Materials fabrication from Bombyx mori silk fibroin

Environmental-friendly, flexible silk fibroin-based film as dual-responsive shape memory material

Bio-based shape memory materials have attracted wide attention due to their biocompatibility, degradability and safety. However, designing and manufacturing wearable bio-based shape memory films with excellent flexibility and toughness is still a challenge. In this work, silk fibroin substrate with a β-sheet structure was combined with a tri-block shape memory copolymer to prepare a transparent composited shape memory film. The silk fibroin-based film showed a dual-responsive shape memory function, which can respond to both temperature and water stimuli. This film has a sensitive water-responsive shape memory, which starts deforming after exposure to water for 3 s and fully recovers in 30 s. In addition, the composite film shows highly stretchable (>300 %) and could maintain its high tensile properties after 5 cycles of regeneration. The films also exhibited rapid degradation ability. This study provides new insights for the design of dual-responsive shape memory materials by combining biocompatible matrix and multi-block SMP to simultaneously enhance the mechanical properties, which can be used for intelligent packaging, medical supplies, soft actuators and wearable devices.

A multifunctional silk-hyaluronic acid self-healing hydrogel laden with alternatively activated macrophage-derived exosomes reshape microenvironment of diabetic wound and accelerate healing

The impairment of phenotype switching of pro-inflammatory M1 to pro-healing M2 macrophage induced by hyperglycemic microenvironment often elevates oxidative stress, impairs angiogenesis, and leads to chronic non-healing wounds in diabetic patients. Administration of M2 macrophage-derived exosomes (M2Exo) at wound site is known to polarize M1 to M2 macrophage and can accelerate wound healing by enhancing collagen deposition, angiogenesis, and re-epithelialization. In the present study, M2Exo were conjugated with oxidized hyaluronic acid and mixed with PEGylated silk fibroin to develop self-healing Exo-gel to achieve an efficient therapy for diabetic wounds. Exo-gel depicted porous networked morphology with self-healing and excellent water retention behaviour. Fibroblast cells treated with Exo-gel showed significant uptake of M2Exo that increased their proliferation and migration in vitro. Interestingly, in a diabetic wound model of wistar rats, Exo-gel treatment induced 75 % wound closure within 7 days with complete epithelial layer regeneration by modulating cytokine levels, stimulating fibroblast-keratinocyte interaction and migration, angiogenesis, and organized collagen deposition. Taken together, this study suggests that Exo-gel depict properties of an excellent wound healing matrix and can be used as a therapeutic alternative to treat chronic non-healing diabetic wounds.

Stepwise degradable PGA-SF core-shell electrospinning scaffold with superior tenacity in wetting regime for promoting bone regeneration

Regenerating bone in the oral and maxillofacial region is clinically challenging due to the complicated osteogenic environment and the limitation of existing bone graft materials. Constructing bone graft materials with controlled degradation and stable mechanical properties in a physiological environment is of utmost importance. In this study, we used silk fibroin (SF) and polyglycolic acid (PGA) to fabricate a coaxial PGA-SF fibrous scaffold (PGA-SF-FS) to meet demands for bone grafts. The SF shell exerted excellent osteogenic activity while protecting PGA from rapid degradation and the PGA core equipped scaffold with excellent tenacity. The experiments related to biocompatibility and osteogenesis (e.g., cell attachment, proliferation, differentiation, and mineralization) demonstrated the superior ability of PGA-SF-FS to improve cell growth and osteogenic differentiation. Furthermore, in vivo testing using Sprague-Dawley rat cranial defect model showed that PGA-SF-FS accelerates bone regeneration as the implantation time increases, and its stepwise degradation helps to match the remodeling kinetics of the host bone tissue. Besides, immunohistochemical staining of CD31 and Col-1 confirmed the ability of PGA-SF-FS to enhance revascularization and osteogenesis response. Our results suggest that PGA-SF-FS fully utilizing the advantages of both components, exhibites stepwise degradation and superior tenacity in wetting regime, making it a promising candidate in the treatment of bone defects.

In-situ observation of silk nanofibril assembly via graphene plasmonic infrared sensor

Silk nanofibrils (SNFs), the fundamental building blocks of silk fibers, endow them with exceptional properties. However, the intricate mechanism governing SNF assembly, a process involving both protein conformational transitions and protein molecule conjunctions, remains elusive. This lack of understanding has hindered the development of artificial silk spinning techniques. In this study, we address this challenge by employing a graphene plasmonic infrared sensor in conjunction with multi-scale molecular dynamics (MD). This unique approach allows us to probe the secondary structure of nanoscale assembly intermediates (0.8-6.2 nm) and their morphological evolution. It also provides insights into the dynamics of silk fibroin (SF) over extended molecular timeframes. Our novel findings reveal that amorphous SFs undergo a conformational transition towards β-sheet-rich oligomers on graphene. These oligomers then connect to evolve into SNFs. These insights provide a comprehensive picture of SNF assembly, paving the way for advancements in biomimetic silk spinning.

3D Porous Edible Scaffolds from Rye Secalin for Cell-Based Pork Fat Tissue Culturing

Cellular agriculture holds hope for a sustainable alternative to conventional meat, yet multiple technical challenges remain. These include the large-scale production of edible scaffolds and culturing methods for fat tissues, which are key to meat texture, flavor, and nutritional values. Herein. we disclose our method in the facile fabrication of sponge-like plant protein scaffolds by applying commercial sugar cubes as highly permeable templates. The prepared secalin scaffolds feature a high porosity of 85-90%, fully interconnected pores, and high water stability. The mechanical properties of scaffolds could be tuned by varying sugar-to-protein weight ratio and post-water annealing treatment. Moreover, murine preadipocytes (3T3-L1) and porcine adipose-derived stem cells (ADSCs) readily infiltrate, adhere, proliferate, and differentiate on the secalin scaffolds to develop a fat tissue morphology. A cultured fat tissue was produced by culturing porcine ADSCs for 12 days, which remarkably resembles conventional porcine subcutaneous adipose tissue in appearance, texture, flavor, and fatty acid profiles. The research demonstrates the great potential of sponge-like secalin scaffolds for cultured fat tissue production.

Modulation of Canine Adipose-Derived Mesenchymal Stem/Medicinal Signalling Cells with Ascorbic Acid: Effect on Proliferation and Chondrogenic Differentiation on Standard Plastic and Silk Fibroin Surfaces

Ascorbic acid (AA) plays a crucial role in both the proliferation and chondrogenic differentiation potential of mesenchymal stem/medicinal signalling cells (MSCs); these are both key aspects of their general therapeutic use and their increasing use in veterinary medicine. Current immunomodulatory therapies require efficient expansion of MSCs in the laboratory, while emerging tissue regeneration strategies, such as cartilage or bone repair, aim to use differentiated MSCs and modulate the expression of chondrogenic and hypertrophic markers. Our aim was to investigate whether the addition of AA to the growth medium enhances the proliferation of canine adipose-derived MSCs (cAMSCs) grown on standard plastic surfaces and whether it affects chondrogenic differentiation potential on silk fibroin (SF) films. We assessed cell viability with trypan blue and proliferation potential by calculating population doubling. Chondrogenic induction on SF films was assessed by Alcian blue staining and gene expression analysis of chondrogenic and hypertrophic genes. The results showed that growth medium with AA significantly enhanced the proliferation of cAMSCs without affecting cell viability and modulated the expression of chondrogenic and hypertrophic genes of cAMSCs grown on SF films. Our results suggest that AA may be used in growth medium for expansion of cAMSCs and, at the same time, provide the basis for future studies to investigate the role of AA and SF in chondrogenic differentiation of MSCs.

Silk-based wearable devices for health monitoring and medical treatment

Previous works have focused on enhancing the tensile properties, mechanical flexibility, biocompatibility, and biodegradability of wearable devices for real-time and continuous health management. Silk proteins, including silk fibroin (SF) and sericin, show great advantages in wearable devices due to their natural biodegradability, excellent biocompatibility, and low fabrication cost. Moreover, these silk proteins possess great potential for functionalization and are being explored as promising candidates for multifunctional wearable devices with sensory capabilities and therapeutic purposes. This review introduces current advancements in silk-based constituents used in the assembly of wearable sensors and adhesives for detecting essential physiological indicators, including metabolites in body fluids, body temperature, electrocardiogram (ECG), electromyogram (EMG), pulse, and respiration. SF and sericin play vital roles in addressing issues related to discomfort reduction, signal fidelity improvement, as well as facilitating medical treatment. These developments signify a transition from hospital-centered healthcare toward individual-centered health monitoring and on-demand therapeutic interventions.

Flexible Meso Electronics and Photonics Based on Cocoon Silk and Applications

Flexible electronics, applicable to enlarged health, AI big data medications, etc., have been one of the most important technologies of this century. Due to its particular mechanical properties, biocompatibility, and biodegradability, cocoon silk (or SF, silk fibroin) plays a key role in flexible electronics/photonics. The review begins with an examination of the hierarchical meso network structures of SF materials and introduces the concepts of meso reconstruction, meso doping, and meso hybridization based on the correlation between the structure and performance of silk materials. The SF meso functionalization was developed according to intermolecular nuclear templating. By implementation of the techniques of meso reconstruction and functionalization in the refolding of SF materials, extraordinary performance can be achieved. Relying on this strategy, particularly designed flexible electronic and photonic components can be developed. This review covers the latest ideas and technologies of meso flexible electronics and photonics based on SF materials/meso functionalization. As silk materials are biocompatible and human skin-friendly, SF meso flexible electronic/photonic components can be applied to wearable or implanted devices. These devices are applicable in human physiological signals and activities sensing/monitoring. In the case of human-machine interaction, the devices can be applicable in in-body information transmission, computation, and storage, with the potential for the combination of artificial intelligence and human intelligence.

Silk Fibroin-Laponite Porous Microspheres as Cell Microcarriers for Osteogenic Differentiation

Silk fibroin (SF) has garnered significant attention as a natural polymer for fabricating porous scaffolds in various engineering applications. However, the limited osteoinductive property of SF has hindered its efficacy in bone repair applications. In this study, we constructed an SF-based injectable porous microcarrier that is doped with laponite (LAP), containing magnesium ions (Mg2+). The influence of freezing temperatures and concentrations of SF and LAP on the structural parameters of SF-LAP microcarriers was investigated. The SF-LAP microcarrier exhibited a porosity of 76.7 ± 1.2% and a controlled pore size of 24.6 ± 4.0 μm. At the 6 weeks of in vitro degradation test, a mild alkaline level in culture medium containing SF-LAP microcarriers was detected. The release of Mg2+ from the SF-LAP microcarrier was maintained at a concentration within the range of 1.2-2.3 mM during the 6 weeks. The seeded human adipose-derived stem cells in the SF-LAP microcarrier demonstrated a significant enhancement in osteogenic differentiation compared with cells seeded in the pure SF microcarrier, as evidenced by quantitative alkaline phosphatase activity and the expression of osteogenic marker genes. These findings underscore the potential of the SF-LAP microcarrier as an ideal cell carrier in the treatment of bone defects.

Targeting Diverse Wounds and Scars: Recent Innovative Bio-design of Microneedle Patch for Comprehensive Management

Wounds and the subsequent formation of scars constitute a unified and complex phased process. Effective treatment is crucial; however, the diverse therapeutic approaches for different wounds and scars, as well as varying treatment needs at different stages, present significant challenges in selecting appropriate interventions. Microneedle patch (MNP), as a novel minimally invasive transdermal drug delivery system, has the potential for integrated and programmed treatment of various diseases and has shown promising applications in different types of wounds and scars. In this comprehensive review, the latest applications and biotechnological innovations of MNPs in these fields are thoroughly explored, summarizing their powerful abilities to accelerate healing, inhibit scar formation, and manage related symptoms. Moreover, potential applications in various scenarios are discussed. Additionally, the side effects, manufacturing processes, and material selection to explore the clinical translational potential are investigated. This groundwork can provide a theoretical basis and serve as a catalyst for future innovations in the pursuit of favorable therapeutic options for skin tissue regeneration.

Effect of rheological behaviors of polyacrylonitrile grafted sericin solution on film structure and mechanical properties

Sericin protein possesses excellent biocompatibility, antioxidation, and processability. Nevertheless, manufacturing large quantities of strong and tough pure regenerated sericin materials remains a significant challenge. Herein, we design a lightweight structural sericin film with high ductility by combining radical chain polymerization reaction and liquid-solid phase inversion method. The resulting polyacrylonitrile grafted sericin films exhibit the ability to switch between high strength and high toughness effortlessly, the maximum tensile strength and Young's modulus values are 21.92 ± 1.51 MPa and 8.14 ± 0.09 MPa, respectively, while the elongation at break and toughness reaches up to 344.10 ± 35.40 % and 10.84 ± 1.02 MJ·m-3, respectively. Our findings suggest that incorporating sericin into regenerated films contributes to the transformation of their mechanical properties through influencing the entanglement of molecular chains within polymerized solutions. Structural analyses conducted using infrared spectroscopy and X-ray diffraction confirm that sericin modulates the mechanical properties by affecting the transition of condensed matter conformation. This work presents a convenient yet effective strategy for simultaneously addressing the recycling of sericin as well as producing regenerated protein-based films that hold potential applications in biomedical, wearable, or food packaging.

Local application of gingiva-derived mesenchymal stem cells on experimental periodontitis in rats

BACKGROUND

Stem cell-based approaches in regenerative periodontal therapy have been used in different experimental models. In this study, the effect of local application of gingival mesenchymal stem cells (GMSC) in fibroin/chitosan oligosaccharide lactate hydrogel (F/COS) on periodontal regeneration was evaluated using experimental periodontitis model in rats.

METHODS

Mesenchymal stem cells were isolated from the gingiva of rats and characterized. Viability tests and confocal imaging of GMSC in hydrogels were performed. Healthy control without periodontitis (Health; H; n=10), control with periodontitis but no application (Periodontitis; P; n=10), only hydrogel application (F/COS; n=10), and GMSC+F/COS (n=10) four groups were formed for in vivo studies. Experimental periodontitis was created with silk sutures around the maxillary second molars. GMSC labeled with green fluorescent protein (GFP) (250,000 cells/50 μL) in F/COS were applied to the defect. Animals were sacrificed at 2nd and 8th weeks and maxillae of the animals were evaluated by micro-computed tomography (micro-CT) and histologically. The presence of GFP-labeled GMSC was confirmed at the end of 8 weeks.

RESULTS

Micro-CT analysis showed statistically significant new bone formation in the F/COS+GMSC treated group compared with the P group at the end of 8 weeks (p < 0.05). New bone formation was also observed in the F/COS group, but the statistical analysis revealed that this difference was not significant when compared with the P group (p > 0.05). Long junctional epithelium formation was less in the F/COS+GMSC group compared with the P group. Periodontal ligament and connective tissue were well-organized in F/COS+GMSC group.

CONCLUSION

The results showed that local GMSC application in hydrogel contributed to the formation of new periodontal ligament and alveolar bone in rats with experimental periodontitis. Since gingiva is easly accessible tissue, it is promising for autologous cell-based treatments in clinical applications.

Silk fibroin-based inks for in situ 3D printing using a double crosslinking process

The shortage of tissues and organs for transplantation is an urgent clinical concern. In situ 3D printing is an advanced 3D printing technique aimed at printing the new tissue or organ directly in the patient. The ink for this process is central to the outcomes, and must meet specific requirements such as rapid gelation, shape integrity, stability over time, and adhesion to surrounding healthy tissues. Among natural materials, silk fibroin exhibits fascinating properties that have made it widely studied in tissue engineering and regenerative medicine. However, further improvements in silk fibroin inks are needed to match the requirements for in situ 3D printing. In the present study, silk fibroin-based inks were developed for in situ applications by exploiting covalent crosslinking process consisting of a pre-photo-crosslinking prior to printing and in situ enzymatic crosslinking. Two different silk fibroin molecular weights were characterized and the synergistic effect of the covalent bonds with shear forces enhanced the shift in silk secondary structure toward β-sheets, thus, rapid stabilization. These hydrogels exhibited good mechanical properties, stability over time, and resistance to enzymatic degradation over 14 days, with no significant changes over time in their secondary structure and swelling behavior. Additionally, adhesion to tissues in vitro was demonstrated.

An Injectable silk-based hydrogel as a novel biomineralization seedbed for critical-sized bone defect regeneration

The healing process of critical-sized bone defects urges for a suitable biomineralization environment. However, the unsatisfying repair outcome usually results from a disturbed intricate milieu and the lack of in situ mineralization resources. In this work, we have developed a composite hydrogel that mimics the natural bone healing processes and serves as a seedbed for bone regeneration. The oxidized silk fibroin and fibrin are incorporated as rigid geogrids, and amorphous calcium phosphate (ACP) and platelet-rich plasma serve as the fertilizers and loam, respectively. Encouragingly, the seedbed hydrogel demonstrates excellent mechanical and biomineralization properties as a stable scaffold and promotes vascularized bone regeneration in vivo. Additionally, the seedbed serves a succinate-like function via the PI3K-Akt signaling pathway and subsequently orchestrates the mitochondrial calcium uptake, further converting the exogenous ACP into endogenous ACP. Additionally, the seedbed hydrogel realizes the succession of calcium resources and promotes the evolution of the biotemplate from fibrin to collagen. Therefore, our work has established a novel silk-based hydrogel that functions as an in-situ biomineralization seedbed, providing a new insight for critical-sized bone defect regeneration.

Multi-spectral photoacoustic imaging combined with acoustic radiation force impulse imaging for applications in tissue engineering

Tissue engineering is a dynamic field focusing on the creation of advanced scaffolds for tissue and organ regeneration. These scaffolds are customized to their specific applications and are often designed to be complex, large structures to mimic tissues and organs. This study addresses the critical challenge of effectively characterizing these thick, optically opaque scaffolds that traditional imaging methods fail to fully image due to their optical limitations. We introduce a novel multi-modal imaging approach combining ultrasound, photoacoustic, and acoustic radiation force impulse imaging. This combination leverages its acoustic-based detection to overcome the limitations posed by optical imaging techniques. Ultrasound imaging is employed to monitor the scaffold structure, photoacoustic imaging is employed to monitor cell proliferation, and acoustic radiation force impulse imaging is employed to evaluate the homogeneity of scaffold stiffness. We applied this integrated imaging system to analyze melanoma cell growth within silk fibroin protein scaffolds with varying pore sizes and therefore stiffness over different cell incubation periods. Among various materials, silk fibroin was chosen for its unique combination of features including biocompatibility, tunable mechanical properties, and structural porosity which supports extensive cell proliferation. The results provide a detailed mesoscale view of the scaffolds' internal structure, including cell penetration depth and biomechanical properties. Our findings demonstrate that the developed multimodal imaging technique offers comprehensive insights into the physical and biological dynamics of tissue-engineered scaffolds. As the field of tissue engineering continues to advance, the importance of non-ionizing and non-invasive imaging systems becomes increasingly evident, and by facilitating a deeper understanding and better characterization of scaffold architectures, such imaging systems are pivotal in driving the success of future tissue-engineering solutions.

In vivo bioluminescence imaging of the intracerebral fibroin-controlled AAV-α-synuclein diffusion for monitoring the central nervous system and peripheral expression

Among the several animal models of α-synucleinopathies, the well-known viral vector-mediated delivery of wild-type or mutated (A53T) α-synuclein requires new tools to increase the lesion in mice and follow up in vivo expression. To this end, we developed a bioluminescent expression reporter of the human A53T-α-synuclein gene using the NanoLuc system into an AAV2/9, embedded or not in a fibroin solution to stabilise its expression in space and time. We first verified the expression of the fused protein in vitro on transfected cells by bioluminescence and Western blotting. Next, two groups of C57Bl6Jr mice were unilaterally injected with the AAV-NanoLuc-human-A53T-α-synuclein above the substantia nigra combined (or not) with fibroin. We first show that the in vivo cerebral bioluminescence signal was more intense in the presence of fibroin. Using immunohistochemistry, we find that the human-A53T-α-synuclein protein is more restricted to the ipsilateral side with an overall greater magnitude of the lesion when fibroin was added. However, we also detected a bioluminescence signal in peripheral organs in both conditions, confirmed by the presence of viral DNA corresponding to the injected AAV in the liver using qPCR.

Silk fibroin-based scaffolds for tissue engineering

Silk fibroin is an important natural fibrous protein with excellent prospects for tissue engineering applications. With profound studies in recent years, its potential in tissue repair has been developed. A growing body of literature has investigated various fabricating methods of silk fibroin and their application in tissue repair. The purpose of this paper is to trace the latest developments of SF-based scaffolds for tissue engineering. In this review, we first presented the primary and secondary structures of silk fibroin. The processing methods of SF scaffolds were then summarized. Lastly, we examined the contribution of new studies applying SF as scaffolds in tissue regeneration applications. Overall, this review showed the latest progress in the fabrication and utilization of silk fibroin-based scaffolds.

Intelligent perceptual textiles based on ionic-conductive and strong silk fibers

Endowing textiles with perceptual function, similar to human skin, is crucial for the development of next-generation smart wearables. To date, the creation of perceptual textiles capable of sensing potential dangers and accurately pinpointing finger touch remains elusive. In this study, we present the design and fabrication of intelligent perceptual textiles capable of electrically responding to external dangers and precisely detecting human touch, based on conductive silk fibroin-based ionic hydrogel (SIH) fibers. These fibers possess excellent fracture strength (55 MPa), extensibility (530%), stable and good conductivity (0.45 S·m-1) due to oriented structures and ionic incorporation. We fabricated SIH fiber-based protective textiles that can respond to fire, water, and sharp objects, protecting robots from potential injuries. Additionally, we designed perceptual textiles that can specifically pinpoint finger touch, serving as convenient human-machine interfaces. Our work sheds new light on the design of next-generation smart wearables and the reshaping of human-machine interfaces.

Engineering sulfated polysaccharides and silk fibroin based injectable IPN hydrogels with stiffening and growth factor presentation abilities for cartilage tissue engineering

The extracellular matrix (ECM) presents a framework for various biological cues and regulates homeostasis during both developing and mature stages of tissues. During development of cartilage, the ECM plays a critical role in endowing both biophysical and biochemical cues to the progenitor cells. Hence, designing microenvironments that recapitulate these biological cues as provided by the ECM during development may facilitate the engineering of cartilage tissue. In the present study, we fabricated an injectable interpenetrating hydrogel (IPN) system which serves as an artificial ECM and provides chondro-inductive niches for the differentiation of stem cells to chondrocytes. The hydrogel was designed to replicate the gradual stiffening (as a biophysical cue) and the presentation of growth factors (as a biochemical cue) as provided by the natural ECM of the tissue, thus exemplifying a biomimetic approach. This dynamic stiffening was achieved by incorporating silk fibroin, while the growth factor presentation was accomplished using sulfated-carboxymethyl cellulose. Silk fibroin and sulfated-carboxymethyl cellulose (s-CMC) were combined with tyraminated-carboxymethyl cellulose (t-CMC) and crosslinked using HRP/H2O2 to fabricate s-CMC/t-CMC/silk IPN hydrogels. Initially, the fabricated hydrogel imparted a soft microenvironment to promote chondrogenic differentiation, and with time it gradually stiffened to offer mechanical support to the joint. Additionally, the presence of s-CMC conferred the hydrogel with the property of sequestering cationic growth factors such as TGF-β and allowing their prolonged presentation to the cells. More importantly, TGF-β loaded in the developed hydrogel system remained active and induced chondrogenic differentiation of stem cells, resulting in the deposition of cartilage ECM components which was comparable to the hydrogels that were treated with TGF-β provided through media. Overall, the developed hydrogel system acts as a reservoir of the necessary biological cues for cartilage regeneration and simultaneously provides mechanical support for load-bearing tissues such as cartilage.

Tunable thermal diffusivity of silk protein assemblies based on their structural control and photo-induced chemical cross-linking

Silk, which has excellent mechanical properties and is lightweight, serves as a structural material in natural systems. However, the structural and functional applications of silk in artificial systems have been limited due to the difficulty in controlling its properties. In this study, we demonstrate the tunable thermal diffusivity of silk-based assemblies (films) based on secondary structural control and subsequent cross-linking. We found that the thermal diffusivity of the silk film is increased by the formation of β-sheet structures and dityrosine between Tyr residues adjacent to the β-sheet structures. Our results demonstrate the applicability of silk proteins as material components for thermally conductive biopolymer-based materials.

Impact of the Reduction Time-Dependent Electrical Conductivity of Graphene Nanoplatelet-Coated Aligned Bombyx mori Silk Scaffolds on Electrically Stimulated Axonal Growth

Graphene-based nanomaterials, renowned for their outstanding electrical conductivity, have been extensively studied as electroconductive biomaterials (ECBs) for electrically stimulated tissue regeneration. However, using eco-friendly reducing agents like l-ascorbic acid (l-Aa) can result in lower conductive properties in these ECBs, limiting their full potential for smooth charge transfer in living tissues. Moreover, creating a flexible biomaterial scaffold using these materials that accurately mimics a specific tissue microarchitecture, such as nerves, poses additional challenges. To address these issues, this study developed a microfibrous scaffold of Bombyx mori (Bm) silk fibroin uniformly coated with graphene nanoplatelets (GNPs) through a vacuum coating method. The scaffold's electrical conductivity was optimized by varying the reduction period using l-Aa. The research systematically investigated how different reduction periods impact scaffold properties, focusing on electrical conductivity and its significance on electrically stimulated axonal growth in PC12 cells. Results showed that a 48 h reduction significantly increased surface electrical conductivity by 100-1000 times compared to a shorter or no reduction process. l-Aa contributed to stabilizing the reduced GNPs, demonstrated by a slow degradation profile and sustained conductivity even after 60 days in a proteolytic environment. β (III) tubulin immunostaining of PC12 cells on varied silk:GNP scaffolds under pulsed electrical stimulation (ES, 50 Hz frequency, 1 ms pulse width, and amplitudes of 100 and 300 mV/cm) demonstrates accelerated axonal growth on scaffolds exhibiting higher conductivity. This is supported by upregulated intracellular Ca2+ dynamics immediately after ES on the scaffolds with higher conductivity, subjected to a prolonged reduction period. The study showcases a sustainable reduction approach using l-Aa in combination with natural Bm silk fibroin to create a highly conductive, mechanically robust, and stable silk:GNP-based aligned fibrous scaffold. These scaffolds hold promise for functional regeneration in electrically excitable tissues such as nerves, cardiac tissue, and muscles.

Tuning the Biodegradation Rate of Silk Materials via Embedded Enzymes

Conventional thinking when designing biodegradable materials and devices is to tune the intrinsic properties and morphological features of the material to regulate their degradation rate, modulating traditional factors such as molecular weight and crystallinity. Since regenerated silk protein can be directly thermoplastically molded to generate robust dense silk plastic-like materials, this approach afforded a new tool to control silk degradation by enabling the mixing of a silk-degrading protease into bulk silk material prior to thermoplastic processing. Here we demonstrate the preparation of these silk-based devices with embedded silk-degrading protease to modulate the degradation based on the internal presence of the enzyme to support silk degradation, as opposed to the traditional surface degradation for silk materials. The degradability of these silk devices with and without embedded protease XIV was assessed both in vitro and in vivo. Ultimately, this new process approach provides direct control of the degradation lifetime of the devices, empowered through internal digestion via water-activated proteases entrained and stabilized during the thermoplastic process.

Polydopamine-Coated Silk Fiber with Controllable Length for Enhanced Hemostatic Application

The development of highly effective hemostatic materials with high biocompatibility and outstanding performance is vital to the field of biomaterials. In this study, we develop a hemostatic fiber material that exhibits high biocompatibility and excellent performance. By incorporating polydopamine (PDA) into the alkaline treatment of silk fibroin (SF), we achieve PDA-coated SF fibers with lengths that can be controlled by the alkaline concentration. The PDA coating significantly enhances the hemostatic ability of the silk fibers and exhibits superior performance in both in vitro and ex vivo experiments. By performing animal studies involving a mouse liver puncture model and a femoral vein incision model, we demonstrate the remarkable hemostatic capability of the PDA-coated SF fibers, as evidenced by the lower blood loss compared to that of a commercial hemostat powder. These findings highlight the potential of applying a PDA-assisted alkaline treatment to SF fibers to efficiently create hemostatic fibers with controllable lengths, which would be promising candidates for clinical hemostatic applications.

Harvesting Silk Fibers from Plodia interpunctella: Role of Environmental Rearing Conditions in Fiber Production and Properties

Silk fibers are produced by a wide variety of insects. The silkworm Bombyx mori (Bombyx) was domesticated because the physical properties of its silk fibers were amenable to the production of fine textiles. Subsequently, engineers have regenerated silk fibroin to form biomaterials. The monocular focus on Bombyx silk has underutilized the expanse of diverse silk proteins produced by more than 100,000 other arthropods. This vast array of silk fibers could be utilized for biomedical engineering challenges if sufficient rearing and purification processes are developed. Herein, we show that the moth, Plodia interpunctella (Plodia), represents an alternative silk source that is easily reared in highly regulated culture environments allowing for greater consistency in the silk produced. We controlled the temperature, resource availability (larvae/gram diet), and population density (larvae/mL) with the goal of increasing silk fiber production and improving homogeneity in Plodia silk proteins. We determined that higher temperatures accelerated insect growth and reduced life cycle length. Furthermore, we established initial protocols for the production of Plodia silk with optimal silk production occurring at 24 °C, with a resource availability of 10 larvae/gram and a population density of 0.72 larvae/mL. Population density was shown to be the most prominent driving force of Plodia silk mat formation among the three parameters assessed. Future work will need to link gene expression, protein production and purification, and resulting mechanical properties as a function of environmental cues to further transition Plodia silk into regenerated silk fibroin biomaterials.

Genipin-Cross-Linked Silk Fibroin/Alginate Dialdehyde Hydrogel with Tunable Gelation Kinetics, Degradability, and Mechanical Properties: A Potential Candidate for Tissue Regeneration

Genipin-cross-linked silk fibroin (SF) hydrogel is considered to be biocompatible and mechanically robust. However, its use remains a challenge for in situ forming applications due to its prolonged gelation process. In our attempt to facilitate the in situ fabrication of a genipin-mediated SF hydrogel, alginate dialdehyde (ADA) was utilized as a reinforcement template. Here, SF/ADA-based hydrogels with different compositions were synthesized covalently and ionically. Incorporating ADA into the SF hydrogel increased pore size (44.66-174.66 μm), porosity (61.59-80.40%), and the equilibrium swelling degree (7.60-30.17). Moreover, a wide range of storage modulus and compressive modulus were obtained by adjusting the proportions of SF and ADA networks within the hydrogel. The in vitro cell analysis using preosteoblast cells (MC3T3-E1) demonstrated the cytocompatibility of all hydrogels. Overall, the covalently and ionically cross-linked SF/ADA hydrogel represents a promising solution for in situ forming hydrogels for applications in tissue regeneration.

Nanocomposite Methacrylated Silk Fibroin-Based Scaffolds for Bone Tissue Engineering

The treatment of bone defects is a clinical challenge. Bone tissue engineering is gaining interest as an alternative to current treatments, with the development of 3D porous structures (scaffolds) helpful in promoting bone regeneration by ensuring temporary functional support. In this work, methacrylated silk fibroin (SilMA) sponges were investigated as scaffolds for bone tissue engineering by exploiting the combination of physical (induced by NaCl salt during particulate leaching) and chemical crosslinking (induced by UV-light exposure) techniques. A biomimetic approach was adopted to better simulate the extracellular matrix of the bone by introducing either natural (mussel shell-derived) or synthetic-origin hydroxyapatite nanoparticles into the SilMA sponges. The obtained materials were characterized in terms of pore size, water absorption capability and mechanical properties to understand both the effect of the inclusion of the two different types of nanoparticles and the effect of the photocrosslinking. Moreover, the SilMA sponges were tested for their bioactivity and suitability for bone tissue engineering purposes by using osteosarcoma cells, studying their metabolism by an AlamarBlue assay and their morphology by scanning electron microscopy. Results indicate that photocrosslinking helps in obtaining more regular structures with bimodal pore size distributions and in enhancing the stability of the constructs in water. Moreover, the addition of naturally derived hydroxyapatite was observed to be more effective at activating osteosarcoma cell metabolism than synthetic hydroxyapatite, showing a statistically significant difference in the AlamarBlue measurement on day 7 after seeding. The methacrylated silk fibroin/hydroxyapatite nanocomposite sponges developed in this work were found to be promising tools for targeting bone regeneration with a sustainable approach.

A Cu(Ⅱ)-eluting coating through silk fibroin film on ZE21B alloy designed for in situ endotheliazation biofunction

In the cardiovascular field, coating containing copper used to catalyze NO (nitric oxide) production on non-degradable metal surfaces have shown unparalleled expected performance, but there are few studies on biodegradable metal surfaces. Magnesium-based biodegradable metals have been applied in cardiovascular field in large-scale because of their excellent properties. In this study, the coating of copper loaded in silk fibroin is fabricated on biodegradable ZE21B alloy. Importantly, the different content of copper is set to investigate the effects of on the degradation performance and cell behavior of magnesium alloy. Through electrochemical and immersion experiments, it is found that high content of copper will accelerate the corrosion of magnesium alloy. The reason is the spontaneous micro-batteries between copper and magnesium with the different standard electrode potentials, that is, the galvanic corrosion accelerates the corrosion of magnesium alloy. Moreover, the coating formed through silk fibroin by the right amount copper not only have a protective effect on the ZE21B alloy substrate, but also promotes the adhesion and proliferation of endothelial cells in blood vessel micro-environment. The production of NO catalyzed by copper ions makes this trend more significant, and inhibits the excessive proliferation of smooth muscle cells. These findings can provide guidance for the amount of copper in the coating on the surface of biodegradable magnesium alloy used for cardiovascular stent purpose.

Programming temporal stiffness cues within extracellular matrix hydrogels for modelling cancer niches

Extracellular matrix (ECM) stiffening is a common occurrence during the progression of many diseases, such as breast cancer. To accurately mimic the pathophysiological context of disease within 3D in vitro models, there is high demand for smart biomaterials which replicate the dynamic and temporal mechanical cues of diseased states. This study describes a preclinical disease model, using breast cancer as an example, which replicates the dynamic plasticity of the tumour microenvironment by incorporating temporal (3-week progression) biomechanical cues within a tissue-specific hydrogel microenvironment. The composite hydrogel formulation, integrating adipose-derived decellularised ECM (AdECM) and silk fibroin, was initially crosslinked using a visible light-mediated system, and then progressively stiffened through spontaneous secondary structure interactions inherent between the polymer chains (∼10-15 kPa increase, with a final stiffness of 25 kPa). When encapsulated and cultured in vitro, MCF-7 breast cancer cells initially formed numerous, large spheroids (>1000 μm2 in area), however, with progressive temporal stiffening, cells demonstrated growth arrest and underwent phenotypic changes resulting in intratumoral heterogeneity. Unlike widely-investigated static mechanical models, this stiffening hydrogel allowed for progressive phenotypic changes to be observed, and fostered the development of mature organoid-like spheroids, which mimicked both the organisation and acinar-structures of mature breast epithelium. The spheroids contained a central population of cells which expressed aggressive cellular programs, evidenced by increased fibronectin expression and reduction of E-cadherin. The phenotypic heterogeneity observed using this model is more reflective of physiological tumours, demonstrating the importance of establishing temporal cues within preclinical models in future work. Overall, the developed model demonstrated a novel strategy to uncouple ECM biomechanical properties from the cellular complexities of the disease microenvironment and offers the potential for wide applicability in other 3D in vitro disease models through addition of tissue-specific dECM materials.

Silk fibroin/methacrylated gelatine/hydroxyapatite biomimetic nanofibrous membranes for guided bone regeneration

By mimicking in vivo bionic microenvironment and promoting osteogenic differentiation, the hybrid organic-inorganic nanofibrous membranes provide promising potential for guided bone regeneration (GBR) in the treatment of clinical bone defects. To develop a degradable and osteogenic membrane for GBR by combining the natural biomacromolecule silk fibroin (SF) and gelatine with the bioactive nano hydroxyapatite (nHA), the anhydride-modified gelatine-nano hydroxyapatite (GelMA-nHA) composites were synthesized in situ and introduced into silk fibroin to prepare nanofibrous membranes with different ratios using electrospinning and photocrosslinking. The nanofibrous membranes, particularly those with a mass ratio of 7:2:1, were found to exhibit satisfactory elongation at break up to 110 %, maintain the nanofibrous structure for up to 28 days, and rapidly form bone-like apatite within 3 days, thus offering advantages when it comes to guided bone regeneration. In vitro cell results showed that the SF/GelMA/nHA membranes had excellent biocompatibility and enhanced osteogenic differentiation of hBMSCs. In vivo studies revealed that the hybrid composite membranes can improve bone regeneration of critical-sized calvarial defects in rat model. Therefore, the novel hybrid nanofibrous membrane is proposed to be a alternative candidate for creating a bionic microenvironment that promotes bone regeneration, indicating their potential application to bone injury treatment.

An injectable and photocurable methacrylate-silk fibroin/nano-hydroxyapatite hydrogel for bone regeneration through osteoimmunomodulation

Tissue engineering has emerged as a promising approach for addressing bone defects. Most of the traditional 3D printing materials predominantly relying on polymers and ceramics. Although these materials exhibit superior osteogenic effects, their gradual degradation poses a limitation. Digital light processing (DLP) 3D bioprinting that uses natural biomaterials as bioinks has become one of the promising strategies for bone regeneration. In this study, we introduce a hydrogel biomaterial derived from silk fibroin (SF). Notably, we present the novel integration of nano-hydroxyapatite (nHA) into the hydrogel, forming a composite hydrogel that rapidly cross-links upon initiation. Moreover, we demonstrate the loading of nHA through non-covalent bonds in SilMA. In vitro experiments reveal that composite hydrogel scaffolds with 10 % nHA exhibit enhanced osteogenic effects. Transcriptomic analysis indicates that the composite hydrogel promotes bone regeneration by inducing M2 macrophage polarization. Furthermore, rat femoral defect experiments validate the efficacy of SilMA/nHA10 in bone regeneration. This study synthesis of a simple and effective composite hydrogel bioink for bone regeneration, presenting a novel strategy for the future implementation of digital 3D printing technology in bone tissue engineering.

Fabrication of multifunctional silk nanofibril/hyaluronic acid scaffold for spinal cord repair

Bioactive scaffolds accurately mimicking the structure and composition of the extracellular matrix have garnered significant interest in tissue engineering. In this study, we developed a platform utilizing natural silk nanofibrils, hyaluronic acid, and basic fibroblast growth factor for the purpose of promoting spinal cord regeneration by creating an optimal microenvironment. The bioactive scaffold exhibited notable characteristics such as high porosity and hydrophilicity, attributed to its unique nanostructure, high connectivity, and polysaccharide composition. Furthermore, the pore size of the scaffold can be adjusted within the range of 90 μm to 120 μm by varying the content of hyaluronic acid. In vitro, human umbilical vein endothelial cells were seeded into the scaffold, demonstrating enhanced cell viability. The scaffold facilitated cell proliferation and migration. In vivo experiments on rats indicated that the scaffold had a beneficial impact on spinal cord regeneration, creating a conducive environment for motor function recovery of the rats. This effect may be attributed to the scaffold's ability to stimulate axon growth and neuronal survival, as well as inhibit the formation of glial scars, as evidenced by the decreased expression of growth associated protein-43, microtubule-associated protein 2, and neurofilament-200. This study presents a promising method to develop a feasible bioscaffold for the treatment of spinal cord injury.

Sustainable Bombyx mori's silk fibroin for biomedical applications as a molecular biotechnology challenge: A review

Silk is a natural engineering material with a unique set of properties. The major constituent of silk is fibroin, a protein widely used in the biomedical field because of its mechanical strength, toughness and elasticity, as well as its biocompatibility and biodegradability. The domestication of silkworms allows large amounts of fibroin to be extracted inexpensively from silk cocoons. However, the industrial extraction process has drawbacks in terms of sustainability and the quality of the final medical product. The heterologous production of fibroin using recombinant DNA technology is a promising approach to address these issues, but the production of such recombinant proteins is challenging and further optimization is required due to the large size and repetitive structure of fibroin's DNA and amino acid sequence. In this review, we describe the structure-function relationship of fibroin, the current extraction process, and some insights into the sustainability of silk production for biomedical applications. We focus on recent advances in molecular biotechnology underpinning the production of recombinant fibroin, working toward a standardized, successful and sustainable process.

Bioactive nanomaterials kickstart early repair processes and potentiate temporally modulated healing of healthy and diabetic wounds

Slow-healing and chronic wounds represent a major global economic and medical burden, and there is significant unmet need for novel therapies which act to both accelerate wound closure and enhance biomechanical recovery of the skin. Here, we report a new approach in which bioactives that augment early stages of wound healing can kickstart and engender effective wound closure in healthy and diabetic, obese animals, and set the stage for subsequent tissue repair processes. We demonstrate that a nanomaterial dressing made of silk fibroin and gold nanorods (GNR) stimulates a pro-neutrophilic, innate immune, and controlled inflammatory wound transcriptomic response. Further, Silk-GNR, lasered into the wound bed, in combination with exogeneous histamine, accelerates early-stage processes in tissue repair leading to effective wound closure. Silk-GNR and histamine enhanced biomechanical recovery of skin, increased transient neoangiogenesis, myofibroblast activation, epithelial-to-mesenchymal transition (EMT) of keratinocytes and a pro-resolving neutrophilic immune response, which are hitherto unknown activities for these bioactives. Predictive and temporally coordinated delivery of growth factor nanoparticles that modulate later stages of tissue repair further accelerated wound closure in healthy and diabetic, obese animals. Our approach of kickstarting healing by delivering the "right bioactive at the right time" stimulates a multifactorial, pro-reparative response by augmenting endogenous healing and immunoregulatory mechanisms and highlights new targets to promote tissue repair.

Decoding silkworm spinning programmed by pH and metal ions

Silk is one of the toughest fibrous materials known despite spun at ambient temperature and pressure with water as a solvent. It is a great challenge to reproduce high-performance artificial fibers comparable to natural silk by bionic for the incomplete understanding of silkworm spinning in vivo. Here, we found that amphipol and digitonin stabilized the structure of natural silk fibroin (NSF) by a large-scale screening in vitro, and then studied the close-to-native ultrastructure and hierarchical assembly of NSF in the silk gland lumen. Our study showed that NSF formed reversible flexible nanofibrils mainly composed of random coils with a sedimentation coefficient of 5.8 S and a diameter of about 4 nm, rather than a micellar or rod-like structure assembled by the aggregation of globular NSF molecules. Metal ions were required for NSF nanofibril formation. The successive pH decrease from posterior silk gland (PSG) to anterior silk gland (ASG) resulted in a gradual increase in NSF hydrophobicity, thus inducing the sol-gelation transition of NSF nanofibrils. NSF nanofibrils were randomly dispersed from PSG to ASG-1, and self-assembled into anisotropic herringbone patterns at ASG-2 near the spinneret ready for silkworm spinning. Our findings reveal the controlled self-assembly mechanism of the multi-scale hierarchical architecture of NSF from nanofibrils to herringbone patterns programmed by metal ions and pH gradient, which provides novel insights into the spinning mechanism of silk-secreting animals and bioinspired design of high-performance fibers.

Selenium-silk microgels as antifungal and antibacterial agents

Antimicrobial resistance is a leading threat to global health. Alternative therapeutics to combat the rise in drug-resistant strains of bacteria and fungi are thus needed, but the development of new classes of small molecule therapeutics has remained challenging. Here, we explore an orthogonal approach and address this issue by synthesising micro-scale, protein colloidal particles that possess potent antimicrobial properties. We describe an approach for forming silk-based microgels that contain selenium nanoparticles embedded within the protein scaffold. We demonstrate that these materials have both antibacterial and antifungal properties while, crucially, also remaining highly biocompatible with mammalian cell lines. By combing the nanoparticles with silk, the protein microgel is able to fulfill two critical functions; it protects the mammalian cells from the cytotoxic effects of the bare nanoparticles, while simultaneously serving as a carrier for microbial eradication. Furthermore, since the antimicrobial activity originates from physical contact, bacteria and fungi are unlikely to develop resistance to our hybrid biomaterials, which remains a critical issue with current antibiotic and antifungal treatments. Therefore, taken together, these results provide the basis for innovative antimicrobial materials that can target drug-resistant microbial infections.

Diatom-inspired silicification process for development of green flexible silica composite aerogels

In this study, we have developed novel biomimetic silica composite aerogels and cryogels for the first time, drawing inspiration from the natural diatom's silicification process. Our biomimetic approach involved the modification of tyrosinase-mediated oxidized silk fibroin (SFO) surfaces with polyethyleneimine (PEI). This modification introduced ample amine groups onto the SF polymer, which catalyzed the silicification of the SFO-PEI gel surface with silicic acid. This process emulates the catalytic function of long-chain polyamines and silaffin proteins found in diatoms, resulting in a silica network structure on the primary SFO-PEI network gel's surface. The SFO-PEI gel matrix played a dual role in this process: (1) It provided numerous amine functional groups that directly catalyzed the silicification of silicic acid on the porous structure's exterior surface, without encapsulating the created silica network in the gel. (2) It served as a flexible mechanical support facilitating the creation of the silica network. As a result, the final ceramic composite exhibits a mechanically flexible nature (e.g., cyclic compressibility up to 80% strain), distinguishing it from conventional composite aerogels. By mimicking the diatom's silicification process, we were able to simplify the development of silica-polymer composite aerogels. It eliminates the need for surfactants, multi-step procedures involving solvent exchange, and gel washing. Instead, the reaction occurs under mild conditions, streamlining the composite aerogels fabrication process.

Trends and advances in silk based 3D printing/bioprinting towards cartilage tissue engineering and regeneration

Cartilage repair remains a significant clinical challenge in orthopedics due to its limited self- regeneration potential and often progresses to osteoarthritis which reduces the quality of life. 3D printing/bioprinting has received vast attention in biofabrication of functional tissue substitutes due to its ability to develop complex structures such as zonally structured cartilage and osteochondral tissue as per patient specifications with precise biomimetic control. Towards a suitable bioink development for 3D printing/bioprinting, silk fibroin has garnered much attention due to its advantageous characteristics such as shear thinning behavior, cytocompatibility, good printability, structural fidelity, affordability, and ease of availability and processing. This review attempts to provide an overview of current trends/strategies and recent advancements in utilizing silk-based bioinks/biomaterial-inks for cartilage bioprinting. Herein, the development of silk-based bioinks/biomaterial-inks, its components and the associated challenges, along with different bioprinting techniques have been elaborated and reviewed. Furthermore, the applications of silk-based bioinks/biomaterial-inks in cartilage repair followed by challenges and future directions are discussed towards its clinical translations and production of next-generation biological implants.

Thermodynamic Analysis of Silk Fibroin-Graphite Hybrid Materials and Their Morphology

Silk fibroin (SF) is a β-sheet-rich protein that is responsible for the remarkable tensile strength of silk. In addition to its mechanical properties, SF is biocompatible and biodegradable, making it an attractive candidate for use in biotic/abiotic hybrid materials. A pairing of particular interest is the use of SF with graphene-based nanomaterials (GBNs). The properties of this interface drive the formation of well-ordered nanostructures and can improve the electronic properties of the resulting hybrid. It was previously demonstrated that SF can form lamellar nanostructures in the presence of graphite; however, the equilibrium morphology and associated driving interactions are not fully understood. In this study, we characterize these interactions between SF and SF lamellar with graphite using molecular dynamics (MD) simulations and umbrella sampling (US). We find that SF lamellar nanostructures have strong orientational and spatial preferences on graphite that are driven by the hydrophobic effect, destabilizing solvent-protein interactions and stabilizing protein-protein and protein-graphite interactions. Finally, we show how careful consideration of these underlying interactions can be applied to rationally modify the nanostructure morphology.

Covalent Grafting of Functionalized MEW Fibers to Silk Fibroin Hydrogels to Obtain Reinforced Tissue Engineered Constructs

Hydrogels are ideal materials to encapsulate cells, making them suitable for applications in tissue engineering and regenerative medicine. However, they generally do not possess adequate mechanical strength to functionally replace human tissues, and therefore they often need to be combined with reinforcing structures. While the interaction at the interface between the hydrogel and reinforcing structure is imperative for mechanical function and subsequent biological performance, this interaction is often overlooked. Melt electrowriting enables the production of reinforcing microscale fibers that can be effectively integrated with hydrogels. Yet, studies on the interaction between these micrometer scale fibers and hydrogels are limited. Here, we explored the influence of covalent interfacial interactions between reinforcing structures and silk fibroin methacryloyl hydrogels (silkMA) on the mechanical properties of the construct and cartilage-specific matrix production in vitro. For this, melt electrowritten fibers of a thermoplastic polymer blend (poly(hydroxymethylglycolide-co-ε-caprolactone):poly(ε-caprolactone) (pHMGCL:PCL)) were compared to those of the respective methacrylated polymer blend pMHMGCL:PCL as reinforcing structures. Photopolymerization of the methacrylate groups, present in both silkMA and pMHMGCL, was used to generate hybrid materials. Covalent bonding between the pMHMGCL:PCL blend and silkMA hydrogels resulted in an elastic response to the application of torque. In addition, an improved resistance was observed to compression (∼3-fold) and traction (∼40-55%) by the scaffolds with covalent links at the interface compared to those without these interactions. Biologically, both types of scaffolds (pHMGCL:PCL and pMHMGCL:PCL) showed similar levels of viability and metabolic activity, also compared to frequently used PCL. Moreover, articular cartilage progenitor cells embedded within the reinforced silkMA hydrogel were able to form a cartilage-like matrix after 28 days of in vitro culture. This study shows that hybrid cartilage constructs can be engineered with tunable mechanical properties by grafting silkMA hydrogels covalently to pMHMGCL:PCL blend microfibers at the interface.

Multi- and Gray-Scale Thermal Lithography of Silk Fibroin as Water-Developable Resist for Micro and Nanofabrication

Silk fibroin (SF) is a natural material with polymorphic structures that determine its water solubility and biodegradability, which can be altered by exposing it to heat. Here, a hybrid thermal lithography method combining scalable microscale laser-based patterning with nanoscale patterning based on thermal scanning probe lithography is developed. The latter enables in addition grayscale patterns to be made. The resolution limit of the writing in silk fibroin is studied by using a nanoscale heat source from a scanned nanoprobe. The heat thereby induces local water solubility change in the film, which can subsequently be developed in deionized water. Nanopatterns and grayscale patterns down to 50 nm lateral resolution are successfully written in the silk fibroin that behaves like a positive tone resist. The resulting patterned silk fibroin is then applied as a mask for dry etching of SiO2 to form a hard mask for further nano-processing. A very high selectivity of 42:1 between SiO2 and silk fibroin is obtained allowing for high-aspect ratio structure to be fabricated. The fabricated nanostructures have very low line edge roughness of 5 ± 2 nm. The results demonstrate the potential of silk fibroin as a water-soluble resist for hybrid thermal lithography and precise micro/nanofabrication.

Advancements in drug-loaded hydrogel systems for bone defect repair

Bone defects are primarily the result of high-energy trauma, pathological fractures, bone tumor resection, or infection debridement. The treatment of bone defects remains a huge clinical challenge. The current treatment options for bone defects include bone traction, autologous/allogeneic bone transplantation, gene therapy, and bone tissue engineering amongst others. With recent developments in the field, composite scaffolds prepared using tissue engineering techniques to repair bone defects are used more often. Among the various composite scaffolds, hydrogel exhibits the advantages of good biocompatibility, high water content, and degradability. Its three-dimensional structure is similar to that of the extracellular matrix, and as such it is possible to load stem cells, growth factors, metal ions, and small molecule drugs upon these scaffolds. Therefore, the hydrogel-loaded drug system has great potential in bone defect repair. This review summarizes the various natural and synthetic materials used in the preparation of hydrogels, in addition to the latest research status of hydrogel-loaded drug systems.

Self-Sanitization in a Silk Nanofibrous Network for Biodegradable PM0.3 Filters with In Situ Joule Heating

In the contemporary way of life, face masks are crucial in managing disease transmission and battling air pollution. However, two key challenges, self-sanitization and biodegradation of face masks, need immediate attention, prompting the development of innovative solutions for the future. In this study, we present a novel approach that combines controlled acid hydrolysis and mechanical chopping to synthesize a silk nanofibrous network (SNN) seamlessly integrated with a wearable stainless steel mesh, resulting in the fabrication of self-sanitizable face masks. The distinct architecture of face masks showcases remarkable filtration efficiencies of 91.4, 95.4, and 98.3% for PM0.3, PM0.5, and PM1.0, respectively, while maintaining a comfortable level of breathability (ΔP = 92 Pa). Additionally, the face mask shows that a remarkable thermal resistance of 472 °C cm2 W-1 generates heat spontaneously at low voltage, deactivating Escherichia coli bacteria on the SNN, enabling self-sanitization. The SNN exhibited complete disintegration within the environment in just 10 days, highlighting the remarkable biodegradability of the face mask. The unique advantage of self-sanitization and biodegradation in a face mask filter is simultaneously achieved for the first time, which will open avenues to accomplish environmentally benign next-generation face masks.

From Basic Principles of Protein-Polysaccharide Association to the Rational Design of Thermally Sensitive Materials

Biology resolves design requirements toward functional materials by creating nanostructured composites, where individual components are combined to maximize the macroscale material performance. A major challenge in utilizing such design principles is the trade-off between the preservation of individual component properties and emerging composite functionalities. Here, polysaccharide pectin and silk fibroin were investigated in their composite form with pectin as a thermal-responsive ion conductor and fibroin with exceptional mechanical strength. We show that segregative phase separation occurs upon mixing, and within a limited compositional range, domains ∼50 nm in size are formed and distributed homogeneously so that decent matrix collective properties are established. The composite is characterized by slight conformational changes in the silk domains, sequestering the hydrogen-bonded β-sheets as well as the emergence of randomized pectin orientations. However, most dominant in the composite's properties is the introduction of dense domain interfaces, leading to increased hydration, surface hydrophilicity, and increased strain of the composite material. Using controlled surface charging in X-ray photoelectron spectroscopy, we further demonstrate Ca ions (Ca2+) diffusion in the pectin domains, with which the fingerprints of interactions at domain interfaces are revealed. Both the thermal response and the electrical conductance were found to be strongly dependent on the degree of composite hydration. Our results provide a fundamental understanding of the role of interfacial interactions and their potential applications in the design of material properties, polysaccharide-protein composites in particular.

Piezoelectric dressings for advanced wound healing

The treatment of chronic refractory wounds poses significant challenges and threats to both human society and the economy. Existing research studies demonstrate that electrical stimulation fosters cell proliferation and migration and promotes the production of cytokines that expedites the wound healing process. Presently, clinical settings utilize electrical stimulation devices for wound treatment, but these devices often present issues such as limited portability and the necessity for frequent recharging. A cutting-edge wound dressing employing the piezoelectric effect could transform mechanical energy into electrical energy, thereby providing continuous electrical stimulation and accelerating wound healing, effectively addressing these concerns. This review primarily reviews the selection of piezoelectric materials and their application in wound dressing design, offering a succinct overview of these materials and their underlying mechanisms. This study also provides a perspective on the current limitations of piezoelectric wound dressings and the future development of multifunctional dressings harnessing the piezoelectric effect.

Applications and Potentials of a Silk Fibroin Nanoparticle Delivery System in Animal Husbandry

Silk fibroin (SF), a unique natural polymeric fibrous protein extracted from Bombyx mori cocoons, accounts for approximately 75% of the total mass of silk. It has great application prospects due to its outstanding biocompatibility, biodegradability, low immunogenicity, and mechanical stability. Additionally, it is non-toxic and environmentally friendly. Nanoparticle delivery systems constructed with SF can improve the bioavailability of the carriers, increase the loading rates, control the release behavior of the deliverables, and enhance their action efficiencies. Animal husbandry is an integral part of agriculture and plays a vital role in the development of the rural economy. However, the pillar industry experiences a lot of difficulties, like drug abuse while treating major animal diseases, and serious environmental pollution, restricting sustainable development. Interestingly, the limited use cases of silk fibroin nanoparticle (SF NP) delivery systems in animal husbandry, such as veterinary vaccines and feed additives, have shown great promise. This paper first reviews the SF NP delivery system with regard to its advantages, disadvantages, and applications. Moreover, we describe the application status and developmental prospects of SF NP delivery systems to provide theoretical references for further development in livestock production and promote the high-quality and healthy development of animal husbandry.

Transplantation of committed pre-adipocytes from brown adipose tissue improves whole-body glucose homeostasis

Obesity and its co-morbidities including type 2 diabetes are increasing at epidemic rates in the U.S. and worldwide. Brown adipose tissue (BAT) is a potential therapeutic to combat obesity and type 2 diabetes. Increasing BAT mass by transplantation improves metabolic health in rodents, but its clinical translation remains a challenge. Here, we investigated if transplantation of 2-4 million differentiated brown pre-adipocytes from mouse BAT stromal fraction (SVF) or human pluripotent stem cells (hPSCs) could improve metabolic health. Transplantation of differentiated brown pre-adipocytes, termed "committed pre-adipocytes" from BAT SVF from mice or derived from hPSCs improves glucose homeostasis and insulin sensitivity in recipient mice under conditions of diet-induced obesity, and this improvement is mediated through the collaborative actions of the liver transcriptome, tissue AKT signaling, and FGF21. These data demonstrate that transplantation of a small number of brown adipocytes has significant long-term translational and therapeutic potential to improve glucose metabolism.

Omentum Extracellular Matrix-Silk Fibroin Hydroscaffold Promotes Wound Healing through Vascularization and Tissue Remodeling in the Diabetic Rat Model

Nonhealing diabetic wounds are often associated with significant mortality and cause economic and clinical burdens to the healthcare system. Herein, a biomimetic hydroscaffold is developed using omentum tissue-derived decellularized-extracellular matrix (dECM) and silk fibroin (SF) proteins that associate the behavior of a collagenous fibrous scaffold and a hydrogel to reproduce all aspects of the provisional skin tissue matrix. The chemical cross-linker-free in situ gelation property of the two types of SF proteins from Bombyx mori and Antheraea assamensis ensures the adherence of dECM with surrounding tissue on the wound bed, circumventing further suturing. The physicochemical and mechanical properties of the composite hydroscaffold (SF-dECM) were thoroughly evaluated. The hydroscaffolds were found to support the growth and proliferation of human dermal fibroblasts and influence the angiogenic potential of endothelial cells under in vitro conditions. Furthermore, the healing efficacy of the composites was evaluated by generating full-thickness wounds on a streptozotocin-induced diabetic rat model. The presence of dECM components in the composite facilitated the rate of wound closure, granulation tissue formation, and re-epithelialization by providing intrinsic cues to advance the inflammatory stage and stimulating angiogenesis. Collectively, as an off-the-shelf wound dressing requiring only a single topical administration, the SF-dECM hydroscaffold is a promising, cost-effective dressing for the management of chronic diabetic wounds.

Silk Fibroin Materials: Biomedical Applications and Perspectives

The golden rule in tissue engineering is the creation of a synthetic device that simulates the native tissue, thus leading to the proper restoration of its anatomical and functional integrity, avoiding the limitations related to approaches based on autografts and allografts. The emergence of synthetic biocompatible materials has led to the production of innovative scaffolds that, if combined with cells and/or bioactive molecules, can improve tissue regeneration. In the last decade, silk fibroin (SF) has gained attention as a promising biomaterial in regenerative medicine due to its enhanced bio/cytocompatibility, chemical stability, and mechanical properties. Moreover, the possibility to produce advanced medical tools such as films, fibers, hydrogels, 3D porous scaffolds, non-woven scaffolds, particles or composite materials from a raw aqueous solution emphasizes the versatility of SF. Such devices are capable of meeting the most diverse tissue needs; hence, they represent an innovative clinical solution for the treatment of bone/cartilage, the cardiovascular system, neural, skin, and pancreatic tissue regeneration, as well as for many other biomedical applications. The present narrative review encompasses topics such as (i) the most interesting features of SF-based biomaterials, bare SF's biological nature and structural features, and comprehending the related chemo-physical properties and techniques used to produce the desired formulations of SF; (ii) the different applications of SF-based biomaterials and their related composite structures, discussing their biocompatibility and effectiveness in the medical field. Particularly, applications in regenerative medicine are also analyzed herein to highlight the different therapeutic strategies applied to various body sectors.

Plasmonic biochips with enhanced stability in harsh environments for the sensitive detection of prostate-specific antigen

Hollow and porous plasmonic nanomaterials have been demonstrated for highly sensitive biosensing applications due to their distinctive optical properties. Immunosensors, which rely on antibody-antigen interactions, are essential constituents of diverse biosensing platforms owing to their exceptional binding affinity and selectivity. The majority of immunosensors and conventional bioassays needs special storage conditions and cold chain systems for transportation. Prostate-specific antigen (PSA), a serine protease, is widely employed in the diagnosis of prostate cancer. In this study, we present the successful utilization of a biopolymer-preserved plasmonic biosensor with improved environmental stability for the sensitive detection of PSA. The preserved plasmonic biosensors exhibited sustained sensitivity in the detection of PSA, achieving a limit of detection of 10 pg mL-1. Furthermore, these biosensors exhibited remarkable stability at elevated temperatures for one week.

Gold nanobipyramids-based laser-activated sealants for effective skin sealing and repair

Anisotropic gold nanostructures have gained increased attention for biomedical applications because of their remarkable optical properties. An emerging type of gold nanostructure-gold nanobipyramids (AuNBP)-has been shown to exhibit superior absorption properties compared to conventionally used gold nanoparticles, which makes them attractive for photothermal applications. We generated a high-shape-purity dispersion of AuNBP using a seed-mediated method and embedded them as photothermal conversion agents in a silk fibroin matrix to investigate their efficacy in photothermal sealing of incisional wounds in immunocompetent mice. These AuNBP-doped laser-activated sealants, or AuNBP-LASE were able to absorb near-infrared laser energy and convert it to heat, thereby inducing transient hyperthermia in the wound and the surrounding tissue. This photothermal conversion facilitated rapid sealing of the skin tissue by the AuNBP-LASE, which resulted in faster functional recovery of skin barrier function compared to nylon sutures at the early stages of repair. Further, the biomechanical properties of the healing skin closed with AuNBP-LASE those of intact skin more rapidly compared to incisions approximated with sutures. Histology studies indicated higher penetration of the LASE within the volume of the incision in skin tissue, lower scab formation, and a similar epidermal gap compared to conventional suturing. These results demonstrate that AuNBP-LASEs can be effective as wound approximation devices for photothermal sealing.