Chitosan enclosed mesoporous silica nanoparticles as drug nano-carriers: Sensitive response to the narrow pH range

Most pH-sensitive drug delivery systems have been reported to respond to wide ranges of pH or target tissues the pH of which vary considerably, whereas these systems are not able to target diseased tissues like inflammatory tissues and tumor cells (pH 6.8) due to the extremely slight differences between pH of normal tissues (pH 7.4) and them. Consequently, ingenious pH-responsive drug delivery systems are desired to target this kind of abnormal tissues. In the present study, we fabricated a novel pH-sensitive drug delivery system with a 22% loading capacity, which released about 65% and 35% model drug in pH 6.8 and 7.4 after 24 h, respectively. In pH 7.4 release medium, chitosan molecules are orderly aggregated state, which efficiently hinder the release of the guest molecules from nanocarriers. However, in pH 6.8 release medium, chitosan chains are heavily and flexibly entangled in gel state, which is good for the release of guest molecules. The drug delivery system could reduce the drug nonspecific reaction with normal cells but remaining the curative effect.

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► Chitosan wrapped onto mesoporous silica nanoparticle forming pH sensitive film.
► Drug release were controlled by pH-responsive phase transition of chitosan between pH 6.8 and 7.4.
► Drugs may release faster in tumor tissues with low pH than in normal tissues with high pH.