Aqueous protein adsorption at solid surfaces: Surface modification and salt and sugar excipients.

摘要

Protein adsorption at liquid/solid interfaces affects many applications, including protein manufacture and packaging, drug delivery and formulation, biomedical implants, and contact lenses. Optical waveguide lightmode spectroscopy (OWLS) was used to determine the kinetics of protein adsorption. Solution conditions were modified to explore the factors important in protein adsorption. Protein adsorption was generally irreversible and dependent on salt concentration, pH and protein concentration. Monolayer coverage was found, except for hen-egg-white lysozyme, which formed multilayers.; The SiO2/TiO2 waveguide surface of the OWLS was hydrophilic and negatively charged. A positively charged surface was created with amine silanes. A hydrophobic surface was created with an octylsilane coating. For both these surfaces, the amount of protein adsorbed depended on the properties of the protein and the solution conditions. The amount adsorbed on a D-lactonolactone coated surface represented 30% of coverage compared to the SiO2/TiO2 reference surface.; Sugar excipients were shown to reduce the adsorption of ribonuclease A, bovine serum albumin and hen-egg-white lysozyme. The amount of protein adsorbed decreased as the concentration of the sugar increased. At the same sugar concentration, the ability of sugars to reduce protein adsorption followed the trend: trisaccharides > disaccharides > 6-carbon polyols > monosaccharides. This trend in adsorbed protein amounts among thirteen sugars was explained by stabilization of the protein native state in solution by the sugar excipients. The heat of solution of the amorphous saccharide was found to correlate with the amount of protein adsorbed.; Salt excipients are shown to influence protein adsorption. We observed that the amount adsorbed of four proteins, ribonuclease A, bovine serum albumin and hen-egg-white lysozyme, and beta-lactoglobulin followed the salt series Mg+2 > Li+ > Na+ > K+ for cations and Cl- > Br- > I- for anions. The change in adsorption in the presence of different salt types did not result from changes in electrostatic attraction or changes in bulk protein stability. Hydrophobic interactions are known to be one of the main driving forces for protein adsorption. We propose that the reason for the adsorption behavior is due to differences in hydrophobic interactions from changes in water structure.