Colloidal Properties of Surface Coated Colloidal Silica Nanoparticles in Aqueous and Physiological Solutions

Silica nanomaterials have attracted considerable interest as advanced materials in industrial and bio-medical research. This study examined the colloidal properties of silica (SiO2) nanomaterials such as particle size, zeta potential and hydrodynamic size under various aqueous conditions, such as deionized water (DI), phosphate buffered saline (PBS) and human plasma. To examine the effects of size and surface chemistry on the colloidal behavior, colloidal silicas with two different sizes (20 and 100 nm) were selected and their surface was modified with L-arginine under controlled pH conditions. Surface modification did not affect the particle size and morphology in aqueous system but altered the surface charge. All the silica samples showed clear Tyndall effect in DI, PBS, and human plasma under greenish laser irradiation, suggesting that their colloidal properties were well preserved in physiological solutions. We also evaluated the fluorescence quenching of plasma protein upon silica treatment and showed that silica nanomaterials do not induce serious protein aggregation.