Monodispersed Glucose-Responsive Microgels Operating at Physiological Salinity

Abstract

Monodispersed poly(N-isopropylacrylamide) submicrometric microgels modified with a phenylboronic acid (PBA) derivative have been synthesized by precipitation polymerization. Particles with a well-controlled size and adjustable composition were obtained. These particles were found to be glucose responsive at a pH close to the pKa of the PBA derivative, with a swelling degree proportional to the concentration of glucose. In addition, the response to glucose was found to strongly depend on the initial state of the microgel, which depended itself on the initial temperature and the functionalization degree of the particle. This result explained the fundamental difference in the behavior of PBA-poor particles and rich ones in the presence of electrolyte. Interestingly, the latter exhibited a high swelling ratio in the presence of glucose at physiological electrolyte concentration. These particles may serve as building blocks for the design of colorimetric sensors based on the light diffraction of colloidal crystals.

Semibath Polymerization Approach for One-Pot Synthesis of Temperature- and Glucose-Responsive Core-Shell Nanogel Particles

“…However, as the concentration increased to 20 mM, the hydrodynamic diameter of the nanogel greatly increased to be approximately 600 nm. It has also been previously reported [20] that PNIPAm-modified PBA derivative particles were found to be sensitive to glucose at a pH close to the pKa value of APBA (pH of 8.5). The degree of swelling was proportional to the concentration of glucose.…”

“…This change in the solution appearance corresponds to the polymerization of the monomers into cross-linked hydrogel nanoparticles. It has been confirmed that the consumption of APBA is much faster than that of NIPAm in the PNIPAm gel particle formation by polymerization through precipitation [20]. Therefore, the APBA monomers would be completely utilized during the process of polymerization creating coreshell nanogel particles.…”

“…The shelling process was repeated to obtain a thicker layer of the PNIPAm shell. Monodispersed PNIPAm-APBA submicrometric microgel particles with a well-controlled size were also prepared by polymerization through precipitation by Lapeyre et al [20,21]. In their case, they first prepared PNIPAm core microgels by an aqueous free radical polymerization through precipitation.…”

“…Degradable multifunctional [15] and injectable dextran [16] containing microgels composed of glucose-responsive PBA of several hundred nanometers in diameter were synthesized and studied for insulin loading and levels of release in response to glucose. PNIPAm, APBA, and its copolymers have also been studied by many research groups [17][18][19][20][21].…”

Synthesis of Poly(<em>N</em>-isopropylacrylamide) Janus Microhydrogels for Anisotropic Thermo-responsiveness and Organophilic/Hydrophilic Loading Capability

“…Microparticles made of environmentally responsive hydrogels are fascinating candidates for application in drug delivery, 16,17 catalysis, 18 sensing, 19,20 and photonics. 21 Traditional synthetic methods including emulsion polymerization, are used to produce hydrogel microparticles with polydispersity.…”