Construction of site-specific core-shell structured nanocomposite for pH-controlled drug delivery

In this study, a pH-controlled core-shell structured site-specific magnetic nanocomposite for drug delivery was reported. Superparamagnetic Fe3O4 nanoparticles were selected to build its core for magnetic guiding purpose and mesoporous silica molecular sieve MCM-41 was chosen to construct its outer shell. The MCM-41 outer shell has highly ordered hexagonal tunnels therefore would offered enough cargo space for drug molecules. An organic ligand N1-(5H-cyclopenta[1,2-b:5,4-b']dipyridin-5-ylidene)benzene-1,4-diamine (denoted as Dafo-Ph-NH2) was linked to the molecular sieve outer shell. There are two nitrogen atoms at the end of the ligand which are able to donate their lone pair electrons. Acidic drug molecules therefore can be bound to the ligand via weak acid-base reaction. Those drug molecules can be release in low pH solution since the H+ in the solution will compete with the ligand. The final composite was analyzed by electron microscope images, XRD, IR spectra, thermogravimetry and N-2 adsorption/desorption. Its bio-compatibility was evaluated by MTT using L929 fibroblast cell line. Our Dafo-MCM-41@Fe3O4 composite shows pH-controlled and site-specific smart release properties for aspirin in vitro.