Study On The Temperature-and Glucose-Sensitive Copolymer Microgels

Biomolecule recognition responsive hydrogels,which can recognize specific biomolecules and respond to them mimicking the molecule-recognizing process of life activity,are very close to biological tissue.The intelligent systems fabricated from the hydrogels resemble the biological systems with feedback and equilibrium functions,and they have a great deal of potential applications in the fields of bioengineering and biomedicine.In this paper,the glucose molecule recognition responsive microgels were synthesized by surfactant-free emulsion polymerization based on N-isopropylacrylamide(NIPAM)as main monomer and the vinyl monomer with phenylboronic acid group as functional comonomers. The glucose-sensitive microgels were composed of artificial materials without using expensive bioactive substance,so they have the advantage of good stability and low preparation cost.Due to the fact that any surfactant was not used in the synthesis process,there was no surfactant pollution on the surface of the microgels.The glucose-sensitive microgels will potentially be utilized as self-regulated insulin delivery system,in which insulin can be released in respond to body blood glucose concentration,In addition,the glucose-sensitive microgels could be used as the carrier of glucose oxidase,in which the activity of the glucose oxidase can be controlled by glucose concentration in the biochemical reaction system for producing glucose acid.The detailed results are as follows:1.3-acrylamidophenylboronic acid(AAPBA)was synthesized by the condensation reaction between carboxyl acid group(-COOH)and amino group,based on 3-aminophenylboronic acid(APBA)and acrylic acid (AA)as starting materials and N-Ethyl-N'-(3-dimethylaminopropyl) carbodiimide hydrochloride(EDCI)as condensating agent.The product purified by recrystallization was verified by elemental analysis,FTIR,¹H NMR,UVand MS.The synthesis mechanism of AAPBA was speculated to be divided into two steps:in the first step,the 0-acylcarbamide intermediate was formed by the reaction between ethylcarbodiimide groups of EDCI and carboxyl groups of acrylic acids;in the second step, AAPBA was formed by the reaction between 0-acylcarbamide intermediates and amino groups of APBA.2.The poly(NIPAM-co-AAPBA)microgels were prepared by surfactant-free emulsion polymerization.The microgels displayed spherical shape and very narrow size distribution from the results obtained by scanning electron microscopy(SEM)and dynamic laser light scattering(DLLS),indicating that there was extremely short nucleation period without second nucleation process.The hydrodynamic diameters and swelling ratios of the microgels decreased with the increase of AAPBA component content.The poly(NIPAM-co-AAPBA)microgels were both temperature- and glucose- sensitive,their volume phase transition temperature(VPTT)decreased with the increase of AAPBA component content within the microgels. 3.The poly(NIPAM-co-VPBA)copolymer microgels were prepared by surfactant-free emulsion polymerization,in which 4-vinyl phenylboronic acid(VPBA)was used as functional comonomer.The chemical structure of the microgels was verified by the content analysis of B element,fourier transform infrared spectroscopy(FTIR)and ¹¹B NMR.The hydrodynamic diameters and swelling ratios of the microgels decreased with the increase of VPBA component content.In neutral water media, the physically crosslinked points within the microgels were formed between the polymer chains by the hydrophobic interaction between VPBA units.The poly(NIPAM-co-VPBA)microgels were temperature-sensitive,their VPTT decreased with the increase of VPBA component content.In the water media of pH=10.5,the microgels were glucose-sensitive,and the increase magnitude of their hydrodynamic diameters with the glucose concentration in the media was reduced with the enhancement of VPBA component content within the microgels.