Preparation of dual pH- and temperature- sensitive nanogels for curcumin delivery

Curcumin (Cur) is a valuable ingredient from turmeric with many bioactivities. Cur was used in various traditional therapies. However, the low solubility and poor bioavailability limit its therapeutic application. In this work, we preparation the dual pH- and thermo-sensitive nanogels (NGs) from poly-N-isopropylacrylamide (PNIPAm) and polyacrylamide (PAAm) [P(NIPAAm-co-AAm) NGs] to delivery Cur. The P(NIPAAm-co-AAm) NGs were characterized by SEM, TEM, ¹H-NMR, XPS, FT-IR, and DLS. The cytotoxicity test on the liver cancer cells (HepG2 cells) showed low cytotoxicity and high biocompatibility of the NGs. The NGs were also subjected to pH and temperature-sensitive in vitro Cur-loading and Cur-release experiments. We control the pH and temperature conditions to switch the NGs between swelling and deswelling to loading and releasing Cur. The synthesized copolymer PNIPAm-co-PAAm HG showed about ~65% of Cur loading. The zeta potential of NGs was decreased when the pH conditions increased and the phage transition of NGs happened at 40 ℃ with concentration-dependent properties. After 4 h under pH 5.5 and 40 °C, nearly 100% of Cur has successfully been released from the NGs. The newly synthesized NGs could release the drug according to the physical stimulus (i.e. pH and temperature). Therefore, the NGs have potential application value in solid tumor-targeted therapy.