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

Chemiluminescent (CL) reagent N-(4-aminobutyl)-N-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.