Aqueous Solution of a Basic Ionic Liquid: A Perspective Solvent for Extraction and Regeneration of Silk Powder from Bombyx mori Silk Cocoons

Abstract

The rationale behind this study was to investigate the potential new low cost and biocompatible aqueous choline based ionic liquid for dissolution and regeneration of silk fibroin obtained from the mulberry silkworm. The silk due to its high biocompatibility and mechanical properties finds many applications in the field of biomedical science. Earlier, silk extraction methods have issues of either extraction efficiency or environmental concerns. The ionic liquid is a relatively green solvent was used to dissolve silk fibroin and optimized the process with respect to variables like temperature, time, stirring speed, type of ionic liquid and maximum dissolution ability. The dissolution process was observed through the naked eye as well as using optical microscopy. The optimized conditions at which maximum dissolution i.e. 25% was obtained, are heating the mixture at 50 °C for 2 h. Various analytical characterization such as scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy, X-ray diffraction (XRD), Zeta potential, nuclear magnetic resonance (1H NMR) and thermogravimetric analysis (TGA) was performed for cocoon, fiber and regenerated silk powder in order to understand the effect of ionic liquid treatment. FTIR, NMR and Raman spectra shows the characteristic peaks assigned to the silk. SEM analysis shows nanoparticles of silk fibroin powder. The crystallinity and thermal stabilities were decreased for regenerated silk as observed from XRD and TGA analysis. The nano-silk exhibited a zeta potential of − 24.6 ± 3 mV.