Enzyme-responsive silica mesoporous supports capped with azopyridinium salts for controlled delivery applications.

The preparation of a new capped silica mesoporous material, Rh-Azo-S, for on-command delivery applications in the presence of target enzymes is described. The material consists of nanometric mesoporous MCM-41-like supports loaded with Rhodamine B and capped with an azopyridine derivative. The material was designed to show "zero delivery" and to display a cargo release in the presence of reductases and esterases, which are usually present in the colon, mainly due to intestinal microflora. The opening and cargo release of Rh-Azo-S in vitro studies were assessed and seen to occur in the presence of these enzymes, whereas no delivery was noted in the presence of pepsine. Moreover, Rh-Azo-S nanoparticles were used to study controlled Rhodamine B dye delivery in intracellular media. HeLa cells were employed for testing the "non"-toxicity of nanoparticles. Moreover, delivery of the dye in these cells, through internalization and enzyme-mediated gate opening, was confirmed by confocal microscopy. Furthermore, the nanoparticles capped with the Azo group and loaded with a cytotoxic camptothecin (CPT) were also prepared (solid CPT-Azo-S) and used as delivery nanodevices in HeLa cells. When this solid was employed, the cell viability decreased significantly due to internalization of the nanoparticles and delivery of the cytotoxic agent.
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