Relationship between the glutathione-responsive degradability of thiol-organosilica nanoparticles and the chemical structures

Stimuli-responsive degradable silica nanoparticles (NPs) are active topics of nanomaterial research, because they are expected to be low health-risk nanocarriers capable of controlled release of drugs. Among various stimuli-responsive silica NPs, disulfide bond-containing NPs show degradability by glutathione reduced form (GSH). Here, we synthesized and characterized three kinds of thiol-organosilica NPs made from 3-mercaptopropyltrimethoxysilane (MPMS) and 3-mercaptopropyl(dimethoxy)methylsilane (MPDMS). MPMS NPs, MPDMS NPs, and MPMS–MPDMS hybrid NPs revealed that the abundance ratio of disulfide bonds to thiols increased with the increase in content rate of MPDMS in thiol-organosilica NPs. We also revealed that thiol-organosilica NPs, which have disulfide bonds, are GSH-responsive degradable silica NPs using an electron microscopy and Ellman’s tests. Furthermore, we synthesized fluorescent MPMS–MPDMS NPs, including rhodamine B, and demonstrated the GSH-responsive release of dye from the NPs. These experiments indicate the potential of thiol-organosilica NPs, which have disulfide bonds as a GSH-responsive drug carrier.