Multifunctional polymer drug loading system with pH-sensitive, fluorescent and targeting property

IA multifunctional drug loading system with pH-sensitive, fluorescent and targeting property was fabricated. Firstly, the amphipathic N-octyl-N'-(2-carboxyl-cyclohexamethenyl) chitosan (OCCC) was prepared by grafting hydrophobic octyl group and hydrophilic hexahydrophthalic anhydride onto chitosan, then it was modified with folic acid (FA) and thiazole orange (TO) using polyethylene glycol (PEG) as the link to fabricate a multifunctional drug loading system TO-PEG-OCCC-PEG-FA. Its chemical structure was determined by Fourier transform infrared spectroscopy (FT-IR), elemental analysis, differential scanning calorimetry (DSC) analysis, UV-vis and fluorescence spectrometer, and the results showed that the substitution degree of hydrophobic/hydrophilic group onto chitosan were 41.4% and 59.1% respectively. The FA and TO were successfully grafted onto chitosan using PEG as link, and their grafting degree were 5.1% and 0.216% respectively. The fabricated multifunctional chitosan micelle with a concentration of 10mg/mL showed a 42.76% encapsulation efficiency on 5-fluorouracil, and it was stable under physiological pH (pH=7.4), but showed an excellent pH-sensitive drug release property under acid environment (pH=4.0). Additionally, the drug release amount could reach up to 95% during 4h.