In vivo anti-tumor efficacy of docetaxel-loaded thermally responsive nanohydrogel

Thermally responsive poly(N-isopropylacrylamide-co-acrylamide) (P(NIPA-co-AAm)) nanohydrogel (NHG) with a diameter of about 50 nm and a lower critical solution temperature (LCST) of about 40 °C was synthesized by a previously reported precipitation polymerization method. The physical properties including LCST, diameter and morphology were characterized. Four hydrophobic model drugs (5-fluorouracil (5-FU), fluorescein, docetaxel (DTX) and near-infrared dye-12 (NIRD-12)) with different hydrophilicities were respectively entrapped into the nanoparticles and their in vitro release kinetics from NHG was investigated. DTX was ultimately chosen as the goal anti-tumor drug and optimally entrapped into NHG with a drug loading content (DLC) of 7.38% and encapsulation efficiency (EE) of 73.8%. An in vitro drug release test indicated that DTX-loaded NHG had zero-order release kinetics at 43 °C. The respective anti-tumor efficacy of DTX-loaded NHG with or without hyperthermia on tumor tissue was evaluated in Kunming mice-bearing S180 sarcoma. The inhibition rates of DTX-loaded NHG with or without hyperthermia were 78.15% and 48.78%, respectively. DTX-loaded NHG also showed much lower toxicity during the therapeutic procedure. Results indicated that this kind of thermally responsive, drug-loaded NHG could be used as a promising strategy for tumor therapy with the help of local hyperthermia treatment.