Ultrathin mesoporous BiOCl nanosheets-mediated liposomes for photoelectrochemical immunoassay with in-situ signal amplification

Photoelectrochemical sensor for nitrite determination based on the etching of BiOCl/Zn0.5Cd0.5S

A rapid photoelectrochemical (PEC) sensor was constructed for nitrite detection in food based on the one-step chemical etching strategy of BiOCl/Zn0.5Cd0.5S (BOC/ZCS) nanocomposites by nitrite. BOC/ZCS heterojunction was prepared by a simple coprecipitation method, and it was found that BOC/ZCS showed significant photoelectrochemical (PEC) activity. The results of this study confirmed that the decrease in the photocurrent of the sensor was linked to the etching of ZCS by nitrite under acidic conditions. Under optimized conditions, the BOC/ZCS-based PEC sensor showed good analytical properties for detecting nitrite, with linear ranges of 1-100 μM and 100-600 μM. The detection limit of the sensor was 0.41 μM (S/N = 3). Excellent repeatability, reproducibility, low background noise, and immunity to interference were demonstrated using the proposed system, and satisfactory results were achieved for the nitrite assay using real samples. These results demonstrate a new method for nitrite detection developed using the proposed PEC sensor.

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.

Near-infrared light-enhanced colorimetric signal amplification strategy for tumor marker detection based on MoS2/CuO/Au nanocomposite

A novel signal amplification strategy was developed by combining near-infrared light with MoS2/CuO/Au nanocomposite for building a colorimetric immunoassay. First, MoS2/CuO/Au nanocomposite was synthesized by precipitation and photoreduction methods and characterized by scanning electron microscopy (SEM) and X-ray powder diffraction (XRD). MoS2/CuO/Au nanocomposite has oxidase-like activity and can oxidize TMB to form a blue product (TMBox). Further, the catalytic oxidation of TMB was accelerated under near-infrared (NIR) laser radiation. The sandwich-type colorimetric immunoassay was constructed using MoS2/CuO/Au nanocomposite. Under the enhancement of near-infrared light, carcinoembryonic antigen (CEA) was sensitively detected in the range 0.1 to 40 ng/mL with the limit of detection of 0.03 ng/mL. Moreover, the immunosensor has excellent selectivity and anti-interference, good repeatability, and stability.

An ultrasensitive electrochemical immunosensor based on meso-PdN NCs and Au NPs/N-CNTs for quantitative cTnI detection

Electrochemical immunosensors have gained considerable attention in detecting human disease markers due to their excellent specificity, high sensitivity, and facile operation. Herein, a rational-designed sandwich-type electrochemical immunosensor is constructed for the sensitive detection of cardiac troponin I (cTnI) using nitrogen-doped carbon nanotubes loaded with gold nanoparticles (Au NPs/N-CNTs) as substrate and highly active mesoporous palladium-nitrogen nanocubes (meso-PdN NCs) as secondary antibody markers. Benefitting from its large specific surface area (638.04 m2 g-1) and high nitrogen content, novel polydopamine (PDA)/ halloysite nanotubes (HNTs) hybrid derived one-dimensional (1D) N-CNTs can provide more binding sites for the in-situ growth of Au NPs to connect Ab1. Furthermore, as an ideal substrate material, Au NPs/N-CNTs exhibit finely tuned mesoporous structures and outstanding conductivity, which facilitate the mass and electron transfer during the electrocatalysis process. Besides, highly concave surfaces and crystalline mesopores of meso-PdN NCs expose more surfaces and crevices, providing abundant reactive sites for H2O2 reduction. Remarkably, the as-obtained immunosensor presented a wide linear range (from 10 fg mL-1 to 100 ng mL-1) and an excellent low detection limit (9.85 fg mL-1). This study may offer new insights into the precise fabrication of efficient electrochemical immunosensors for various clinical diagnosis applications.

Surface plasmon resonance-enhanced photoelectrochemical immunoassay with Cu-doped porous Bi2WO6 nanosheets

The development of rapid screening sensing platforms to improve pre-screening mechanisms in community healthcare is necessary to meet the significant need for portable testing in biomarker diagnostics. Here, we designed a portable smartphone-based photoelectrochemical (PEC) immunoassay for carcinoembryonic antigen (CEA) detection using Cu-doped ultrathin porous Bi2WO6 (CuBWO) nanosheets as the photoactive material. The CuBWO nanosheets exhibit a fast photocurrent response and excellent electrical transmission rate under UV light due to their surface plasmon resonance effect (SPR). The method uses glucose oxidase-labeled secondary antibody as a signal indicator for sandwich-type immune conjugation. In the presence of the target CEA, the electrons and holes generated at the surface of the photo-excited ultrathin porous CuBWO were rapidly consumed by the production of H2O2 from glucose oxidase oxidizing glucose, resulting in a weakened photocurrent signal. The photocurrent intensity increased logarithmically and linearly with increasing CEA concentration (0.02-50 ng mL-1), with a detection limit of 15.0 pg mL-1 (S/N = 3). The system provides a broader idea for inferring the electron-hole transport mechanism in ultrathin porous nanosheet layer materials and developing efficient PEC sensors.

A signal "switch-on" photoelectrochemical sensor based on a 3D-FM/BiOI heterostructure for the sensitive detection of l-ascorbic acid

A highly efficient 3D flower MoS2 (3D-FM)-based heterostructure photocatalyst (3D-FM/BiOI) was successfully obtained via a simple hydrothermal synthesis strategy. 3D-FM/BiOI showed prominent photoelectrochemical performance, distinguished stability and good selectivity. The introduction of 3D-FM, by promoting the photoelectric property attributed to it, facilitated the separation of photogenerated electron-hole pairs. Since the redox process of l-ascorbic acid (l-AA) resulted in an increasing photocurrent of 3D-FM/BiOI, a signal "switch-on" photoelectrochemical sensor (PECS) was designed to sensitively determine l-AA for the first time. Under optimized conditions, the 3D-FM/BiOI PECS worked over a wide range from 1 μM to 0.8 mM with a low detection limit of 0.05 μM (S/N = 3). The PECS was successfully exploited for l-AA sensing in human urine with excellent accuracy and applicability, demonstrating its practical precision and superb serviceability. Furthermore, the 3D-FM/BiOI PECS exhibited satisfactory selectivity and stability, providing a great potential platform for the construction of an l-AA sensor in various practical samples and complicated environments.

Recent Progress in Photoelectrochemical Sensing of Pesticides in Food and Environmental Samples: Photoactive Materials and Signaling Mechanisms

Pesticides have become an integral part of modern agricultural practices, but their widespread use poses a significant threat to human health. As such, there is a pressing need to develop effective methods for detecting pesticides in food and environmental samples. Traditional chromatography methods and common rapid detection methods cannot satisfy accuracy, portability, long storage time, and solution stability at the same time. In recent years, photoelectrochemical (PEC) sensing technology has gained attention as a promising approach for detecting various pesticides due to its salient advantages, including high sensitivity, low cost, simple operation, fast response, and easy miniaturization, thus becoming a competitive candidate for real-time and on-site monitoring of pesticide levels. This review provides an overview of the recent advancements in PEC methods for pesticide detection and their applications in ensuring food and environmental safety, with a focus on the categories of photoactive materials, from single semiconductor to semiconductor-semiconductor heterojunction, and signaling mechanisms of PEC sensing platforms, including oxidation of pesticides, steric hindrance, generation/decrease in sacrificial agents, and introduction/release of photoactive materials. Additionally, this review will offer insights into future prospects and confrontations, thereby contributing novel perspectives to this evolving domain.