Fig. 4.

AA-mediated pH microenvironments of PEG hydrogels. a Schematic representation of the copolymerization of AA with PEG and the pH of the microenvironments of poly(PEG-co-AA) hydrogel particles with different AA contents (0, 5, 15, 30, and 45%). The insets are their corresponding fluorescent photographs. b Absorbance at 652 nm and visual colors of oxTMB catalyzed by MNP@PEG (black bars) and MNP@PEG-co-AA (red bars) in PBS (pH 7.0) using H₂O₂ as a substrate or coupled with the GOX-catalyzed glucose oxidation reaction. c Relative activity changes of MNPs encapsulated in different PEG-co-AA with AA contents ranging from 0 to 45%. Assay conditions: MNP@PEG-co-AA was incubated with 1.25 mM H₂O₂ and 43.75 μM TMB in PBS (pH 7.0), and the absorbance was monitored at 652 nm