@article { ISI:000336942100020, title = {Investigation of C-C bond formation mediated by bombyx mori silk fibroin materials}, journal = {ACS Sustainable Chemistry \& Engineering}, volume = {2}, number = {6}, year = {2014}, month = {JUN}, pages = {1510-1517}, publisher = {AMER CHEMICAL SOC}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {

The formation of C-C bonds is a prerequisite for all life on earth. Understanding the role of proteins in mediating the formation of these bonds is important for understanding biological mechanisms in evolution, as well as for designing {\textquoteleft}{\textquoteleft}green catalysts{\textquoteright}{\textquoteright}. In this work, the ability of silk fibroin (SF) proteins to mediate selective C-C bond formation under mild conditions was comprehensively evaluated and compared between different SF-based materials and other proteins. Aqueous SF solution (ASFS), freeze-dried SF (FDSF), mesoporous SF (MPSF), and SF hydrogel (SFHG) materials were prepared and characterized by a variety of techniques including, among others, FE-SEM, ICP-OES, FT-IR, and TGA. The nitroaldol (Henry) reaction, Knoevenagel condensation, and direct aldol reaction were used as models for this study, in which the recovery and reusability of the protein was also evaluated.

}, keywords = {Aldol-like reactions, C-C Bond formation, Knoevenagel condensation, Proteins, Silk fibroin}, issn = {2168-0485}, doi = {10.1021/sc500184r}, author = {Kuehbeck, Dennis and Ghosh, Munmun and Sen Gupta, Sayam and Diaz, David Diaz} } @article {44242, title = {pH dependent sophorolipid assemblies and their influence on gelation of silk fibroin protein}, journal = {Materials Chemistry and Physics}, volume = {203}, year = {2018}, month = {JAN }, pages = {9-16}, type = {Article}, abstract = {

Sophorolipid (SL), a bio-derived surfactant is an excellent gelling agent for natural fibrous protein, silk fibroin (SF) leading to potential biomedical applications. Interaction of SF with SL has been shown to accelerate the formation of hydrogel with the rate being dependent on the form of SL used. Here, we examine the effect of pH on SL-SF interaction and gel formation by employing rheology, fluorescence spectroscopy, SANS and NMR. The results indicate that the size of SL assemblies decrease as pH increases from acidic to alkaline and significantly impacts the association of SL and SF. The association of SF and SL is mainly via hydrophobic interactions, with the SL molecules forming bead like structures along the SF chain. The increased charge on the acidic form of SL at higher pH results in greater repulsion between acidic SL molecules, which are bound to the hydrophobic sites of SF, leading to rapid chain unfolding and subsequent gelation. (C) 2017 Elsevier B.V. All rights reserved.

}, keywords = {Assemblies, Nuclear magnetic resonance spectroscopy, pH, Silk fibroin, Small angle neutron scattering, Sophorolipid}, issn = {0254-0584}, doi = {10.1016/j.matchemphys.2017.09.045}, author = {Dubey, Parul and Kumar, Sugam and Ravindranathan, Sapna and Vasudevan, Sahana and Aswal, Vinod K. and Rajamohanan, Pattuparambil R. and Nisal, Anuya and Prabhune, Asmita} } @article {46749, title = {Silk fibroin 3D microparticle scaffolds with bioactive ceramics: chemical, mechanical, and osteoregenerative characteristics}, journal = {Advanced Engineering Materials}, volume = {22}, year = {2020}, month = {DEC}, pages = {2000458}, type = {Article}, abstract = {

Preparation of 3D scaffolds for bone tissue engineering (BTE) is a challenging task as it requires appropriate pore size and porosities, mechanical properties, and controlled bioerosion rate. The focus of this work is the fabrication of silk fibroin (SF) 3D microparticle scaffolds with the incorporation of hydroxyapatite (HA) and calcium sulfate (CaS) as bioceramics. Physicochemical characterization shows approximate to 30\% filler loading and approximate to 40\% optimum porosity with \>100 mu m pore size for these filled/unfilled scaffolds. Nanoindentation studies show improved Young{\textquoteright}s modulus at microparticle level with the incorporation of bioceramics. SF-HA scaffolds showed three fold increase in Young{\textquoteright}s modulus, whereas SF-CaS showed two fold increase. In vitro bioerosion study results in early bioerosion with SF-CaS scaffold, whereas prolonged bioerosion with SF-HA scaffold. In vitro osteoregenerative potential is analyzed by estimating alkaline phosphatase (ALP), bone morphogenetic protein-2 (BMP-2), and osteocalcin (OCN). SF CaS supports early stage differentiation while SF 50\% HA predominantly supports late stage. The expression of TNF-alpha suggests a reduced risk of immune rejection. This work, therefore, concludes that although SF supports bone tissue regeneration, the choice of bioceramic enhances the applicability in various clinical scenarios by providing a controlled bioerosion rate, tunable speed of osteoregeneration, and improved load bearing capacities.

}, keywords = {bioceramics, bioerosion, osteogenic differentiation, Silk fibroin, stem cells}, issn = {1438-1656}, doi = {10.1002/adem.202000458, Early Access Date = AUG 2020}, author = {Parekh, Nimisha A. and Deshpande, V. Rucha and Shukla, Swati G. and Nisal, Anuya A.} } @article {47405, title = {Silk fibroin and ceramic scaffolds: comparative in vitro studies for bone regeneration}, journal = {Bioengineering \& Translational Medicine}, year = {2021}, month = {APR}, pages = {e10221}, type = {Article; Early Access}, abstract = {

Synthetic bone void fillers based on calcium ceramics are used to fill cavities in the bone and promote bone regeneration. More recently, silk fibroin (SF), a protein polymer obtained from Bombyx mori silkworm, has emerged as a promising material in bone void filling. In this work, we have compared the safety and efficacy of two types of silk fibroin-based bone void fillers with currently used and commercially available ceramic bone void fillers (based on calcium sulphate, beta tricalcium phosphate, and beta tricalcium phosphate with hydroxyapatite). Further, we have also evaluated these two types of SF scaffolds, which have strikingly different structural attributes. The biocompatibility of these scaffolds was comparable as assessed by cytotoxicity assay, cellular adhesion assay, and immunogenic assay. Ability of the scaffolds to support differentiation of human mesenchymal stem cells (hMSCs) into an osteoblastic lineage was also evaluated in an in vitro differentiation experiment using reverse transcriptase polymerase chain reaction analysis. These results revealed that cells cultured on SF scaffolds exhibit higher expression of early to late markers such as Runx2, BMPs, collagen, osterix, osteopontin, and osteocalcin as compared with ceramic-based scaffolds. This observation was further validated by studying the expression of alkaline phosphatase and calcium deposition. We also show that scaffolds made from same material of SF, but characterized by very different pore architectures, have diverse outcome in stem cell differentiation.

}, keywords = {beta tricalcium phosphate, bone regeneration, bone void filler, calcium sulphate, hMSCs, hydroxyapatite, osteoblasts, scaffold, Silk fibroin}, doi = {10.1002/btm2.10221, Early Access Date = APR 2021}, author = {Deshpande, Rucha and Shukla, Swati and Sayyad, Raeesa and Salunke, Shalmali and Nisal, Anuya and Venugopalan, Premnath} } @article {48176, title = {Silk fibroin and recombinant elastin blend nano-coatings for implantable medical devices}, journal = {Materials Today Communications}, volume = {33}, year = {2022}, month = {DEC}, pages = {104875}, type = {Article}, abstract = {

Silicone breast implants are conventionally used to reconstruct the shape and size of the breast in breast cancer patients. However, rate of failure of implants due to formation of capsular contracture is significantly high. Recent studies have shown that coating the surface of the implant with a biocompatible polymer can mitigate this risk. Here, we have modified the surface of implant using a biocompatible natural biopolymer silk fibroin (SF). Further, we have developed formulations of SF with a recombinantly produced elastin-like-peptide (ELP) and compared their performance with a known anti-fouling hydrophilic polymer - polyethylene oxide (PEO). Microscopic and spectroscopic characterization confirm the formation of uniform coatings. These coatings have been also characterized for their ability to resists crack formation. Further, the coatings have been evaluated for their biological performance. Our studies show that addition of 25 wt\% of ELP to SF significantly enhances the crack resistance for the coatings. In addition, SF/ELP coatings reduce the adsorption of blood plasma proteins by more than 80 \%. Preliminary analysis shows that the SF/ELP blend coatings are non-cytotoxic and support adhesion, growth and proliferation of fibroblast cells. The study therefore demonstrates that SF/ELP coatings have the potential to mitigate the risk of breast implant failure.

}, keywords = {Blood plasma, Crack resistance, Protein adsorption, Recombinant elastin, Silk fibroin}, doi = {10.1016/j.mtcomm.2022.104875}, author = {Joseph, Emmanuel and Kane, Kartiki and Parekh, Nimisha and Nisal, Anuya and Janorkar, V. Amol} } @article {48079, title = {Silk fibroin microparticle scaffold for use in bone void filling: safety and efficacy studies}, journal = {ACS Biomaterials Science \& Engineering}, volume = {8}, year = {2022}, month = {MAR}, pages = {1226-1238}, type = {Article}, abstract = {

Silk fibroin (SF) is a natural biocompatible protein polymer extracted from cocoons of silkworm Bombyx mori. SF can be processed into a variety of different forms and shapes that can be used as scaffolds to support bone regeneration. Threedimensional (3D) SF scaffolds have shown promise in bone-void -filling applications. In in vitro studies, it has been demonstrated that a microparticle-based SF (M-RSF) scaffold promotes the differentiation of stem cells into an osteoblastic lineage. The expression of differentiation markers was also significantly higher for M-RSF scaffolds as compared to other SF scaffolds and commercial ceramic scaffolds. In this work, we have evaluated the in vitro and in vivo biocompatibility of M-RSF scaffolds as per the ISO 10993 guidelines in a Good Laboratory Practice (GLP)-certified facility. The cytotoxicity, immunogenicity, genotoxicity, systemic toxicity, and implantation studies confirmed that the M-RSF scaffold is biocompatible. Further, the performance of the MRSF scaffold to support bone formation was evaluated in in vivo bone implantation studies in a rabbit model. Calcium sulfate (CaSO4) scaffolds were chosen as reference material for this study as they are one of the preferred materials for bone-void -filling applications. M-RSF scaffold implantation sites showed a higher number of osteoblast and osteoclast cells as compared to CaSO4 implantation sites indicating active bone remodeling. The number density of osteocytes was double for M-RSF scaffold implantation sites, and these M-RSF scaffold implantation sites were characterized by enhanced collagen deposition, pointing toward a finer quality of the new bone formed. Moreover, the M-RSF scaffold implantation sites had a negligible incidence of secondary fractures as compared to the CaSO4 implantation sites (similar to 50\% sites with secondary fracture), implying a reduction in postsurgical complications. Thus, the study demonstrates that the M-RSF scaffold is nontoxic for bone-void -filling applications and facilitates superior healing of fracture defects as compared to commercial calcium-based bone void fillers.

}, keywords = {Biocompatibility, biological safety, bone void filler, ISO 10993, M-RSF, Serioss, Silk fibroin}, issn = {2373-9878}, doi = {10.1021/acsbiomaterials.1c01103}, author = {Deshpande, Rucha and Shukla, Swati and Kale, Amod and Deshmukh, Narendra and Nisal, Anuya and Venugopalan, Premnath} }