Functional Magnetic Mesoporous Silica Microparticles Capped with an Azo-Derivative: A Promising Colon Drug Delivery Device

[EN] Magnetic micro-sized mesoporous silica particles were used for the preparation of a gated material able to release an entrapped cargo in the presence of an azo-reducing agent and, to some extent, at acidic pH. The magnetic mesoporous microparticles were loaded with safranin O and the external surface was functionalized with an azo derivative 1 (bearing a carbamate linkage) yielding solid S1. Aqueous suspensions of S1 at pH 7.4 showed negligible safranin O release due to the presence of the bulky azo derivative attached onto the external surface of the inorganic scaffold. However, in the presence of sodium dithionite (azoreductive agent), a remarkable safranin O delivery was observed. At acidic pH, a certain safranin O release from S1 was also found. The pH-triggered safranin O delivery was ascribed to the acid-induced hydrolysis of the carbamate moiety that linked the bulky azo derivatives onto the mesoporous inorganic magnetic support. The controlled release behavior of S1 was also tested using a model that simulated the gastro intestinal tract.
We thank the Spanish Government (projects MAT2015-64139-C4-1-R and AGL2015-70235C2-2-R (MINECO/FEDER)) and the Generalitat Valenciana (project PROMETEOII/2014/047) for support. AHT thanks to the Spanish MEC for his FPU grant. The authors also thank the Electron Microscopy Service at the Universitat Politecnica de Valencia for support. SCSIE (Universitat de Valencia) is also gratefully acknowledged for all the equipment employed. NMR was registered at the U26 facility of ICTS "NANBIOSIS" at the Universitat de Valencia. The authors thanks L.A. Villaescusa for his helpful discussion about the 1H-NMR analysis of the composition of loaded and functionalized supports.