Stimuli-Responsive Conformational Conversion of Peptide Gatekeepers for Controlled Release of Guests from Mesoporous Silica Nanocontainers

The use of peptides as gatekeepers for payloads of mesoporous silica nanoparticles would allow triggering the release of guests by various biological stimuli. We investigated the effect of peptide conformation on their gatekeeping capability by employing two model peptides with a turn or a random structure. The conformation-dependent gatekeeping properties provided an opportunity to utilize the conformational conversion of peptides as a valuable motif for stimuli-responsive gatekeepers. Based on that investigation, we demonstrated that Fmoc-CGGC-SS-Si, which exhibited a zero-release property without any stimuli due to a turn-like conformation induced by the intramolecular disulfide bond, can be triggered to release guests by converting its conformation to a random structure, induced by reduction of the disulfide bond upon addition of glutathione. We further demonstrated that the conformational conversion of Fmoc-CGGC by Zn(II) ion can also be utilized as a triggering motif.