Bioactive silica-based nanomaterials for doxorubicin delivery: Evaluation of structural properties associated with release rate

This study investigated the use of a novel particle-type formulation, composed of a sol–gel derived bioactive silica-poly(dimethylsiloxane) composite containing calcium and phosphate, as a slow release delivery system for an anticancer drug (doxorubicin hydrochloride, DOX). DOX in the solution form was in situ incorporated into the composite network during the sol–gel process. The DOX loaded-formulation was immersed in a simulated body fluid (SBF) having ion concentrations and a pH value nearly equal to those of human blood plasma. The effect of different drug loads and particle sizes — on the release profiles in such biomimetic conditions was studied. The bioactivity was examined in vitro with respect to the ability of hydroxyapatite layer to form on the surface of residual DOX-loaded formulation as a result of contact with SBF. The infrared absorption spectra, scanning electron microscopy, nitrogen gas adsorption/desorption, and X-ray powder diffraction studies were conducted before and after contact of the formulation with SBF. The results show that all the DOX-loaded formulations are characterized by mesoporosity with the uniform pore-size-distribution. The release profiles of DOX consisted of two sequential zero order-controlled stages with distinctly different release rates. After 20 days of DOX release, a semicrystalline carbonated hydroxyapatite with a highly developed porous structure was formed, indicative of their bioactive character. Furthermore, these new covered-particle-type formulations released DOX over 1 month at a constant rate.