A universal “signal-on” and “photocurrent-polarity-switching” responsive photoelectrochemical aptasensing platform for dual-target assay based on two-hanging-arms tetrahedral DNAs

The independent detection of photocurrent changes caused by different targets on a single photoelectrochemical (PEC) sensing platform is a key problem for dual-target PEC assay. Herein, taking influenza A (H1N1) hemagglutinin (HA) and SARS-CoV-2 spike receptor-binding domain (RBD) proteins as models, a universal PEC aptasensing platform with two-hanging-arms tetrahedral DNAs (TDN) was developed for independent detections of dual targets based on HA-induced "signal-on" and RBD-induced "photocurrent-polarity-switching" photocurrent-response strategies. The thiol-labeled TDN with two hanging arms that could capture the aptamers of HA and RBD were immobilized on ZIF-67-derived Co/NC@CdS dodecahedra via Cd-S bond to form Co/NC@CdS-TDN-Apts hybrids. When HA (or RBD) was present, the aptamer was detached from Co/NC@CdS-TDN-Apt hybrids due to the specific binding with HA (or RBD). After magnetic separation, tDNA1-Ag2S (or tDNA2-CuO@phosphomolybdic acid hydrate (PMo12)) connected with Co/NC@CdS-TDN via the hybridization reaction between tDNA1 (or tDNA2) and the hanging arms of TDN, causing an enhanced anodic photocurrent (or a distinct cathodic photocurrent) owing to the enhancing effect of Ag2S nanoparticles (or the photocurrent-polarity-switching effect of CuO@PMo12 octahedra). With different photocurrent polarities, independent detection of HA and RBD was achieved. By altering the related aptamers, this PEC aptasensing platform can be extended to another dual-target assay.