Synthesis of oxidized pullulan coated mesoporous silica for pH-sensitive drug delivery

The past decades have witnessed the development of mesoporous silica as an attractive carrier for controlled drug delivery due to its outstanding mesoporous feature, facile surface functionalization and good biocompatibility. In this work, -NH2 grafted mesoporous silica nanoparticles (NH2-MSN) were first synthesized for the loading of 5-fluorouracil (5-FU), and then the drug loaded NH2-MSN were coated with oxidized pullulan (oxPL) via Schiff base reaction for the encapsulation of 5-FU. The resultant drug carrier, 5-FU/MSN/oxPL, was fully characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Dynamic light scattering (DLS), H-1 NMR, Fourier transform infrared (FT-IR) spectroscopy and nitrogen adsorption/desorption isotherms, respectively. Finally, controlled delivery of 5-FU from the carrier was investigated. Since the acylhydrazone bond between MSN and oxPL is prone to be hydrolyzed under acidic conditions, the encapsulated 5-FU is easily released from the MSN/oxPL carrier in acidic environment due to the separation of oxPL coating from MSN. Cytotoxicity of the developed carrier was also evaluated using LO2 and HepG2 cell lines by conventional CCK-8 assay.