Enhanced Anti-Interference Photoelectrochemical DNA Bioassay: Grafting a Peptide-Conjugated Hairpin DNA Probe on a COF-Based Photocathode

Precise and sensitive analysis of specific DNA in actual human bodily fluids is crucial for the early diagnosis of major diseases and for a deeper understanding of DNA functions. Herein, by grafting a peptide-conjugated hairpin DNA probe to a covalent organic framework (COF)-based photocathode, a robust anti-interference photoelectrochemical (PEC) DNA bioassay was explored, which could specifically resist potential interference from nonspecific proteins and reducing species. Human immunodeficiency virus (HIV) DNA was used as the target DNA (tDNA) for the PEC DNA bioassay. The vinyl-functionalized COF (COF-V) was modified with meso-tetra(4-carboxyphenyl)-porphine (TCPP) and polydopamine (PDA) to fabricate a PDA/TCPP/COF-V photocathode, which served as the photocurrent signal transducer. Toward the unconventional recognition element, a hairpin DNA probe (hDNA) was efficiently linked with a linear zwitterionic peptide (LZP) to form the LZP-hDNA bioconjugate, which was then grafted onto the COF-based photocathode. The grafting of the LZP generated a sturdy anti-interference interface on the signal transducer. For tDNA probing, AgInS₂ (AIS) quantum dots acted as signal quenchers, marked on signaling DNA (sDNA) to obtain AIS-sDNA labeling, and a striking drop in the photocurrent signal was achieved through λ-exonuclease (λ-Exo)-aided target recycling. This novel peptide-conjugated hairpin DNA probe endowed the PEC DNA bioassay with an impressive anti-interference property without requiring tedious steps. By combining the excellent photoelectric properties of the COF-based photocathode with an effective signaling strategy, accurate and sensitive results for tDNA probing were achieved.