Controlled release of Captopril by regulating the pore size and morphology of ordered mesoporous silica

In order to control the release of water-soluble drug Captopril (CapH(2)), a series of mesoporous silica materials has been prepared, using three kinds of surfactants C16TAB, C12TAB, and EO20PO70EO20, respectively. It has been found that the loading amount of the drug was related to the BET surface area of the mesoporous silica. MCM-41(16) with the highest surface area possesses the largest loading amount, which is up to 33.99 wt%. The loading and release kinetics (in vitro in simulated stomach fluid) showed that both of them were affected not only by the pore diameter but also by the morphologies of mesoporous silica materials. A rapid drug loading could be achieved either by enlarging pore sizes or by reducing particle sizes. And CapH(2)/SBA-15 delivery system with the largest pore diameter of 7.39 nm has exhibited the fastest release rate. While CapH(2)/MCM-41(12) system with the smallest pore diameter of 1.65 nm and sphere morphology (120-250 nm in size) has a faster release rate than that of CapH(2)/MCM-41(16) system with 2.17 nm pore diameter and rodlike morphology (ca. 20 mu m in length). By comparing the release rate of CapH(2)/MCM-41(16) in a simulated stomach fluid with that in the proximal intestine fluid, it was found that the release media played a key role on the drug delivery profiles. (c) 2005 Elsevier Inc. All rights reserved.