An enzyme-free glucose sensor based on a Ni-doped triblock hydrogel for ionic conduction and fruit testing

We present an enzyme-free glucose sensor for on-site fruit testing based on a Ni-doped triblock hydrogel that couples ionic-channel conduction with hydrogen-bond–reinforced mechanics. In the hydrogel, the NiCl 2 -hydrogel (Ni-HG) pair generates continuous ion pathways that enhance charge transport, while phytic acid establishes multi-point hydrogen bonding and moisture retention, yielding a robust, highly adhesive network that conforms to diverse electrode formats. Within this hydrated, ion-permeable scaffold, Ni 2 + /Ni 3+ (Ni(OH) 2 /NiOOH) functions as a built-in redox mediator, enabling selective, enzyme-free oxidation of glucose in alkaline media. Under optimized conditions, the Ni-HG/GCE sensor delivers a broad linear range of 0.05–6.6 mM, limit detection of 10 μM, with high selectivity against common electroactive species, good repeatability, and reliable performance in real fruit samples. The hydrogel architecture supports rapid amperometric response and stable operation, while its strong adhesion and mechanical compliance facilitate integration with screen-printed electrodes for low-cost, disposable use. These attributes establish a practical platform for fast, sensitive, and selective glucose quantification in fresh produce and point-of-use food monitoring.