Preparation and protein adsorption of silica-based composite particles for blood purification therapy

Silica gel macrospheres of a few millimeters in diameter were fabricated via the sol-gel route using water glass, calcium chloride, and sodium alginate as the precursor components. TiO₂ coating on the silica gel macrosphere surface was conducted by soaking them in titania sol derived from hydrolysis of tetraethylorthotitanate (TEOT) under varied pH (HNO₃), and temperature (50-80°C). X-ray diffraction analysis indicated deposition of anatases, and particular deposition (<1μm) on the surface was confirmed by scanning electron microscopy. Protein adsorption behavior was examined as a function of pH of the hydrolysis of TEOT, using bovine serum albumin (BSA) and lysozyme (LSZ) as the model proteins. BSA adsorption was little affected by the pH, while some effects were found for LSZ adsorption. BSA adsorption saturated at 20-25 min contact, while LSZ adsorption took longer time for the saturation. Moreover, BSA was adsorbed almost twice as much as LSZ, when saturation adsorption was compared. An effect of residual calcium ions with better affinity to BSA was proposed for partial interpretation since surface charge could not account for those adsorption behaviors.