An in situ quenching electrochemiluminescence biosensor amplified with aptamer recognition-induced multi-DNA release for sensitive detection of pathogenic bacteria

Enzymatically Mediated In Situ Generation of Z-Scheme Bi2S3/Bi2MoO6 Heterojunction-Based Organic Photoelectrochemical Transistor for METTL3/METTL14 Detection

The OPECT biosensing platform, which connects optoelectronics and biological systems, offers significant amplification and more possibilities for research in biological applications. In this work, a homogeneous organic photoelectrochemical transistor (OPECT) biosensor based on a Bi2S3/Bi2MoO6 heterojunction was constructed to detect METTL3/METTL14 protein activity. The METTL3/METTL14 complex enzyme was used to catalyze adenine (A) on an RNA strand to m6A, protecting m6A-RNA from being cleaved by an E. coli toxin (MazF). Alkaline phosphatase (ALP) catalyzed the conversion of Na3SPO3 to H2S through an enzymatic reaction. Due to the adoption of the strategy of no fixation on the electrode, the generated H2S was easy to diffuse to the surface of the ITO electrode. The Bi2S3/Bi2MoO6 heterojunction was formed in situ through a chemical replacement reaction with Bi2MoO6, improving photoelectric conversion efficiency and realizing signal amplification. Based on this "signal on" mode, METTL3/METTL14 exhibited a wide linear range (0.00001-25 ng/μL) between protein concentration and photocurrent intensity with a limit of detection (LOD) of 7.8 fg/μL under optimal experimental conditions. The applicability of the developed method was evaluated by investigating the effect of four plasticizers on the activity of the METTL3/METTL14 protein, and the molecular modeling technique was employed to investigate the interaction between plasticizers and the protein.

Colorimetric biosensor based on aptamer recognition-induced multi-DNA release and peroxidase-mimicking three-way junction DNA-Ag/PtNCs for the detection of Salmonella typhimurium

Salmonella typhimurium, as a major foodborne pathogen, poses a serious threat to public health safety worldwide. Here, we present a colorimetric biosensor based on aptamer recognition-induced multi-DNA release and peroxidase-mimicking three-way junction DNA-silver/platinum bimetallic nanoclusters (3WJ/DNA-Ag/PtNCs) for the detection of S. typhimurium. In this method, S. typhimurium specifically binds to the aptamer and releases multiple cDNAs to form the three-way junction DNA structure and synthesize silver/platinum bimetallic nanoclusters, which induces signaling changes. Interestingly and importantly, the use of 3WJ/DNA as the template for synthesizing Ag/PtNCs gives the method an extremely low background signal. Under the optimal conditions, the constructed biosensor had a linear response range of 2.6 × 102-2.6 × 106 CFU/mL and a detection limit of 2.6 × 102 CFU/mL for the detection of S. typhimurium. In addition, the proposed method can effectively detect S. typhimurium in milk.

Shared hairpin structure electrochemiluminescence biosensor based on Au@Ni-Co metal organic frameworks for simultaneous detection of Pb(II) and S.aureus

The excessive content of lead (Pb(II)) and Staphylococcus aureus (S.aureus) seriously harms the quality of aquatic products. In this paper, a highly sensitive electrochemiluminescence (ECL) biosensor was constructed using the synergistic effect of Au NPs@Nickel-Cobalt-Metal-organic frameworks (Au@Ni-Co-MOFs) and double potential resolution function of urchin-like Au@luminol and Cadmium sulfide quantum dots (CdS QDs) for synchronous detection of Pb(II) and S.aureus in aquatic products. Au@Ni-Co-MOFs as the base material, its cube structure can improve the surface active area and sensitivity of the sensor, providing more catalytic active sites for the two functional probes. Urchin-like Au@luminol binding aptamer DNA2 specifically recognizes Pb(II), CdS QDs binding aptamer DNA3 specifically recognizes S.aureus, which collaboratively catalyzed hydrogen peroxide reduction to produce two electrochemiluminescence signals. The shared hairpin structure DNA1 binds stably to Au@Ni-Co-MOFs via the Au-S bond, and the two functional probes are complementary paired with the DNA1 respectively to ensure the specificity of the aptamer. According to the ECL intensity changes of different potentials signal sources, the synchronous detection of Pb(II) and S.aureus with different concentrations is realized. The sensor realizes the detection of two targets in aquatic products and provides a new strategy for the simultaneous detection of multiple targets.

Advances in signal amplification strategies applied in pathogenic bacteria apta-sensing analysis-A review

Pathogenic bacteria are primarily kinds of food hazards that provoke serious harm to human health via contaminated or spoiled food. Given that pathogenic bacteria continue to reproduce and expand once they contaminate food, pathogenic bacteria of high concentration triggers more serious losses and detriments. Hence, it is essential to detect low-dose pollution at an early stage with high sensitivity. Aptamers, also known as "chemical antibodies", are oligonucleotide sequences that have attracted much attention owing to their merits of non-toxicity, small size, variable structure as well as easy modification of functional group. Aptamer-based bioanalysis has occupied a critical position in the field of rapid detection of pathogenic bacteria. This is attributed to the unique advantage of using aptamers as recognition elements in signal amplification strategies. The signal amplification strategy is an effective means to improve the detection sensitivity. Some diverse signal amplification strategies emphasize the synthesis and assembly of nanomaterials with signal amplification capabilities, while others introduce various nucleic acid amplification techniques into the detection system. This review focuses on a variety of signal amplification strategies employed in aptamer-based detection approaches to pathogenic bacteria. Meanwhile, we provided a detailed introduction to the design principles and characteristics of signal amplification strategies, as well as the improvement of sensor sensitivity. Ultimately, the existing issues and development trends of applying signal amplification strategies in apta-sensing analysis of pathogenic bacteria are critically proposed and prospected. Overall, this review discusses from a new perspective and is expected to contribute to the further development of this field.

Nanoparticles-assisted aptamer biosensing for the detection of environmental pathogens

Given the importance of public health, it is crucial to develop quick, targeted, highly sensitive, and accurate technologies to monitor pathogenic microbes in response to the growing concerns of food and environmental safety. Although conventional approaches for microbiological detection are available, they are laborious, and often skill demanding. Therefore, such approaches are incompetent in the on-site or high-throughput assessment of pathogenic microbes. Numerous efforts have been made to develop biosensors that use nucleic acid aptamer as the biorecognition element, which would avoid the abovementioned limitations. Incorporating nanomaterials (NMs) into aptamer-based biosensors (aptasensors) improves their sensitivity and specificity, opening exciting possibilities for various applications, such as bioanalysis of food and environmental samples. Over the last decade, nanomaterial-conjugated aptasensors have seen a steadily rising demand. To this end, the main goal of this study is to demonstrate the novelty in the design of nanomaterial-conjugated aptasensors and how they can be used to detect different pathogenic microbes in water and food. The intent of this paper is to evaluate the cutting-edge techniques that have appeared in nano-aptasensors throughout the past few years, such as manufacturing procedures, analytical credibility, and sensing mechanisms. Additionally, the fundamental performance parameters of aptasensing techniques (such as detection limits, and sensing ranges response) were also used to evaluate their practical applicability. Finally, it is anticipated that this study will inspire innovative ideas and techniques for the construction and use of aptasensors for monitoring pathogenic microorganisms in food, drinks, recreational water, and wastewater.

Vancomycin-modified nitrogen and chloride doped carbon dots and their application as a Staphylococcus aureus probe

In this research, N, Cl-doped carbon dots (N, Cl-CDs) were prepared in choline chloride-glycerol deep eutectic solvent (DES) by microwave method. N, Cl-CDs surface was modified with vancomycin for detection of Staphylococcus aureus (S. aureus) bacteria in the range of 10²-10⁷ colony-forming unit per milliliter (CFU/mL). The detection limit was 10¹ CFU/mL. Morphology and structure of N, Cl-CDs were characterized by transmission electron microscopy (TEM), X-ray photon spectroscopy (XPS), photoluminescence spectroscopy, FT-IR spectroscopy, energy dispersive X-ray spectroscopy (EDXS) and zeta potential. The prepared N, Cl-CDs had excellent dispersion in water, particle size range of 2-3 nm, and quantum yield of 38.75%. Speed, wide linear range and more convenient were advantages of new probe with respect to other methods.

Recent Advances in Electrochemical Biosensors for Food Control

The rapid and sensitive detection of food contaminants is becoming increasingly important for timely prevention and treatment of foodborne disease. In this review, we discuss recent developments of electrochemical biosensors as facile, rapid, sensitive, and user-friendly analytical devices and their applications in food safety analysis, owing to the analytical characteristics of electrochemical detection and to advances in the design and production of bioreceptors (antibodies, DNA, aptamers, peptides, molecular imprinted polymers, enzymes, bacteriophages, etc.). They can offer a low limit of detection required for food contaminants such as allergens, pesticides, antibiotic traces, toxins, bacteria, etc. We provide an overview of a broad range of electrochemical biosensing designs and consider future opportunities for this technology in food control.

Mycobacteriophage Derived Lipoarabinomannan Binding Protein for Recognizing Non-Tuberculosis Mycobacteria

Non-tuberculosis mycobacteria (NTM) is one family of pathogens usually leading to nosocomial infections. Exploration of high-performance biological recognition agent plays a pivotal role for the development of point-of-care testing device and kit for detecting NTM. Mycobacterium smegmatis (M. smegmatis) is a NTM which has been frequently applied as an alternative model for highly pathogenic mycobacteria. Herein, a recombinant tail protein derived from mycobacteriophage SWU1 infecting M. smegmatis was expressed with Escherichia coli system and noted as GP89. It shows a fist-like structure according to the results of homology modeling and ab initio modeling. It is confirmed as a lipoarabinomannan (LAM) binding protein, which can recognize studied NTM genus since abundant LAM constructed with d-mannan and d-arabinan is distributed over the mycobacterial surface. Meanwhile an enhanced green fluorescent protein (eGFP)-fused GP89 protein was acquired with a fusion expression technique. Then GP89 and eGFP-fused GP89 were applied to establish a sensitive and rapid method for fluorescent detection of M. smegmatis with a broad linear range of 1.0 × 10² to 1.0 × 10⁶ CFU mL^-1 and a low detection limit of 69 CFU mL^-1. Rapid and reliable testing of antimicrobial susceptibility was achieved by the GP89-based fluorescent method. The present work provides a promising recognition agent for studied NTM and opens an avenue for clinical diagnosis of NTM-induced infections.

A New Method for Abrin Detection Based on the Interaction between Target Molecules and Fluorescently Labeled Aptamers on Magnetic Microspheres

A quantitative structure-activity relationship (QSAR) model for the structure and affinity of abrin aptamers was established. A higher affinity abrin aptamer based on the established QSAR model was screened by site-directed mutagenesis. The fluorescence quenching effect between magnetic microspheres and fluorescent molecules was studied for the first time. A new method for abrin detection based on the interaction between target molecules and fluorescently labeled aptamers on magnetic microspheres was developed, with the detection limit of 5 ng mL^-1. This method can overcome the influence of complex environmental interferents in abrin detection and can meet the analysis requirements for simulated samples such as water, soil, and food.

Novel integrating polymethylene blue nanoparticles with dumbbell hybridization chain reaction for electrochemical detection of pathogenic bacteria

Pathogenic bacteria infections pose a major threat to human health which can be found in contaminated food and infected humans. Herein, an electrochemical sensor was developed for pathogenic bacteria assay using a dual amplification strategy of polymethylene blue nanoparticles (pMB NPs) and dumbbell hybridization chain reaction (DHCR). The strong binding ability of aptamer to targets endowed outstanding performance in identifying Staphylococcus aureus (S. aureus) among other typical bacteria. The released T strands were hybridized with capture DNA on electrode surface which triggered DHCR in the presence of two dumbbell-shaped helper DNA, leading to the formation of extended and tight dsDNA polymers. In combination with pMB NPs (redox indicators), S. aureus was quantitatively detected in a range of 10-10⁸ CFU/mL and the detection limit reached 1 CFU/mL. Moreover, this sensor was successfully applied for S. aureus detection in human serum and foods, demonstrating the reliability in practical applications.

Shared-cathode closed bipolar electrochemiluminescence cloth-based chip for multiplex detection

Electrochemiluminescence (ECL) chips have been widely used in the field of medical diagnosis. However, most of these chips currently in use are costly and require high amounts of sample. In this work, we present, for the first time, a shared-cathode closed bipolar electrochemiluminescence (SC-CBP-ECL) cloth-based chip, which can be used for multiplex detection. The SC-CBP-ECL chips ($0.03-0.05 for each chip) are manufactured using carbon ink- and wax-based screen-printing techniques, without the need for expensive and complex fabrication equipment. Under optimised conditions, the SC-CBP-ECL chips were successfully used for coinstantaneous detection of glucose in double ECL systems (i.e., Ru(bpy)₃²⁺ and luminol), with corresponding linear ranges of 0.05-1 mM and 0.05-10 mM, and detection limits of 0.0382 mM and 0.0422 mM. To our knowledge, this is the first report on the application of fibre material-based closed bipolar electrodes (C-BPE) combined with double ECL systems. Furthermore, the SC-CBP-ECL chips exhibit an acceptable specificity and good reproducibility and stability and can be used for glucose detection in human serum samples with a good agreement compared with the clinical method. Finally, the SC-CBP-ECL chips could be successfully used for simultaneous detection of seven glucose samples and also show potential for simultaneous detection of three different targets (hydrogen peroxide [H₂O₂], glucose, and uric acid [UA]). Therefore, we believe that the chip described in this study has broad potential application in the field of cost-effective multiplex detection.

A spatially resolved ratiometric electrochemiluminescence immunosensor for myoglobin detection using Au@Ag2S as signal amplification tags

A spatially resolved ratiometric ECL immunosensor for myoglobin detection was developed via resonance energy transfer for signal amplification.