Chitosan-Covered Pd@Pt Core–Shell Nanocubesfor Direct Electron Transfer in Electrochemical Enzymatic GlucoseBiosensor

摘要

Development of biosensors with high sensitivity, high spatial resolution, and low cost has received significant attention for their applications in medical diagnosis, diabetes management, and environment-monitoring. However, achieving a direct electrical contact between redox enzymes and electrode surfaces and enhancing the operational stability still remain as challenges. Inorganic metal nanocrystals (NCs) with precisely controlled shape and surface structure engineered with an appropriate organic coating can help overcome the challenges associated with their stability and aggregation for practical biosensor applications. Herein, we describe a facile, room-temperature, seed-mediated solution-phase route to synthesize monodisperse Pd@Pt core–shell nanocubes with subnanometer-thick platinum (Pt) shells. The enzyme electrode consisting of Pd@Pt core–shell NCs was first covered with a chitosan (CS) polymer and then glucose oxidase (GOx) immobilized by a covalent linkage to the CS. This polymer permits covalent immobilization through active amino (−NH) side groups to improve the stabilityand preserve the biocatalytic functions while the Pd@Pt NCs facilitateenhanced direct electron transfer (DET) in the biosensor. The resultantbiosensor promotes DET and exhibits excellent performance for thedetection of glucose, with a sensitivity of 6.82 μA cm^–2 mM^–1 and a wide linear range of 1–6 mM.Our results demonstrate that sensitive electrochemical glucose detectionbased on Pd@Pt core–shell NCs provides remarkable opportunitiesfor designing low-cost and sensitive biosensors.