Silk biomaterials are known for biomedical and tissue engineering applications including drug delivery and implantable devices owing to their biocompatible and a wide range of ideal physico-chemical ...properties. Herein, we present a critical overview of the progress of silk-based matrices in skin regeneration therapeutics with an emphasis on recent innovations and scientific findings. Beginning with a brief description of numerous varieties of silks, the review summarizes our current understanding of the biological properties of silk that help in the wound healing process. Various silk varieties such as silkworm silk fibroin, silk sericin, native spider silk and recombinant silk materials have been explored for cutaneous wound healing applications from the past few decades. With an aim to harness the regenerative properties of silk, numerous strategies have been applied to develop functional bioactive wound dressings and viable bio-artificial skin grafts in recent times. The review examines multiple inherent properties of silk that aid in the critical events of the healing process such as cell migration, cell proliferation, angiogenesis, and re-epithelialization. A detailed insight into the progress of silk-based cellular skin grafts is also provided that discusses various co-culture strategies and development of bilayer and tri-layer human skin equivalent under in vitro conditions. In addition, functionalized silk matrices loaded with bioactive molecules and antibacterial compounds are discussed, which have shown great potential in treating hard-to-heal wounds. Finally, clinical studies performed using silk-based translational products are reviewed that validate their regenerative properties and future applications in this area.
The review article discusses the recent advances in silk-based technologies for wound healing applications, covering various types of silk biomaterials and their properties suitable for wound repair and regeneration. The article demonstrates the progress of silk-based matrices with an update on the patented technologies and clinical advancements over the years.
The rationale behind this review is to highlight numerous properties of silk biomaterials that aid in all the critical events of the wound healing process towards skin regeneration. Functionalization strategies to fabricate silk dressings containing bioactive molecules and antimicrobial compounds for drug delivery to the wound bed are discussed. In addition, a separate section describes the approaches taken to generate living human skin equivalent that have recently contributed in the field of skin tissue engineering.
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Current advances in skin tissue engineering and wound healing augur well for the development of split or full thickness skin substitutes to recapitulating the native functional skin. These engineered ...skin substitutes have fared successfully in recent years with exploration of various emerging technologies. As a result, recent clinical practice has been highly evolved incorporating various engineered skin substitutes as an adjunct to accelerate healing and improvement of quality of life in long-term. This review seeks to bring the researchers through various emerging and innovative approaches being developed and utilized for accelerating wound healing and skin regeneration. In order to attempt this, we reviewed various design considerations for skin repair and impact of several smart technologies viz., in situ 3D printing, portable bioprinters, electrosprayers and in situ forming hydrogels that have significantly improved wound healing and skin therapeutics. Furthermore, numerous cellular therapies such as effect of immunomodulation, stromal vascular fraction treatments, micro RNA (miRNA) and small interfering RNA (siRNA) based skin therapeutics have been thoroughly discussed. Finally, an update of clinical trials along with critical analysis of properties and benefits of different emerging technologies in healing certain types of wounds, prime challenges and future prospects in skin tissue engineering are discussed.
Cartilage tissue is deprived of intrinsic self-regeneration capability; hence, its damage often progresses to a chronic condition which reduces the quality of life. Toward the fabrication of ...functional tissue substitutes, three-dimensional (3D) bioprinting has progressed vastly over the last few decades. However, this progress is challenged by the difficulty in developing suitable bioink materials as most of them require toxic chemical cross-linking. In this study, our goal was to develop a cross-linker-free bioink with optimal rheology for polymer extrusion, aqueous, and nontoxic processing and offers structural support for cartilage regeneration. Toward this, we use the self-gelling ability of silk fibroin blends (
and
) along with gelatin as a bulking agent. Silk and gelatin interact with each other through entanglement and physical cross-linking. The ink was rheologically and structurally optimized for printing efficiency in printing grid-like structures. The printed 3D constructs show optimal swelling capability, degradability, and compressive strength. Further, the construct supports the growth and proliferation of encapsulated chondrocytes and formation of the cartilaginous extracellular matrix as indicated by the increased sulfated glycosaminoglycan and collagen contents. This was further corroborated by the upregulation of chondrogenic gene expression with minimal hypertrophy of chondrocytes. Additionally, the construct demonstrates in vitro and in vivo biocompatibility. Notably, the ink demonstrates good print fidelity for printing anatomical structures such as the human ear enabled by optimized extrudability at adequate resolution. Altogether, the results indicate that the developed cross-linker-free silk-gelatin polymer-based bioink demonstrated high potential for its 3D bioprintability and application in cartilage tissue engineering.
Sericin, a principal constituent of silk, is widely used in various biomedical applications. In addition, conferring protection against free radicals and oxidative damage add more value to its ...therapeutic potential. However, the antioxidant (AO) properties of silk sericin (SS) remains contingent on extraction procedures. In the present study, we have evaluated the effect of different extraction methods (conventional, autoclaving, urea, alkali and acid-degradation) on AO properties of SS from three Indian silk varieties Antheraea assamensis (AA), Philosamia ricini (PR) and Bombyx mori (BM). The physico-chemical characterization studies revealed that the molecular weight of SS isolates of each method ranged from 10 to 220kDa along with varied protein structural biochemistry. SS extracts using urea-degradation (BM, PR and AA), conventional method and alkali-degradation (BM) displayed high percentage of β-sheets, random coils and turns. Acid-degraded SS (PR, followed by AA and BM) showed the highest total flavonoid content while conventional method (PR), autoclaving (AA) and alkali-degradation (BM) displayed lowest flavonoid levels. Interestingly, SS extracted by autoclaving (BM and AA), acid-degradation (PR), conventional and alkali-degradation (BM, AA and PR) methods exhibited 50% reduction of 2, 2-diphenyl-1-picrylhydrazyl (DPPH) radical. Moreover, the efficacy of antioxidant potential of SS extracted by different methods was found to be in the order of “alkali>autoclaving>conventional” as demonstrated in L929 cells. Correspondingly, the anti-lipid peroxidation activity of SS extracted by alkali method (AA, BM and PR) further confirmed better AO properties amid others. Thus, the present study demonstrates that the extraction methods may significantly affect AO activity of SS which might be of importance for potential cosmetic applications.
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•Physical and chemical methods produce different molecular weight of SS peptides.•SS exhibits ROS scavenging activity.•SS protect cells from oxidative stress.•SS shows suppression of lipid peroxidation.
Vascular tissue engineering has made prodigious progress in recent years by converging multidisciplinary approaches. Latest technological advancements foster the development of next‐generation ...tissue‐engineered vascular grafts (TEVGs) for treating various vasculopathies. While traditional therapeutic methods rely on bypassing the severely damaged vessels with synthetic counterparts with no growth potential, contemporary perspectives focus on biodegradable conduits bestowing an inherent remodeling capability. This review highlights emerging innovative trends and technologies adopted to pragmatically fulfill current scientific needs while improving overall TEVG performance in pre‐clinical and clinical settings. A comprehensive overview of various milestones achieved in the past few decades is first summarized, followed by an appraisal of the significant hurdles for clinical translation. The latest techniques to rationally address critical challenges, viz., intimal hyperplasia, thrombosis, constructive graft remodeling, and adequate neo‐tissue formation are discussed. Finally, an update on ongoing clinical trials is provided and future perspectives required to persuade TEVGs to become a clinical reality are delineated.
Vascular tissue engineering is a rapidly growing field of regenerative medicine, which strives to find innovative solutions for vascular reconstruction. This review summarizes various milestones achieved in the past few decades, followed by an appraisal of the significant hurdles for clinical translation. The latest innovative multidisciplinary approaches to rationally address the most pressing clinical challenges are vividly discussed.
Articular cartilage damage poses huge burden on healthcare sector globally due to its extremely weak inherent regenerative ability. Three‐dimensional (3D) bioprinting for development of cartilage ...mimic constructs using composite bioinks serves as an emerging perspective. However, difficulty in development of suitable bioink and chemical crosslinking associated inherent toxicity hamper widespread adoption of this technique. To circumvent this, a photo‐polymerizable hydrogel‐based bioink which helps in recapitulation of the complex cartilage microenvironment is pertinent. Herein, a photo‐crosslinkable bioink containing different concentrations of silk methacrylate (SilMA) and polyethylene glycol diacrylate (PEGDA) was mixed with chondrocytes for biofabrication of 3D bioprinted cartilage constructs. The rheological properties, printability of bioink and physico‐chemical characterization of printed hydrogel constructs were examined along with cartilaginous tissue formation. The printed SilMA‐PEGDA hydrogel constructs possessed proper internal porous structure and demonstrated most reliable rheological properties, printability along with good mechanical, and degradation properties suitable for cartilage regeneration. Live/dead staining showed cytocompatibility of the 3D‐bioprinted SilMA‐PEGDA constructs. Moreover, a marked increase in cell number and DNA content was observed within the cartilaginous tissue as indicated by cell viability and DNA content quantitation. Biochemical evaluation confirmed the neocartilage formation within SilMA‐PEGDA bioprinted constructs as revealed by enhanced deposition of cartilage specific extracellular matrix‐sulphated GAG (sGAG) and collagen type II (>2‐fold increase, p < 0.001) with time. Finally, immunohistochemical analysis indicated expression of collagen type II and aggrecan which corroborated with cartilaginous tissue formation. Taken together, we conclude that SilMA‐PEGDA bioink could be suitable candidate for bioprinting chondrocytes to support cartilage tissue repair and regeneration.
The global volume of skin damage or injuries has major healthcare implications and, accounts for about half of the world's annual expenditure in the healthcare sector. In the last two decades, ...tissue-engineered skin constructs have shown great promise in the treatment of various skin-related disorders such as deep burns and wounds. The treatment methods for skin replacement and repair have evolved from utilization of autologous epidermal sheets to more complex bilayered cutaneous tissue engineered skin substitutes. However, inadequate vascularization, lack of flexibility in drug/growth factors loading and inability to reconstitute skin appendages such as hair follicles limits their utilization for restoration of normal skin anatomy on a routine basis. Recent advancements in cutting-edge technology from stem cell biology, nanotechnology, and various vascularization strategies have provided a tremendous springboard for researchers in developing and manipulating tissue engineered skin substitutes for improved skin regeneration and wound healing. This review summarizes the overview of skin tissue engineering and wound healing. Herein, developments and challenges of various available biomaterials, cell sources and in vitro skin models (full thickness and wound healing models) in tissue-engineered skin research are discussed. Furthermore, central to the discussion is the inclusion of various innovative strategies starting from stem cells, nanotechnology, vascularization strategies, microfluidics to three dimensional (3D) bioprinting based strategies for generation of complex skin mimics. The review then moves on to highlight the future prospects of advanced construction strategies of these bioengineered skin constructs and their contribution to wound healing and skin regeneration on current practice.
Abstract Pore architecture in 3D polymeric scaffolds is known to play a critical role in tissue engineering as it provides the vital framework for the seeded cells to organize into a functioning ...tissue. In this report, we investigated the effects of different freezing temperature regimes on silk fibroin protein 3D scaffold pore microstructure. The fabricated scaffolds using freeze-dry technique were used as a 3D model to monitor cell proliferation and migration. Pores of 200–250 μm diameter were formed by slow cooling at temperatures of −20 and −80 °C but were found to be limited in porosity and pore interconnectivity as observed through scanning electron microscopic images. In contrast, highly interconnected pores with 96% porosity were observed when silk solutions were rapidly frozen at −196 °C. A detailed study was conducted to assess the affect of pore size, porosity and interconnectivity on human dermal fibroblast cell proliferation and migration on these 3D scaffolds using confocal microscopy. The cells were observed to migrate within the scaffold interconnectivities and were found to reach scaffold periphery within 28 days of culture. Confocal images further confirmed normal cell attachment and alignment of actin filaments within the porous scaffold matrix with well-developed nuclei. This study indicates rapid freeze-drying technique as an alternative method to fabricate highly interconnected porous scaffolds for developing functional 3D silk fibroin matrices for potential tissue engineering, biomedical and biotechnological applications.
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Bombyx mori silk fibroin (BMSF) as biopolymer has been extensively explored in wound healing applications. However, limited study is available on the potential of silk fibroin (SF) ...from non-mulberry (Antheraea assama and Philosamia ricini) silk variety. Herein, we have developed non-mulberry SF (NMSF) based electrospun mats functionalized with epidermal growth factor (EGF) and ciprofloxacin HCl as potential wound dressing. The NMSF based mats exhibited essential properties of wound dressing like biocompatibility, high water retention capacity (440%), water vapor transmission rate (∼2330gm−2day−1), high elasticity (∼2.6MPa), sustained drug release and antibacterial activity. Functionalized NMSF mats enhanced the proliferation of human dermal fibroblasts and HaCaT cells in vitro as compared to non-functionalized mats (p⩽0.01) showing effective delivery of EGF. Extensive in vivo wound healing assesment demonstrated accelerated wound healing, enhanced re-epithelialization, highly vascularized granulation tissue and higher wound maturity as compared to BMSF based mats. NMSF mats treated wounds showed regulated deposition of mature elastin, collagen and reticulin fibers in the extracellular matrix of skin. Presence of skin appendages and isotropic collagen fibers in the regenerated skin also demonstrated scar-less healing and aesthetic wound repair.
A facile fabrication of a ready-to-use bioactive wound dressing capable of concomitantly accelerating the healing process as well as deposition of the extracellular matrix (ECM) to circumvent further scarring complicacies has become a focal point of research. In this backdrop, our present work is based on non-mulberry silk fibroin (NMSF) electrospun antibiotic loaded semi-occlusive mats, mimicking the ECM of skin in terms of morphology, topology, microporous structure and mechanical stiffness. Regulation of ECM deposition and isotropic orientation evinced the potential of the mat as an instructive platform for skin regeneration. The unique peptide motifs of NMSF assisted the augmented recruitment of fibroblast, keratinocytes and endothelial cells leading to accelerated wound healing. Early progression of mature granulation, faster re-epithelialization and angiogenesis in the wounds in in vivo rabbit model forwarded the blended nanofibrous mats of NMSF and PVA ferrying EGF, apt for scarless healing.
Pro-oxidative stress induced by dietary polyphenols elevates reactive oxygen species (ROS) production in cancer cells, which subsequently leads to oxidative stress-mediated apoptosis. Sericin, a ...principal component of silk is associated with a mixture of polyphenols and flavonoids, possesses various biomedical attributes including anticancer activity. In the present study, we have evaluated the pro-oxidative effect of Bombyx mori sericin (BMS), Antheraea assamensis sericin (AAS), and Philosamia ricini sericin (PRS) against different cancer cells. Cytotoxicity of silk sericin (SS) evaluated using A431, SAS, and MCF-7 cells showed ≥50% reduction in their viability at 4 mg/mL. Intracellular ROS levels, cell cycle arrest, and apoptosis assessed using flow cytometry corroborated that SS treatment elevated the intracellular ROS levels, caused cell cycle arrest at the sub-G1 phase and resulted in apoptotic cell death. SS treated A431 and SAS cells showed upregulation of p53 and dysregulation of Bax and Bcl-2 gene expression. Whereas, AAS treated MCF-7 cells showed upregulation of Bax and downregulation of Bcl-2 gene expression. AAS treated MCF-7 and SAS cells showed downregulation of Bcl-2 protein expression in comparison to their control cells. Thus, the present study demonstrates that the pro-oxidative effect induced by SS suppresses the cancer growth indicating its potential anticancer activity.
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•SS induced 50% growth inhibition in cancer cells.•SS induced redox imbalance in cancer cells.•AAS decrease SOD activity in cancer cells.•AAS treatment cause depletion of mitochondrial membrane potential in MCF-7 cells.•SS induced apoptosis in MCF-7, SAS and A431 cells.
