A pH-responsive drug delivery system based on chitosan coated mesoporous silica nanoparticles

Herein, we report a core–shell pH-responsive drug-carrier based on chitosan-coated mesoporous silica nanospheres. The efficient positively charged polymer (chitosan) coating is realized by the phosphoramidate covalent bonding between phosphonate groups on the surface of the mesoporous silica nanoparticles (MSNs) and amino groups on chitosan. A pH-responsive release of ibuprofen has been achieved by varying the shell structure of positively charged chitosan in the designed pH 4.0–7.4 solution. Under basic conditions, chitosan forms a gel like structure which is insoluble and hence prevents ibuprofen release at pH 7.4. When the pH is below its PI (6.3), the drug has been released due to protonation of the amino group on chitosan. These results imply that the chitosan coated-MSNs are promising platforms to construct pH-responsive controlled drug delivery systems.