Preparation of a Novel Amino Functionalized Fluorescein-doped Silica Nanoparticle for pH Probe

Abstract

A novel type of amino functionalized core-shell fluorescein isothiocyanate-doped silica nanoparticles was synthesized using a simple and effective approach of reverse microemulsion. Isothiocyanate coupled with a silane coupling agent, 3-aminopropyltrimethoxysilane, was incorporated into silica sphere and the dye molecules were bound with silica sphere through hydrolysis and polymerization of tetraethoxysilane and 3-aminopropyl-trimethoxysilane. With the covalent binding between the dye molecules and silica sphere, the leakage of the dye was avoided. With amino groups on the surface, the nanoparticles can be directly conjugated with biological molecules with no need of surface modification. The nanoparticles were pH sensitive, highly fluorescent and highly photostable. The pH response range and pH responsive linear range were 2.8~8.5 and 4.6~8.0, respectively. More interestedly, the nanoparticles could be phagocytosed by murine neural stem cell and could be applied to detect pH value for single alive cell.