High-Efficiency CdSe Quantum Dots/Fe3O4@MoS2/S2O82- Electrochemiluminescence System Based on a Microfluidic Analysis Platform for the Sensitive Detection of Neuron-Specific Enolase

Microfluidic Immunosensor Platform for Sensitive Detection of Human Epidermal Growth Factor Receptor-2 Based on Enhanced Cathode Electrochemiluminescence of Bimetallic Nanoclusters

In this work, a microfluidic immunosensor chip was developed by incorporating microfluidic technology with electrochemiluminescence (ECL) for sensitive detection of human epidermal growth factor receptor-2 (HER2). The immunosensor chip can achieve robust reproducibility in mass production by integrating multiple detection units in a series. Notably, nanoscale materials can be better adapted to microfluidic systems, greatly enhancing the accuracy of the immunosensor chip. Ag@Au NCs closed by glutathione (GSH) were introduced in the ECL microfluidic immunosensor system with excellent and stable ECL performance. The synthesized CeO2-Au was applied as a coreaction promoter in the ECL signal amplification system, which made the result of HER2 detection more reliable. In addition, the designed microfluidic immunosensor chip integrated the biosensing system into a microchip, realizing rapid and accurate detection of HER2 by its high throughput and low usage. The developed short peptide ligand NARKFKG (NRK) achieved an effective connection between the antibody and nanocarrier for improving the detection efficiency of the sensor. The immunosensor chip had better storage stability and sensitivity than traditional detection methods, with a wide detection range from 10 fg·mL-1 to 100 ng·mL-1 and a low detection limit (LOD) of 3.29 fg·mL-1. In general, a microfluidic immunosensor platform was successfully constructed, providing a new idea for breast cancer (BC) clinical detection.

Ultrasensitive detection of zearalenone based on electrochemiluminescent immunoassay with Zr-MOF nanoplates and Au@MoS2 nanoflowers

In this work, an effective competitive-type electrochemiluminescence (ECL) immunosensor was constructed for zearalenone determination by using Zr-MOF nanoplates as the ECL luminophore and Au@MoS2 nanoflowers as the substrate material. Zr-MOF have an ultra-thin sheet-like structure that accelerates the transfer of electrons, ions and co-reactant intermediates, which exhibited strong and stable anodic luminescence. The three-dimensional Au@MoS2 nanoflowers would form a thin film modification layer on the glassy carbon electrode (GCE). And its good electrical conductivity and higher specific surface area utilization further improving the sensitivity of the ECL immunosensor. Under the optimized conditions, the proposed immunosensor exhibited satisfactory stability, sensitivity and accuracy, and its ECL signal was proportional to the logarithm of ZEN concentration (0.0001-100 ng/mL) and the limit of detection (LOD) was 0.034 pg/mL. In addition, the results of recovery experiment acquired for wheat flour and pig urine samples further proved the feasibility of the immunosensor for the detection of real samples, indicating its potential for ultrasensitive detection of ZEN.

Reticular Heterojunction for Organic Photoelectrochemical Transistor Detection of Neuron-Specific Enolase

Reticular heterojunctions on the basis of metal-organic frameworks (MOFs) and covalent organic frameworks (COFs) have sparked considerable interest in recent research endeavors, which nevertheless have seldom been studied in optoelectronic biosensing. In this work, its utilization for organic photoelectrochemical transistor (OPECT) detection of the important cancer biomarker of neuron-specific enolase (NSE) is reported. A MOF@COF@CdS quantum dots (QDs) heterojunction is rationally designed to serve as the photogating module against the polymeric channel. Linking with a sandwich complexing event, target-dependent alternation of the photogate is achieved, leading to the changed photoelectric conversion efficiency as indicated by the amplified OPECT signals. The proposed assay demonstrates good analytical performance in detecting NSE, featuring a linear detection range from 0.1 pg mL-1 to 100 ng mL-1 , with a detection limit of 0.033 pg mL-1 .

Rapid and sensitive electrochemiluminescence detection using easily fabricated sensor with an integrated two-electrode system

The electrochemiluminescence (ECL) behavior of a tri(2,2'-bipyridyl)ruthenium(ii) (Ru(bpy)32+)/tripropylamine (TPrA) system was investigated in sensor chips with two kinds of integrated two-electrode systems, which included screen-printed electrodes (SPE) and physical vapor deposition (PVD) electrodes. Firstly, under excitation with an optimal transient potential (TP) within 100 ms, the ECL assay could be carried out on the microchips using an Au & Au electrode system, emitting strong and stable light signal. Secondly, on the PVD chip, the ECL intensity initiated by optimal TP was eight times stronger than the peak light signal emitted by the linear sweep voltammetry model. Finally, the logarithmic ECL intensities exhibited a linear increase with the logarithmic concentrations of Ru(bpy)32+ in both the SPE and PVD chips without any reference electrode (RE). Typically, the integration of an interdigital two-electrode system in the microchip significantly enhanced the ECL sensitivity of Ru(bpy)32+ because the large relative area between the working electrode (WE) and counter electrode (CE) achieved a highly efficient mass transfer. This improvement enabled the establishment of a reliable linear relationship across a wide concentration range, spanning from 1 pM to 1 μM (R2 = 0.998). Therefore, the exceptional ECL response of the Ru(bpy)32+/TPrA system on microfluidic chips using a two-electrode system and the TP excitation model has been demonstrated. This suggests that ECL chips without a RE have broad potential for the rapid and sensitive detection of multiple targets.

Triple signal-enhanced electrochemiluminescence strategy using iron-based metal-organic frameworks modified with Ru(II) complexes for carcino-embryonic antigen detection

The development of a highly efficient electrochemiluminescence (ECL) emitter represents an effective strategy for enhancing the sensitivity and repeatability of ECL immunosensors. In this study, a sandwich-type ECL immunosensor with triple enhancement was developed to detect carcino-embryonic antigen (CEA). This sensor is based on a porous structure of iron-based metal-organic framework (NH2-MIL-88(Fe)), encapsulating the luminescent tris(2,2'-bipyridine)ruthenium (II) (Ru (bpy)32+), Au@MoS2 with a 3D nanoflower structure as an enhanced substrate. In this system, the MOFs framework encapsulated luminophore was realized to solve its water solubility to reach stable luminescence, as well as the triple enhancement effect based on the principle of amino catalysis, Mo4+/Mo6+ active site conversion, and gold nanoparticles (Au NPs) promotion, which significantly enhanced the detection sensitivity. Furthermore, the ECL immunosensor demonstrated successful application in the highly sensitive and selective detection of CEA, achieving a detection limit of 38.9 fg mL-1. The sensor demonstrates remarkable sensitivity, specificity, stability, repeatability, and practicality in the analysis of human serum samples. This investigation presents a highly effective approach for the ultrasensitive detection of trace proteins.

Efficient Electrochemiluminescence Sensing in Microfluidic Biosensors: A Review

Microfluidic devices are capable of handling 10-9 L to 10-18 L of fluids by incorporating tiny channels with dimensions of ten to hundreds of micrometers, and they can be fabricated using a wide range of materials including glass, silicon, polymers, paper, and cloth for tailored sensing applications. Microfluidic biosensors integrated with detection methods such as electrochemiluminescence (ECL) can be used for the diagnosis and prognosis of diseases. Coupled with ECL, these tandem devices are capable of sensing biomarkers at nanomolar to picomolar concentrations, reproducibly. Measurement at this low level of concentration makes microfluidic electrochemiluminescence (MF-ECL) devices ideal for biomarker detection in the context of early warning systems for diseases such as myocardial infarction, cancer, and others. However, the technology relies on the nature and inherent characteristics of an efficient luminophore. The luminophore typically undergoes a redox process to generate excited species which emit energy in the form of light upon relaxation to lower energy states. Therefore, in biosensor design the efficiency of the luminophore is critical. This review is focused on the integration of microfluidic devices with biosensors and using electrochemiluminescence as a detection method. We highlight the dual role of carbon quantum dots as a luminophore and co-reactant in electrochemiluminescence analysis, drawing on their unique properties that include large specific surface area, easy functionalization, and unique luminescent properties.

Potential-Resolved Electrochemiluminescence Multiplex Immunoassay for Florfenicol and Chloramphenicol in a Single Sample

The simultaneous detection of multiple antibiotic residues in food is of great significance for food safety. In this work, a novel dual-potential electrochemiluminescence (ECL) immunoassay was designed for the simultaneous detection of chloramphenicol and fluorfenicol residues in food. Ru@MOF was used as an anodic probe, and SnS2 QDs-PEI-Au-MoS2 was used as a cathodic probe. Notably, the coreactant for both luminophores was K2S2O8, avoiding interactions caused by different kinds of coreactants. Au nanoparticles functionalized with a nitrogen- and sulfur-doped graphene oxide-modified glassy carbon electrode to improve the electron transfer efficiency and provide a larger surface area for immobilization of antigen. The linear range for the detection of florfenicol was determined to be 0.1-1000 ng mL-1 with a detection limit of 0.03 ng mL-1, and the linear range for the detection of chloramphenicol was 0.01-1000 ng mL-1 with a detection limit of 3.2 pg mL-1 by recording the ECL responses at two different excitation potentials. The proposed immunoassay achieved a more stable recovery in the detection of actual samples and provided a new analytical method for the simultaneous detection of florfenicol and chloramphenicol residues with high sensitivity and specificity.

Electrochemiluminescence resonance energy transfer between a Ru-ZnMOF self-enhanced luminophore and a double quencher ZnONF@PDA to detect NSE

The construction of advanced systems capable of accurately detecting neuron-specific enolase (NSE) is essential for rapidly diagnosing small-cell lung cancer. In this study, an electrochemiluminescence (ECL) resonance energy transfer immunosensor was proposed for the ultra-sensitive detection of NSE. The co-reactants C2O42- and Ru(bpy)32+ were integrated to form a self-enhanced ECL luminophore (Ru-ZnMOF) as the ECL donor. The abundant carboxyl functional groups of Ru-ZnMOF supported antibody 1 via an amidation reaction. Polydopamine-modified zinc dioxide nanoflowers, as ECL acceptors, inhibited Ru-ZnMOF ECL signaling. The linear range of NSE was 10 fg mL-1 to 100 ng mL-1 with a detection limit of 3.3 fg mL-1 (S/N = 3), which is suitably low for determining NSE in real samples.

PEG-functionalized black phosphorus quantum dots as stable and biocompatible electrochemiluminescence luminophores for sensitive detection of tumor biomarker

Despite black phosphorous (BP) QDs possess the merits of size-tunable band-gap, high electron mobility, and intrinsic defects, the spontaneous agglomeration and rapid oxidation of BP QDs in aqueous solution caused low electrochemiluminescence (ECL) efficiency and unstable ECL signal, which confined its further application of biological analysis. Herein, polyethylene glycol-functionalized BP QDs (PEG@BP QDs) were prepared showing an efficient and stable ECL response, which is attributed to the fact that PEG as protectant not only effectively prevented the spontaneous agglomeration, but also restrained the rapid oxidation of BP QDs in aqueous solution. As proof-of-concept, PEG@BP QDs were used as an efficient ECL emitter to combine with palindrome amplification-induced DNA walker to construct a sensitive ECL aptasensing platform for detecting cancer marker mucin 1 (MUC1). Interestingly, with the aid of positively charged thiolated PEG, the reaction rate of DNA walker on the electrode interface was clearly increased for the recovery of the ECL signal. The ECL aptasensor provides sensitive determination with the detection limit of 16.5 fg/mL. The proposed strategy paves a path for the development of efficient and stable ECL nanomaterials to construct biosensors for biosensing and clinical diagnosis.

Polyacrylic acid/polyethylene glycol hybrid antifouling interface for photoelectrochemical immunosensing of NSE based on ZnO/CdSe

In this paper, a novel photoelectrochemical (PEC) immunosensor based on ZnO/CdSe semiconductor composite material was constructed to detect neuron-specific enolase (NSE) in a super-sensitive and quantitative way. The antifouling interface composed of polyacrylic acid (PAA) and polyethylene glycol (PEG) can prevent non-specific proteins from adhering to the electrode surface. As an electron donor, ascorbic acid (AA) can increase the photocurrent's stability and intensity by clearing away photogenerated holes. Because of the specific recognition between antigen and antibody, the quantitative detection of NSE can be achieved. The PEC antifouling immunosensor based on ZnO/CdSe has a wide linear range (0.10 pg mL^-1-100 ng mL^-1) and a low detection limit (34 fg mL^-1), which has potential application in the clinical diagnosis of small cell lung cancer.

Microfluidic platforms integrated with nano-sensors for point-of-care bioanalysis

Microfluidic technology provides a portable, cost-effective, and versatile tool for point-of-care (POC) bioanalysis because of its associated advantages such as fast analysis, low volumes of reagent consumption, and high portability. Along with microfluidics, the application of nanomaterials in biosensing has attracted lots of attention due to their unique physical and chemical properties for enhanced signal modulation such as signal amplification and signal transduction for POC bioanalysis. Hence, an enormous number of microfluidic devices integrated with nano-sensors have been developed for POC bioanalysis targeting low-resource settings. Herein, we review recent advances in POC bioanalysis on nano-sensor-based microfluidic platforms. We first briefly summarized the different types of cost-effective microfluidic platforms, followed by a concise introduction to nanomaterial-based biosensors. Then, we highlighted the application of microfluidic platforms integrated with nano-sensors for POC bioanalysis. Finally, we discussed the current limitations and perspective trends of the nano-sensor-based microfluidic platforms for POC bioanalysis.