Thermal self-regulatory smart biosensor based on horseradish peroxidase-immobilized phase-change microcapsules for enhancing detection of hazardous substances

Abstract

Conventional enzyme-based biosensors are highly sensitive to operation temperature due to a strong temperature dependency of biocatalytic activity. Aiming to enhance the biosensing detection of hazardous substances at high ambient temperatures, we focused on the design and construction of a thermal self-regulatory smart biosensor through an innovative combination of phase change material (PCM) and bioelectrocatalytic material. A bioelectrocatalytic phase-change microcapsule system was first fabricated by microencapsulating n-eicosane as a PCM core in the TiO2 shell and then depositing polypyrrole (PPy) as an electroactive coating layer on the surface of TiO2 shell, followed by immobilizing horseradish peroxidase on the surface of PPy coating layer through physical adsorption. The resultant microcapsules exhibit a regular spherical morphology and layer-by-layer core–shell microstructure with the desired chemical compositions. The microcapsules not only exhibit a good thermal management ability to perform effective temperature regulation under a latent-heat capacity of approximately 115 J/g, but also reveal high thermal impact resistance and good thermal cycle stability for the long-term thermal management application in biosensors. A working electrode was modified with the microcapsules obtained above and then used to construct an electrochemical biosensing system imparted with a thermal self-regulation capability. With a high sensitivity of 5.571 µA·L·µmol−1·cm−2 and a low detection limit of 5.384 µmol/L at 55 °C, the resultant smart biosensor exhibits a better determination ability to detect catechol as a model hazardous substance at high operation temperatures than conventional biosensors thanks to the in-situ thermal management derived from its n-eicosane core. This study provides a new approach for development of thermal self-regulatory smart biosensors with an enhanced identification capability to detect hazardous substances over a wide range of temperatures.