Tailoring the glucose-responsive volume phase transition behaviour of Ag@poly(phenylboronic acid) hybrid microgels: from monotonous swelling to monotonous shrinking upon adding glucose at physiological pH

We develop a class of polymer–inorganic hybrid microgels, comprising Ag nanoparticle cores covered by a poly(3-acrylamidophenylboronic acid-co-2-(dimethylamino)ethyl acrylate) [p(3-VAPBA-co-DMAEA)] gel shell, to demonstrate that the volume phase transition behaviour of poly(phenylboronic acid) gels can be tailored from exhibiting monotonous swelling to monotonous shrinking upon adding glucose at a physiological pH of 7.4, via varying the feeding ratio of monomers DMAEA (introducing positive charges by ionization) to 3-VAPBA (introducing negative charges through the formation of a glucose–boronate complex) in the synthesis. The counterbalance of the positive and negative charges at particular glucose concentrations is a key parameter to enable this tailoring. Accompanied by this tailoring, the photoluminescence of the hybrid microgels is tuned from glucose-responsive “turn-off” to “turn-on”, in which the latter displays an improved glucose-sensing performance in both artificial tear fluid (a model for low glucose concentrations) and urine (for high glucose concentrations).