Advancing polarity-transcendent design: Development of a photoelectrochemical sensor with extended detection range.

In photoelectrochemical (PEC) sensors, traditional detection modes such as "signal-on", "signal-off", and "polarity-switchable" limit target signals to a single polarity range, necessitating novel design strategies to enhance the operational scope. To overcome this limitation, we propose, for the first time, a "polarity-transcendent" design concept that enables a continuous response across the polarity spectrum, significantly broadening the sensor's concentration detection range. This concept is exemplified in our new "background-enhanced signal-off polarity-switchable" (BESOPS) mode, where the model analyte let-7a activates a cascade shearing reaction of a DNAzyme walker in conjunction with CRISPR/Cas12a, quantitatively peeling off Cu2O-H2 strands at the Cu2O/TiO2 electrode interface to expose the TiO2 surface. This exposure generates an anodic photocurrent at the expense of the cathodic photocurrent from Cu2O/TiO2, facilitating a seamless transition of the target signal from cathodic to anodic. Through systematic experiments and comparative analyses, the BESOPS sensor demonstrates highly sensitive and precise quantification of let-7a, with a detection limit of 2.5 aM and a broad operating range of 10 aM to 10 nM. Its performance exceeds most reported sensor platforms, highlighting the significant potential of our polarity-transcendent design in expanding the operational range of PEC sensors. This innovative approach paves the way for developing next-generation PEC sensors with enhanced applicability and heightened sensitivity in various critical fields.

Target-Triggered Multiple-Polarity-Switchable Multiplexed Photoelectrochemical Platform.

Convenient and accurate quantification of disease-relevant multitargets is essential for community disease screening. However, in the field of photoelectrochemical (PEC) sensors for multisubstance detection, research on the continuous detection of multiple targets using a polarity-switching mode is scarce. In this study, a multiplexed PEC bioassay was developed based on a target-triggered "anodic-cathodic-anodic" multiple-polarity-switchable mode. Employing miRNA-21 and miRNA-141 as model analytes, the photosensitive material combinations of Cu2O/gold nanoparticles (AuNPs)/TiO2 and CdS/AuNPs/TiO2 were successively formed through the specific binding of different whisker branches of Whisker-DNA to Cu2O-H1 and the CdS-tripod DNA ring, respectively. This process reverses the photocurrent polarity from anodic to cathodic and then back to anodic upon detecting different targets, resulting in the high-sensitivity quantification of various biological targets with reduced interference. To enhance the device's utility and affordability in community disease screening, integrating a capacitor and a multimeter-smartphone connection simplifies the assembly and reduces costs. In developing the PEC sensor, the device demonstrated linear detection ranges for miRNA-21 and miRNA-141 from 0.01 fM to 10 nM. Detection limits for miRNA-21 and miRNA-141 were established at 3.2 and 4.3 aM, respectively. The innovative target-triggered multiple-polarity-switchable mode offers adaptability for other multitarget detections by simply modifying the structure of the whisker branches and the combination of photosensitive materials.