To elucidate the importance of the size of capping agents in stimulus-induced release systems from mesoporous silica nanoparticles (MSNs), the effectiveness of poly(propylene imine) dendrimers in controlling the model dye release was studied. MCM-41-type MSNs were synthesized and characterized. Fluorescent compounds (fluorescein disodium salt and carboxyfluorescein) were loaded in the porous structure of the MSNs and entrapped in the silica matrix with the dendrimers of generations I through V by anchoring dendrimers on the MSN surface through disulfide bonds. Stimulus-induced release of the cargo was studied in the presence of dithiothreitol (DTT). Dendrimers of generations I and II were found to be more effective in model drug retention and subsequent release than higher generations. Moreover, MSNs modified with larger amounts of dendrimers lowered the cargo release in the presence of DTT. Besides, pH decrease only was able to trigger release of the cargo. These findings are of importance for optimizing drug delivery systems based on responsive MSNs as they enable tuning of the amount of the released cargo by choosing the capping agent of appropriate size.
COBISS.SI-ID: 5234714
Turn-on fluorescent mesoporous silica nanoparticle-based system was synthesized and characterized. Fluorescein-containing silica nanoparticles were grafted with a dark quencher via disulfide bond. The quencher rendered nanoparticles non-fluorescent by Förster resonance energy transfer (FRET) mechanism. Nanoparticles regained fluorescence upon reduction of disulfides and dissociation of quencher from the particles’ surface. Evident increase of fluorescence of both, suspension and pellet, was present in dithiothreitol-treated sample, while much lower increase was observed in absence of dithiotreitol. Further studies revealed fluorescence intensity is dependent on the concentration of the reducing agent. The present system provides a visual information regarding the onset of the stimulus and, simultaneously, release of the molecules into the medium, thus acting as a release sensor.
COBISS.SI-ID: 5300250