Synthesis and characterization of sericin-capped gold nanoparticles

In this study, sericin-capped gold nanoparticles (S-AuNP) were synthesized by using the silk sericin isolated from Bombyx mori silkworm cocoon. Sericin solutions having different concentrations (0.25%, 0.5 ve 1) and pH values (8 and 12) were added to fixed amount of gold salt (1 mM) to obtain experimental groups (S-AuNP0.25, S-AuNP0.5, S-AuNP1). Red color shift and distinct surface plasmon resonance (SPR) peaks observed at 520-530 nm wavelenghts in all groups were indicative of nanoparticle synthesis. However, these red color shift and peaks were not clear in pH 12. According to FTIR analyses, N-H, O-H and C=0 functional groups of sericin might have played a role in reduction reaction. In TEM images, both the average particle size and distribution of S-AuNPs increased with increasing sericin concentration. Sericin rendered the surface charge of nanoparticles negative and the increase in negative zeta potential of S-AuNP0.5 and S-AuNP1 showed that they were more stable in water than S-AuNP0.25. This result was confirmed with stability in salt experiments. S-AuNP0.25 lost its stability in salt after 1 day incubation, but the other groups remained stable as long as 7 days. As a whole, the most convenient group was assumed to be S-AuNP0,5. Such nanoparticles sythesized in this manner could have potential applications in biomedical sector such as nanosized drug delivery systems and so on.