Protein extraction and cytotoxicity abilities of colloidal gold-coated silica hybrid nanoparticles

Monodisperse non-hybrid silica and hybrid colloidal silica of <= 200 nm decorated with small Au nanoparticles (NPs) were synthesized in a simple single-step method. Non-hybrid silica NPs were synthesized in the absence and presence of different twin tail cationic surfactants, while tiny Au NPs were grown under in situ reaction conditions on non-hybrid silica synthesized previously by using cationic dextran. Bio-applicability and cytotoxicity of both hybrid as well as non-hybrid silica NPs were tested by using them for the extraction of protein fractions from complex aqueous protein solutions and treating them with blood cells, respectively. Both non-hybrid and hybrid silica NPs demonstrate excellent ability to extract proteins fractions predominantly of relatively low molecular masses, i.e., similar to 80 kDa. Extraction preferences between both kinds of silica became prominent when predominantly hydrophobic proteins such zein and rice proteins were used rather than mainly polar protein like BSA. Applicability for more complex biological fluid like serum indicated the competitive extractions among strongly versus weakly bound proteins. With significant bearing in in vivo conditions, hybrid silica was potentially toxic towards the blood cells in comparison to non-hybrid silica. It stems from the collective interactions of silica as well as nanometallic surfaces of Au NPs to interact with the blood cells causing hemolysis and hence may not be the suitable vehicles for drug release in systemic circulation.