Preparation And Properties Of Glucose-responsive Microgels Containing Phenylboronic Acid Group

As a large population has suffered from diabetes and threatened by the complications of diabetes, this disease becomes one of the worldwide healthy concerns. However, so far, the major treatments of it have afflicted the patients’life and also been inefficient. Therefore, a kind of smart material that has the glucose-responsive properties is required, which can be used to relieve the suffer of patients. Thus, the research of glucose-responsive smart polymer has attracted more and more attention. With respect to the stability, biocompatibility, mechanism of drug release and feasibility of mass production for the future application, the glucose and thermo reponsive microgels contained PBA have been prepared by emulsion polymerization.A group of poly(NIPAm-co-AA) microgels were synthesized by change the adding amount of emulsifier, initiator and stirring speed. The diameter of these microgels were tested to find the influence of recipe and stirring speed of the synthesis process on the diameters. It is concluded that the diameter increased as the amount of emulsifier decreased and also the stirring speed decreased; the diameter increased as the amount of initiator increased. We synthesized AAPBA, the glucose-responsive monomer. Through emulsion polymerization, NIPAm and AAPBA were copolymerized with MBA serving as cross-linker, to obtain poly(NIPAm-co-AAPBA) microgel. IR was used to demonstrate structure of the microgels.A seris of poly(NIPAm-co-AAPBA) microgels were prepared by change the amount of AAPBA in recipe. The diameters of the microgels under different conditions were tested, in order to research the influence of AAPBA content, glucose concentration, pH value and temperature of surrounding on the glucose-reponsive swelling behavior of the microgels. It was concluded that the glucose-reponsive swelling behavior of the microgels intensified as the AAPBA content increased and the glucose concentration increased. In addition, the glucose-responsive behavior of the microgel only took place when the pH value of environment was higher than the pKa of PBA functional group and when the temperaure of environment was lower than Lower Critical Solution Temperature (LCST) of the microgel.The hydrophilic monomer, AA, and the hydrophobic monomer, MA, were empolyed to the system, respectively, to prepare poly(NEPAm-co-AAPBA-co-AA) and poly(NIPAm-co-AAPBA-co-MA) microgels, in order to improve the thermo properties of the microgels. The diameters of microgels were tested under different temperaturein buffer solution. It is concluded that the introduction of AA increased LCST of the microgels, while the introduction of MA decreased LCST of the microgels. As the amount of introduced AA increased, the LCST of poly(NIPAm-co-AAPBA-co-AA) increased. In addition, with testing the diameter of microgels under different glucose concentration and temperature in buffer solution with differen pH value, we found that Sample1of poly(NIPAm-co-AAPBA-co-AA) microgel, which had the highest AA content, performed most favorable glucose-reponsive swelling behavior under physiological temperature. It showed swelling ratio of5.33,7.34and8.09in the buffer solution(pH9.18) with glucose concentration of lg/L,2g/L,3g/L. However, in the buffer solution(pH6.86), the microgel hardly respond to glucose. Therefore, in the future research of this system, certain modification should be made on the structure of PBA functional group to decrease pKa value, and thus to enable this kind of glucose-repsonsive microgel system to be applicated to the drug release system in vivo.