Azobenzene Polyesters Used as Gate‐Like Scaffolds in Nanoscopic Hybrid Systems

The synthesis and characterisation of new capped silica mesoporous nanoparticles for on‐command delivery applications is reported. Functional capped hybrid systems consist of MCM‐41 nanoparticles functionalised on the external surface with polyesters bearing azobenzene derivatives and rhodamine B inside the mesopores. Two solid materials, Rh‐PAzo8‐S and Rh‐PAzo6‐S, containing two closely related polymers, PAzo8 and PAzo6, in the pore outlets have been prepared. Materials Rh‐PAzo8‐S and Rh‐PAzo6‐S showed an almost zero release in water due to steric hindrance imposed by the presence of anchored bulky polyesters, whereas a large delivery of the cargo was observed in the presence of an esterase enzyme due to the progressive hydrolysis of polyester chains. Moreover, nanoparticles Rh‐PAzo8‐S and Rh‐PAzo6‐S were used to study the controlled release of the dye in intracellular media. Nanoparticles were not toxic for HeLa cells and endocytosis‐mediated cell internalisation was confirmed by confocal microscopy. Furthermore, the possible use of capped materials as a drug‐delivery system was demonstrated by the preparation of a new mesoporous silica nanoparticle functionalised with PAzo6 and loaded with the cytotoxic drug camptothecin (CPT‐PAzo6‐S). Following cell internalisation and lysosome resident enzyme‐dependent gate opening, CPT‐PAzo6‐S induced CPT‐dependent cell death in HeLa cells.