Synthesis and characterization of nanoporous SiO₂/pHEMA biocomposites

Porous SiO₂/pHEMA biocomposites were synthesized in situ by incorporating silica nanoparticles with a hydroxyethyl methacrylate (HEMA) monomer, following a UV-induced photopolymerization. The nanostructure of the composites was characterized and the resulting physical properties were examined. The release kinetics of the model molecule-vitamin B12-and the hemocompatibility of the porous SiO₂/pHEMA composites were investigated. Heterogeneous reaction kinetics is proposed to be the formation mechanism of the nanoporosity in the pHEMA matrix as a result of incorporating silica nanoparticles following photopolymerization. Experimental results also demonstrated that the incorporation of the silica nanoparticles into the pHEMA matrix not only enhanced the mechanical property but also maintained a good hemocompatibility of the resulting biocomposites. In addition, it was observed that the drug release profile of the composites (in the form of a membrane) can be precisely regulated from a two-stage pattern to one-stage pattern by varying the concentration of both the SiO₂ nanoparticles and HEMA monomer during synthesis. The permeability of the model drug was enhanced by two orders of magnitude from 4.22 × 10^-7cm²/h to 3.92 × 10^-5cm²/h by controlling the micro-to-nanostructure of the composites. The platelet adhesion experiment demonstrated low aggregation of the platelets on the surface of the biocomposite membranes, indicating a promising antithrombotic property.