Yang HWhitby CPTravas-Sejdic J2025-12-092025-12-01Yang H, Whitby CP, Travas-Sejdic J. (2025). pH-responsive compartmentalized alginate beads enable spatial control of sequential nanozyme reactions. Chemical Engineering Journal. 525.1385-8947https://mro.massey.ac.nz/handle/10179/73928Controlling two-step sequential catalytic reactions through external stimuli is a powerful approach for developing responsive chemical systems with potential applications in, for example, logic-gated sensing, process-sequence checking and programmable pollutant remediation. Here, a pH-responsive compartmentalized hydrogel bead system was fabricated via coaxial microfluidic electrospray, in which gold (Au) and iron oxide (Fe<inf>3</inf>O<inf>4</inf>) nanozymes were spatially segregated into distinct domains. We systematically assessed the pH-dependent reactivity of Au and Fe<inf>3</inf>O<inf>4</inf> nanozymes between pH 2 and 9 to evaluate individual catalytic activities. Au nanoparticles (AuNPs) exhibited glucose oxidase (GOx)-like activity at pH 8–9, quantified by a cobalt‑carbonate (Co/CO₃) UV–vis assay, while Fe<inf>3</inf>O<inf>4</inf> NPs showed strong peroxidase (POD)-like activity at pH 2–3, quantified by 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS) oxidation. Leveraging this pH-selective behaviour, the Au-rich domain catalyses glucose oxidation to generate hydrogen peroxide (H<inf>2</inf>O<inf>2</inf>), which then diffuses into the Fe<inf>3</inf>O<inf>4</inf>-rich domain for decomposition. Compared to free and single hydrogel system, the compartmentalized system enhances the reaction efficiency by minimizing interference between nanozymes through spatial separation.CC BY 4.0(c) 2025 The Author/shttps://creativecommons.org/licenses/by/4.0/Compartmentalized nanozymesSequential catalysisHydrogel beadspH-responsiveCoaxial electrosprayJournal article10.1016/j.cej.2025.1706461873-3212journal-articlehttps://orcid.org/0000-0002-1394-2334170646S1385894725114915