Synthesis of temperature-responsive P(vinyl pyrrolidone-co-methyl methacrylate) micelle for controlled drug release

Abstract

In the study we synthesized thermo-responsive amphiphilic P(vinyl pyrrolidone-co-Methyl methacrylate) (P(VP-co-MMA)) polymers at varying ratios (100/0, 95/5, 94/6, and 92.5/7.5), which were used further for the synthesis of thermo-responsive micelles. The 1H-NMR results revealed the successful copolymerization of VP with MMA without any chemical deterioration. Further, it was observed that the variations in monomers molar ratio showed no prominent effect on the critical micelle concentration of any copolymeric solution. Although micellar self-assembly was observed in all the monomers molar ratio, the degree of self-assembly was directly proportional to the content of MMA monomer. Moreover, the formation of micelles is favored from all the prepared copolymers due to the high hydrophilic monomeric content in the copolymers. In addition, as-synthesized micelles were spherical and had almost similar diameter, that is, 70–90 nm. Moreover, the loading % of Nile red was also similar in all the self-assembled micelles. It was observed that the lower critical solution temperature (LCST) of the polymer decreases with an increase in MMA content, and at 95/5 molar ratio the LCST of P(VP-co-MMA) was around 40 °C, which is suitable for in vivo drug delivery system. Moreover, high payload release, that is, 44%, was measured from P(VP-co-MMA) (95/5) at 45 °C, as compared to 33% payload release at 37 °C, suggesting that micelles formed from P(VP-co-MMA) (95/5) could be suitable for in vivo drug delivery.