Dual carminic acid/hemin-marked DNA probes for simultaneously detecting CV-A16 and EV-A71 based on the mechanism of dimer to monomer transition

This study aimed to prepare two hairpin-structure DNA probes by conjugating carminic acid (CA) or hemin into two ends of specific genes of coxsackievirus A16 (CV-A16) and enterovirus A71 (EV-A71) (probe CV-A16-CA and probe EV-A71-hemin ). Then, probe CV-A16-CA and probe EV-A71-hemin as the signal molecules were adsorbed onto NH 2 -MIL-53 (Al) (MOF). Based on these biocomposites, an electrochemical biosensor with dual-signal outputs for simultaneous assay of CV-A16 and EV-A71 was constructed. The stem-loops of probes switched both CA and hemin monomer to dimer, reducing the electrical activity of both CA and hemin. Subsequently, the target-induced opening of the stem-loop switched both CA and hemin dimers to monomers, resulting in two nonoverlapping increasing electrical signals. This sensitively reflected the concentration of target CV-A16 and target EV-A17 ranging from 10 −10 to 10 −15  M with a detection limit of 0.19 and 0.24 fM. This strategy was mainly applied to the simultaneous determination of target CV-A16 and target EV-A17 in 100% serum with satisfactory results. The MOF combined with the high loading capacity broke through the intrinsic limitation on sensitivity using the traditional methods. An increase of three orders of magnitude was observed. This study involved simple one-step detection, and only a simple replacement of a gene could trigger its potential in clinical and diagnostic applications.