Multifunctional silk fibroin – Poly(L-lactic acid) porous nanofibers: Designing adjustable nanopores to control composite properties and biological responses

Nano-scale renewable porous materials have a wide range of applications in the biomedical field such as tissue engineering and biosensors due to their high biocompatibility and large surface area. In this study, a composite of silk fibroin and poly(L-lactic acid) was electrospun together to form a porous nanofiber biomaterial with 11 blending ratios to tune the porosity of the single fibers (19.3–49%). This is highly advantageous as porous fibers effectively promoted cell attachment and proliferation while also manipulating cell growth. The protein-polymer molecular interactions, structures and crystal contents, as well as the melting and glass transition behaviors of the composites were determined. Results reveal that varying silk fibroin content can directly tune the nanopore structure of each individual fiber. The composite nanofibers have a much higher thermal stability when compared to the pure silk or PLA nanofibers. Besides, as the SF concentration increased from 0% to 100%, the hydrophilicity of the electrospun composite fibers increased (contact angle decreased from 135° to 103°), and the enzymatic degradation residues also increased from 20% to 95%. This study provides a unique method for tuning nano-fabrication properties of electrospun protein-polymer fibers that can be widely useful in the fields of biomedicine and sustainable materials

Ultrasound regulated flexible protein materials: Fabrication, structure and physical-biological properties.

Ultrasound can be used in the biomaterial field due to its high efficiency, easy operation, no chemical treatment, repeatability and high level of control. In this work, we demonstrated that ultrasound is able to quickly regulate protein structure at the solution assembly stage to obtain the designed properties of protein-based materials. Silk fibroin proteins dissolved in a formic acid-CaCl solution system were treated in an ultrasound with varying times and powers. By altering these variables, the silks physical properties and structures can be fine-tuned and the results were investigated with Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA), gas permeability and water contact angle measurements. Ultrasonic treatment aids the interactions between the calcium ions and silk molecular chains which leads to increased amounts of intermolecular β-sheets and α-helix. This unique structural change caused the silk film to be highly insoluble in water while also inducing a hydrophilic swelling property. The ultrasound-regulated silk materials also showed higher thermal stability, better biocompatibility and breathability, and favorable mechanical strength and flexibility. It was also possible to tune the enzymatic degradation rate and biological response (cell growth and proliferation) of protein materials by changing ultrasound parameters. This study provides a unique physical and non-contact material processing method for the wide applications of protein-based biomaterials