Glucose Oxidase/ <i>o</i> -Phenylenediamine Interfaces on Dendritic Pt Microneedles for Highly Sensitive and Selective Continuous Glucose Monitoring Sensors

Microneedle-based glucose sensors offer a minimally invasive and wearable platform for real-time monitoring. However, conventional enzyme immobilization methods often lack spatial precision and show limited compatibility with miniaturized electrode architectures. Here, we present an electrodeposition strategy for localized and controlled immobilization of glucose oxidase at microneedle tips. Dendritic platinum was engineered via potentiostatic diffusion-limited growth, significantly increasing electroactive surface area and enzyme loading capacity. This yielded an enhanced catalytic response with a maximum current density of ∼200 μA/cm² during glucose oxidation, thereby improving sensitivity. To ensure selectivity, <i>o</i>-phenylenediamine electropolymerization time was optimized to balance glucose permeability with suppression of electroactive interferents, reducing interferent-to-glucose current ratios to below 4.0% in artificial interstitial fluid. In human trials, the microneedle sensor operated stably and exhibited a sensitivity of 137.7 nA·(mg/dL)^-1 (≈2.48 μA·mM^-1), with strong linearity (<i>R</i>² = 0.940) across 82-211 mg/dL (≈4.6-11.7 mM). This scalable and tunable fabrication approach addresses the dual challenge of achieving high sensitivity and selectivity in miniaturized enzymatic sensors, offering broad potential for wearable biosensing and personalized healthcare technologies.