Bovine serum albumin adsorption on N-methyl-d-glucamine modified colloidal silica

The adsorption of bovine serum albumin (BSA) onto a N-methyl-d-glucamine (NMDG) modified colloidal silica surface was investigated. NMDG was grafted onto the colloidal silica surface by covalent coupling. The modified nanoparticles were characterized by ATR-IR spectroscopy, zeta-potential analysis and elemental analysis. NMDG made up 9.24% of the weight of the modified nanoparticle. The adsorption of BSA to the NMDG ligand immobilized colloidal silica surface was influenced by protein concentration, pH, ionic strength and temperature. The enthalpy of adsorption of BSA to the NMDG modified silica nanoparticles was −19.7 kJ mol−1. BSA adsorption initially increased as ionic strength increased to around 50 mM, then decreased to reach a plateau value around 500 mM. The maximum BSA adsorption capacity of the NMDG modified nanoparticles was 7.46 mg g−1 nanoparticles at pH 5.5. A higher or lower pH dramatically decreased BSA adsorption. These results indicate that electrostatic interactions dominate BSA adsorption onto NMDG modified nanoparticles.