An ultrasensitive aptasensor for 8-hydroxy-2′-deoxyguanosine of human urine detection based on COFTAPB-DMTP@MWCNT-COOH nanocomposites and CeFeOx-C@Au@Apt nanoprobe

An ultrasensitive electrochemical aptasensor was proposed for quantitative detection of 8-hydroxy-2′-deoxyguanosine (8-OHdG). Covalent organic framework (COFTAPB-DMTP) and carboxylated multi-walled carbon nanotubes (MWCNT-COOH) were used to prepare COFTAPB-DMTP@MWCNT-COOH (TAPB, 1,3,5-tris(4-aminopheny) benzene; DMTP, 5-dimethoxybenzene-1,4-dicarboxaldehyde) nanocomposites as the electrode sensing platform. COFTAPB-DMTP@MWCNT-COOH displayed excellent biocompatibility, a large specific surface area, and efficient conductivity, facilitating accelerated electron transfer rates. Furthermore, the cerium iron oxide–carbon nanocomposites (CeFeOx-C) derived from UiO-66-CeFe bimetallic organic framework showed outstanding peroxidase-like activity. Gold nanoparticles-modified CeFeOx-C effectively loads 8-OHdG-aptamer, yielding novel CeFeOx-C@Au@Apt nanoprobes. CeFeOx-C@Au@Apt nanoprobes were immobilized on the electrode via base pairing to thiolated cDNA and the signal change was detected in the environment of hydroquinone and H2O2. In the presence of 8-OHdG, Apt-cDNA unwound, leading to CeFeOx-C@Au@Apt to fall off the electrode, thereby causing distinguishable electrochemical variations. The optimized aptasensor for 8-OHdG showed a wide linear range from 10 fg/mL to 50 ng/mL, with a low detection limit of 1.06 fg/mL. The reliability of this aptasensor was confirmed using human urine samples, yielding satisfactory results, highlighting its potential in evaluating the extent of oxidative DNA damage. Crucially, the aptasensor's ideal performance position it as a promising approach for detecting various biomolecules through modifications the aptamers sequence modifications.