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Rational utilization of the rich light‐bio‐matter interplay taking place in single‐cell analysis represents a new technological direction in the field. The light‐fueled operation is expected to achieve advanced photoelectrochemical (PEC) single‐cell analysis with unknown possibilities. Here, a PEC nanoreactor capable of single‐cell sampling and near zero‐background Faradaic detection of intracellular microRNA (miR) is devised by the construction of a small reaction chamber accommodating the target‐triggered hybridization chain reaction for binding the metallointercalator of [Ru(bpy)2(dppz)]2+ as the signal reporter. Light stimulation of the dsDNA/metallointercalator adduct will induce the generation of photocurrents, underpinning a zero‐biased and near zero‐background PEC method toward Faradaic detection of non‐electrogenic miR at the single‐cell level. Using this nanotool, lower miR concentration in the near‐nucleus region than that in the main cytosol was revealed. [ABSTRACT FROM AUTHOR]

Sensitive and specific detection of DNA is of great significance for clinical diagnosis. In this paper, an effective cascade signal amplification strategy was introduced into photoelectrochemical (PEC) biosensor for ultrasensitive detection of human T-cell lymphotropic virus type I (HTLV-I) DNA. This proposed signal amplification strategy integrates λ-exonuclease (λ-Exo) aided target recycling with hybridization chain reaction (HCR) and enzyme catalysis. In the presence of target DNA (tDNA) of HTLV-I, the designed hairpin DNA (h 1 DNA) hybridized with tDNA, subsequently recognized and cleaved by λ-Exo to set free tDNA. With the λ-Exo aided tDNA recycling, an increasing number of DNA fragments (output DNA, oDNA) were released from the digestion of h 1 DNA. Then, triggered by the hybridization of oDNA with capture DNA (cDNA), numerous biotin-labeled hairpin DNAs (h 2 DNA and h 3 DNA) could be loaded onto the photoelectrode via the HCR. Finally, avidin-labeled alkaline phosphatase (avidin-ALP) could be introduced onto the electrode by specific interaction between biotin and avidin. The ALP could catalyze dephosphorylation of phospho-L-ascorbic acid trisodium salt (AAP) to generate an efficient electron donor of ascorbic acid (AA), and thereby greatly increasing the photocurrent signal. By utilizing the proposed cascade signal amplification strategy, the fabricated PEC biosensor exhibited an ultrasensitive and specific detection of HTLV-I DNA down to 11.3 aM, and it also offered an effective strategy to detect other DNAs at ultralow levels. [ABSTRACT FROM AUTHOR]

We report herein the energy transfer (ET) between semiconducting polymer dots (Pdots) and gold nanoparticles (Au NPs) in a photoelectrochemical (PEC) system and its feasibility for cathodic bioanalysis application. Specifically, COOH-capped Pdots were first fabricated and then assembled onto the indium-tin oxide (ITO) surface, followed by the modification of single-strand (ss) DNA probe (pDNA). After the DNA hybridization with the Au NPtethered complementary ssDNA (Au NP-tDNA), the Au NPs were brought into the close proximity of Pdots. Upon light stimulation, photoluminescence (PL) was annihilated, fluorescence was attenuated, and the photocurrent intensity was evidently decreased. This ET-based PEC DNA sensor exhibited a linear range from 1 fM to 10 pM with a detection limit of 0.97 fM at a signal-to-noise ratio of 3. The present work first exploited the ET between Pdots and Au NPs, and we believe this phenomenon will spark new interest in the study of various Pdots-based ET-influenced PEC systems and thus catalyze increasing studies for specific bioanalytical purposes. [ABSTRACT FROM AUTHOR]

An enhanced photoelectrochemical (PEC) aptasensor was developed by coupling exciton energy transfer (EET) with exonuclease aided target recycling. Thrombin was selected as the target analyte. CdS quantum dots (QDs) as energy donors were first modified on the TiO2 film to form a TiO2/CdS heterostructure, and then complementary DNA (cDNA) of the thrombin aptamer probe (pDNA) was immobilized. Au nanoparticles (AuNPs) as energy acceptors were labeled at the 3′ end of pDNA to form AuNP-pDNA composites. After pDNA hybridized with cDNA, the EET occurred and the photocurrent reduced evidently. When the mixture of thrombin and RecJ exonuclease was introduced, pDNA specifically bound with thrombin, leading to the separation of AuNP-pDNA composites from the electrode. As RecJ exonuclease could cleave single-strand pDNA from 5′-3′, the captured thrombin was set free and it recurrently binds with the rest of pDNA. As a result, the EET was broken, to a large extent, and the photocurrent clearly picked up. This signal-on PEC aptasensor shows a low detection limit and good selectivity for target analysis. [ABSTRACT FROM AUTHOR]

Target biomarker detection with high accuracy in biological sample is necessary for the constructed immunoassays. Herein, a novel and enhanced cathodic immunosensor supported by photoanode was designed for sensitive and specific detection of human chorionic gonadotropin (HCG). Specifically, the electrode of TiO 2 nanotube with N doping (TiO 2 :N) was fabricated and assembled with AgInS 2 quantum dots (QDs) to acquire the TiO 2 :N/AgInS 2 photoanode. For the sensing cathode, Pt nanoparticles (NPs) were decorated on carbon nanotubes (CNTs) to prepare the CNT/Pt cathodic matrix and was used to modify capture HCG antibody (Ab). In this photoelectrochemical (PEC) sensing system, the TiO 2 :N/AgInS 2 photoanode served as the signal-converting element to produce prominent current signal, while the immune recognition events occurred on the sensing cathode to evidently change the initial current signal from steric hindrance effect. Profiting by excellent photoelectric property and good anti-interference ability of this featured PEC system, the developed cathodic immunosensor demonstrated high sensitivity and specificity for the detection of target HCG antigen (Ag). This photoanode-supported cathodic sensing strategy provided a potential path forward to exploit other enhanced PEC immunosensors in the application of biological samples. An efficient and feasible photoanode-supported cathodic sensing strategy was proposed to develop a robust PEC immunosensor for sensitive and specific detection of HCG in the biological sample. [Display omitted] • An effective photoanode-supported cathodic sensing strategy was proposed to build robust PEC immunosensor. • The TiO 2 :N/AgInS 2 photoanode as the signal-converting element showed excellent photoelectric property. • The CNT/Pt cathodic matrix with good electrical conductivity and catalytic activity was used to anchor Ab. • The PEC immunosensor demonstrated high sensitivity and specificity for target HCG detection. [ABSTRACT FROM AUTHOR]

An efficient two-electrode strategy with the amplification of BOD label was first put forward to develop a novel PEC biosensing platform with high sensitivity and good selectivity in real biological matrix. [Display omitted] • An efficient two-electrode strategy amplified by BOD labelling was proposed to build PEC biosensing platform. • The ZIS/Fe:TiO 2 photoanode as signal conservation element presented a remarkable photocurrent output. • The BOD-guided signaling strategy for O 2 reduction reaction could change current detection signal evidently. • The PEC biosensing platform demonstrated high sensitivity and good selectivity in real biological matrix. Herein, a novel and robust two-electrode photoelectrochemical (PEC) biosensing platform amplified by bilirubin oxidase (BOD) labelling was reported. This two-electrode operating system was composed of photoanode and sensing biocathode. Carcinoembryonic antigen (CEA) was utilized as a model for probing. Specifically, Fe3+-doped TiO 2 (Fe:TiO 2) nanotubes were first prepared and then deposited with ZnIn 2 S 4 (ZIS) nanocrystals to develop the ZIS/Fe:TiO 2 photoanode. Toward sensing biocathode, after carbon nanotubes (CNTs) and Au nanoparticles (NPs) were modified on conductive glass, an Au/CNT cathodic substrate was fabricated to anchor the CEA aptamer. Complementary DNA (cDNA) of the CEA aptamer was labelled with BOD to form the cDNA-BOD conjugate that amplified the signal through DNA hybridization. Target detection hinged on an evident decline in the current signal generated by terminated amplification of the BOD labels and evident steric hindrance of the captured CEA molecules. Profiting from excellent PEC property of the ZIS/Fe:TiO 2 photoanode and good oxygen-reduction capability of the BOD labels, the two-electrode PEC biosensing platform exhibited high sensitivity. Because of the division of biorecognition with photoanode, the platform also showed satisfactory selectivity in biological matrix. This elegant two-electrode strategy offers a promising path for seeking other robust PEC biosensors applying in complex biological samples. [ABSTRACT FROM AUTHOR]