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 (CapH2), 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-4116 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 CapH2/SBA-15 delivery system with the largest pore diameter of 7.39 nm has exhibited the fastest release rate. While CapH2/MCM-4112 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 CapH2/MCM-4116 system with 2.17 nm pore diameter and rod-like morphology (ca. 20 μm in length). By comparing the release rate of CapH2/MCM-4116 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.