There was a slight increase (0.03–0.06 μm) in diameter of microparticles while immersed in serum containing media. This increase in diameter is possibly due to the adsorption of the serum proteins onto the surface of the silk fibroin microparticles. Furthermore, the values of the polydispersity index of the silk fibroin microparticles, which indicates particle size distribution were found low in all the cases and did not change significantly, showing that the particles have a narrow size distribution and when dispersed in cell culture medium did not aggregate