhibited better performance in mechanical strength and cell adhesion compared to that prepared with water-insoluble MaSp1 (pMaSp1), which might be attributed to the effect of the initial dissolved state of MaSp1 on the microstructure of composite films. Additionally, the molecular weight of MaSp1 was also shown to significantly influence the mechanical strength (enhanced to 1.1- to 2.3-fold) and cell adhesion of composite films, and 72mer of sMaSp1 showed the best physical properties with good bioactivity. This study provides a method to produce recombinant spider silk protein with excellent water solubility, making it possible to utilize this protein under environmentally benign, mild conditions. This paves the way for the application of recombinant spider silk proteins in the development of diverse composite biomaterials.

Fabrication and Evaluation of Electrospun Silk Fibroin/Halloysite Nanotube Biomaterials for Soft Tissue Regeneration

The production of nanofibrous materials for soft tissue repair that resemble extracellular matrices (ECMs) is challenging. Electrospinning uniquely produces scaffolds resembling the ultrastructure of natural ECMs. Herein, electrospinning was used to fabricate Bombyx mori silk fibroin (SF) and SF/halloysite nanotube (HNT) composite scaffolds. Different HNT loadings were examined, but 1 wt% HNTs enhanced scaffold hydrophilicity and water uptake capacity without loss of mechanical strength. The inclusion of 1 wt% HNTs in SF scaffolds also increased the scaffold’s thermal stability without altering the molecular structure of the SF, as revealed by thermogravimetric analyses and Fourier transform infrared spectroscopy (FTIR), respectively. SF/HNT 1 wt% composite scaffolds better supported the viability and spreading of 3T3 fibroblasts and the differentiation of C2C12 myoblasts into aligned myotubes. These scaffolds coated with decellularised ECM from 3T3 cells or primary human dermal fibroblasts (HDFs) supported the growth of primary human keratinocytes. However, SF/HNT 1 wt% composite scaffolds with HDF-derived ECM provided the best microenvironment, as on these, keratinocytes formed intact monolayers with an undifferentiated, basal cell phenotype. Our data indicate the merits of SF/HNT 1 wt% composite scaffolds for applications in soft tissue repair and the expansion of primary human keratinocytes for skin regeneration.

Tetrahedral framework nucleic acids promote diabetic wound healing via the Wnt signalling pathway

Objectives

To determine the therapeutic effect of tetrahedral framework nucleic acids (tFNAs) on diabetic wound healing and the underlying mechanism.

Materials and Methods

The tFNAs were characterized by polyacrylamide gel electrophoresis (PAGE), atomic force microscopy (AFM), transmission electron microscopy (TEM), dynamic light scattering (DLS) and zeta potential assays. Cell Counting Kit‐8 (CCK‐8) and migration assays were performed to evaluate the effects of tFNAs on cellular proliferation and migration. Quantitative polymerase chain reaction (Q‐PCR) and enzyme‐linked immunosorbent assay (ELISA) were used to detect the effect of tFNAs on growth factors. The function and role of tFNAs in diabetic wound healing were investigated using diabetic wound models, histological analyses and western blotting.

Results

Cellular proliferation and migration were enhanced after treatment with tFNAs in a high‐glucose environment. The expression of growth factors was also facilitated by tFNAs in vitro. During in vivo experiments, tFNAs accelerated the healing process in diabetic wounds and promoted the regeneration of the epidermis, capillaries and collagen. Moreover, tFNAs increased the secretion of growth factors and activated the Wnt pathway in diabetic wounds.

Conclusions

This study indicates that tFNAs can accelerate diabetic wound healing and have potential for the treatment of diabetic wounds.

Deciphering the focuses and trends in skin regeneration research through bibliometric analyses

Increasing attention to skin regeneration has rapidly broadened research on the topic. However, no bibliometric analysis of the field’s research trends has yet been conducted. In response to this research gap, this study analyzed the publication patterns and progress of skin regeneration research worldwide using a bibliometric analysis of 1,471 papers comprising 1,227 (83.4%) original articles and 244 (16.6%) reviews sourced from a Web of Science search. Publication distribution was analyzed by country/region, institution, journal, and author. The frequency of keywords was assessed to prepare a bibliometric map of the development trends in skin regeneration research. China and the United States were the most productive countries in the field: China had the greatest number of publications at 433 (29.4%) and the United States had the highest H-index ranking (59 with 15,373 citations or 31.9%). Author keywords were classified into four clusters: stem cell, biomaterial, tissue engineering, and wound dressing. “Stem cells,” “chitosan,” “tissue engineering,” and “wound dressings” were the most frequent keywords in each cluster; therefore, they reflected the field’s current focus areas. “Immunomodulation,” “aloe vera,” “extracellular vesicles,” “injectable hydrogel,” and “three-dimensional (3D) bioprinting” were relatively new keywords, indicating that biomaterials for skin regeneration and 3D bioprinting are promising research hotspots in the field. Moreover, clinical studies on new dressings and techniques to accelerate skin regeneration deserve more attention. By uncovering current and future research hotspots, this analysis offers insights that may be useful for both new and experienced scholars striving to expand research and innovation in the field of skin regeneration.

Electrospun Nanofibers for Wound Management

Electrospun nanofibers show great potential in biomedical applications. This mini review article traces the recent advances in electrospun nanofibers for wound management via various approaches. Initially, we provide a short note on the four phases of wound healing, including hemostasis, inflammation, proliferation, and remodeling. Then, we state how the nanofiber dressings can stop bleeding and reduce the pain. Following that, we discuss the delivery of therapeutics and cells using different types of nanofibers for enhancing cell migration, angiogenesis, and re-epithelialization, resulting in the promotion of wound healing. Finally, we present the conclusions and future perspectives regarding the use of electrospun nanofibers for wound management.

Development of silk fibroin‑sodium alginate scaffold loaded silk fibroin nanoparticles for hemostasis and cell adhesion

During wound healing process, it is essential to promote hemostasis and cell adhesion. Herein, we incorporated a scaffold with nanoparticles to improve the hemostatic properties and stimulate cell adhesion. The nanoparticles were prepared by self-assembling of silk fibroin, and the scaffold loaded nanoparticles were synthesized by crosslinking and freeze-drying. Macroscopical images showed that the nanoparticles distributed uniformly and increased the surface roughness of scaffold pore wall. The addition of nanoparticles decreased the pore size, enhanced the compression strength, lowered the degradation rate, and maintained the resilience and water uptake capacity. Compared with pure scaffold, the scaffold loaded nanoparticles revealed higher blood clotting index and promoted platelets adhesion. Furthermore, in vitro tests showed that scaffold loaded nanoparticles exhibited excellent biocompatibility, and stimulation effects on cell proliferation, migration, and adhesion for both L929 cells and HUVECs. Therefore, the scaffold loaded nanoparticles possessed great potential as a wound dressing for efficient hemostasis and subsequent wound healing.

Antioxidative NAC-Loaded Silk Nanoparticles with Opening Mucosal Tight Junctions for Nasal Drug Delivery: An In Vitro and In Vivo Study

Using nasal routes to deliver drugs to the brain using multifunctional nanoparticles (NPs) to bypass the blood–brain barrier (BBB) might enhance the delivery efficacy. Anti-oxidative N-Acetyl-L-cysteine (NAC)-loaded silk fibroin (SF/NAC) NPs are produced, characterized and studied as a potential delivery vehicle for NAC delivered to the brain via nasal for both in vitro and in vivo studies. The NPs are not cytotoxic to RPMI 2650 cells, mucosal model cells, at a concentration of 6000 μg/mL. The anti-oxidative activities of SF/NAC NPs are demonstrated by high H₂O₂ scavenge capacities of the NPs and shown by mitochondrial superoxide (MitoSOX) immunostaining of human mesenchymal stem cells. Tight junctions in RPMI 2650 cells are opened after 30 min of incubation with SF/NAC NPs, which are demonstrated by measuring the decrease in trans-epithelial electrical resistance (TEER) values and discreteness in ZO-1 stains. The cellular uptake of SF/NAC NPs by RPMI 2650 cells is significantly greater than that for SF NPs and increased with increasing incubation time. In an in vivo imaging study (IVIS) using rats shows that the amount of NAC that is delivered to the brain by SF/NAC NPs increased by 1.40–2.60 times and NAC is retained longer in the nasal cavity than NAC solutions in a 2-h study.

Biological Efficacy Comparison of Natural Tussah Silk and Mulberry Silk Nanofiber Membranes for Guided Bone Regeneration

Biopolymer nanofiber membranes are attracting interest as promising biomaterial scaffolds with a remarkable range of structural and functional performances for guided bone regeneration (GBR). In this study, tussah silk nanofiber (TSn) and Bombyx mori silk nanofiber (BSn) membranes were prepared by physical shearing. The diameters of the TSn and BSn membranes were 146.09 ± 63.56 and 120.99 ± 91.32 nm, respectively. TSn showed a Young's modulus of 3.61 ± 0.64 GPa and a tensile strength of 74.27 ± 5.19 MPa, which were superior to those of BSn, with a Young's modulus of 0.16 ± 0.03 GPa and a tensile strength of 4.86 ± 0.61 MPa. The potential of TSn and BSn membranes to guide bone regeneration was explored. In vitro, the TSn membrane exhibited significantly higher cell proliferation for MC3T3-E1 cells than the BSn membrane. In a cranial bone defect in a rat model, the TSn and BSn membranes displayed superior bone regeneration compared to the control because the membrane prevented the ingrowth of soft tissue to the defective area. Compared to the BSn membrane, the TSn membrane improved damaged bone regeneration, presumably due to its superior mechanical properties, high osteoconductivity, and increased cell proliferation. The TSn membrane has a bionic structure, excellent mechanical properties, and greater biocompatibility, making it an ideal candidate for GBR.

Liquid-type plasma-controlled in situ crosslinking of silk-alginate injectable gel displayed better bioactivities and mechanical properties

Silk is a promising biomaterial for injectable hydrogel, but its long-gelation time and cytotoxic crosslinking methods are the main obstacles for clinical application. Here, we purpose a new in situ crosslinking technique of silk-alginate (S-A) injectable hydrogel using liquid-type non-thermal atmospheric plasma (LTP) in vocal fold (VF) wound healing. We confirmed that LTP induces the secondary structure of silk in a dose-dependent manner, resulting in improved mechanical properties. Significantly increased crosslinking of silk was observed with reduced gelation time. Moreover, controlled release of nitrate, an LTP effectors, from LTP-treated S-A hydrogel was detected over 7 days. In vitro experiments regarding biocompatibility showed activation of fibroblasts beyond the non-cytotoxicity of LTP-treated S-A hydrogels. An in vivo animal model of VF injury was established in New Zealand White rabbits. Full-thickness injury was created on the VF followed by hydrogel injection. In histologic analyses, LTP-treated S-A hydrogels significantly reduced a scar formation and promoted favorable wound healing. Functional analysis using videokymography showed eventual viscoelastic recovery. The LTP not only changes the mechanical structures of a hydrogel, but also has sustained biochemical effects on the damaged tissue due to controlled release of LTP effectors, and that LTP-treated S-A hydrogel can be used to enhance wound healing after VF injury.

Effect of sericin, a silk derived protein, on the amplification of Zika virus in insect and mammalian cell cultures

Sericin, a silk-derived non-immunogenic protein, has been used to improve cell culture performance by increasing viability, cell concentration, and promoting adherence of several cell lines. Here, we hypothesized that the properties of sericin can enhance the amplification of flaviviruses in cell cultures. The propagation of flavivirus is inefficient and limits scientific research. Zika virus (ZIKV) is an important human pathogen that has been widely studied because of its high impact on public health. There is a need to amplify Zika virus both for research and vaccine development. In this work, we show that sericin improves ZIKV amplification in insect (C6/36) and mammalian (Vero) cell cultures, and that it has a cryoprotectant capacity. Supplementation of cell culture media with sericin at 80 µg/mL resulted in a significant increase of 1 log in the concentration of ZIKV infectious particles produced from both cell lines. Furthermore, final virus yields increased between 5 and 10-fold in Vero cells and between 7 and 23-fold in C6/36 cells when sericin was supplemented, compared to control conditions. These results show that sericin is an effective supplement to increase ZIKV production by Vero and C6/36 cells. Additionally, sericin was a suitable cryoprotective agent, and hence an alternative to FBS and DMSO, for the cryopreservation of C6/36 cells but not for Vero cells.

Design and Fabrication of a Dual Protein-Based Trilayered Nanofibrous Scaffold for Efficient Wound Healing

Chronic wound healing is a major threat all over the world. There are currently a plethora of biomaterials-based wound dressings available for wound healing applications. In this study, a dual protein-based (silk fibroin and sericin) nanofibrous scaffold from a natural source (B.mori silkworm cocoons) with antibacterial and antioxidative properties for wound healing was investigated. An electrospun layer-by-layer silk protein-based nanofibrous scaffold was fabricated with a top layer of hydrophobic silk fibroin protein blended with polyvinyl alcohol (PVA), a middle layer of waste protein silk sericin loaded with silver(I) sulfadiazine as an antibacterial agent, and a bottom layer using silk fibroin blended with polycaprolactone (PCL). The trilayered nanofibrous scaffold with a smooth and bead-free morphology demonstrated excellent wettability, slow in vitro degradation, controlled drug release, and potent antibacterial and antioxidant properties. In vitro, the scaffold also demonstrated excellent hemocompatibility and biocompatibility. Furthermore, in vivo wound contraction, histological, and micro-CT investigations show complete wound healing and the formation of new skin tissue in a male Balb/c mouse model treated with the scaffold. The antioxidant properties of the sericin protein and SSD-based triple-layered nanofibrous scaffold protect the wound from bacterial infection and improve wound healing in a mouse model. The current study develops a dual protein-based nanofibrous scaffold with antibacterial and antioxidant properties as a promising wound dressing material.

Protein by-products: Composition, extraction, and biomedical applications

Significant upsurge in animal by-products such as skin, bones, wool, hides, feathers, and fats has become a global challenge and, if not properly disposed of, can spread contamination and viral diseases. Animal by-products are rich in proteins, which can be used as nutritional, pharmacologically functional ingredients, and biomedical materials. Therefore, recycling these abundant and renewable by-products and extracting high value-added components from them is a sustainable approach to reclaim animal by-products while addressing scarce landfill resources. This article appraises the most recent studies conducted in the last five years on animal-derived proteins' separation and biomedical application. The effort encompasses an introduction about the composition, an overview of the extraction and purification methods, and the broad range of biomedical applications of these ensuing proteins.

Exploring bioactive peptides as potential therapeutic and biotechnology treasures: A contemporary perspective

In preceding years, bioactive peptides (BAPs) have piqued escalating attention owing to their multitudinous biological features. To date, many potential BAPs exhibiting anti-cancer activities have been documented; yet, obstacles such as their safety profiles and consumer acceptance continue to exist. Moreover, BAPs have been discovered to facilitate the suppression of Coronavirus Disease 2019 (CoVID-19) and maybe ideal for treating the CoVID-19 infection, as stated by published experimental findings, but their widespread knowledge is scarce. Likewise, there is a cornucopia of BAPs possessing neuroprotective effects that mend neurodegenerative diseases (NDs) by regulating gut microbiota, but they remain a subject of research interest. Additionally, a plethora of researchers have attempted next-generation approaches based on BAPs, but they need scientific attention. The text format of this critical review is organized around an overview of BAPs' versatility and diverse bio functionalities with emphasis on recent developments and novelties. The review is alienated into independent sections, which are related to either BAPs based disease management strategies or next-generation BAPs based approaches. BAPs based anti-cancer, anti-CoVID-19, and neuroprotective strategies have been explored, which may offer insights that could help the researchers and industries to find an alternate regimen against the three aforementioned fatal diseases. To the best of our knowledge, this is the first review that has systematically discussed the next-generation approaches in BAP research. Furthermore, it can be concluded that the BAPs may be optimal for the management of cancer, CoVID-19, and NDs; nevertheless, experimental and preclinical studies are crucial to validate their therapeutic benefits.

Sulforaphane Ameliorates the Intestinal Injury in Necrotizing Enterocolitis by Regulating the PI3K/Akt/GSK-3β Signaling Pathway

Objective

Necrotizing enterocolitis (NEC) is a serious neonatal disease; this study aims to investigate the role of sulforaphane (SFN) in NEC-induced intestinal injury.

Methods

An animal model of NEC was established in newborn mice and intragastrically administrated with SFN; then, the general status and survival of the mice were observed. H&E staining was used to observe the pathological changes of intestinal tissues. ELISA, immunohistochemical staining, and flow cytometry assays were used to detect the levels of inflammatory factors, including TNF-α, IL-6, and IL-17, the expression of Bax, Bcl-2, TLR4, and NF-κB, and the percentages of the Th17 and Treg cells, respectively. GSK-3β expression levels were measured by immunofluorescence. IEC-6 and FHC cells were induced with LPS to mimic NEC in vitro and coincubated with SFN; then, the inflammatory factor levels and cell apoptosis rate were detected. Finally, Western blot was used to assess the expression of PI3K/Akt/GSK-3β pathway-related proteins in vitro and in vivo.

Results

SFN improved the survival rate of NEC mice during modeling, alleviated the severity of the intestinal injury, and reduced the proportion of Th17/Treg cells. SFN could inhibit TLR4 and NF-κB levels, decrease the release of inflammatory factors TNF-α and IL-6, suppress Bax expression, increase Bcl-2 expression, and inhibit apoptosis both in in vitro and in vivo models of NEC. Meanwhile, SFN regulated the expression of PI3K/Akt/GSK-3β pathway-related proteins in vitro and in vivo.

Conclusion

SFN relieved the inflammatory response and apoptosis by regulating the PI3K/Akt/GSK-3β signaling pathway, thereby alleviating NEC in model mice and cells.

Fabrication of SA/Gel/C scaffold with 3D bioprinting to generate micro-nano porosity structure for skin wound healing: a detailed animal in vivo study

Bioprinting has exhibited remarkable promises for the fabrication of functional skin substitutes. However, there are some significant challenges for the treatment of full-thickness skin defects in clinical practice. It is necessary to determine bioinks with suitable mechanical properties and desirable biocompatibilities. Additionally, the key for printing skin is to design the skin structure optimally, enabling the function of the skin. In this study, the full-thickness skin scaffolds were prepared with a gradient pore structure constructing the dense layer, epidermis, and dermis by different ratios of bioinks. We hypothesized that the dense layer protects the wound surface and maintains a moist environment on the wound surface. By developing a suitable hydrogel bioink formulation (sodium alginate/gelatin/collagen), to simulate the physiological structure of the skin via 3D printing, the proportion of hydrogels was optimized corresponding to each layer. These results reveal that the scaffold has interconnected macroscopic channels, and sodium alginate/gelatin/collagen scaffolds accelerated wound healing, reduced skin wound contraction, and re-epithelialization in vivo. It is expected to provide a rapid and economical production method of skin scaffolds for future clinical applications.

Dietary administration of silk microparticles improves the epidermal and dermal regeneration after a skin wounding in gilthead seabream (Sparus aurata L.)

The impact of dietary supplementation with silk fibroin (SF) microparticles on the wound healing process in gilthead seabream (Sparus aurata) skin was studied. A control diet was enriched with different SF levels: 0 (control), 50 (SF50 diet), and 100 (SF100 diet) mg Kg^-1 to form three experimental diets and was fed to seabream for 30 days. Experimental wounds were performed and after 7 days post-wounding (dpw) skin mucus immunity, macroscopic wound closure, and skin regeneration were studied at a microscopic and genetic level. Results indicated that fish fed SF100 did not suffer the decreases in protease and IgM levels observed in the skin mucus of wounded fish fed with the control diet. Macroscopic findings illustrated that dietary SF100 significantly improved the wound closure ratio compared to those reared in the control group. At a microscopic level, changes in the shape of keratocyte cells were evident in the wounded fish. In addition, the intercellular spaces present between epidermal cells and their proliferation in the epidermis, as well as the presence of blood vessels in the dermis were significantly statistically higher in the skin of fish fed the SF100 diet and sampled at 7 dpw compared to those observed in the skin of fish fed the control or SF50 diets. Moreover, regarding the RNA: DNA ratio, statistically significant increases and decreases were observed in fish fed the control and SF100 diet, respectively, in non-wounded and wounded fish. Interestingly, dietary SF100 supplementation improved skin cell proliferation, enhanced the inflammatory phase, and increased the expression of important genes involved in tissue repair and extracellular matrix formation. In conclusion, the SF100 diet can be considered as an appropriate feed additive to improve wound healing in gilthead seabream.

Elastin-like Polypeptides in Development of Nanomaterials for Application in the Medical Field

Elastin-like polypeptides (ELPs) are biopolymers formed by amino acid sequences derived from tropoelastin. These biomolecules can be soluble below critical temperatures, forming aggregates at higher temperatures, which makes them an interesting source for the design of different nanobiomaterials. These nanobiomaterials can be obtained from heterologous expression in several organisms such as bacteria, fungi, and plants. Thanks to the many advantages of ELPs, they have been used in the biomedical field to develop nanoparticles, nanofibers, and nanocomposites. These nanostructures can be used in multiple applications such as drug delivery systems, treatments of type 2 diabetes, cardiovascular diseases, tissue repair, and cancer therapy. Thus, this review aims to shed some light on the main advances in elastin-like-based nanomaterials, their possible expression forms, and importance to the medical field.

Preparation and Characterization of Polysaccharide-Based Hydrogels for Cutaneous Wound Healing

Natural hydrogels are growing in interest as a priority for wound healing. Plant polysaccharides have a variety of biological pharmacological activities, and chitosan hydrogels have proven strong antimicrobial effects, but hydrogels prepared with polysaccharides alone have certain deficiencies. Polysaccharides from flowers of Lonicera japonica Thunb. (LP) and the aerial parts of Mentha canadensis L. (MP) were extracted and oxidized by sodium periodate (NaIO₄) and then cross-linked with oxidized-carboxymethylated chitosan (O-CCS) to develop oxidized plant- polysaccharides-chitosan hydrogels (OPHs). SEM observation showed that OPHs had porous interior structures with interconnecting pores. The OPHs showed good swelling, water-retention ability, blood coagulation, cytocompatibility properties, and low cytotoxicity (classed as grade 1 according to United States Pharmacopoeia), which met the requirements for wound dressings. Then the cutaneous wound-healing effect was evaluated in BALB/C mice model, after 7 days treatment, the wound-closure rate of OPHs groups were all greater than 50%, and after 14 days, all were greater than 90%, while the value of the control group was only 72.6%. Of them, OPH-2 and OPH-3 were more favorable to the wound-healing process, as the promotion was more significant. The plant polysaccharides and CS-based hydrogel should be a candidate for cutaneous wound dressings.

Skin-like wound dressings with on-demand administration based on in situ peptide self-assembly for skin regeneration

Burn injuries without the normal skin barrier usually cause skin wound infections, and wound dressings are necessary. Although various dressings with antibacterial ability have already been developed, the biosafety and administration mode are still bottleneck problems for further application. Herein, we designed skin-like wound dressings based on silk fibroin (SF), which are modified with the gelatinase-cleavable self-assembled/antibacterial peptide (GPLK) and epidermal growth factor (EGF). When a skin wound is infected, the gelatinase over-secreted by bacteria can cut the GPLK peptides, leading to the in situ self-assembly of peptides and the resultant high-efficiency sterilization. Compared with the commercial antibacterial dressing, the SF-GPLK displayed a faster wound healing rate. When a skin wound is not infected, the GPLK peptides remain in the SF, realizing good biosafety. Generally, the EGF can be released to promote wound healing and skin regeneration in both cases. Therefore, skin-like SF-GPLK wound dressings with on-demand release of antibacterial peptides provide a smart administration mode for clinical wound management and skin regeneration.

Volumetric Scalability of Microfluidic and Semi-Batch Silk Nanoprecipitation Methods

Silk fibroin nanoprecipitation by organic desolvation in semi-batch and microfluidic formats provides promising bottom-up routes for manufacturing narrow polydispersity, spherical silk nanoparticles. The translation of silk nanoparticle production to pilot, clinical, and industrial scales can be aided through insight into the property drifts incited by nanoprecipitation scale-up and the identification of critical process parameters to maintain throughout scaling. Here, we report the reproducibility of silk nanoprecipitation on volumetric scale-up in low-shear, semi-batch systems and estimate the reproducibility of chip parallelization for volumetric scale-up in a high shear, staggered herringbone micromixer. We showed that silk precursor feeds processed in an unstirred semi-batch system (mixing time > 120 s) displayed significant changes in the nanoparticle physicochemical and crystalline properties following a 12-fold increase in volumetric scale between 1.8 and 21.9 mL while the physicochemical properties stayed constant following a further 6-fold increase in scale to 138 mL. The nanoparticle physicochemical properties showed greater reproducibility after a 6-fold volumetric scale-up when using lower mixing times of greater similarity (8.4 s and 29.4 s) with active stirring at 400 rpm, indicating that the bulk mixing time and average shear rate should be maintained during volumetric scale-up. Conversely, microfluidic manufacture showed high between-batch repeatability and between-chip reproducibility across four participants and microfluidic chips, thereby strengthening chip parallelization as a production strategy for silk nanoparticles at pilot, clinical, and industrial scales.

Antibacterial properties of functionalized silk fibroin and sericin membranes for wound healing applications in oral and maxillofacial surgery

Oral wounds are among the most troublesome injuries which easily affect the patients' quality of life. To date, the development of functional antibacterial dressings for oral wound healing remains a challenge. In this regard, we investigated antibacterial silk protein-based membranes for the application as wound dressings in oral and maxillofacial surgery. The present study includes five variants of casted membranes, i.e., i) membranes-silver nanoparticles (CM-Ag), ii) membranes-gentamicin (CM-G), iii) membranes-control (without functionalization) (CM-C), iv) membranes-silk sericin control (CM-SSC), and v) membranes-silk fibroin/silk sericin (CM-SF/SS), and three variants of nonwovens, i.e., i) silver nanoparticles (NW-Ag), ii) gentamicin (NW-G), iii) control (without functionalization) (NW-C). The surface structure of the samples was visualized with scanning electron microscopy. In addition, antibacterial testing was accomplished using agar diffusion assay, colony forming unit (CFU) analysis, and qrt-PCR. Following antibacterial assays, biocompatibility was evaluated by cell proliferation assay (XTT), cytotoxicity assay (LDH), and live-dead assay on L929 mouse fibroblasts. Findings indicated significantly lower bacterial colony growth and DNA counts for CM-Ag with a reduction of bacterial counts by 3log levels (99.9% reduction) in CFU and qrt-PCR assay compared to untreated control membranes (CM-C and CM-SSC) and membranes functionalized with gentamicin (CM-G and NW-G) (p < 0.001). Similarly, NW-G yielded significantly lower DNA and colony growth counts compared to NW-Ag and NW-C (p < 0.001). In conclusion, CM-Ag represented 1log level better antibacterial activity compared to NW-G, whereas NW-G showed better cytocompatibility for L929 cells. As data suggest, these two membranes have the potential of application in the field of bacteria-free oral wound healing. However, provided that loading strategy and cytocompatibility are adjusted according to the antibacterial agents' characteristic and fabrication technique of the membranes.

Sustainable Antibacterial and Anti-Inflammatory Silk Suture with Surface Modification of Combined-Therapy Drugs for Surgical Site Infection

Silk sutures with antibacterial and anti-inflammatory functions were developed for sustained dual-drug delivery to prevent surgical site infections (SSIs). The silk sutures were prepared with core-shell structures braided from degummed silk filaments and then coated with a silk fibroin (SF) layer loaded with berberine (BB) and artemisinin (ART). Both the rapid release of drugs to prevent initial biofilm formation and the following sustained release to maintain effective concentrations for more than 42 days were demonstrated. In vitro assays using human fibroblasts (Hs 865.Sk) demonstrated cell proliferation on the materials, and hemolysis was 2.4 ± 0.8%, lower than that required by ISO 10993-4 standard. The sutures inhibited platelet adhesion and promoted collagen deposition and blood vessel formation. In vivo assessments using Sprague-Dawley (SD) rats indicated that the coating reduced the expression of pro-inflammatory cytokines interleukin-10 (IL-10) and tumor necrosis factor-α (TNF-α), shortening the inflammatory period and promoting angiogenesis. The results demonstrated that these new sutures exhibited stable structures, favorable biocompatibility, and sustainable antibacterial and anti-inflammatory functions with potential for surgical applications.

Genetically engineered FGF1-sericin hydrogel material treats intrauterine adhesion and restores fertility in rat

Endometrial injury can cause intrauterine adhesions (IUA) and induce the formation of endometrial fibrosis, leading to infertility and miscarriage. At present, there is no effective treatment method for severe IUA and uterine basal injury with adhesion area larger than 1/3 of the uterus. In this study, we prepared FGF1 silk sericin hydrogel material (FGF1-SS hydrogel) to treat endometrial injury and prevent endometrial fibrosis. Compared with the silk sericin hydrogel material (WT-SS hydrogel), FGF1-SS hydrogel significantly promotes the cell migration and infiltration ability of endometrial stromal cells (ESCs). More importantly, FGF1-SS hydrogel can release FGF1 stably for a long time and inhibit The ESCs injury model forms fibrosis through the TGF-β/Smad pathway. In the IUA rat model, FGF1-SS hydrogel treatment effectively restored the number of uterine glands and uterine wall thickness in rats, with a fertility rate of 65.1 ± 6.4%. The results show that FGF1-SS hydrogel is expected to be a candidate to prevent IUA.

A Review on Antibacterial Silk Fibroin-based Biomaterials: Current State and Prospects

Bacterial contamination of biomaterials is a common problem and a serious threat to human health worldwide. Therefore, the development of multifunctional biomaterials that possess antibacterial properties and can resist infection is a continual goal for biomedical applications. Silk fibroin (SF), approved by U.S. Food and Drug Administration (FDA) as a biomaterial, is one of the most widely studied natural polymers for biomedical applications due to its unique mechanical properties, biocompatibility, tunable biodegradation, and versatile material formats. In the last decade, many methods have been employed for the development of antibacterial SF-based biomaterials (SFBs) such as physical loading or chemical functionalization of SFBs with different antibacterial agents and bio-inspired surface modifications. In this review, we first describe the current understanding of the composition and structure-properties relationship of SF as a leading-edge biomaterial. Then we demonstrate the different antibacterial agents and methods implemented for the development of bactericidal SFBs, their mechanisms of action, and different applications. We briefly address their fabrication methods, advantages, and limitations, and finally discuss the emerging technologies and future trends in this research area.

Mixing and flow-induced nanoprecipitation for morphology control of silk fibroin self-assembly

Tuning silk fibroin nanoparticle morphology using nanoprecipitation for bottom-up manufacture is an unexplored field that has the potential to improve particle performance characteristics. The aim of this work was to use both semi-batch bulk mixing and micro-mixing to modulate silk nanoparticle morphology by controlling the supersaturation and shear rate during nanoprecipitation. At flow rates where the shear rate was below the critical shear rate for silk, increasing the concentration of silk in both bulk and micro-mixing processes resulted in particle populations of increased sphericity, lower size, and lower polydispersity index. At high flow rates, where the critical shear rate was exceeded, the increased supersaturation with increasing concentration was counteracted by increased rates of shear-induced assembly. The morphology could be tuned from rod-like to spherical assemblies by increasing supersaturation of the high-shear micro-mixing process, thereby supporting a role for fast mixing in the production of narrow-polydispersity silk nanoparticles. This work provides new insight into the effects of shear during nanoprecipitation and provides a framework for scalable manufacture of spherical and rod-like silk nanoparticles.

Collagen Fibril-Assembled Skin-Simulated Membrane for Continuous Molecular Separation

A skin-simulated thin-film-composite membrane was fabricated using a vacuum-assisted interfacial polymerization method. A negatively charged surface-selective layer on a polyacrylonitrile (PAN) substrate was cross-linked using trimesoyl chloride to form polyamide and polyester with a three-layer structure that was similar to skin. The loading of collagen fibrils assembled on the membrane surface was varied, and a selective layer was obtained, of which the thickness, morphology, and hydrophilicity can be manipulated. The optimal membrane decorated with 0.5 mg of collagen fibril had a selective layer thickness of around 130 nm with pure water permeability up to 84.7 LMH bar^-1. Furthermore, the membrane exhibited impressive rejections toward dyes (Congo red with a molecular weight of 696.68 Da: 99.6%, reactive blue 19 with a molecular weight of 626.54 Da: 99.8%, and Coomassie blueG-250 with a molecular weight of 854.02 Da: 98.6%) while high permeations of Na₂SO₄ and NaCl were achieved. This facile strategy provides a useful guideline for constructing bionic membranes through biomaterials.

An Image-Analysis-Based Method for the Prediction of Recombinant Protein Fiber Tensile Strength

Silk fibers derived from the cocoon of silk moths and the wide range of silks produced by spiders exhibit an array of features, such as extraordinary tensile strength, elasticity, and adhesive properties. The functional features and mechanical properties can be derived from the structural composition and organization of the silk fibers. Artificial recombinant protein fibers based on engineered spider silk proteins have been successfully made previously and represent a promising way towards the large-scale production of fibers with predesigned features. However, for the production and use of protein fibers, there is a need for reliable objective quality control procedures that could be automated and that do not destroy the fibers in the process. Furthermore, there is still a lack of understanding the specifics of how the structural composition and organization relate to the ultimate function of silk-like fibers. In this study, we develop a new method for the categorization of protein fibers that enabled a highly accurate prediction of fiber tensile strength. Based on the use of a common light microscope equipped with polarizers together with image analysis for the precise determination of fiber morphology and optical properties, this represents an easy-to-use, objective non-destructive quality control process for protein fiber manufacturing and provides further insights into the link between the supramolecular organization and mechanical functionality of protein fibers.

Light-Triggered Adhesive Silk-Based Film for Effective Photodynamic Antibacterial Therapy and Rapid Hemostasis

Successful control of massive hemorrhage in deep wounds with irregular shape and low elasticity still remains great challenges in the clinic. As the wound sites are usually at risk of bacterial infection, it is necessary to design an ideal hemostatic agent with rapid hemostasis and excellent antibacterial activity. In this study, we developed a light responsive hemostatic film for effective handling of liver bleeding with promising photodynamic therapy against S. aureus onnear infrared (NIR) irradiation. Based on silk fibroin, the film exhibited desirable biocompatibility and mechanical property as a hemostat tape. Significantly, the film tape achieved excellent tissue adhesion and hemostasis in vivo within 2 min of UV exposure, which would have a great potential as a multifunctional biomedical material in the field of tissue repair such as wound healing, bone repair, and nerve regeneration.

Cellular Interaction of Human Skin Cells towards Natural Bioink via 3D-Bioprinting Technologies for Chronic Wound: A Comprehensive Review

Skin substitutes can provide a temporary or permanent treatment option for chronic wounds. The selection of skin substitutes depends on several factors, including the type of wound and its severity. Full-thickness skin grafts (SGs) require a well-vascularised bed and sometimes will lead to contraction and scarring formation. Besides, donor sites for full-thickness skin grafts are very limited if the wound area is big, and it has been proven to have the lowest survival rate compared to thick- and thin-split thickness. Tissue engineering technology has introduced new advanced strategies since the last decades to fabricate the composite scaffold via the 3D-bioprinting approach as a tissue replacement strategy. Considering the current global donor shortage for autologous split-thickness skin graft (ASSG), skin 3D-bioprinting has emerged as a potential alternative to replace the ASSG treatment. The three-dimensional (3D)-bioprinting technique yields scaffold fabrication with the combination of biomaterials and cells to form bioinks. Thus, the essential key factor for success in 3D-bioprinting is selecting and developing suitable bioinks to maintain the mechanisms of cellular activity. This crucial stage is vital to mimic the native extracellular matrix (ECM) for the sustainability of cell viability before tissue regeneration. This comprehensive review outlined the application of the 3D-bioprinting technique to develop skin tissue regeneration. The cell viability of human skin cells, dermal fibroblasts (DFs), and keratinocytes (KCs) during in vitro testing has been further discussed prior to in vivo application. It is essential to ensure the printed tissue/organ constantly allows cellular activities, including cell proliferation rate and migration capacity. Therefore, 3D-bioprinting plays a vital role in developing a complex skin tissue structure for tissue replacement approach in future precision medicine.

Fiber-Based Biopolymer Processing as a Route toward Sustainability

Some of the most abundant biomass on earth is sequestered in fibrous biopolymers like cellulose, chitin, and silk. These types of natural materials offer unique and striking mechanical and functional features that have driven strong interest in their utility for a range of applications, while also matching environmental sustainability needs. However, these material systems are challenging to process in cost-competitive ways to compete with synthetic plastics due to the limited options for thermal processing. This results in the dominance of solution-based processing for fibrous biopolymers, which presents challenges for scaling, cost, and consistency in outcomes. However, new opportunities to utilize thermal processing with these types of biopolymers, as well as fibrillation approaches, can drive renewed opportunities to bridge this gap between synthetic plastic processing and fibrous biopolymers, while also holding sustainability goals as critical to long-term successful outcomes.

Black, Caspian Seas and Central Asia Silk Association (BACSA) for the Future of Sericulture in Europe and Central Asia

Simple Summary

This paper describes the 16-years long activity of the Black Caspian Seas and Central Asia Silk Association, which was founded in 2005 to revive the sericultural activity in the area indicated by its own denomination. The reasons why this Association was established are described as a direct consequence of the decline in the sericulture agroindustry following the collapse of the Soviet Union and the world cocoon/raw silk decrease of production (except for China and India) since the 90s of the 20th century. Therefore, the enlargement of its membership to countries outside of the boundaries of the geographical area is outlined as well as its internal organization and the actions performed to promote the interaction among the member countries, especially the biyearly conferences. The international scenario is depicted to explain the criticalities experienced in promoting sericultural activities in the region, as well as the opportunities offered by the new applications of the silk, silk proteins and mulberry derivatives.

Abstract

The history and recent activities of the Black Caspian Seas and Central Asia Silk Association are presented in this paper: the countries that participated in its foundation, the FAO’s action to revitalize sericulture in Eastern Europe and Central Asia, the following widening of the Association geographical limits of to enclose other European countries, which were not well-represented in other similar organizations. Some statistical data are illustrated for a better description of the scenario in which the BACSA executive board acted: the world silk production quantity and the relative production of BACSA countries in respect to the Chinese expansion. The themes treated in the BACSA conferences are reported to explain which matters the Executive Board considered the most relevant for the relaunch of this activity in relationships to the international challenges in the subsequent years; the project proposals that were presented to international donors are summarized. A SWOT (Strengths, Weaknesses, Opportunities, Threats) analysis is shown, where key-factors in determining the strengths and weaknesses of this organization and its member countries for a successful re-establishment of sericulture, are considered. In addition, future trends of sericulture with regard to innovative productions and the Green Deal are examined.

Silk fibroin crosslinked glycyrrhizic acid and silver hydrogels for accelerated bacteria-infected wound healing

Antibacterial hydrogels have been intensively studied as wound dressings. Silk fibroin (SF) was chemical crosslinked to glycyrrhizic acid (GA) and silver to fabricate a hydrogel dressing with both antibacterial and anti-inflammatory properties. The SF/Ag/GA hydrogel exhibited high water content with acceptable mechanical properties, combined the good biocompatibility and biodegradability of SF, the antibacterial activity of silver, and the anti-inflammatory property of GA, capable to promote tissue regeneration during wound healing process, offering great potential as an alternative for wound dressings. This article is protected by copyright. All rights reserved.

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

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

The myth of antibiotic spider silk

Spider silk is frequently attributed antimicrobial properties. This notion is based on studies reporting antimicrobial activity (AMA) of spider silk; however, close inspection of these studies reveals that the evidence is conflicting, and at best anecdotal. We performed a systematic study of antimicrobial properties of different silk types from seven species across the spider phylogeny. We found no evidence of AMA of silk in direct contact and disc diffusion assays against Gram-negative Escherichia coli and Pseudomonas putida, and the Gram-positive Bacillus subtilis. Furthermore, staining experiments and fluorescence microscopy showed the presence of live bacteria on silk surfaces indicating no antimicrobial effect on direct contact. A critical evaluation of the literature reveals that published tests of AMA are scarce and that all the studies claiming positive results are compromised by methodological shortcomings. Our analysis demonstrates that the common notion that spider silk is antimicrobial is not supported by empirical data.

Immune Response to Silk Sericin-Fibroin Composites: Potential Immunogenic Elements and Alternatives for Immunomodulation

The unique properties of silk proteins (SPs), particularly silk sericin (SS) and silk fibroin (SF), have attracted attention in the design of scaffolds for tissue engineering over the past decades. Since SF has good mechanical properties, while SS displays bioactivity, scaffolds combining both proteins should exhibit complementary properties enhancing the potential of these materials. Unfortunately, SS-SF composites can generate chronic immune responses and their immunogenic element is not completely clear. The potential of SS-SF composites in tissue engineering, elements which may contribute to their immunogenicity, and alternatives for their preparation and design, to modulate the immune response and take advantage of their useful properties, are discussed in this review. It is known that SS can enhance β-sheet formation in SF, which may act as hydrophobic regions with a strong affinity for adsorption proteins inducing the chronic recruitment of inflammatory cells. Therefore, tailoring the exposure of hydrophobic regions at the scaffold surface should represent a viable strategy to modulate the immune response. This can be achieved by coating SS-SF composites with SS or other hydrophilic polymers, to take advantage of their antibiofouling properties. Research is still needed to realize the full potential of these composites for tissue engineering.

Silk biomaterials for vascular tissue engineering applications

Vascular tissue engineering is a rapidly growing field of regenerative medicine, which strives to find innovative solutions for vascular reconstruction. Considering the limited success of synthetic grafts, research impetus in the field is now shifted towards finding biologically active vascular substitutes bestowing in situ growth potential. In this regard, silk biomaterials have shown remarkable potential owing to their favorable inherent biological and mechanical properties. This review provides a comprehensive overview of the progressive development of silk-based small diameter (<6 mm) tissue-engineered vascular grafts (TEVGs), emphasizing their pre-clinical implications. Herein, we first discuss the molecular structure of various mulberry and non-mulberry silkworm silk and identify their favorable properties at the onset of vascular regeneration. The emergence of various state-of-the-art fabrication methodologies for the advancement of silk TEVGs is rationally appraised in terms of their in vivo performance considering the following parameters: ease of handling, long-term patency, resistance to acute thrombosis, stenosis and aneurysm formation, immune reaction, neo-tissue formation, and overall remodeling. Finally, we provide an update on the pre-clinical status of silk-based TEVGs, followed by current challenges and future prospects. STATEMENT OF SIGNIFICANCE: Limited availability of healthy autologous blood vessels to replace their diseased counterpart is concerning and demands other artificial substitutes. Currently available synthetic grafts are not suitable for small diameter blood vessels owing to frequent blockage. Tissue-engineered biological grafts tend to integrate well with the native tissue via remodeling and have lately witnessed remarkable success. Silk fibroin is a natural biomaterial, which has long been used as medical sutures. This review aims to identify several favorable properties of silk enabling vascular regeneration. Furthermore, various methodologies to fabricate tubular grafts are discussed and highlight their performance in animal models. An overview of our understanding to rationally improve the biological activity fostering the clinical success of silk-based grafts is finally discussed.

The biological applications of DNA nanomaterials: current challenges and future directions

DNA, a genetic material, has been employed in different scientific directions for various biological applications as driven by DNA nanotechnology in the past decades, including tissue regeneration, disease prevention, inflammation inhibition, bioimaging, biosensing, diagnosis, antitumor drug delivery, and therapeutics. With the rapid progress in DNA nanotechnology, multitudinous DNA nanomaterials have been designed with different shape and size based on the classic Watson-Crick base-pairing for molecular self-assembly. Some DNA materials could functionally change cell biological behaviors, such as cell migration, cell proliferation, cell differentiation, autophagy, and anti-inflammatory effects. Some single-stranded DNAs (ssDNAs) or RNAs with secondary structures via self-pairing, named aptamer, possess the ability of targeting, which are selected by systematic evolution of ligands by exponential enrichment (SELEX) and applied for tumor targeted diagnosis and treatment. Some DNA nanomaterials with three-dimensional (3D) nanostructures and stable structures are investigated as drug carrier systems to delivery multiple antitumor medicine or gene therapeutic agents. While the functional DNA nanostructures have promoted the development of the DNA nanotechnology with innovative designs and preparation strategies, and also proved with great potential in the biological and medical use, there is still a long way to go for the eventual application of DNA materials in real life. Here in this review, we conducted a comprehensive survey of the structural development history of various DNA nanomaterials, introduced the principles of different DNA nanomaterials, summarized their biological applications in different fields, and discussed the current challenges and further directions that could help to achieve their applications in the future.

The Fabrication of a Gellan Gum-Based Hydrogel Loaded With Magnesium Ions for the Synergistic Promotion of Skin Wound Healing

To accelerate serious skin burn wound healing in a convenient manner, an interpenetrating network of hydrogel consisting of gellan gum and polyacrylamide was synthesized by chemical crosslinking and Mg2+ ion immersion techniques. The prepared Mg2+@PAM/GG hydrogel was characterized by morphology, water vapor loss, swelling ratio, rheological properties, tensile mechanical, biocompatibility, and flow cytometry study. The results show that Mg2+@PAM/GG hydrogel's mechanical strength could be enhanced by the dual network structure and physical crosslinking agent Mg2+ ions. In addition, the tension strength of Mg2+@PAM/GG hydrogel is obviously increased from 86 to 392 kPa, the elongation at break increased from 84 to 231%, and crosslinking density N increased from 4.3 to 7.2 mol/m3 compared with pure GG hydrogel. The cumulative release curve of Mg2+ ions shows that the multiple release mechanism of Mg2+ ions belong to non-Fick's diffusion. Meanwhile, in vitro experiments show that Mg2+@PAM/GG double network hydrogel has favorable proliferation and an NF-κB pathway inhibition property for fibroblast cells. Finally, the healing effect of the Mg2+@PAM/GG was evaluated in a rat full-thickness burn model. The animal study demonstrates that Mg2+@PAM/GG could accelerate the healing efficiency in case of the sustained-released Mg2+ ions in wound beds. Considering this excellent performance, this convenient prepared hydrogel has great potential as a commercial application for skin full-thickness burn healing materials.

Liquid-type nonthermal atmospheric plasma enhanced regenerative potential of silk-fibrin composite gel in radiation-induced wound failure

Delayed wound healing in heavily irradiated areas is a serious clinical complication that makes widespread therapeutic use of radiation difficult. Efficient treatment strategies are urgently required for addressing radiation-induced wound failure. Herein, we applied liquid-type nonthermal atmospheric plasma (LTP) to a silk-fibrin (SF) composite gel to investigate whether controlled release of LTP from SF hydrogel not only induced favorable cellular events in an irradiated wound bed but also modulated the SF hydrogel microstructure itself, eventually facilitating the development of a regenerative microenvironment. Scanning electron microscopy and Fourier-transform infrared spectroscopy revealed that LTP modulated the microstructures and chemical bindings of the SF gel. Improved cell viability, morphology, and extracellular matrix depositions by the LTP-treated SF hydrogel were identified with wound-healing assays and immunofluorescence staining. An irradiated random-pattern skin-flap animal model was established in six-week-old C57/BL6 mice. Full-thickness skin was flapped from the dorsum and SF hydrogel was placed underneath the raised skin flap. Postoperative histological analysis of the irradiated random-pattern skin-flap mice model suggested that LTP-treated SF hydrogel much improved wound regeneration and the inflammatory response compared to the SF hydrogel- and sham-treated groups. These results support that LTP-treated SF hydrogel significantly enhanced irradiated wound healing. Cellular and tissue reactions to released LTP from the SF hydrogel were favorable for the regenerative process of the wound; furthermore, mechanochemical properties of the SF gel were improved by LTP.

Bioinspired Design of Sericin/Chitosan/Ag@MOF/GO Hydrogels for Efficiently Combating Resistant Bacteria, Rapid Hemostasis, and Wound Healing

Due to the spread of drug-resistant bacteria in hospitals, the development of antibacterial dressings has become a strategy to control wound infections caused by bacteria. Here, we reported a green strategy for in situ biomimetic syntheses of silver nanoparticles@organic frameworks/graphene oxide (Ag@MOF-GO) in sericin/chitosan/polyvinyl alcohol hydrogel. Ag@MOF-GO was synthesized in situ from the redox properties of tyrosine residues in silk sericin without additional chemicals, similar to a biomineralization process. The sericin/chitosan/Ag@MOF-GO dressing possessed a high porosity, good water retention, and a swelling ratio. The hemolysis rate of the composite was 3.9% and the cell viability rate was 131.2%, which indicated the hydrogel possessed good biocompatibility. The composite also showed excellent lasting antibacterial properties against drug-sensitive and drug-resistant pathogenic bacteria. The composite possessed excellent hemostatic activity. The coagulation effect of the composite may be related to its effect on the red blood cells and platelets, but it has nothing to do with the activation of coagulation factors. An in vitro cell migration assay confirmed and an in vivo evaluation of mice indicated that the composite could accelerate wound healing and re-epithelialization. In summary, the composite material is an ideal dressing for accelerating hemostasis, preventing bacterial infection, and promoting wound healing.

Fabrication of gelatin/silk fibroin/phage nanofiber scaffold effective against multidrug resistant Pseudomonas aeruginosa

OBJECTIVE

The alarming rise of multi-drug resistant (MDR) Pseudomonas aeruginosa has prompted the World Health Organization to consider it a serious threat to human health. Although phage (Phg), an effective antibacterial treatment option, can maintain long-term infectivity via lyophilized storage, freeze-drying can be expensive and time-consuming. Thus, we propose electrospun gelatin/fibroin (G/F) nanofibrous formulation for dehydrating and storing phage against MDR P. aeruginosa.

SIGNIFICANCE

The formulation of phage within the nanofibrous structure of the electrospun G/F scaffold would result in antimicrobial activity against MDR P. aeruginosa leading to enhanced wound healing.

METHODS

Phg effective against MDR P. aeruginosa was isolated, characterized and loaded within G/F nanofibers by electrospinning. Morphology, crystallinity and thermal stability as well as the antimicrobial activity and the biocompatibility of the developed G/F/Phg nanofibers were determined.

RESULTS

Phg-loaded G/F nanofibers revealed an amorphous structure with good thermal stability at temperatures below 300 °C and exhibited effective antibacterial activity against MDR P. aeruginosa with ∼2 log reduction in the bacterial count which increased to ∼4 log reduction in bacterial count after 16 h as compared to both the G/F nanofibers and the negative control. Lack of cytotoxic effects on cultured fibroblasts supported the biocompatibility of G/F/Phg nanofibers.

CONCLUSION

The developed G/F/Phg nanofibers are able to maintain the viability of phage and represent a promising antimicrobial dressing for wounds infected with MDR P. aeruginosa.

Current knowledge of immunomodulation strategies for chronic skin wound repair

In orchestrating the wound healing process, the immune system plays a critical role. Hence, controlling the immune system to repair skin defects is an attractive approach. The highly complex immune system includes the coordinated actions of several immune cells, which can produce various inflammatory and antiinflammatory cytokines and affect the healing of skin wounds. This process can be optimized using biomaterials, bioactive molecules, and cell delivery. The present review discusses various immunomodulation strategies for supporting the healing of chronic wounds. In this regard, following the evolution of the immune system and its role in the wound healing mechanism, the interaction between the extracellular mechanism and immune cells for acceleration wound healing will be firstly investigated. Consequently, the immune-based chronic wounds will be briefly examined and the mechanism of progression, and conventional methods of their treatment are evaluated. In the following, various biomaterials-based immunomodulation strategies are introduced to stimulate and control the immune system to treat and regenerate skin defects. Other effective methods of controlling the immune system in wound healing which is the release of bioactive agents (such as antiinflammatory, antigens, and immunomodulators) and stem cell therapy at the site of injury are reviewed.

Asiaticoside-laden silk nanofiber hydrogels to regulate inflammation and angiogenesis for scarless skin regeneration

Scarless skin regeneration remains a challenge due to the complicated microenvironment involved in wound healing. Here, the hydrophobic drug, asiaticoside (AC), was loaded inside silk nanofiber hydrogels to achieve bioactive and injectable matrices for skin regeneration. AC was dispersed in aqueous silk nanofiber hydrogels with retention of biological functions that regulated inflammatory reactions and vascularization in vitro. After implantation in full-thickness wound defects, these AC-laden hydrogel matrices achieved scarless wound repair. Inflammatory reactions and angiogenesis were regulated during inflammation and remodeling, which was responsible for wound regeneration similar to normal skin. Both in vitro and in vivo studies demonstrated promising applications of these AC-laden silk hydrogels towards scarless tissue regeneration.