Synthesis of poly(N-isopropylacrylamide)-co-poly(phenylboronate ester) acrylate and study on their glucose-responsive behavior

We introduced thermo-sensitive poly(N-isopropylacrylamide) (PNIPAM) into the polymer structure of poly(ethylene glycol)-block-poly(phenylboronate ester) acrylate (MPEG-block-PPBDEMA) by block and random polymerization pathways in order to investigate the effect of polymer architecture on the glucose-responsiveness and enhance their insulin release controllability. By following the structure, the continuous PNIPAM shell of the triblock polymer MPEG-block-PNIPAM-block-PPBDEMA collapsing on the glucose-responsive PPBDEMA core formed the polymeric micelles with a core-shell-corona structure, and MPEG-block-(PNIPAM-rand-PPBDEMA) exhibited core-corona micelles in which the hydrophobic core consisted of PNIPAM and PPBDEMA segments when the environmental temperature was increased above low critical solution temperature (LCST) of PNIPAM. The micellar morphologies can be precisely controlled by temperature change between 15 and 37°C. As a result, the introduction of PNIPAM greatly enhanced the overall stability of insulin encapsulated in the polymeric micelles in the absence of glucose over incubation 80 h at 37°C. Comparing to MPEG-block-PNIPAM-block-PPBDEMA, the nanocarriers from MPEG-block-(PNIPAM-rand-PPBDEMA) showed great insulin release behavior which is zero insulin release without glucose, low release at normal blood glucose concentration (1.0 mg/mL). Therefore, these nanocarriers may be served as promising self-regulated insulin delivery system for diabetes treatment.