Advanced Biofabrication of Functional Silk Fibroin Hydrogels for Tissue Engineering Applications

Hydrogels prepared from silk fibroin (SF) – a unique fibrous protein material, have attracted immense research interest in recent years due to their excellent mechanical properties, biocompatibility, and ease of blending with other materials. However, SF hydrogels prepared by traditional methods possess a simple network structure and single functionality featured mainly by passive support for cells, which severely restricts their utility in complex biological situations. Through the use of advanced fabrication techniques, the functionality of SF hydrogels can be expanded to meet a broad spectrum of applications. Examples of functionality include, but are not limited to, high-strength hydrogels (tensile/compressive strength/modulus \u3e 1 MPa), adhesive hydrogels, and hydrogels with tuneable microstructure and shape. This thesis aimed at incorporation of these functionalities in SF hydrogels by employing novel fabrication techniques

Electrowriting of silk fibroin: Towards 3D fabrication for tissue engineering applications

Electrowriting (EW) successfully combines the principles of two widely studied biofabrication techniques; 3D printing and electrospinning, and is capable of producing complex architectures, with submicron resolutions. However, the EW process so far is limited mainly to thermoplastic polymers of synthetic origin such as poly ε-caprolactone. Herein we demonstrate the EW of silk fibroin (SF) on an in-house build setup to identify the compatibility of water-based SF ink with EW. More specifically, we optimized the SF ink composition and investigated the effect of EW process parameters including ink concentration, collector translation speed, applied voltage, and distance between nozzle and collector on filament orientation and diameter. During SF ink preparation, control over the silk degumming process and ink concentration enabled modulation of rheology and surface tension properties of SF inks. We envision that the EW of hydrophilic SF will offer a new class of material structures with biological properties akin to natural systems

Characterization and antibacterial property of Kapok fibers treated with chitosan/AgCl-TiO2 colloid

The aim of this research is to investigate the antibacterial activity of Kapok fibers modified with AgCl/TiO2 and Chitosan colloid. A very simple, single-step (pad-dry-cure) method was used for the application of AgCl/TiO2 and Chitosan colloid on kapok fibers, the chemicals used are easily available. Different blend ratios of chitosan and AgCl/TiO2 colloid were applied to the bleached kapok fibers and antibacterial properties were assayed against gram positive (Staphylococcus aureus) and Gram-negative (Escherichia coli) bacteria. The treated kapok fibers were characterized by Fourier Transform Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). It was observed that the bacterial growth was significantly reduced in the samples which had a higher concentration of chitosan and AgCl/TiO2 colloid. However, a significant reduction in bacterial growth with the use of this colloid was observed

Optimizing Synergistic Silica–Zinc Oxide Coating for Enhanced Flammability Resistance in Cotton Protective Clothing

This study reports process optimization studies of silica and zinc oxide-based flame-retardant (FR) coatings on cotton fabric for protective clothing and enhanced flammability properties. The experiments were designed by central composite design (CCD) using response surface methodology (RSM) to assess the synergistic protective effects of silica and zinc oxide FR coating. These prepared sols were coated on cotton fabrics by a simple dip dry cure process. The resulting FR-finished fabrics were characterized by SEM, mechanical properties, flame retardancy, and air permeability. SEM results confirmed the homogenous spreading of particles on cotton fabrics. From TGA results, it was noticed that the incorporation of silica and ZnO in the prepared nano-sols results in improved thermal stability of the FR-finished fabrics. These sol–gel-treated FR cotton fabrics showed excellent comfort properties, which shows their suitability for fire-retardant protective clothing. RSM analysis proved that the predicted values are in good agreement with the experimental values since R2 values for time to ignite, flame spread time, and air permeability were greater than 0.90. The optimized concentration of silica and ZnO in FR-finished fabrics was found to be 0.302% and 0.353%, respectively, which was further confirmed by confirmatory experiments. The optimization analysis successfully optimized the process for synergistic coating of silica and zinc oxide nanoparticles for enhanced flammability properties of FR cotton fabric for protective clothing

Controllable Production of Natural Silk Nanofibrils for Reinforcing Silk-Based Orthopedic Screws

As a natural high-performance material with a unique hierarchical structure, silk is endowed with superior mechanical properties. However, the current approaches towards producing regenerated silk fibroin (SF) for the preparation of biomedical devices fail to fully exploit the mechanical potential of native silk materials. In this study, using a top-down approach, we exfoliated natural silk fibers into silk nanofibrils (SNFs), through the disintegration of interfibrillar binding forces. The as-prepared SNFs were employed to reinforce the regenerated SF solution to fabricate orthopedic screws with outstanding mechanical properties (compression modulus > 1.1 GPa in a hydrated state). Remarkably, these screws exhibited tunable biodegradation and high cytocompatibility. After 28 days of degradation in protease XIV solution, the weight loss of the screw was ~20% of the original weight. The screws offered a favorable microenvironment to human bone marrow mesenchymal stem cell growth and spread as determined by live/dead staining, F-action staining, and Alamar blue staining. The synergy between native structural components (SNFs) and regenerated SF solutions to form bionanocomposites provides a promising design strategy for the fabrication of biomedical devices with improved performance