Fabrication of Co-Doped Covalent Organic Framework Nanosheets with Mild Interlayer Stress for Quantitative Detection of Alzheimer’s Disease Biomarkers

Alzheimer’s disease (AD) seriously affects human health worldwide. Nicotinamide adenine dinucleotide (NADH) and glutamate are important biomarkers of AD, which play an indispensable role in the pathogenesis of AD. Herein, two ligands were used to synthesize a layered covalent organic framework (TPCOF) via amide bond formation, which was loaded with cobalt to obtain Co-TPCOF. TPCOF has a twisted 2D layered structure, along with large interlayer spacing and porosity, enabling precise Co coordination and stable loading of metal nanoparticles/enzymes to support electrocatalysis. A Co-TPCOF was immobilized on a screen-printed electrode (SPE) to catalyze the oxidation of NADH. After that, the oxidation product NAD+ of NADH and the NAD+-dependent dehydrogenase immobilized on the electrode jointly catalyzed the glutamate in the solution. COFs’ unique structures endow Co-TPCOFs with excellent NADH catalytic activity. The Co-TPCOF/SPE showed good linearity for NADH (10 nM-5 mM, LOD 7.07 nM) and GDH/Co-TPCOF/SPE for glutamate (50 μM-5 mM, LOD 3.74 μM). The biosensor can sensitively detect trace NADH and glutamate in human serum, providing an adequate technical means and theoretical reference for the pathological research of AD.