Outside-in stepwise functionalization of mesoporous silica nanocarriers for matrix type sustained release of fluoroquinolone drugs.

In this study, we propose outside-in stepwise functionalization of MCM-41-type mesoporous silica for use as a high-efficiency matrix drug delivery nanosystem aimed at the insoluble antibacterial agent fluoroquinolone. Thiol (-SH) modification on the surface of the nanocarrier and aminopropyl groups (-NH2) in the channels give the system a framework for sustained drug release for 72 h with drug loading capacity of 58.64% as a result of the completely opposite electrostatic interaction between drug molecules of thiol and amino. Unusually, abundant crystals of drug molecules were observed by transmission electron microscopy (TEM) in channels of the nanocarriers, caused by self-organization under the electrostatic attraction of the grafting groups. The elevated crystallinity of drug molecules loaded in the functional mesoporous MCM-41 nanoparticles was proved also through wide-angle XRD. Analysis of the release profiles highlighted the low cytotoxicity and excellent biocompatibility of the modified nanocarriers in vitro. Compared with single functionalization, the outside-in stepwise process can completely modify the deep inner of the channel and achieve effective internal drug loading of mesoporous materials. We believe that this method is not only of use for framework sustained-release tablets, but also other clinical medicine and chemical engineering.