To investigate the efficiency of different concentrations of genipin and silk fibroin (SF): chitosan (CS) ratios on the package and release of SF-CS composite microspheres.

Selected the microspheres with a SF: CS ratio of 1:1 to encapsulate different concentrations of bovine serum albumin (BSA) and compared their encapsulation efficiency and sustained-release rate with those of pure chitosan microspheres. SF-CS microspheres were prepared with emulsion cross-linking technique. The microspheres were observed by scanning electron microscope. Size distribution was measured by a laser particle size analyzer. X-ray diffractometry (XRD), fourier transform infrared spectroscopy (FTIR) and thermogravimetricanalyzer (TGA) were used to analyze their structural characteristics. BCA method was used for determination of the drug entrapment, loading rate and cumulative release of the total drug.

The five types of microspheres (m (CS): m (SF) = 1:0.5, 0.1 g or 0.5 g genipin; m (CS): m (SF) = 1:1, 0.05 g or 1 g genipin; m (CS): m (SF) = 1:2, 0.5 g eniping) had a more spherical shape and smooth surface with particle size between 70-147 μm. The microspheres prepared with m (CS): m (SF) of 1:1 and 0.05 g genipin in the presence of 10 mg, 20 mg, or 50 mg BSA of BSA burst-released (30.79±3.43)%, (34.41±4.46)%, or (41.75±0.96)% of the entrapped BSA on the first day, and cumulatively released (75.20±2.52)%, (79.16±4.31)%, and (89.04±4.68)% in 21 d, respectively. The pure CS microspheres prepared in the presence of 10 mg BSA burst-released (39.53±1.76)% on the first day and cumulatively released (83.57±2.33)% of the total encapsulated BSA in 21 d.

The SF-CS composite microspheres had a higher sustained release rate than the pure CS microspheres and may be a better drug carrier.