Herein a photoelectrochemical (PEC) and electrochemical (EC) dualmode biosensor with cationic N,N-bis(2-(trimethylammonium iodide)propylene)perylene-3,4,9,10-tetracarboxydiimide (PDA + )-decorated multifunctional DNA spheres in situ generated on an electrode was proposed for sensitive and accurate detection of miRNA-141. By employing a target-related ternary "Y" structure cleavage cycling reaction, the target DNA was converted into massive output DNA anchored on a TiO 2 substrate, and hence triggering the rolling circle amplification (RCA) reaction. Upon addition of magnesium ions and PDA + , the long DNA tails of the RCA product were condensed in situ to form multifunctional DNA spheres. Notably, the distance between DNA spheres and TiO 2 substrate was short, thus forming an effective PDA + −TiO 2 sensitization structure with fast electron transfer for acquiring an extremely enhanced PEC signal with assistance of ascorbic acid (AA). Meanwhile, cationic PDA + with a large planar π−π skeleton enabled favorable redox-activity and substantial loading on DNA spheres, directly producing an obviously well-defined cathodic peak for implementing EC biodetection on the same sensing platform. This approach not only avoided difficult assembly of diverse signal indicators but also significantly improved the sensitivity by utilizing cleavage cycling amplification and RCA strategies. Moreover, the distinct dual-response signals from two different transduction mechanisms and independent signal transduction can mutually support accuracy improvement. As a result, detection ranges of 0.1 fM to 1 nM for PEC and 2 fM to 500 pM for EC were obtained for miRNA-141, providing a universal and efficient biosensing method with promising applications in bioanalysis and early disease diagnosis.

In this work, a click reaction-triggered wavelengthresolved dual-signal output photoelectrochemical (PEC) biosensor with DNAzymes-assisted cleavage recycling amplification was proposed for sensitive triplex metal ions assay. Substantial DNA fragments azido-S 1 and azido-S 2 , derived from the Pb 2+ (target 1) and Mg 2+ (target 2) dependent cleavage cycle of DNAzymes, respectively, were grafted efficiently on the same alkynyl-DNA (capture DNA) modified electrode via the Cu 2+ (target 3) and ascorbic acid (AA) cocatalyzed click reaction, which thus could be subsequently used for immobilization of two different photoactive nanomaterials labeled with single DNA to generate distinguishing dual-signal output for simultaneously sensitive detection of Pb 2+ and Mg 2+ . Furthermore, the control variable method was used for detecting Cu 2+ by altering the concentration of Cu 2+ in the click reaction. Owing to the usage of the click reaction and target-converted signal amplifying strategy, the utilization rate of cycle output DNAs was largely increased, significantly improving the detection sensitivity of the proposed approach. As a result, low detection limits down to picomolar were acquired for the detection of Pb 2+ , Mg 2+ , and Cu 2+ , providing a versatile, efficient, and sensitive PEC method for multiple assays of various targets such as metal ions, small molecules, and tumor markers.

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In this work, hydrazine-functionalized perylene diimide derivative supramolecular (HPDS), a novel self-enhanced donor–acceptor-donor (D-A-D) type aggregates with excellent photoelectric activity, was synthesized by a facile one-pot green route and further applied in construction of coreactant-free photoelectrochemical (PEC) biosensor for ultrasensitive DNA assay. Impressively, the HPDS formed by D-A-D units not only possessed effectively shorted electron-transfer path between donor and acceptor, but also presented a desiring aggregate state via the π–π stacking of perylene core and hydrogen bonding of the terminal moiety, thereby acquiring a high density electron flow for generating the extremely high PEC signal. Experimental data showed that the well film-formed HPDS aggregate could produce an exciting photocurrent intensity about 6-fold stronger than that of precursor perylene dianhydride with donor N2H4 in detection buffer and even 12-fold than that of perylene dianhydride only. In this respect, the resultant HPDS aggregate as a novel self-enhanced PEC signal tag was adopted to fabricate the coreactant-free PEC biosensor with the help of target dual-recycling-induced bipedal DNA walker cascade amplification strategy for ultrasensitive DNA (a fragment of TP53 gene) assay. The proposed biosensor showed a high sensitivity with a low detection limit down to femtomole level, providing a new avenue for sensitive bioanalysis and clinical diagnosis.