A halide perovskite/lead sulfide heterostructure with enhanced photoelectrochemical performance for the sensing of alkaline phosphatase (ALP)

Ultrasensitive Organic Photoelectrochemical Transistor Biosensor Based on DNA as Nanocarrier for Efficient Immobilization of Signal Probe with Pimping Background

Organic photoelectrochemical transistor (OPECT) assays are mainly focused on the improvement of photoactive materials at the gating interface, which leads to an enhanced initial signal alongside significant background noise. This phenomenon can cause considerable deviations and impose limits on target detection. In this study, we achieved sensitive and low-background detection of alkaline phospholipase (ALP) activity using single-stranded DNA (ssDNA) as a nanocarrier to effectively immobilizing CdS quantum dots (QDs) sensitizing UiO-66. Specifically, ssDNA-labeled CdS QDs could be connected to UiO-66 via Zr-O-P bonds, while sodium tripolyphosphate (STPP) interfered with the binding of CdS QD-ssDNA to UiO-66 due to an occupancy effect. The hydrolysis of STPP, catalyzed by ALP, diminished this occupancy effect, allowing for increased binding of CdS QDs-ssDNA to UiO-66 and thereby enhancing the responsive signal. The competitive dynamic between STPP and ssDNA allowed for controlled binding of CdS QDs-ssDNA photosensitizers on UiO-66, thus realizing sensitive detection of ALP. This organic integration of biological modulation and signal amplification in OPECT has led to the creation of a novel sensing platform for detecting ALP concentrations ranging from 0.005 to 100 U·L-1, and the detection limit is 0.0012 U·L-1, thus paving the way for innovative approaches to sensitively monitor ALP activity.

Hairpin probe-based one-pot multiplex isothermal amplification combined with bifunctional G-quadruplex (IHP-GT) for the detection of alkaline phosphatase

Abnormal alkaline phosphatase (ALP) levels have been linked to breast cancer, prostate cancer, bone damage, gingivitis and abnormal liver function. Monitoring ALP levels is important for better diagnosis and treatment of these diseases. Detection of ALP by colorimetric methods is very portable in terms of signal reading, but still suffers from low sensitivity. SERS can achieve high sensitivity detection, but cannot be separated from large precision instruments. Therefore, researchers have worked to optimize various aspects of the sensor, such as sensitivity, detection time, and operating procedures, to enable portable and rapid ALP detection. Isothermal amplification using simple system components meets the current demand for rapid, portable assays. We have developed a novel one-pot high-efficiency ALP assay strategy called IHP-GT. IHP-GT performs a one-step cascade amplification using only one probe (IGHP) as a template. The phosphorylated primer P binds to IGHP, forming a P/IGHP structure. At this point, the G-quadruplex closes and no signal is generated. In the presence of ALP, primer P is dephosphorylated to remove the restriction and then amplified in a cascade using IGHP as a template to release the full G-quadruplex structure. The single-stranded G-quadruplex will bend to form a secondary structure, facilitating secondary amplification starting with primer AT to produce PrG and P'. The PrG structure will trigger triple amplification, enabling cascade amplification. The G-quadruplex structure produced by cascade amplification has the dual role of promoting amplification of primer AT and binding to ThT to produce a fluorescent signal. The IHP-GT method provides a highly sensitive detection of ALP in less than 90 min and has been successfully used to analyze ALP in human serum samples. In addition, IHP-GT can be used to screen for ALP inhibitors. Importantly, we lyophilized the IHP-GT reaction components into powder form for user-friendly poc testing.

Signal amplification strategies in photoelectrochemical sensing of carcinoembryonic antigen

Early detection of cancer markers is critical for cancer diagnosis and cancer therapy since these markers may indicate cancer risk, incidence, and disease prognosis. Carcinoembryonic antigen (CEA) is a type of non-specific and broad-spectrum cancer biomarker commonly utilized for early cancer diagnosis. Moreover, it serves as an essential tool to assess the efficacy of cancer treatment and monitor tumor recurrence as well as metastasis, thus garnering significant attention for precise and sensitive CEA detection. In recent years, photoelectrochemical (PEC) techniques have emerged as prominent methods in CEA detection due to the advantages of PEC, such as simple equipment requirements, cost-effectiveness, high sensitivity, low interference from background signals, and easy of instrument miniaturization. Different signal amplification methods have been reported in PEC sensors for CEA analysis. Based on these, this article reviews PEC sensors based on various signal amplification strategies for detection of CEA during the last five years. The advantages and drawbacks of these sensors were discussed, as well as future challenges.

Development of photoelectrochemical immunosensor based on halide perovskite protected by organometallic compounds for determining interleukin-17A (IL-17A)

The overexpression of interleukin-17A (IL-17A) is closely associated with the pathogenesis of autoimmune diseases and cancer, rendering precise identification of IL-17A level critical for disease diagnosis and prognosis monitoring. In this study, CsPbBr3 nanoclusters (NCs) were embedded in C16H14Br2O6Pb2 organometallic compound (Pb-MA MOC) via a hot injection approach. Through this way, the issue of CsPbBr3 NCs susceptible to decomposition in water was solved, and the photocurrent intensity that is generated by CsPbBr3 was significantly enhanced. A highly sensitive photoelectrochemical (PEC) sensor for detecting IL-17A in human serum was developed using CsPbBr3/Pb-MA as the photoactive material. The electrode was initially modified with CsPbBr3/Pb-MA. Then, antibody-modified Fe3O4 magnetic nanoparticles (MNs) with target analyte IL-17A captured, and IL-17A antibody-modified Au@CuNi diatomic catalyst (DAC) formed sandwich immune complex structure on the electrode. The existence of CuNi DAC led to a substantial reduction in photoelectric signal intensity due to oxidation of ascorbic acid in the supporting electrolyte. The photocurrent intensity exhibited linear correlation with IL-17A concentration within the range 15-750 pg/mL, and achieving an impressive detection limit of 1 pg/mL. Moreover, the sensor was successfully applied to the determination of IL-17A in human serum, suggesting its potential clinical applications.

Natural Deep Eutectic Solvents as Absorbing Solution and Preparation Solvent of Perovskite Nanocrystals Simultaneously for CH3I Gas Visual Sensing

Methyl iodide (CH3I) gas as a toxic gas causes great harm to organisms due to its high volatility and high reactivity with biological nucleophiles. Unfortunately, the sensing and detection of CH3I gas are challenging because of the diffusive nature of the gases and its low concentrations in the environment. Herein, we have developed a fast, green, and sensitive CH3I gas visual sensing method based on the capture technology of toxic gases by natural deep eutectic solvents (NADESs) coupled to the halide rapid exchange capability of perovskite nanocrystals (PNCs). In this strategy, NADESs are used as an absorption solution to adsorb gaseous CH3I, while simultaneously exposing I- through the action of the nucleophilic reagent; then, CsPbBr3 PNCs were synthesized in NADESs and used as sensing material to achieve I- exchange. Benefiting from the capture and enrichment of CH3I gas, the sensitivity of the gas sensor was highly improved. The sensor exhibited the lowest detection limit (limits of detection) of 164.15 μmol/m3, below the minimum safe level for human inhalation, which is 200 μmol/m3. This breakthrough offers greater possibilities for the quantitative detection of CH3I gas.

Long-term stable electrochemiluminescence of perovskite quantum dots in aqueous media

We develop a novel electrochemiluminescence (ECL) emitter of aqueous-based perovskite quantum dots, with long-term stable ECL emission in aqueous media. Moreover, an electron transfer annihilation mechanism of ECL generation is proposed, revealed by the experimental results. This study opens a door for exploring efficient perovskite-based ECL emitters.

Oxygen vacancies-driven signal enhanced photoelectrochemical sensor for mercury ions detection

Mercury ion (Hg2+) poses a serious threat to human health due to its high toxicity. In this study, a smartphone-based photoelectrochemical sensor based on oxygen vacancies (OVs) driven signal enhancement for mercury ion detection was designed. BiVO4-x/Bi2S3/AuNPs were combined with T-Hg2+-T recognition mode to construct a multi-sandwich photoelectrochemical sensor. On the one hand, the OVs can increase the adsorption of light by the materials and enhance the photocurrent response as well as the superconductivity of Au NPs to accelerate the charge transfer at the electrode interface. On the other hand, the multi-sandwich structure was exploited to increase the binding site of Hg2+, as well as the T-Hg2+-T structure for sensitive recognition of Hg2+ and signal amplification. The sensor showed good linearity for Hg2+ concentration in the range of 0.1 nM-1.0 μM with a detection limit of 4.8 pM (S/N = 3). Eventually the smartphone-based real-time detection sensor is expected to contribute to the future analysis of heavy metal ions.

Detection of alkaline phosphatase activity with a CsPbBr3/Y6 heterojunction-based photoelectrochemical sensor

An ultra-sensitive photoelectrochemical (PEC) sensor based on perovskite composite was developed for the determination of alkaline phosphatase (ALP) in human serum. In contrast to CsPbBr3 or Y6 that generated anodic current, the heterojunction of CsPbBr3/Y6 promoted photocarriers to separate and generated cathodic photocurrent. Ascorbic acid (AA) was produced by ALP hydrolyzing L-ascorbic acid 2-phosphate trisodium salt (AAP), which can combine with the holes on the photoelectrode surface, accelerating the transmission of photogenerated carriers, leading to enhanced photocurrent intensity. Thus, the enhancement of PEC current was linked to ALP activity. The PEC sensor exhibits good sensitivity for detection of ALP owing to the unique photoelectric properties of the CsPbBr3/Y6 heterojunction. The detection limit of the sensor was 0.012 U·L-1 with a linear dynamic range of 0.02-2000 U·L-1. Therefore, this PEC sensing platform shows great potential for the development of different PEC sensors.

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.

Target-Induced Photocurrent-Polarity-Switching PEC Sensing Platform Based on In Situ Generation of Oxygen Vacancy-Modulated Energy Band Structures

The polarity of the photocurrent can be modulated by tunable bipolar photoelectrochemical (PEC) behavior, which is anticipated to address the issues of high background signal caused by traditional unidirectional increasing/decreasing response and false-positive/false-negative problems. Here, a new approach is suggested for the first time, which employs a target-induced enzyme-catalyzed reaction and in situ oxygen vacancy (OV) generation to achieve heterojunction photocurrent switching for highly sensitive detection of alkaline phosphatase (ALP). Among them, the ALP can catalyze the decomposition of ascorbic acid phosphate to produce ascorbic acid, which not only acts as an electron donor to change the redox environment but also acts as a reducing agent to introduce OVs into BiOBr semiconductors in cooperation with illumination. The introduction of vacancies can effectively modulate the energy band structure of BiOBr, while with the change of redox conditions, the transfer path of photogenerated carriers is changed, thus realizing the switching of photocurrents, which leads to its use in the construction of a negative-background anti-interference PEC sensing platform, achieving a wide linear range from 0.005 to 500 U·L-1 with a low detection limit of 0.0017 U·L-1. In conclusion, the photocurrent switching operation of this system is jointly regulated by chemistry, optics, and carrier motion, which provides a new idea for the construction of a PEC sensing platform based on photocurrent polarity switching.

Construction of Metal Organic Framework-Derived Fe-N-C Oxidase Nanozyme for Rapid and Sensitive Detection of Alkaline Phosphatase

Alkaline phosphatase (ALP) is a phosphomonoester hydrolase and serves as a biomarker in various diseases. However, current detection methods for ALP rely on bulky instruments, extended time, and complex operations, which are particularly challenging in resource-limited regions. Herein, we synthesized a MOF-derived Fe-N-C nanozyme to create biosensors for the coulometric and visual detection of ALP. Specifically, we found the Fe-N-C nanozyme can efficiently oxidize 3,3',5,5'-tetramethylbenzidine (TMB) to generate blue-colored tetramethyl benzidine (TMBox) without the need for H2O2. To construct the biosensor, we incorporated the ALP enzymatic catalytic reaction to inhibit the oxidation of TMB by Fe-N-C oxidase nanozyme. This biosensor showed rapid and highly sensitive detection of ALP in both buffer and clinical samples. The limit of detection (LOD) of our approach could be achieved at 3.38 U L-1, and the linear range was from 5 to 60 U L-1. Moreover, we also developed a visual detection for ALP by using a smartphone-based assay and facilitated practical and accessible point-and-care testing (POCT) in resource-limited areas. The visual detection method also achieved a similar LOD of 2.12 U L-1 and a linear range of 5-60 U L-1. Our approach presents potential applications for other biomarker detections by using ALP-based ELISA methods.

One-Step Ultrasonic Preparation of Stable Bovine Serum Albumin-Perovskite for Fluorescence Analysis of L-Ascorbic Acid and Alkaline Phosphatase

Halide lead perovskite has attracted increased attention due to its excellent optical properties. However, the poor stability of the halide lead perovskite nanocrystals has been a major obstacle to their application in biosensing. Here, we proposed a method to synthesize CsPbBr3/BSA NCs perovskite using bovine serum albumin (BSA) as a zwitterion ligand. Then, a fluorescent sensor for alkaline phosphatase determination based on CsPbBr3/BSA NCs was successfully built via the interaction of L-ascorbic acid (AA) with BSA on the perovskite surface. Under optimal conditions, the sensor showed a linear concentration range from 50 to 500 μM with a detection limit of 28 μM (signal-to-noise ratio of 3) for AA, and demonstrated a linear concentration range from 40 to 500 U/L with a detection limit of 15.5 U/L (signal-to-noise ratio of 3) for alkaline phosphatase (ALP). In addition, the proposed fluorescent biosensor exhibited good selectivity and recovery in the determination of ALP in human serum. This strategy offers an innovative way for enhancing the water stability of lead halide perovskite and promoting their application in biosensing areas.