Ferricyanide stimulated cathodic photoelectrochemistry of flower-like bismuth oxyiodide under ambient air: A general strategy for robust bioanalysis

Most of the current cathodic photoelectrochemical (PEC) bioassays either rely on dissolved oxygen as a signal reporting molecule or are interfered by atmospheric oxygen (if using other molecules than oxygen as the signaling molecule), which leads to their monotonous detection mechanism, vulnerable/nonadjustable performance, complicated instrument and time consuming operation. Herein, we develop an innovative, oxygen independent cathodic PEC bioassay with distinct advantages of robust performance, simple instrument/facile operation, as well as sensitive and prompt readout. Specifically, taking the ochratoxin A (OTA) as a model analyte, the detection combines the largely augmented photocurrent of flower-like bismuth oxyiodide (BiOI) microspheres by potassium ferricyanide (K 3 [Fe(CN) 6 ]) under aerobic conditions, the highly selective aptamer recognition as well as the powerful exonuclease-catalyzed target recycling amplification. Removal of the surface immobilized DNA under the cooperative effects of OTA induced double-stranded DNA (dsDNA) dissociation and RecJ f exonuclease mediated digestion of the released single-stranded DNA results in enhanced flux of K 3 [Fe(CN) 6 ] to the photoelectrode, enables a “signal-on” and “label-free” mode for OTA detection with high sensitivity and good selectivity. It also shows acceptable results for the detection of OTA spiked in wine samples. Since the detection takes place in ambient air and is not interfered by the atmospheric oxygen, this facile and robust cathodic PEC biosensing system displays promising applicability for on-site and real-time diagnosis. More significantly, it is extensible as a general strategy for versatile cathodic PEC bioanalysis.