Influence of the chemistry of an organosilica surface on the adsorption of proteins from water-salt solutions

摘要

A two-component organosilica/protein system was investigated by adsorption methods using as an example the interaction of silicopolymethylsiloxane (SG-PMS) and its CuII ion-modified forms with the basic protein trypsin and the acidic protein albumin in water-salt solutions. It has been shown that the principal surface chemical features of the organosilica which influence the adsorption of protein molecules on its surface are the ratio of alternating hydrophilic and hydrophobic groups present, the ampholitic character of the silanol groups, the pH value of the point of zero charge (pzc), the pH of the medium, the concentration of the modifying reagent (CuII ion) employed, the contact time and the solid/liquid phase ratio of the system. Sorption equilibrium was achieved within 60 min for trypsin and within 180 min for albumin for the organosilicas employed. The symbiotic nature of the contact time, solid/liquid phase ratio and the quantity of CuII ions involved in the modification of the organosilica was demonstrated for the adsorption of both trypsin and albumin while the opposite effect was found for pH (linear adsorption for trypsin but exhibiting a maximum for albumin at a pH value near its isoelectric point of 4.7) and for the concentration of adsorbates employed, particularly for albumin where the structure of the amino acid influenced the pH value of its isoelectric point.