Published online by Cambridge University Press: 10 February 2011
A sparingly soluble model drug, phenytoin (5,5-diphenyl-hydantoin, denoted as PT), was added during hydrolysis and polycondensation of tetra orthoethyl silicate (TEOS). The average size of the composite primary particles after in situ recrystallization of PT and gelation of silica was 2–3nm. The extent of hydrogen bond (HB) in PT was reduced after the complex formation (CF), while many PT molecules were attached by HB on the surface of silica gel. The apparent solubility to ethanol decreased to 29%∼18% by CF. The firstorder rate constant of dissolution of PT into H20 increased by CF up to 40 times. Addition of acrylamide also enhanced the dissolution rate. Mechanisms of faster dissolution were discussed in terms of the hydrogen bond reformation and microstructure.