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Item pH-responsive compartmentalized alginate beads enable spatial control of sequential nanozyme reactions(Elsevier BV, Netherlands, 2025-12-01) Yang H; Whitby CP; Travas-Sejdic JControlling 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 (Fe3O4) nanozymes were spatially segregated into distinct domains. We systematically assessed the pH-dependent reactivity of Au and Fe3O4 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 Fe3O4 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 (H2O2), which then diffuses into the Fe3O4-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.Item Dual-network hydrogel capsules for controlled molecular transport via pH and temperature responsiveness(Elsevier Inc, 2025-01) Yang H; Whitby CP; Travas-Sejdic JWe have developed innovative core-shell hydrogel capsules with a dual-network shell structure designed for precise control of molecular transport in response to external stimuli such as pH and temperature. The capsules were fabricated using a combination of microfluidic electrospray techniques and water-in-water (w/w) core-shell droplets templating. The primary network of the shell, calcium alginate (Ca-Alg), with a pKa around 3.4, exhibits sensitivity to pH. The secondary network of the shell, poly(ethylene glycol) methyl ether methacrylate (PEGMA), undergoes a volume phase transition near 60 °C. These properties enable precise molecular transport control in/out of the capsules by modulating the surface charges through varying pH and modifying pore size through temperature changes. Moreover, the dual-network shell structure not only significantly enhances the mechanical strength of the capsules but also improves their stability under external stimulus, ensuring structural integrity during the transport of molecules. This research lays the groundwork for further investigations into the multimodal stimuli-responsive hydrogel systems to control molecular transport, important in applications such as sensors and reactors for chemical cascade reactions.