One-step preparation of organosiloxane-derived silica particles

Silica particles and their derivatives with meso-structure attracted much attention, but they were synthesized through complicated multi-step procedure. Considering biomedical application, no surfactants, used in almost all cases above, should be employable due to fear of their toxicity. The present study explored one-step sol-gel preparation of silica particles with biomedical functionalities, starting from Stöber-type systems, and characterized by Transmission Electron Micrograph or ²⁹Si MAS NMR spectroscopy. The Ca-containing particles, derived from the precursor system tetraethoxysilane (TEOS)-H₂O-C₂H₅OH (EtOH)-CaCl ₂-NH₄OH, consisted of primary particles of - IO nm, and were spherical in shape with the diameter of - 1000 nm, where Ca bridged Si-O- on the opposite particle surface. In contrast, the Ca-free particles were smaller with 400-500 nm in size due to the absence of such bridging effects. In addition, the Ca-containing ones deposited petal-like apatite within one week in Kokubo's simulated body fluid (SBF), which was interpreted in terms of the Ca release from the particles. Amino-modified silica particles were derived from the sol-gel precursor system aminopropyltriethoxysilane (APTES)-TEOS-H ²O-EtOH where APTES behaved not only as the catalyst but also a reactant; i.e., this was a self-catalyzed sol-gel system. Hydrogen bonding among the amino group of APTES on one particle surface and with Si-O- on the other was suggested to work in agglomeration of the primary particles. Bovine serum albumin was covalently fixed on the APTES-silica surface, suggesting their applicability of proteins or other growth factor delivery.