Combined Transition-Metal/Enzyme Dual Catalytic System for Highly Intensive Glow-Type Chemiluminescence-Functionalized CaCO₃ Microspheres

Abstract

Chemiluminescent (CL) reagent <i>N</i>-(4-aminobutyl)-<i>N</i>-ethylisoluminol (ABEI)-functionalized CaCO₃ microspheres with a dual catalytic system consisting of Co²⁺ and horseradish peroxidase (HRP) (HRP/ABEI/Co²⁺-CaCO₃ MPs) were synthesized via a facile method for the first time. Co²⁺ was linked onto HRP/ABEI/Co²⁺-CaCO₃ MPs through both coordination and electrostatic interactions, while ABEI and HRP were encapsulated into HRP/ABEI/Co²⁺-CaCO₃ MPs via electrostatic interaction and adsorption. The as-prepared HRP/ABEI/Co²⁺-CaCO₃ MPs possessed a spherical shape with a mean size of 1.3 ± 0.3 μm and porous structure. They exhibited highly intensive "glow-type" CL emission, which was visible by naked eyes in a dark room for 10 h. The HRP/ABEI/Co²⁺-CaCO₃ with dual catalytic system produced more intensive "glow-type" CL emission in the first 3 h as compared with ABEI/Co²⁺-CaCO₃ and HRP/ABEI/CaCO₃, both of which merely possessed a single catalyst in their systems. Moreover, the CL intensity of HRP/ABEI/Co²⁺-CaCO₃ MPs during the first hour outperforms all the previously reported long-lasting chemiluminescence-functionalized micro/nanomaterials (CF-M/NMs), such as the firefly-mimicking intensive and long-lasting ABEI/Co²⁺/chitosan hydrogels. The outstanding CL performance of HRP/ABEI/Co²⁺-CaCO₃ MPs is attributed to high loading of CL reagents and catalysts in CaCO₃ MPs and high catalytic efficiency and good stability of the dual catalytic system consisting of Co²⁺ complex and HRP. The HRP/ABEI/Co²⁺-CaCO₃ MPs are neutral materials with highly intensive and persistent emission as well as good biocompatibility, rendering them excellent biomaterials for various bioassays. We envisage that this excellent material holds great promise in vast application fields, such as bioassays, bioimaging, environmental monitoring, and life science etc.