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Polyurethane–polyurea (PUUa) reactive prepolymers with adjusted hydrophobic and hydrophilic dangling chains to achieve multiwalled sub-30 nm nanoparticles are presented. The combination of an amphiphilic and a hydrophobic prepolymer at the oil–water interface creates a stratified shell by hydrophobic interactions. These novel nanostructures enhance the encapsulation stability of lipophilic compounds compared to monowalled nanostructures and facilitate the selective and ordered functionalization along the multiwalled shell with bioactive motifs. As proof of concept, PUUa nanoparticles have been engineered with disulfide bonds and an αvβ3 integrin-selective cyclic RGD peptide (cRGDfK) providing our system with glutathione (GSH) triggered controlled release and cell targeting specificity to U87 tumor cells.

[EN] We report the design, synthesis, characterization and in vitro testing of a novel nanodrug based on a covalent linking model that allows intracellular controlled release of the pharmaceutical payload. A new synthetic strategy is implemented by direct coupling of as-synthesized (pyridin-2-yldisulfanyl)alkyl carbonate derivatives of camptothecin (CPT) with thiol groups of silica hybrid nanoparticles containing a non-porous core and a mesoporous shell. Upon reaction with thiols in physiological conditions, disulfide bridge cleavage occurs, releasing the naked drug after an intramolecular cyclization mechanism. Additional incorporation of a fluorophore into particles core facilitates imaging at the subcellular level for the monitoring of uptake and delivery. Confocal microscopy experiments in HeLa cervix cancer cells confirms that nanoparticles enter the cells by endocytosis but are able to escape from endo-lysosomes and enter the cytosolic compartment to release their cargo. The incorporation to cells of L-buthionine-sulfoximine, a glutathione inhibitor allows concluding that the intracellular releasing mechanism is mainly driven by the reducing activity of this tripeptide. This camptothecin nanoplatform shows the same cytotoxic activity than the free drug and is clearly superior to those release systems depending on enzymatic hydrolysis (as determined by calculation of the IC50 ratios)., This work was financially supported by "Comision Interministerial de Ciencia y Tecnologia" of Spain (projects CSD2009-00050 and MAT2012-39290-C02-02), and grants from CIBER-BBN (NanoMets Intramural Grant) "Fondo de Investigaciones Sanitarias - Instituto de Salud Carlos III" (PI080771) y "Universidad Catolica de Valencia San Vicente Martir" (PI2011-011-010). CM thanks the Spanish "Ministerio de Economia y Competitividad" for a FPU Ph.D. studentship (AP2008-02851). SSA thanks the "Universidad Catolica de Valencia San Vicente Martir" for a Ph.D. studentship.