Photoelectrochemical Biosensor Research Articles

Triple-Mode Sensor Coupled by Photoelectrochemical, Electrochromic, and Spectral Signals for Sensitive Visualized Detection of Nonylphenol.

Conventional photoelectrochemical (PEC) biosensors suffer from the difficulty of visualizing rapid detection and limited accuracy due to a single-signal output. Here, we develop a PEC, electrochromic (EC), and spectral (ST) triple-mode platform for the sensitive visualized detection of nonylphenol (NP). First, the reasonably stepped Fermi energy level arrangement between the defective TiO2 anode and MoO3 cathode enables a remarkable photocurrent response (Mode 1). Then, MoO3 itself is a widely used EC candidate, which can react with free Li-ions to form a LixMoO3 intermediate, and its color will change from white to blue accordingly (Mode 2). More importantly, MoO3 is also a Li-ion host and the potential of LixMoO3 depends on the inserted Li-ion quantity deduced by spectral analysis on residual Li-ions in the electrolyte (Mode 3). The EC signal endows fast visual detection, and triple-mode cross-validation improves reliability and accuracy. As a result, this PEC-EC-ST triple-mode molecularly imprinted sensor has a wide linear range (1-5000 μg L-1), a low detection limit (0.18 μg L-1), selectivity, stability, reproducibility, and actual sample detection capability. This innovative multimode platform not only improves detection reliability but also broadens applications of electrochromic/energy storage materials in biosensors.

HOF-101-based dual-mode biosensor for photoelectrochemical/electrochemiluminescence detection and imaging of oxytetracycline

A unique hydrogen-bonded organic frameworks (HOF-101)-based photoelectrochemical (PEC) and electrochemiluminescence (ECL) dual-mode biosensor using polydopamine nanoparticles (PDAs) as quencher was constructed for ultrasensitive detection and imaging of oxytetracycline (OXY). In particular, HOF-101 was a superior ECL material and can be observed with the naked eye. Furthermore, it also had outstanding PEC signal, so HOF-101 was a new dual-signal material with excellent performance, thus it was explored to realize dual-mode detection. As the main component of natural melanin, PDAs not only had good biocompatibility, but also contained rich functional groups on the surface. Additionally, PDAs had excellent light absorption ability and poor conductivity, which made it the excellent photoquencher. In this work, PDAs were introduced on the surface of HOF-101 to quench its ECL and PEC signals by using the dual-aptamer sandwich method, achieving ultrasensitive detection of antibiotic OXY. Particularly for ECL detection, HOF-101 was firstly used to visually detect OXY. The detection range can reach 0.1 pM-100 nM, and the limit of detection (LOD) can reach 0.04 pM. This work showed a great contribution to the development of new ECL-PEC materials and ECL visualization analysis, which had outstanding application potential in the fields of food safety and biochemical analysis.

Rational design an oval heterostructure and tight linking interface of ZnS@CdS(3) for sensitively photoelectrochemical bioanalysis of PSA

Photoactive material with heterostructures could be effectively employed to promote the photoelectrochemical (PEC) property. Herein, two species heterostructured ZnS@CdS(1−2) composites derived from ZIF-8-S MOFs via a sulfofication reaction in situ using Cd(NO3)2, CdC12 cadmium reagents, and further gained the oval ZnS@CdS(3) after annealing the ZnS@CdS(2). Under irradiation, the PEC results showed that the photocurrent response of ZnS@CdS(3) signally enhanced compared to disordered heterostructures of ZnS@CdS(1), ZnS@CdS(2) and pure ZnS or CdS. It was ascribed to the staggered levels based on matching band-gap to form type II heterojunction of ZnS@CdS(3) could facilitate photo-induced electron/hole (e-/h+) separation and transfer. The obtained photoelectric material with a tight connecting interface also could reduce the carriers transport distance. Besides, the structured and well-distributed ZnS@CdS(3) was beneficial to improve synergistic effect on every component, which resulting in violently photocurrent output. This ZnS@CdS(3) modified ITO electrode to create the PEC biosensor (BSA/anti-PSA/ZnS@CdS(3)/ITO) had been successfully applied for the PSA detection with a wide linear range of 0.001 ∼ 150 ng mL−1 and ultralow detection limit of 0.27 pg mL−1. This research innovatively designed a close contact heterojunction interface with superior PEC nature for biosensor preparations.

NAD+ mediated photoelectrochemical biosensor for histone deacetylase Sirt1 detection based on CuO-BiVO4-AgNCs heterojunction and hybridization chain reaction amplification

BackgroundHistone deacetylate Sirt1 has been involved in many important biological processes and is closely related to the occurrence and development of many diseases. Therefore, the accurate detection of Sirt1 is of great significance for the diagnosis and treatment of diseases caused by Sirt1 and the development of related drugs. ResultsIn this work, a photoelectrochemical biosensor was developed for Sirt1 detection based on the NAD + mediated Sirt1 recognition and E. Coli DNA ligase activity. CuO-BiVO4p-n heterojunction was employed as the photoactive material, rolling circle amplification (RCA), hybridization chain reaction (HCR) and AgNCs were used as triple signal amplifications. As a bifunctional cofactor, NAD+ played a crucial role for Sirt1 detection, where the peptide deacetylation catalyzed by Sirt1 consumed NAD+, and the decreased amount of NAD + inhibited the activity of E. Coli DNA ligase, leading to the failure on RCA reaction, and improving the HCR reaction. Finally, AgNCs were generated using C-rich DNA as carrier. The surface plasmon effect of AgNCs and its heterojunction with CuO and BiVO4 accelerated the transfer rate of photogenerated carriers and improved the photocurrent signal. When the detection range was 0.001–200 nM, the detection limit of the biosensor was 0.76 pM (S/N = 3). SignificanceThe applicability of the method was evaluated by studying the effects of known inhibitors nicotinamide and environmental pollutant halogenated carbazole on Sirt1 enzyme activity. The results showed that this method can be used as a new platform for screening Sirt1 enzyme inhibitors, and also provided a new biomarker for evaluating the ecotoxicological effects of environmental pollutants.

Photoelectrochemical biosensor with Au@PTCA Schottky junction and multiple sandwich structures for Hg2+ sensitive detection

Herein, a novel photoelectrochemical (PEC) biosensor was built on the strength of gold nanoparticles@3,4,9,10-Perylene tetracarboxylic (Au@PTCA) Schottky junction and multiple sandwich structures caused by thymine-Hg2+-thymine (T-Hg2+-T) and base complementary pairing, realizing the highly sensitive detection of mercury ion (Hg2+). The proposed Au@PTCA Schottky junction was formed by using PTCA as carrier and Au NPs as signal enhancer, which could significantly improve photoelectric conversion efficiency, resulting in a strong initial PEC signal. The multiple sandwich structures possessed high steric hindrance effect, which could directly block external electron supply and light harvesting, giving rise to a significantly quenched PEC signal. In addition, the execution of the multiple sandwich structures could extinguish initial PEC signal produced by Au@PTCA Schottky junction, acquiring the comparison of various PEC signals, thereby fulfilling the quantitative detection of Hg2+. The experimental results showed that the PEC signal was gradually suppressed as the Hg2+ concentration increased in the range of 10 pM to 10 μM and the detection limit was 3.33 pM under optimal conditions, giving the sensor the advantages of high selectivity and excellent stability. This study demonstrated a promising method for sensitive detection of Hg2+ and offered a valuable approach with potential applications in environmental detection, biological analysis, and medical research.

Recent advances on portable photoelectrochemical biosensors for diagnostics

AbstractEfficient and accurate diagnostic methods are important for human health monitoring and prevention of major diseases, so the establishment of efficient and convenient testing methods for clinical diagnosis is urgent. Photoelectrochemical (PEC) biosensors have attracted much attention because of their high sensitivity, low detection background, and especially the advantages of combining photoexcitation and electrochemical detection. With the rapid development of integrated circuit technology many wireless transmissions of highly aggregated portable micro devices are manufactured, its small size, easy to carry, and the ability to visualize the results of the test is shown to be the potential for the application of such devices. This review aims to cover recent advances in PEC biosensing within the field of portable detection, including the principles of PEC biosensors, common photovoltaic materials, and scalable fabrication techniques for portable PEC biosensing. Future prospects in the field are also discussed.

Synergistic integration of MoOx co-catalyst with oxygen vacancies-engineered on BiVO4 for enhancing the sensitivity of photoelectrochemical DNA biosensing

Photoelectrochemical (PEC) biosensors of deoxyribonucleic acid (DNA) hybridization with simultaneously high signal-to-noise ratio and low limit-of-detection remains greatly challenging owing to the rapid recombination of photogenerated carriers of photoelectrode. Herein, we report an efficient strategy to amplify the photocurrent signal by coupling the MoOx co-catalysts and surface oxygen vacancies (Ov) of BiVO4 as photoelectrode (MoOx/BiVO4-Ov). Using a simple in situ solution impregnation method, non-noble metal MoOx nanoparticles can be grown uniformly onto BiVO4, subsequently, abundant surface Ov of MoOx/BiVO4 is induced by N2-plasma treatment. The coupling of MoOx and surface Ov on BiVO4 can efficiently promote the separation of photogenerated carriers, as a result, the optimized MoOx/BiVO4-Ov shows an excellent photocurrent response of 300.52 μA/cm2 under simulated sunlight illumination, which is 59.6 and 5.4 times higher than that of pristine BiVO4 and MoOx/BiVO4, respectively. Furthermore, the PEC biosensor based on MoOx/BiVO4-Ov demonstrates an excellent sensitivity toward DNA hybridization (10 pM to 10 μM) with a calculated detection limit down to 0.0549 pM. Moreover, this PEC biosensor exhibits specific selectivity as well as high stability. The proposed amplification strategy by the synergistic effect of co-catalysts and defects is valuable for the construction of efficient sensors for the early diagnosis of multiple diseases.

Synergistic effect of photoelectrochemical aptasensor based on staggered gap ZnO/BiFeO3 heterojunction coupled with cDNA-CdS sensitizer enabling ultrasensitive assay of kanamycin

Using staggered-gap ZnO/BiFeO3 heterojunction as photoactive materials and cDNA-CdS as the sensitizer for sensitive Kanamycin (KAN) detection, we have created a unique signal-off biosensing platform. The ZnO/BiFeO3 heterojunction provides active sites for aptamer loading and enhances photocurrent responsiveness. Rapid interfacial charge transfer and the separation efficiency of photo-generated carriers are enhanced by sensitization of the ternary heterojunction ZnO/BiFeO3/CdS. Signal-amplified quenching occurs when sensitizers are replaced with sterically hindered KAN. Because of the aptamer's greater affinity for KAN, the replacement of CdS causes a decrease in photocurrent response. Additionally, the weakly conductive aptamer-KAN complex causes steric hindrance, which exacerbates the photoelectrochemical signal-damping effect even more. The photoelectrochemical aptasensor exhibits excellent selectivity and stability, detecting KAN within the range of 0.00005825–0.233 μg/mL with a detection limit of 0.0466 ng/mL (S/N = 3). This work demonstrates the potential of perovskite oxides and their heterostructures for advanced photoelectrochemical biosensing applications.

Magnetically Controlled and Addressable Photoelectrochemical Sensor Array with Self-Calibration for the Label-Free Detection of Amyloid β-Proteins.

A label-free addressable photoelectric immunosensor array was designed for the detection of amyloid β-proteins based on magnetic separation and self-calibration strategies. In this paper, Na2Ti6O13 with a flower-like morphology was prepared by the hydrothermal method; after continuously combining Fe3O4 and CdS, it was endowed with magnetism and better photoelectric activity. Subsequently, a series of reactions occurred in the solution, and the magnetic separation method was used to enrich the target. On the other hand, the ITO glass was separated into eight sites (2 × 4) using magnets, and a light shield was utilized to prevent light exposure, resulting in addressable and continuous detection. After the uniform preparation of magnetic photoelectric materials and precise control of testing conditions, the relative errors among different sites have been effectively reduced. Moreover, incorporating a self-calibration strategy has allowed the sensor array to achieve greater accuracy. The proposed photoelectrochemical biosensor exhibits a good relationship with amyloid β-protein ranging from 0.01 to 100 ng mL-1 with a limit of detection of 1.1 pg mL-1 and exhibits excellent specificity, reproducibility, and stability.

CRISPR/Cas13a-mediated dual-modal biosensing platform based on the Zn0.5Cd0.5S/Ti3C2 Schottky heterojunction for the sensitive detection of miRNAs-21

MicroRNAs-21 (miRNAs-21), which promote tumor development and invasion by facilitating tumor cell proliferation and inhibiting apoptosis, is identified as a reliable biomarker for early cancer detection and prognosis. Herein, a CRISPR/Cas13a-mediated dual-modal biosensing platform was designed based on the Zn0.5Cd0.5S/Ti3C2 (ZCS/TC) Schottky heterojunction and implemented for monitoring miRNAs-21. Specifically, two-dimensional TC nanosheets with a large surface-to-volume ratio produced ample growth sites for the ZCS nanosphere. Moreover, the formation of Schottky heterojunctions at the ZCS/TC interface, validated by density functional theory calculations, can enhance their photoelectric conversion efficiency, providing a satisfactory initial signal for the subsequent implementation of a photoelectrochemical (PEC) biosensor. Furthermore, with the assistance of the MnO2-mediated CRISPR-Cas13a strategy, the dual-mode detection of miRNAs-21 was initiated via visualization and the use of the PEC biosensor. Under the optimized conditions, the linear range of the biosensor for detecting miRNAs-21 was 0.5 fM-1.0 nM and the detection limit was 0.21 fM. The developed platform can be used for the early detection and monitoring of various diseases, specifically cancer, and help create more research opportunities in this field.

Integrating multiple probes for simplifying signal-on photoelectrochemical biosensing of microRNA with ultrasensitivity and wide detection range based on biofunctionalized porous ferroferric oxide and hypotoxic quaternary semiconductor

A facile and signal-on photoelectrochemical (PEC) biosensing strategy was designed based on hypotoxic Cu2ZnSnS4 NPs nanoparticles (NPs) and biofunctionalized Fe3O4 NPs that integrated recognition units with signal elements, without the need for immobilization of probes on the electrode. Cu2ZnSnS4 NPs were used as the PEC substrate to produce intensive and stable photocurrent. The porous magnetic Fe3O4 NPs displayed favorable loading capacity for CdS QDs and easy biofunctionalization by negatively charged capture DNA (cDNA). cDNA sealed the pore of Fe3O4 NPs, avoiding the escape of CdS QDs as a PEC sensitizer. After hybridizing with target microRNA (miRNA), cDNA split away off Fe3O4 NPs whose porous channel might open and release sealed CdS QDs (signal element), resulting in a dramatical enhancement of PEC response. Herein, miRNA hardly contacted with CdS QDs, effectively avoiding harm to the target miRNA. This proposed strategy simplified procedures of assembly and made the biorecognition process sufficient for promoting a stationary quantity of probes, which was expected to obtain satisfactory performance for bioassay. Using miRNA-155 as a model analyte and combining with duplex-specific nuclease (DSN)-assisted amplification, a simplified and signal-on PEC biosensing platform for miRNA-155 with wonderful performance was proposed. DSN-assisted amplification further promoted PEC signal increment, leading to ulteriorly improving sensitivity (detection limit of 0.17 fM) and linear range (6.5 orders of magnitude) for miRNA-155 assay. Moreover, the developed PEC biosensing platform exhibited satisfactory stability, excellent specificity, and favorable accuracy for miRNA-155, which would have a promising prospect for monitoring miRNA expression in tumor cells.

Photoelectrochemical sensor for histone deacetylase Sirt1 detection based on Z-scheme heterojunction of CuS–BiVO4 photoactive material and the cyclic etching of MnO2 by NADH

A novel photoelectrochemical (PEC) biosensor was constructed for histone deacetylase Sirt1 detection based on the Z-Scheme heterojunction of CuS–BiVO4 and reduced nicotinamide adenine dinucleotide (NADH) induced cyclic etching of MnO2 triggered by Sirt1 enzyme catalytic histone deacetylation event. Based on the Z-Scheme heterojunction, the photoactivity of the CuS–BiVO4 was improved greatly due to the highly effective separation of the photogenerated electron-hole pairs. In the presence of MnO2 nanosheets on the CuS–BiVO4/ITO electrode surface, the photocurrent decreased due to the inhibition effect of MnO2. However, this inhibition effect was eliminated by the incubation of MnO2/CuS–BiVO4/ITO with NADH, where NADH was produced in the deacetylation process of acetylated peptide catalyzed by Sirt1 with NAD+. The formed NADH etched MnO2, resulting in an increased photocurrent. In this process, NADH was oxidized to produce NAD+, which further involved the deacetylation process. Based on this cycle, the photocurrent of the biosensor was improved greatly and the sensitive and selective detection of Sirt1 was achieved. The biosensor presented a wide linear range from 0.005 to 10 nM with the low detection limit of 3.38 pM (S/N = 3). In addition, the applicability of the developed method was evaluated by investigating the effect of sodium butyrate and perfluorohexane sulfonate on Sirt1 activity.

Contactless photoelectrochemical biosensors based on hierarchical MXene/Bi2S3 nanosheets with the branched hybridization chain reaction

Ethyl carbamate, a substance frequently occurring in fermented foods, seriously affects people's health; however, poor sensitivity constrains the development of ethyl carbamate sensors. In this work, hierarchical Bi2S3/MXene nanosheets were synthesized using a hydrothermal method, and experimentally their coupled UV light is an efficient NH3 sensing material. Meanwhile, the density functional theory (DFT) confirms that the MXene/Bi2S3 nanosheet interface has an excellent ability to adsorb NH3, resulting in a change of photocurrent. As a proof-of-concept, a highly sensitive ethyl carbamate photoelectrochemical (PEC) biosensor was constructed based on the ammonia generation strategy of glutamate dehydrogenase coupled to the branched hybridization chain reaction (bHCR). Specifically, the target-triggered bHCR enriches a large number of enzyme-encapsulated liposomes, while the enzymatic NH3-generation reaction will cause a change in the Bi2S3/MXene photocurrent, which completes the target detection process. Under optimal conditions, the constructed PEC biosensors exhibited superior analytical performance toward ethyl carbamate in the range of 0.01 μg/mL to 1 μg/mL and limit of detection (LOD) down to 0.001 μg/mL. In addition, it offers an effective method for food safety monitoring due to its excellent stability, fast response, and maneuverability on real samples (red wine, yellow wine, and brandy).

Magnetic photoactive Fe3O4@Sb2S3 nanospheres assisted homogeneous photoelectrochemical–electrochemical biosensing platform integrating with MOFs-derived bifunctional NPC@Thi nanopolyhedra-mediated dual “signal-on” strategy for protein tyrosine kinase activity

Abnormal protein tyrosine kinase (PTK) expression is associated with various diseases and thus it is of great significance in analysis of PTK activity via a reliable method. Herein, magnetic photoactive Fe3O4@Sb2S3 nanospheres and bifunctional thionine-embedded metal organic frameworks (MOFs)-derived nitrogen-doped porous carbon (NPC@Thi) nanopolyhedra were successfully synthesized for constructing a highly sensitive magnetic-assisted homogeneous photoelectrochemical (PEC)–electrochemical (EC) dual-mode biosensing platform for the detection of PTK (c-Src) activity. The Fe3O4@Sb2S3 nanospheres with good magnetic and photoactive properties assisted adequate biological recognition in a homogeneous system, simplified sample separation and facilitated sensor construction. After c-Src-mediated specific recognition, bifunctional NPC@Thi nanopolyhedra were connected to Fe3O4@Sb2S3 nanospheres. NPC@Thi not only enhanced the photocurrent of Fe3O4@Sb2S3 but also acted as the electrochemical probe. Thus, highly sensitive and reliable dual “signal-on” assay of c-Src activity with wide linear response ranges and low detection limits was achieved by the successful cooperation of PEC (10 fM to 10 nM, 7.2 fM) and EC (5 fM to 10 nM, 3.8 fM) biosensing strategies. The proposed homogeneous PEC–EC dual-mode biosensing platform is prospective to be extended to the analysis of other PTK activity and the discovery of PTK-targeted drug.

Self-powered photoelectrochemical sensor activated by In2O3/CdTe@ZnS-photoanode coupled with manganese porphyrin-double quenching for methyltransferase detection

A unique self-powered photoelectrochemical (PEC) biosensor is fabricated by integrating CuInS2 nanoflowers (CIS NFs) photocathode and CdTe@ZnS/In2O3 photoanode for sensitive detection of methyltransferase (Dam MTase). CdTe@ZnS quantum dots (QDs)-modified porous In2O3 with excellent photoelectric activity was used as photoanode, and CIS NFs were used as photocathode for biosensing interface. The direct electron transfer and synergistic enhancement of the dual-electrode guarantees sufficient photocurrent driving force for the self-powered PEC system without external power supply. Under the action of Dam MTase and endonuclease Dpn I (Dam-Dpn I), Hp DNA on the electrode was broken down into single-stranded DNA (ssDNA) to immobilize the manganese porphyrin-rich (MnPP) DNA networks. MnPP can not only acted as a burst probe to quench the photocurrent, but also as a mimetic enzyme to catalyze the generation of benzo-4-chloro-hexadienone (4-CD) precipitation in the presence of H2O2, which further reduces the photocurrent, leading to obvious change of PEC signal for Dam MTase detection. The sensor combines excellent photocatalytic performance and anti-interference of self-powered PEC sensor to achieve efficient detection of Dam MTase. The proposed strategy of integrating photocathode and photoanode offers a promising avenue for developing other high-performance PEC sensors for many biologicals.

Comparing defect-assisted interfacial charge transfer in CdS/PSA and CdS/TiO2[sbnd]NTAs nanoheterojunctions for enhanced photodegradation and biosensing

Firstly, oxygen vacancy defects are intentionally introduced in the preparation process of TiO2 nanotube arrays (TiO2-NTAs) and porous silicon arrays (PSA) films through the anodic oxidation method after annealing treatment, as expected. Then, CdS/TiO2-NTAs and CdS/PSA heterostructures are successfully fabricated using the electrodeposition method, incorporating abundant surface vacancy defects. The crafted CdS/TiO2-NTAs nanoheterojunctions presented elevated photoelectrochemical (PEC) performances and sensing activities compared with that of CdS/PSA, validating by photodegradation and PEC biosensing tests, which mainly ascribed to the synergistic effect between the promoted carriers separation efficiency and boosted surface active sites induced by vacancies defects. Furthermore, a comparative and comprehensive interfacial charge transfer mechanism and qualitative dynamic processes for CdS/TiO2-NTAs and CdS/PSA type-II nanoheterojunctions are proposed, revealing an enlarged staggered band offset between CdS and TiO2-NTAs. The evaluation of this band offset was conducted using nanosecond time-resolved transient photoluminescence and steady photoluminescence spectra, respectively. Following this scheme, the photodegradation rate for CdS/TiO2-NTAs nanocomplex toward degradation of MO was 92.8% and 1.06 times than that of CdS/PSA; while the PEC biosensing performance for CdS/TiO2-NTAs showed a detection range 0 – 600 μM and limit of detection of 2.3 μM, with a sensitivity of 456 mA cm−2M−1.

Organic-inorganic cascade-sensitized nanoarchitectonics for photoelectrochemical detection of β2-MG protein

Herein, a novel photoelectrochemical (PEC) immunoassay based on organic-inorganic BiVO4/rGO/FeOOH/C dot as cascade-sensitized photoactive material was fabricated for the ultrasensitive detection of β2-MG protein. Specifically, the composite BiVO4/rGO/FeOOH/C dot integrated the merits of high light absorption efficiency of organic material with fast electric carrier mobility of inorganic material. Additionally, the composite possessed a narrow energy level gradient, result in that the utilization of light energy improved greatly. More importantly, the composite with well-matched energy level would mediate multi-electron transport, thereby effectively promoting electron transfer and improving charge separation with an excellent photocurrent. Thereafter, through a typical sandwiched immunoreaction, quencher SiO2-labeled antibody that related to target was captured on electrode to decrease the initial photocurrent signal. The results showed that the proposed immunosensor exhibited high sensitivity and excellent stability in the linear range from 0.1 pg/mL to 1 μg/mL with a detection limit of 0.0383 pg/mL. This PEC biosensor offers a well-matched organic-inorganic cascade-sensitized strategy, providing novel insights to explore the high-performance photoactive material for application in early diagnosis of diseases.

Femtomolar endogenous adenosine triphosphate-responded photoelectrochemical biosensor based on Au@Cu2O core-shell nanocubes for the ultrasensitive determination of Escherichia coli O157:H7 in foods

Sensitive and precise determination of virulent foodborne pathogens is significant for food safety. Herein, an ultrasensitive photoelectrochemical (PEC) bioanalysis was developed using the endogenous adenosine triphosphate (ATP)-responded Au@Cu2O core-shell nanocubes (Au@Cu2O NCs) to measure Escherichia coli O157: H7 (E. coli O157:H7) in food. Briefly, the phage-functionalized gold wire was used to specifically recognize the target pathogen. With the bacteriolysis of lysozyme, the endogenous ATP molecules were emitted from the captured target bacteria and enriched by another ATP aptamer-modified gold wire. Following the exchange with complementary DNA (cDNA) chains, the bonded ATP would be released. It could simultaneously etch the Au@Cu2O NCs and compete with external circuit electrons to combine photogenerated holes on the Au@Cu2O NCs-modified screen-printed electrode. With the synergy of the two signal amplification mechanisms, a significant attenuation of photocurrent signal appeared even with femtomolar ATP. Therefore, the purpose of ultrasensitive determination of E. coli O157:H7 was realized, which depended on the endogenous ATP rather than exogenous signal probes. The proposed biosensor presented a good analysis performance within 10–106 CFU/mL with a detection limit of 5 CFU/mL. Besides, its specificity, repeatability, and stability were also investigated and acceptable. The detection results for food samples matched well with the results detected by the plate counting method. This work gives an innovative and sensitive signal amplification strategy for PEC bioassays in foodborne pathogens detection.

A “signal-on” cathodic photoelectrochemical biosensor based on Cu-MOF@Cu2O heterostructure for L-cysteine detection

Cathodic photoelectrochemical (PEC) sensor has attracted extensive attention as a convenient and efficient detection method. In this study, a “signal-on” cathodic PEC sensor based on Cu-MOF modified Cu2O heterostructure (Cu-MOF@Cu2O) has been successfully constructed for L-Cysteine (L-CySH) detection. Compared with Cu-MOF and Cu2O, the photocurrent response of Cu-MOF@Cu2O heterostructure are significantly enhanced due to the improved visible light capturing ability and photoelectric conversion efficiency. For the detection of L-CySH, L-CySH can be coupled to the electrode surface via CuS bond and further oxidized by copper ions (Cu2+) to form L-Cystine (L-CySSyC). Then, the L-CySSyC serves as the electron acceptor to scavenge the photogenerated electron of Cu-MOF@Cu2O, resulting in the increase of photocurrent response. The linear concentration range for L-CySH detection is 0.5–500.0 μM, and the detection limit is 0.32 μM. Furthermore, this sensor also has been obtained satisfactory results for L-CySH detection in real urine samples.

Bi2WO6/Ti3C2 MXene Quantum Dots Heterostructure-Based Label-Free Photoelectrochemical Aptamer Sensor for Ultrasensitive Kanamycin Monitoring

As Kanamycin (KAN) is an amino-glycoside antibiotic and has seriously negative effects towards human health, it is urgent to develop an effective way for KAN monitoring. Herein, Bi2WO6/Ti3C2 MXene quantum dots (Bi2WO6/Ti3C2 QDs) heterostructure was synthesized by electrostatically driven assembly and hydrothermal method. On the basis of a Bi2WO6/Ti3C2 QDs heterostructure, a novel aptamer-based anodic photoelectrochemical (PEC) sensing platform was constructed. Through the formation of Au–S bond, the mercapto-group modified aptamers were immobilized as a recognition unit for KAN. Under visible light irradiation, this PEC platform exhibits excellent signal-on photocurrent in the presence of KAN. A log-linear response is observed over a KAN concentration range from 0.01 nM to 50 nM, with a detection limit of 0.005 nM. Moreover, this aptamer-sensor can accurately detect KAN in animal product samples, with recoveries ranging from 94.2% to 101.3%. Overall, this work demonstrates the considerable potential of component reconstitution in PEC biosensors for real sample analysis, providing a new perspective on PEC sensor development.