Biofunctionalization of silica microspheres for protein separation.

Mercapto-silica (SiO2-SH) microspheres were prepared via direct hydrolysis of 3-mercaptopropyltrimethoxysilane (MPS) in a basic aqueous solution. The content of surface thiol group (SH) of SiO2-SH microspheres was measured by Ellman's reagent method and X-ray photoelectron spectroscopy (XPS) and the content of surface thiol group of SiO2-SH microspheres is strongly dependent on the reaction conditions. The thermal stability of SiO2-SH microspheres was evaluated by thermogravimetric (TG) analysis, which tended to reduce with the increase of content of surface thiol groups. SiO2-SH microspheres can be easily modified with reduced glutathione (GSH) to generate SiO2-GSH microspheres for the affinity separation of Glutathione S-transferase (GST). Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) was performed to examine the validity of the separation procedure. The results showed that SiO2-GSH microspheres were efficient in GST affinity separation from mixed proteins.