Photoelectrochemical Biosensor Research Articles

Heterostructured BiVO4/CoPi nanoarrays as high-efficiency photoanode and AuPt nanodendrites as nanozyme for sensitive sensing of miRNA 141

MicroRNA (miRNA) is a new class of tumor biomarkers in human body for early diagnosis and therapy of cancers, whose detection has scientific significance and potential applications. Herein, a sensitive heterostructured BiVO4/CoPi photoelectrochemical (PEC) biosensor was established for sensing miRNA 141 with assistance of home-synthesized AuPt nanodendrites (NDs) as nanozyme. Specifically, the BiVO4/CoPi heterostructures displayed rough worm-like internetworks, as characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). In parallel, the PEC and UV–vis diffuse reflectance spectroscopy tests confirmed their excellent optical property, combined by discussing the interfacial electron transfer mechanism. Additionally, the AuPt NDs displayed superior peroxidase-like property in the presence of H2O2 as identified by benchmarked tetramethylbenzidine (TMB) oxidation, coupled by showing remarkable catalysis for 3-amino-9-ethylcarbazole (AEC) oxidation to form biocatalytic precipitation (BCP). Integrated by a cyclic enzyme strategy, the developed PEC biosensor exhibited a wider linear range of 5 fM ∼1 pM and a lower limit of detection (LOD) as low as 0.17 fM (S/N = 3). This work provides some valuable insights for sensitive analysis of tumor-associated miRNA in clinic.

Metal-organic framework-enabled surface state passivation integrating with single-nuclease-propelled multistage amplification for ultrasensitive lab-on-paper photoelectrochemical biosensing

The surface states and photoinduced corrosion in the photoelectrode can severely reduce the photocurrent signal and stability of photoelectrochemical (PEC) sensor, which imposes a great challenge on the improvement of analytical performance. Herein, metal–organic framework (MOF)-enabled surface passivation strategy is proposed to passivate surface states, suppress photocorrosion and facilitate interfacial charge transport. In the concrete, zeolitic imidazolate framework-8 (ZIF-8), which serves as the passivation layer, is in-situ assembled on the surface of paper-based ZnO nanorods (NRs) array to restrain the charge trapping at the surface states and keep ZnO NRs from photocorrosion, thereby substantially enhancing the photocurrent signal and durability. Moreover, the unique single-nuclease-propelled multistage amplification (SNMA) and triple-helix molecular switch (THMS)-conformation-transition-mediated signal quenching strategies are also designed to further improve the sensitivity. The SNMA process can convert target microRNA-141 into quadruple amount of useful output DNA strands (trigger DNA) in one duplex-specific nuclease (DSN) cleavage cycle assisted by succedent DSN cleavage of DNA duplexes, guaranteeing a higher target amplification efficiency. Subsequently, the THMS structure which anchors double amount of signal enhancers to the photoelectrode surface can be disassembled by the resulted trigger DNA, therefore achieving powerful signal amplification. Profiting from the MOF-enabled surface state passivation and elegantly designed signal amplification strategies, the ultrasensitive detection of microRNA-141 is realized with a liner range from 0.2 fM to 2 nM and detection limit of 72 aM, which provides a promising paradigm for developing high-performance lab-on-paper PEC biosensing platform.

(Invited) Development of New Strategies for Bringing Photoelectrochemical Biosensing to the Point-of-Need

Photoelectrochemistry combines light excitation with electrochemical readout for lowering the bias voltage needed for performing electrochemical reactions. As a result, when used in biosensing, photoelectrochemical signal readout reduces the background signals, lowering the limit-of-detection of such biosensors. To enable photoelectrochemical (PEC) signal readout to be applied to point-of-need biosensing, we have taken a three tiered approach focused on improving the understanding of signal transduction in PEC Biosensing, developing label-free assays, and creating handheld readout platforms.In this work, we developed a system using DNA as a nano-ruler to control the distance between plasmonic nanoparticles and PEC electrodes. This system was used to rationally-design PEC material systems for signal-on biosensing. Using this materials architecture, we developed a signal-on biosensor without target labeling for detecting DNA hybridization. This assay uses sequential DNA hybridization to generate a PEC signal. First, the DNA target is captured on probe-modified photoelectrodes. This is followed by hybridization of the unbound probes with DNA strands modified with plasmonic labels. The plasmonic label modulates the PEC signal, increasing the measured PEC current at low target concentrations. To enable biosensing at the point-of-need, we also developed a handheld PEC reader. The integration of plasmonic nanoparticles with PEC electrodes, label-free DNA assays, and handheld PEC readout paves the way toward bringing point-of-need PEC Biosensing.

Z-scheme Bi2O3/CuBi2O4 heterojunction enabled sensitive photoelectrochemical detection of aflatoxin B1 for health care, the environment, and food

Designing a photoelectrochemical (PEC) biosensor with preponderant sensitivity and anti-interference is a challenge for detecting small molecules in real samples with complex matrices. To this end, the Bi2O3/CuBi2O4 was synthesized in one step to enhance visible light's absorption ability, transferring the interfacial carrier's efficiency, a high-active Z-scheme heterojunction, and a photocathode biosensor was proposed. For the first time, we used the density functional theory to verify a Z-scheme transfer pathway of photogenerated electrons in Bi2O3/CuBi2O4 and the energy band structure of Bi2O3 and CuBi2O4, respectively. Bi2O3/CuBi2O4-based PEC biosensor was developed for competive immunoassay of small molecular, aflatoxin B1 (AFB1) as an example, resulting in a low detection limit of 297.4 fg/mL and a linear range of 1.4 pg/mL-280 ng/mL in urine, water, peanut, and wheat samples. Using spiked experiments, the satisfied repeatability, reproducibility, stability, and specificity of the Bi2O3/CuBi2O4-based PEC biosensor indicated a promise for application in health care, the environment, and food.

A duplex-specific nuclease assisted photoelectrochemical biosensor based on MoS2@ReS2/Ti3C2 hybrid for ultrasensitive detection of colorectal cancer-related piRNA-31,143

piR-31,143 has been identified as a potential biomarker for the diagnosis of colorectal cancer (CRC). However, the current detection methods have complicated operations and high cost, which restrict its clinical application. In the present work, we reported a new photoelectrochemical (PEC) biosensor based on MoS2@ReS2/Ti3C2 hybrid and duplex-specific nuclease (DSN) assisted signal amplification mechanism for ultrasensitive detection of piRNA-31,143 from human serum. The formation of the type I heterostructure between MoS2 and ReS2 and the doping of Ti3C2 contributed to high photocurrent response. The presence of piR-31,143 triggered the chain displacement reaction and enzymatic cyclic amplification reaction on the electrode surface with the assistance of DSN, leading to the collapse of the composite probe system. Consequently, the photocurrent of the PEC biosensor was proportional to the concentration of piR-31,143. The linear detection range and calculated detection limit of the PEC biosensor were 10−1–106 fM and 23 aM, respectively. The stability of the photocurrent under 15 consecutive on-off irradiations (with a relative standard deviation of 1.17%) and the specific response to piR-31,143 demonstrated the reliability of the PEC biosensor. In addition, the practicability of the PEC biosensor was verified by batch detection of human serum. The area under the receiver operating characteristic curve used to distinguish CRC patients from healthy controls was 0.942 with 100% specificity, demonstrating the developed method is a promising approach for the diagnosis of CRC. Statement of significanceThe clinical translation of piRNAs for cancer diagnosis is hindered by efficacy of detection techniques due to tedious sample processing and costly instrumentation. Herein, we fabricated a photoelectrochemical biosensor for the ultrasensitive detection of piR-31,143 with 10 μL serum in vitro. MoS2@ReS2/Ti3C2 greatly enhances the photocurrent response while duplex-specific nuclease improves the detection sensitivity and avoids false positives. By transforming the recognition sequence of the probe, the sensor can be applied to a variety of piRNAs detection for different diseases. In addition, the electrode can be recycled which is beneficial to reduce the cost of detection. With suitable automation and further optimization, our work may serve as core component in the development of an accurate and efficient diagnosis method.

Carbon-black combined with TiO2 and KuQ as sustainable photosystem for a reliable self-powered photoelectrochemical biosensor

Since our first work published in Electrochemistry Communication in 2010 (12, 346–350), many carbon black-(CB) based electrochemical printed (bio)sensors have been reported in the literature, addressing voltammetric and potentiometric measurements. Herein, we report the first photoelectrochemical biosensor based on a printed electrode modified with CB. In detail, the photoelectrochemical sensor has been designed by using, in addition to CB, and TiO2, KuQ dye because the use of only TiO2 and CB still requires UV irradiation, while KuQ is characterized by a broad and intense absorption spectrum in the visible region allowing for an easy set-up with a cost-effective portable laser. Once optimized the fabrication and working conditions, namely the solvent for the TiO2 dispersion (i.e. water/dimethylformamide (1:1 v/v)), the amount of TiO2/KuQ to cast onto the working electrode surface (i.e. 4 μg), the applied potential (i.e. +0.4 V), and the working solution (i.e. Tris buffer at pH 8.8), the sensor was challenged for NADH measurement obtaining a linear range up to 8 mM and a detection limit, calculated as 3 σb/slope, equal to 20 µM. The subsequent immobilization of Alcohol Dehydrogenase demonstrated the capability of this biosensor to detect ethanol up to 1 M, with the detection limit equal to 0.062 mM, indicating that the CB-TiO2/KuQ modification can regenerate the coenzyme even in the immobilized form, with improved analytical performances in terms of enhancement of the linearity. Finally, ethanol was detected in a real sample, i.e. white wine, with a good recovery value of 91.60 ± 0.01%, demonstrating the applicability of the developed miniaturized biosensor in white wine samples.

Contactless Photoelectrochemical Biosensor Based on the Ultraviolet-Assisted Gas Sensing Interface of Three-Dimensional SnS2 Nanosheets: From Mechanism Reveal to Practical Application.

This work reports a contactless photoelectrochemical biosensor based on an ultraviolet-assisted gas sensor (UV-AGS) with a homemade three-dimensional (3D)-SnS2 nanosheet-functionalized interdigitated electrode. After rigorous examination, it was found that the gas responsiveness accelerated and the sensitivity increased using the UV irradiation strategy. The effects of the interlayer structure and the Schottky heterojunction on the gas-sensitive response of O2 and NH3 under UV irradiation were further investigated theoretically by 3D electrostatic field simulations and first-principles density functional theory to reveal the mechanism. Finally, a UV-AGS device was developed to quantify the blood ammonia bioassay in a small-volume whole blood sample by alkalizing blood to release gas-phase ammonia with a linear range of 25-5000 μM with a limit of detection (LOD) of 29.5 μM. The device also enables a rapid immunoassay of human cardiac troponin I (cTnI) with a linear range of 0.4-25.6 ng/mL and an LOD of 0.37 ng/mL using a urease-labeled antibody as the immune recognition molecule. Both analyses showed satisfying specificity and stability, suggesting that the device can be applied to practical assays and is of great potential to increase the value of gas-sensitive sensors in chemical biosensing.

A novel split-type photoelectrochemical biosensor based on double-strand specific nuclease-assisted cycle amplification coupled with plasmonic Ag enhanced BiVO4 performance for sensitive detection of microRNA-155

A novel split-type and signal-on photoelectrochemical (PEC) biosensor was proposed based on double-strand specific nuclease (DSN)-assisted recycling amplification coupled with photodeposited Ag enhanced BiVO4 photoanode for sensitive detection of microRNA (miRNA)− 155. In the presence of target miRNA, the capture DNA (cDNA) modified with silver nanocube（AgNC）would hybridize with the miRNA, then DSN-assisted cycle amplification was triggered, leading to the release of AgNCs. The released AgNCs were acidolyzed and photodeposited on the BiVO4 electrode. Compared with the BiVO4 electrode, an enhanced photocurrent could be achieved at this obtained BiVO4/Ag electrode. And the morphology change from worm-like nanoparticles to nanosheets after Ag photodeposition was observed for the first time. This PEC signal enhancement was mainly contributed to the synergistic action of localized surface plasmon resonance (LSPR) effect of Ag, Schottky junction formed between BiVO4 and Ag, and the formation of BiVO4 nanosheets with larger specific surface area. The PEC signal enhancement was positively related to the miRNA-155 concentration, so this method could be used to sensitively and selectively detect miRNA-155. A limit of detection of 8 aM could be achieved. This strategy does not require layer-by-layer modification of the electrode, so it is easy to operate, and owns good stability.

Ultrasensitive photoelectrochemical biosensor based on black/red phosphorus heterojunction@Bi2Te3 hybrid and enzymatic signal amplification for the detection of colorectal cancer-related piRNA-823

Piwi-interacting RNAs (piRNAs) are a class of noncoding small RNAs that have been identified as promising biomarkers for cancer detection. However, the development of emerging detection methods for piRNAs has not attracted widespread attention. In this work, we proposed an ultrasensitive photoelectrochemical (PEC) biosensor that combines photosensitive hybrid with enzymatic signal amplification strategy for detecting colorectal cancer (CRC)-related piRNA-823. The synergy of the type-II heterostructure between red phosphorus (RP) and black phosphorus (BP), the photothermal effect of BP, and the excellent electron transfer capability and thermoelectric effect of Bi2Te3 endowed the BP/RP heterojunction@Bi2Te3 hybrid with excellent photoelectric conversion performance. The connection of the poorly conductive composite probe system (SiO2-COOH-p2-p1) significantly reduced the photocurrent. The target triggered the release of SiO2-COOH-p2 from the electrode surface and the subsequent specific cleavage of p1 by duplex-specific nuclease, which significantly restored the photocurrent. The released target could react with other composite probes to form a photocurrent signal-increasing cycle. The PEC biosensor showed a linear detection range of 0.1–106 fM and a calculated detection limit of 0.016 fM. In addition, the PEC biosensor exhibited a stable photocurrent response under continuous on-off irradiation and could clearly distinguish the target from the mismatch sequences. The accuracy of the PEC biosensor in detecting piRNA-823 in clinical serum samples was verified by RT–qPCR, and the PEC biosensor could distinguish healthy controls from CRC patients. This work provides a new strategy for ultrasensitive liquid biopsy of piRNAs.

Surface Plasmon-Enhanced Photoelectrochemical Sensor Based on Au Modified TiO2 Nanotubes.

Based on the enhanced charge separation efficiency of the one-dimensional structure and strong surface plasmon resonance (SPR) of gold, a gold modified TiO2 nanotube (Au/TiO2NTs) glucose photoelectrochemical (PEC) sensor was prepared. It could be activated by visible red light (625 nm). Under optimal conditions, the Au/TiO2NTs sensor exhibited a good sensitivity of 170.37 μA·mM−1·cm−2 in the range of 1–90 μM (R2 = 0.9993), and a detection limit of 1.3 μM (S/N = 3). Due to its high selectivity, good anti-interference ability, and long-term stability, the fabricated Au/TiO2NTs sensor provides practical detection of glucose. It is expected to be used in the construction of non-invasive PEC biosensors.

A photoelectrochemical biosensor based on b-TiO2/CdS:Eu/Ti3C2 heterojunction for the ultrasensitive detection of miRNA-21

A novel photoelectrochemical (PEC) biosensor based on b-TiO2/CdS:Eu/Ti3C2 heterojunction was developed for ultrasensitive determination of miRNA-21. In this device, the b-TiO2/CdS:Eu/Ti3C2 heterojunction with excellent energy level arrangement effectively facilitated photoelectric conversion efficiency and accelerated the separation of the photogenerated electron hole pairs, which because that the structure of heterojunction overcomes the drawbacks of single material, such as narrow light absorption range, wide band gap, short carrier lifetime, etc., improves light utilization, extends the lifetime of photogenerated electron hole pairs, and promotes electron transfer. Herein, hairpin DNA1 (H1) decorated on the b-TiO2/CdS:Eu/Ti3C2 electrode surface by Cd–S bonds, after H2/miRNA-21 heterduplex was introduced, the strand-displacement reaction (SDR) was triggered between H1 and H2/miRNA-21, accordingly, miRNA-21 was discharged from the H2/miRNA-21 heterduplex, forming the H1/H2 duplex, and the reuse of miRNA-21 was realized. As a signal amplification factor, the signal amplification factor H3–CdSe was hybridized with H1/H2 duplex, which greatly enhanced the sensitivity of the PEC biosensor. Under optimal conditions, the designed PEC biosensor displayed outstanding sensitivity, selectivity and stability with a wide liner range from 1.0 μM to 10.0 fM and a low detection limit of 3.3 fM. The preparation of the optoelectronic material affords a new direction for the progress of heterojunction photovoltaic materials and the construction of the proposed biosensor also provides a new thought for the PEC detection of human miRNA-21 with superior performance. Simultaneously, the established biosensor exhibiting tremendous possibility for detecting other biomarkers and biomolecules in clinical diagnosis fields.

Sensitive photoelectrochemical determination of T4 polynucleotide kinase using AuNPs/SnS2/ZnIn2S4 photoactive material and enzymatic reaction-induced DNA structure switch strategy

We report here Au nanoparticles (AuNPs)/SnS2/ZnIn2S4 as a high-performance active material for sensitive photoelectrochemical (PEC) determination of T4 polynucleotide kinase (T4 PNK) using an enzymatic reaction-induced DNA structure switch strategy. To construct the PEC biosensor, a double-stranded DNA probe consisting of a CdS quantum dots (QDs)-labeled single-stranded DNA (sDNA) and its complementary DNA (cDNA) is immobilized on the AuNPs/SnS2/ZnIn2S4 photoactive material. T4 PNK can catalyze the phosphorylation of 5′–OH–terminated sDNA in the double-stranded DNA probe when ATP is present, and λ-exonuclease can catalyze the degradation of the phosphorylated sDNA into small fragments. Then the cDNA forms a hairpin structure so that CdS QDs and AuNPs are in close contact, which can induce exciton-plasma interactions between CdS QDs and AuNPs. The exciton-plasma interactions significantly boost the photocurrent, enabling the “signal on” PEC determination of T4 PNK in the range of 10−4 - 1 U mL−1 with a detection limit of 6 × 10−5 U mL−1. The PEC biosensor can also be used to screen enzyme inhibitors.

Designing Nanosheet Heterostructures of CuO Grown on Bi2MoO6 as a Photoelectrochemical Biosensor for Detecting Alpha‐Fetoprotein

AbstractBi2MoO6 (BM) was modified with various amounts of CuO. Photoelectrochemical (PEC) tests of the resulting CuO‐doped BM materials showed improved PEC performance. The best PEC performance was obtained for BM containing 5 wt % of CuO. CuO/BM‐5 % was then used as an active material for an Alpha‐fetoprotein (AFP) PEC biosensor. A PEC biosensor‐based CuO/BM‐5 % detected AFP linearly from 0.01–1200 ng ⋅ L−1 with a detection limit of 0.005 ng ⋅ L−1. The photoelectron potential of the CuO/BM‐5 % heterojunction reduced the electron/hole recombination, which explains the excellent PEC performance of this material.

Au NP-Decorated g-C3N4-Based Photoelectochemical Biosensor for Sensitive Mercury Ions Analysis.

Herein, an efficient and feasible photoelectrochemical (PEC) biosensor based on gold nanoparticle-decorated graphitic-like carbon nitride (Au NPs@g-C3N4) with excellent photoelectric performance was designed for the highly sensitive detection of mercury ions (Hg2+) . The proposed Au NPs@g-C3N4 was first modified on the surface of the electrode, which possessed a remarkable photocurrent conversion efficiency and could produce a strong initial photocurrent. Then, the thymine-rich DNA (S1) was immobilized on the surface of the modified electrode via Au–N bonds. Subsequently, 1-hexanethiol (HT) was added to the resultant electrode to block nonspecific binding sites. Finally, the target Hg2+ was incubated on the surface of the modified glassy carbon electrode (GCE). In the presence of target Hg2+, the thymine–Hg2+–thymine (T-Hg2+-T) structure formed due to the selective capture capability of thymine base pairs toward Hg2+, resulting in the significantly decrease of the photocurrent. Thereafter, the proposed PEC biosensor was successfully used for sensitive Hg2+ detection, as it possessed a wide linear range from 1 pM to 1000 nM with a low detection limit of 0.33 pM. Importantly, this study demonstrates a new method of detecting Hg2+ and provides a promising platform for the detection of other heavy metal ions of interest.

Integrating Ti3C2/MgIn2S4 heterojunction with a controlled release strategy for split-type photoelectrochemical sensing of miRNA-21

The harsh operating conditions and time-consuming fabrication process of the photoelectrode modification process have limited the potential applications of photoelectrochemical (PEC) sensors. To overcome these drawbacks, this study introduced a unique split-type PEC biosensor for microRNA-21 (miRNA-21) detection. Specifically, a Ti3C2/MgIn2S4 heterojunction was adopted as the photosensitive material, and a target-controlled glucose release system, comprising a multifunctional porphyrin-based metal-organic framework (PCN-224), was used for signal amplification. The Ti3C2/MgIn2S4 heterojunction effectively separated the photogenerated electrons and holes, and improved the photoelectric conversion efficiency, offering a strong initial photocurrent signal during PEC biosensing. Meanwhile, the porous PCN-224 acted as a nimble nanocontainer that encapsulated glucose using a capture probe (CP). In the presence of miRNA-21, the CP formed a CP-miRNA-21 complex and then detached from PCN-224, controllably releasing the trapped glucose. The oxidization of glucose by glucose oxidase resulted in hydrogen peroxide generation, which acted as a scavenger for the holes generated on the surface of Ti3C2/MgIn2S4, and significantly enhanced the photocurrent response under visible light irradiation. Finally, the sensor exhibited good performance for miRNA-21 detection with a low detection limit (0.17 fM) and wide linearity range (0.5 fM-1.0 nM). Thus, the proposed Ti3C2/MgIn2S4-based split-type PEC sensor is a promising tool for sensitive and accurate detection of miRNA-21 and provides an innovative basis for the preparation of other high-performance sensors.

Dual-Engine Powered Paper Photoelectrochemical Platform Based on 3D DNA Nanomachine-Mediated CRISPR/Cas12a for Detection of Multiple miRNAs.

This work proposed a novel double-engine powered paper photoelectrochemical (PEC) biosensor based on an anode-cathode cooperative amplification strategy and various signal enhancement mechanisms, which realized the monitoring of multiple miRNAs (such as miRNA-141 and miRNA-21). Specifically, C3N4 quantum dots (QDs) sensitized ZnO nanostars and BiOI nanospheres simultaneously to construct a composite photoelectric layer that amplified the original photocurrent of the photoanode and photocathode, respectively. Through the independent design and partition of a flexible paper chip to functionalize injection holes and electrode areas, the bipolar combination completed the secondary upgrade of signals, which also provided biological reaction sites for multitarget detection. With the synergistic participation of a three-dimensional (3D) DNA nanomachine and programmable CRISPR/Cas12a shearing tool, C3N4 QDs lost their attachment away from the electrode surface to quench the signal. Moreover, electrode zoning significantly reduced the spatial cross talk of related substances for multitarget detection, while the universal trans-cleavage capability of CRISPR/Cas12a simplified the operation. The designed PEC biosensor revealed excellent linear ranges for detection of miRNA-141 and miRNA-21, for which the detection limits were 5.5 and 3.4 fM, respectively. With prominent selectivity and sensitivity, the platform established an effective approach for trace multitarget monitoring in clinical applications, and its numerous pioneering attempts owned favorable reference values.

Ti3C2@WSe2 as photoelectractive materials coupling with recombinase polymerase amplification for nucleic acid detection

The photoelectrochemical biosensor based on double redox cycle amplification technology coupled with Tungsten diselenide and MXene-modified electrode was developed. Signal amplification technology is a commonly used method to improve the sensitivity. In this article, in the double redox cycle amplification method, p-aminophenol is used as the signal molecule, and squaric acid acts as a redox indicator. Tris(2-carboxyethyl) phosphine is an excellent reducing agent, which greatly improves the photoelectric response. Tungsten diselenide and MXene are used as photosensitive materials. In the presence of model target, respiratory syncytial virus RNA, the recombinase polymerase amplification process occurred because there is amplification template, so that the signal molecule p-aminophenol will be produced, leading to redox cycle was carried out, and the photocurrent signal is improved. In the absence of syncytial virus RNA, the photocurrent signal is low. The detection range of the biosensor is from 0.2 fM to 80 fM, and the detection limit reaches 30 aM for respiratory syncytial virus RNA. The method of introducing redox cycle amplification and Tungsten diselenide, MXene into photoelectrochemical biosensing provides a new idea for future biological analysis and has application potential.

Two-in-one: Portable piezoelectric and plasmonic exciton effect-based co-enhanced photoelectrochemical biosensor for point-of-care testing of low-abundance cancer markers

In-depth exploration of the local surface plasmon resonance and piezoelectric effects associated with metal can help develop efficient biosensors. Here, we presented for the first time the localized surface plasmon resonance (LSPR) and piezoelectric effects co-enhance the construction of an efficient intra-body phase electric field for the construction of efficient photoelectrochemical (PEC) biosensors. Briefly, the LSPR enhancement and piezoelectric enhancement effects between Ag nanoparticles and the piezoelectric material NaNbO3 were investigated in a PEC biosensor system under the excitation of portable UV light. Notably, the simplified treatment of the basic building blocks of the PEC sensor, including a handheld UV flashlight instead of a physical excitation light source and a digital multimeter instead of an electrochemical workstation. The capture and immunoincubation process of target PSA occurs on separated microtiter plates and hydrogen peroxide, generated by enzyme-linked immunization, induces the directional separation of electrons and holes in the composite heterogeneous material under the excitation of light. The coupling with a digital multimeter allows for real-time monitoring of photocurrents. Further, the effect of Ag deposition on piezoelectric perovskite NaNbO3 was obtained by density functional theory (DFT) calculations. Impressively, under optimized conditions, the system exhibits an ultra-wide linear range and ultra-low detection limits for the target PSA. The system is also comparable to commercially available ELISA kits at the 95% confidence level. This work provides a novel idea of enhanced PEC biosensor for rapid and accurate detection of cancer-related proteins.

In Situ Formation of Bi2MoO6-Bi2S3 Heterostructure: A Proof-Of-Concept Study for Photoelectrochemical Bioassay of l-Cysteine.

A novel signal-increased photoelectrochemical (PEC) biosensor for l-cysteine (L-Cys) was proposed based on the Bi2MoO6–Bi2S3 heterostructure formed in situ on the indium–tin oxide (ITO) electrode. To fabricate the PEC biosensor, Bi2MoO6 nanoparticles were prepared by a hydrothermal method and coated on a bare ITO electrode. When L-Cys existed, Bi2S3 was formed in situ on the interface of the Bi2MoO6/ITO electrode by a chemical displacement reaction. Under the visible light irradiation, the Bi2MoO6–Bi2S3/ITO electrode exhibited evident enhancement in photocurrent response compared with the Bi2MoO6/ITO electrode, owing to the signal-increased sensing system and the excellent property of the formed Bi2MoO6–Bi2S3 heterostructure such as the widened light absorption range and efficient separation of photo-induced electron–hole pairs. Under the optimal conditions, the sensor for L-Cys detection has a linear range from 5.0 × 10−11 to 1.0 × 10−4 mol L−1 and a detection limit of 5.0 × 10−12 mol L−1. The recoveries ranging from 90.0% to 110.0% for determining L-Cys in human serum samples validated the applicability of the biosensor. This strategy not only provides a method for L-Cys detection but also broadens the application of the PEC bioanalysis based on in situ formation of photoactive materials.

Framework-promoted charge transfer for highly selective photoelectrochemical biosensing of dopamine

Traditional photoelectrochemical (PEC) systems with inorganic semiconductors as photoactive materials generally involve effortless recombination of electron-hole pairs, which greatly limit the detection sensitivity. The arrangement of multiple components with tunable bandgaps provides an effective way to accelerate charge transfer. In this work, a framework material with adjustable structure was used to promote the charge transfer in the PEC process. The framework was constructed with 9,10-di(p-carboxyphenyl)anthracene (DPA) ligands as the light collector to coordinate with Zn2+ nodes, which formed an electronegative metal-organic framework (ZnMOF), and showed good conductivity and PEC performance due to the π-π stacking of DPA and the intrareticular charge transfer. Based on the band and charge matching of dopamine (DA) with ZnMOF, the ZnMOF modified electrode as a biosensor showed excellent PEC response to DA with good selectivity, thus realized sensitive detection of DA ranging from 0.03 to 10 μM with a detection limit of 17.7 nM. The biosensor could be used to monitor the release of DA from PC12 cells and evaluate the stimulation of K+ to DA release. The conductive framework material provided an approach to develop highly selective sensing platform for trace bioanalysis.