Non-noble metals coordinated covalent organic frameworks as oxidase-like biocatalysts for light-responsive biomarker sensing

Metal-based enzyme-mimetic biocatalysts exhibit much better enzyme-like activity than metal-free biocatalysts. At the same time, both non-noble and noble metal-based catalysts have been proven to exhibit good biocatalytic activity. It is a great challenge to find extremely sensitive and adaptable biosensors with biocatalytic activity in biotechnology and medical diagnostics. For performance improvement and cost reduction, the development of non-noble metal-based biocatalysts is still of great significance. Here, we disclose that the covalent organic frameworks (COFs) coordinated by cobalt (Co) or nickel (Ni) with specific oxidase-like (OXD-like) activities can serve as intelligent artificial enzymes for light-augmented biocatalytic sensing of biomarkers. Because of the effects of metallic elements on the band gap adjustment, the Ni-COF exhibited the most efficient, selective, and light-responsive OXD-like biocatalytic activity (Km = 0.91 mM, Vmax = 1.50 μM s-1). Moreover, COFs loading metals show superior light-augmented biocatalytic detection capabilities. Notably, Ni-COF exhibits the most efficient and multifaceted diagnostic activity, including the extremely low limit of detection (LOD): 0.34 μM for glutathione and 0.54 μM for L-cysteine, which enables visual assays for abundant reducibility biomarkers. This study offers a unique and efficient non-noble metal-coordinated COF biocatalyst for high-sensitive and low-cost colorimetric detection. It also provides new insights into the design of non-noble metal elements in COF materials with better enzyme-like activities in biocatalytic and biomedical applications.