Protein adsorption to a bioactive glass with special reference to precorrosion

The protein adsorption properties of the bioactive glass S53P4 were studied using albumin, IgG, and fibrinogen solutions (1 mg/mL) as well as diluted plasma, serum, and 1:1:1 mixtures of albumin, IgG, and fibrinogen. The bioactive glass granules (315-500 microns) were used in the experiments without pretreatments or as precorroded with an Si-rich or a Ca,P-rich layer. The protein adsorption properties of S53P4 were compared to a commercial bioactive glass (Bioglass), an inert glass, an experimental glass ceramic, titanium (Ti), and hydroxyapatite (HA). The untreated S53P4 bound in Trisbuffered saline mainly albumin from diluted plasma and serum and the 1:1:1 (1 mg of each) mixture of albumin, IgG, and fibrinogen. No binding of fibrinogen was observed. The omission of NaCl from the buffer used in the experiments increased the number of proteins bound by the S53P4. Most of the albumin bound by the glass could be detached with 0.5-1M NaCl speaking for electrostatic protein bonding. The protein adsorption properties of Bioglass resembled those of S53P4. The Ca,P-rich layer glass, the inert glass, the glass ceramic, HA, and Ti all bound several plasma and serum proteins, including fibrinogen. The Si-rich layer glass showed protein binding properties resembling the untreated glass more than the Ca,P-rich layer glass. The protein adsorption test used in the present study revealed differences in the protein adsorption properties of the studied materials, which may reflect differences in their surface potentials. It also functioned in registration of corrosion-induced changes in the surface properties of the S53P4. As judged by the protein adsorption properties, the untreated S53P4 could have a higher biocompatibility than the two precorroded glasses. Precorrosion, especially the formation of the Ca,P-rich layer, increased the number of proteins bound by the S53P4. Thus, a precorroded glass as compared to the untreated glass could be a better carrier of specific proteins that may be used to improve the biocompatibility of the bioactive glass.