Synthesis of a temperature sensitive graft carbon dioxide-based copolymer and its evaluation as a nano drug carrier

In this study, a temperature sensitive graft carbon dioxide-based copolymer, poly (propylene oxide-co-carbon dioxide-co-allyl glycidyl ether)-poly (N-isopropylacrylamide)-polyethylene glycol monomethyl ether (PPAG-PNIPAm-mPEG) was synthesized by “Click Chemistry”. The hydrophobic main chain, PPAG, was prepared by the copolymerization of propylene oxide (PO) and allyl glycidyl ether (AGE). The branch chains include hydrophilic mPEG and temperature sensitive poly (N-isopropylacrylamide). The structure of the polymer was characterized by 1 H NMR and IR spectroscopy. Avermectin (AVE) was loaded into the nanoparticles to form PPAG-PNIPAm-mPEG@AVE nanoparticles. PPAG-PNIPAm-mPEG could self-assemble into nano-sized micelles in aqueous solution. And the size, zeta potential, critical micelle concentration (CMC) of PPAG-PNIPAm-mPEG nanoparticles can be altered by changing the lengths of the PNIPAm segments. The loading rate and encapsulation rate of PPAG-PNIPAm-mPEG@AVE were 36.98% and 89.98% respectively. The temperature sensitiveness of the nanomaterials was confirmed by DLS. The results show that temperature has a certain effect on the AVE release rate of PPAG-PNIPAm-mPEG@AVE in vitro. With the decrease of PNIPAm chain length, the AVE release rate decreases, and the contact angle of PPAG-PNIPAm-mPEG@AVE decreases compared with that of water.