Silk fibroin microsphere drug carriers perpared under electric fields

Abstract

A silk fibroin gel system (e-gel) formed under weak electric fields has potential utility in drug delivery systems. By controlling the nanostructure of silk fibroin in aqueous solution, an e-gel containing silk fibroin microspheres could be formed even from silk fibroin solutions of low concentration (1%). The size of the microspheres was controlled from about 200 nm to 3 μm by changing the incubation time at 60°C. Silk fibroin microspheres containing bovine serum albumin labeled with fluorescein isothiocyanate (FITC-BSA) were then prepared under weak electric fields to form FITC-BSA-loaded carriers. The uptake of FITC-BSA by the microspheres was increased near a positive electrode because of the negative charge of FITC-BSA following its incorporation into the silk fibroin nano/microspheres. The microspheres showed a sustained release of FITC-BSA over 120 h with 75% initial loading. Considering the mild preparation conditions (low-voltage electric field, room temperature and aqueous environment), the method developed for preparing silk fibroin drug-loaded systems provides a promising way to load proteins and gene medicines with negative charge.