Selectively functionalized mesoporous silica particles with the PEGylated outer surface and the doxorubicin-grafted inner surface: Improvement of loading content and solubility

We prepared selectively functionalized, spherical mesoporous silica particles (SMSPs) with a polyethylene glycol (PEG)-grafted outer surface and a doxorubicin-grafted inner surface for drug delivery. The SMSPs were fabricated by co-condensation of an amphiphilic organotriethoxysilane with a thermally cleavable urethane bond and tetraethoxysilane (TEOS) in the presence of cetyltrimethylammonium bromide (CTAB) under basic conditions. The outer surface of the as-precipitated silica particles was functionalized by grafting with 3-(triethoxysilyl)propyloxy–PEG. The PEG-grafted SMSPs were refluxed in methanol in the presence of HCl, resulting in the removal of surfactant molecules and the formation of a methoxy urethane group tethered to the pore wall. After the reaction of the methoxy urethane group with hydrazine, doxorubicin was chemically introduced into the pores through a pH-sensitive hydrazone linkage. A high loading content was achieved through chemical loading followed by physical loading. The doxorubicin-loaded SMSPs showed a pH-sensitive and sustained release behavior.