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.