A double reaction system induced electrochemiluminescence enhancement based on SnS2 QDs@MIL-101 for ultrasensitive detection of CA242

An electrochemiluminescence sensor based on lanthanide bimetallic MOFs with a "cascade sensitization mechanism" for the sensitive detection of CA242

Lanthanide metal-organic frameworks (Ln-MOFs) broaden the optical sensing applications of lanthanide ions due to the antenna effect between organic ligands and metals. However, the sensitization ability of the ligand to metal ions is limited, and maximizing the sensitization of the electrochemiluminescence behavior of Eu3+ is still a challenge for the application of Ln-MOFs. Therefore, under the guidance of the "cascade sensitization mechanism" based on the antenna effect sensitizing the electrochemiluminescence of bimetallic Ln-MOFs, we proposed Eu/Tb-MOFs with high luminescence intensity as a signal probe. According to the antenna effect, the conjugated structure and high extinction coefficient of the benzene ring of 2-amino terephthalic acid (NH2-BDC) can enhance the ECL luminescence intensity of Eu/Tb-MOFs. Tb3+ can act as an energy bridge between NH2-BDC and Eu3+, buffering the energy gap. The bimetallic sensitization is formed between Tb3+ and Eu3+, which can inhibit the reverse internal flow of energy and ensure the high luminous efficiency of Eu3+. In addition, the nanosphere mixed valence Fe3O4 as a co-reactant accelerator promotes the formation of transient free radical SO4•- through the valence change of Fe2+/Fe3+. The ECL immunosensor constructed by luminophores Eu/Tb-MOFs and nanosphere Fe3O4 provided a new explanation for the ECL self-luminous of Eu/Tb-MOFs.

Strand displacement amplification triggered 3D DNA roller assisted CRISPR/Cas12a electrochemiluminescence cascaded signal amplification for sensitive detection of Ec-16S rDNA

BACKGROUND

Escherichia coli can cause gastrointestinal infection, urinary tract infection and other infectious diseases. Accurate detection of Escherichia coli 16S rDNA (Ec-16S rDNA) in clinical practice is of great significance for the identification and treatment of related diseases. At present, there are various types of sensors that can achieve accurate detection of Ec-16S rDNA. Electrochemiluminescence (ECL) has attracted considerable attention from researchers, which causes excellent performance in bioanalysis. Based on the previous research, it is significance to develop a novel, sensitive and efficient ECL biosensor.

RESULTS

In this work, an ECL biosensor for the detection of Ec-16S rDNA was constructed by integrating CRISPR/Cas12a technology with the cascade signal amplification strategy consisting of strand displacement amplification (SDA) and dual-particle three-dimensional (3D) DNA rollers. The amplification products of SDA triggered the operation of the DNA rollers, and the products generated by the DNA rollers activated CRISPR/Cas12a to cleave the signal probe, thereby realizing the change of the ECL signal. The cascade amplification strategy realized the exponential amplification of the target signal and greatly improved the sensitivity. Manganese dioxide nanoflowers (MnO2 NFs) as a co-reaction promoter effectively enhanced the ECL intensity of tin disulfide quantum dots (SnS2 QDs). A new ternary ECL system (SnS2 QDs/S2O82-/MnO2 NFs) was prepared, which made the change of ECL intensity of biosensor more significant. The proposed biosensor had a response range of 100 aM-10 nM and a detection limit of 27.29 aM (S/N = 3).

SIGNIFICANCE AND NOVELTY

Herein, the cascade signal amplification strategy formed by SDA and dual-particle 3D DNA rollers enabled the ECL biosensor to have high sensitivity and low detection limit. At the same time, the cascade signal amplification strategy was integrated with CRISPR/Cas12a to enable the biosensor to efficiently detect the target. It can provide a new idea for the detection of Ec-16S rDNA in disease diagnosis and clinical analysis.

Electrochemiluminescence of Semiconductor Quantum Dots and Its Biosensing Applications: A Comprehensive Review

Electrochemiluminescence (ECL) is the chemiluminescence triggered by electrochemical reactions. Due to the unique excitation mode and inherent low background, ECL has been a powerful analytical technique to be widely used in biosensing and imaging. As an emerging ECL luminophore, semiconductor quantum dots (QDs) have apparent advantages over traditional molecular luminophores in terms of luminescence efficiency and signal modulation ability. Therefore, the development of an efficient ECL system with QDs as luminophores is of great significance to improve the sensitivity and detection flux of ECL biosensors. In this review, we give a comprehensive summary of recent advances in ECL using semiconductor QDs as luminophores. The luminescence process and ECL mechanism of semiconductor QDs with various coreactants are discussed first. Specifically, the influence of surface defects on ECL performance of semiconductor QDs is emphasized and several typical ECL enhancement strategies are summarized. Then, the applications of semiconductor QDs in ECL biosensing are overviewed, including immunoassay, nucleic acid analysis and the detection of small molecules. Finally, the challenges and prospects of semiconductor QDs as ECL luminophores in biosensing are featured.

Dissolution-Enhanced Luminescence Enhanced Digital Microfluidics Immunoassay for Sensitive and Automated Detection of H5N1

Protein bioassay is a critical tool for the screening and detection of protein biomarkers in disease diagnostics and biological applications. However, the detection sensitivity and system automation of current immunoassays do not meet the emerging demands of clinical applications. Here, we developed a dissolution-enhanced luminescence-enhanced digital microfluidics immunoassay (DEL-DMF), which significantly improves the sensitivity and automation of the protein bioassay. In DEL-DMF, the sample and reagent droplets are controlled to complete the processes of sample transport, immunoreaction, and buffer washing, which not only minimizes sample consumption to 2 μL and enhances the binding efficiency of immunoreaction but also streamlines all the procedures and simplifies the process of immunoassay. Moreover, dissolution-enhanced luminescence using NaEuF₄ NPs as nanoprobes boosts the fluorescence and increases the sensitivity of the bioassay. We demonstrate the enhanced analytical performance of our DEL-DMF immunoassay to detect H5N1 hemagglutinin in human serum and saliva. A limit of detection of 1.16 pM was achieved in less than 0.5 h with only 2 μL sample consumption. Overall, our DEL-DMF immunoassay combines the merits of the microfluidics platform and dissolution-enhanced luminescence, thus affording superior detection sensitivity and system automation for protein biomarkers. This novel immunoassay microsystem holds great potential in clinical and biological applications.

A novel electrochemical immunosensor based on PdAgPt/MoS2 for the ultrasensitive detection of CA 242

Dynamic monitoring of tumor markers is an important way to the diagnosis of malignant tumor, evaluate the therapeutic effect of tumor and analyze the prognosis of cancer patients. As a tumor marker of digestive tract, CA242 is often used to Assess the therapeutic effect of colorectal cancer and pancreatic cancer. In this study, immunosensor technology was used to detect CA242. PdAgPt nanocomposites, which have great advantages in biocompatibility, electrical conductivity and catalytic properties, were prepared by hydrothermal synthesis method. The prepared PdAgPt nanocomposites were loaded onto the surface of molybdenum disulfide (MoS₂) with large surface area, and the new nanocomposites were synthesized. Using PdAgPt/MoS₂ as signal amplification platform, the label-free CA242 electrochemical immunosensor has a wide detection range that extends from 1*10⁻⁴ U/ml to 1*10² U/ml and a low detection limit (LOD, 3.43*10⁻⁵ U/ml) after optimization of experimental conditions. In addition, the CA242 immunosensor designed in this study also performed well in the evaluation of repeatability, selectivity and stability, and was successfully used for the detection of CA242 in human serum sample. Therefore, the label-free electrochemical immunosensor constructed in this study has a broad application prospect in the detection of clinical biomarkers.