Functional modification of silk fibroin from silkworms and its application to medical biomaterials: A review

Silk fibroin (SF) from the silkworm Bombyx mori is a fibrous protein identified as a widely suitable biomaterial due to its biocompatibility, tunable degradation, and mechanical strength. Various modifications of SF protein can give SF fibers new properties and functions, broadening their applications in textile and biomedical industries. A diverse array of functional modifications on various forms of SF has been reported. In order to provide researchers with a more systematic understanding of the types of functional modifications of SF protein, as well as the corresponding applications, we comprehensively review the different types of functional modifications, including transgenic modification, modifications with chemical groups or biologically active substance, cross-linking and copolymerization without chemical reactions, their specific modification methods and applications. Furthermore, recent applications of SF in various medical biomaterials are briefly discussed.

Development of nanostructured formulation from naringenin and silk fibroin and application for inhibition of lipoxygenase (LOX)

A simple low-energy method was used to obtain polymeric nanoparticles containing silk fibroin (SF), fatty butyl esters (oily phase) and the flavonoid naringenin. Experimental planning (Box-Behnken) was applied to investigate the optimal conditions for three factors (variation of the concentrations of SF, naringenin and fatty butyl ester) at three levels, with evaluation of particle size, polydispersity index (PDI) and zeta potential (ZP) as responses. The results showed that the polymeric particle was formed with sizes of 179.6 to 633.9 nm, PDI of 0.33 to 0.77 and ZP of -60.4 to -38.8 mV. The best responses under the optimized conditions (Nari-SF 9 and 15) were characterized through transmission electron microscopy (TEM), Fourier-transform infrared (FT-IR), visible ultraviolet (UV-vis) and fluorescence, which confirmed that coated nanoparticles had been obtained. It was shown that the nanoformulation had excellent stability, the bioavailability of naringenin had been improved through use of the biopolymer and high inhibition of the enzyme lipoxygenase had been achieved in vitro.

Anti-inflammatory potential of baicalein combined with silk fibroin protein in a zebrafish model (Danio rerio)

Baicalein (BA) is a flavonoid with wide-ranging pharmacological activity. However, its biological evaluation is hampered by its low solubility in aqueous medium, making forms of incorporation that improve its solubility necessary. In the present study, BA was combined with a solution of silk fibroin protein (SF), a biomaterial used too as a drug carrier, to evaluate the anti-inflammatory potential of this combination, in vivo, in an experimental model, zebrafish (Danio rerio). Baicalein-silk fibroin (BASF) improved the DPPH (2,2-diphenyl-1-picryl-hydrazyl-hydrate) free radical scavenging rate (95%) in comparison with BA in solution. The acute toxicity study and histopathological analysis in zebrafish showed that BASF has low cytotoxic potential, except for the maxim dose of 2000 mg/kg. The use of BA in combination with SF enhanced the anti-inflammatory effect of flavonoids by inducing inflammatory peritoneal edema through carrageenan and achieved 77.6% inhibition of abdominal edema at a dose of 75 mg/kg. The results showed that the BASF, significantly increases the bioavailability and therapeutic effect of flavonoids and several results observed in this study may help in the development of new drugs.

Chitin and Silk Fibroin Biopolymers Modified by Oxone: Efficient Heterogeneous Catalysts for Knoevenagel Reaction

New materials from silk fibroin (FS-Ox) and chitin (CT-Ox) functionalized with Oxone® salt were developed for application in the synthesis of Knoevenagel adducts. The experiments were performed using benzaldehyde derivatives, malononitrile, and a mixture of water and ethanol as green solvents. The efficiency of conventional and microwave irradiation as heating sources for this reaction was also investigated. When the reactions were performed for 60 min under optimized conditions with conventional heating, twelve Knoevenagel adducts 2a–l were obtained, with good yields for both catalysts (CT-Ox 60–98% and FS-Ox 71–98%). When microwave irradiation was used, the reaction periods were reduced twelvefold, with the same Knoevenagel adducts with good CT-Ox (39–99%) and FS-Ox (35–99%) yields obtained in most cases. The reuse of these materials as catalysts in successive reactions was also evaluated, and CT-Ox FS-Ox were successfully used for 4 and 2 cycles, respectively. The results presented prove the efficiency of the CT-OxFS-Ox catalyst as a promising low-cost and reusable material with suitable catalytic properties to be applied in the aldol condensation reaction in a sustainable way.

Silk Fibroin-Based Materials for Catalyst Immobilization

Silk fibroin is a widely and commercially available natural protein derived from silkworm cocoons. Thanks to its unique amino acid composition and structure, which lead to localized nanoscale pockets with limited but sufficient hydration for protein interaction and stabilization, silk fibroin has been studied in the field of enzyme immobilization. Results of these studies have demonstrated that silk fibroin offers an important platform for covalent and noncovalent immobilization of enzymes through serving as a stabilization matrix/support with high retention of the biological activity of the enzymes of interest. In the hope of providing suggestions for potential future research directions, this review has been written to briefly introduce and summarize key advances in silk fibroin-based materials for immobilization of both enzymes/biocatalysts (including alkaline phosphatase, β-glucosidase, glucose oxidase, lipase, urease, uricase, horseradish peroxidase, catalase, xanthine oxidase, tyrosinase, acetylcholinesterase, neutral protease, α-chymotrypsin, amylase, organophosphorus hydrolase, β-galactosidase, carbonic anhydrase, laccase, zymolyase, phenylalanine ammonia-lyase, thymidine kinase, and several others) and non-enzymatic catalysts (such as Au, Pd, Fe, α-Fe2O3, Fe3O4, TiO2, Pt, ZnO, CuO, Cu2O, Mn3O4, and MnO2).