Fabrication of mulberry leaf extract (MLE)- and tasar pupal oil (TPO)-loaded silk fibroin (SF) hydrogels and their antimicrobial properties

Abstract

Biocomposites have gained tremendous advantages over synthetic composites due to their biocompatibility, sustainable degradation, and ability to easily combine with other substances. In the present study, we have prepared silk fibroin (SF) hydrogel, mulberry leaf extract (MLE), tasar pupal oil (TPO), and their composites, such as TPO-loaded SF hydrogel and MLE-loaded SF hydrogel, and characterized them by using a phase contrast microscope (PCM), scanning electron microscope (SEM) SEM- EDX, and Fourier transform infrared spectroscopy (FTIR). In addition, ¹H-NMR was used for profiling of mulberry leaf extract and GC–MS was used to find tasar pupal oil composition. Further, the disc diffusion method evaluated their antimicrobial activities against S. aureus, E. coli, A. flavus, and A. brassicae. PCM, SEM, and FTIR results validated the conjugation of MLE and SF hydrogel composite; 1H-NMR confirmed the 41 metabolites in MLE, and GC–MS established the composition of tasar pupal oil. Since both composites, such as TPO-loaded SF hydrogel and MLE-loaded SF hydrogel, reduced the S. aureus and E. coli activities at all tested concentrations, the antibacterial results were unambiguous in their conclusion. S. aureus could only be inhibited by SF hydrogel at a high concentration (300 g/ml), despite suppressing E. coli growth at all tested concentrations. At 300 g/ml, MLE demonstrated antibacterial action against S. aureus. Furthermore, at a dosage of 300 g/ml, TPO inhibited both S. aureus and E. coli. Both mulberry leaf extract (at 200 and 300 g/ml) and the MLE-loaded SF hydrogel composite displayed antifungal activity against A. flavus at all tested concentrations (100, 200, and 300 g/ml).