A novel immunosensor for Enterobacter sakazakii based on multiwalled carbon nanotube/ionic liquid/thionine modified electrode

Sandwich capture ultrasensitive sensor based on biohybrid interface for the detection of Cronobacter sakazakii

A simple, rapid and ultrasensitive visual sensing method for the detection of Cronobacter sakazakii (C. sakazakii) based on a biohybrid interface was established. During the entire sensing process, quadruple-cascade amplification showed its superior sensing performance. First, the prepared immunomagnetic beads (IMB) were used to isolate and enrich specific targets from the food matrix. After adding the fusion aptamer, the aptamer sequence specifically recognized the target and formed the immune sandwich structure of antibody-target-fusion aptamer. In addition, the fusion aptamer also included the template sequence of exponential amplification reaction (EXPAR), which contained the antisense sequence of the G-rich sequence. Therefore, a large number of G-rich sequences can be generated after EXPAR can be triggered in the presence of Bst. DNA polymerase, nicking endonuclease, cDNA, and dNTP. They were self-assembled into G-quadruplex structures and then combined with hemin to form G4/hemin DNAzyme, resulting in visible coloration and measuring absorbance at 450 nm for quantitative detection. The assay showed a limit of detection (LOD) of 2 CFU/mL in pure culture and 12 CFU/g in milk powder in optimal conditions. This method provides a promising strategy for rapid and point-of-care testing (POCT) since it does not require DNA extraction, medium culturing, and expensive instrumentation. KEY POINTS: •Single-cell level detection of C. sakazakii with ultrasensitive and rapidness •The fusion aptamer integrated recognition and amplification •Sensing analysis of C. sakazakii based on cascade amplification of biohybrid interface.

Label-Free Electrochemical Immunosensor Based on a Functionalized Ionic Liquid and Helical Carbon Nanotubes for the Determination of Cardiac Troponin I

A label-free electrochemical immunosensor for cardiac troponin I was prepared by using a helical carbon nanotube-supported aldehyde-functionalized ionic liquid. Because of the good conductivity of ionic liquid and helical carbon nanotubes, high sensitivity of the immunosensor was obtained. Functionalized ionic liquid provided binding sites for antibody, which simplified the process of sensor construction. Cardiac troponin I was detected by this immunosensor with a linear range of 0.05-30 ng/mL and a detection limit of 0.03 ng/mL. The electrochemical immunosensor had satisfactory reproducibility, high sensitivity, and acceptable specificity.

Label-Free Electrochemical Immunosensor Based on Ionic Liquid Containing Dialdehyde As a Novel Linking Agent for the Antibody Immobilization

Demand for label-free electrochemical immunosensor has resulted in extensive research in improving the conductivity of a sensing interface and antibody immobilization. In this paper, an electrochemical immunosensor for prostate specific antigen based on dialdehyde-functionalized ionic liquid used as a novel linking reagent to replace glutaraldehyde for the antibody immobilization is described. The novel linking reagent enhanced the conductivity of the sensing interface. Thus, the proposed immunosensor had a wider linear range of 0.05-30 ng mL^-1, with a lower detection limit of 0.04 ng mL^-1 compared with the immunosensor based on glutaraldehyde for the antibody immobilization.

Past, Present and Future of Sensors in Food Production

Microbial contamination management is a crucial task in the food industry. Undesirable microbial spoilage in a modern food processing plant poses a risk to consumers' health, causing severe economic losses to the manufacturers and retailers, contributing to wastage of food and a concern to the world's food supply. The main goal of the quality management is to reduce the time interval between the filling and the detection of a microorganism before release, from several days, to minutes or, at most, hours. This would allow the food company to stop the production, limiting the damage to just a part of the entire batch, with considerable savings in terms of product value, thereby avoiding the utilization of raw materials, packaging and strongly reducing food waste. Sensor systems offer major advantages over current systems as they are versatile and affordable but need to be integrated in the existing processing systems as a process analytical control (PAT) tool. The desire for good selectivity, low cost, portable and usable at working sites, sufficiently rapid to be used at-line or on-line, and no sample preparation devices are required. The application of biosensors in the food industry still has to compete with the standard analytical techniques in terms of cost, performance and reliability.

An amperometric immunosensor based on multi-walled carbon nanotubes-thionine-chitosan nanocomposite film for chlorpyrifos detection

In this work, a novel amperometric immunosensor based on multi-walled carbon nanotubes-thionine-chitosan (MWCNTs-THI-CHIT) nanocomposite film as electrode modified material was developed for the detection of chlorpyrifos residues. The nanocomposite film was dropped onto a glassy carbon electrode (GCE), and then the anti-chlorpyrifos monoclonal antibody was covalently immobilized onto the surface of MWCNTs-THI-CHIT/GCE using the crosslinking agent glutaraldehyde (GA). The modification procedure was characterized by using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Under the optimized conditions, a linear relationship between the relative change in peak current of different pulse voltammetry (DPV) and the logarithm of chlorpyrifos solution concentration was obtained in the range from 0.1 to 1.0 × 10⁵ ng/mL with a detection limit of 0.046 ng/mL. The proposed chlorpyrifos immunosensor exhibited high reproducibility, stability, and good selectivity and regeneration, making it a potential alternative tool for ultrasensitive detection of chlorpyrifos residues in vegetables and fruits.

Scano-magneto immunoassay based on carbon nanotubes/gold nanoparticles nanocomposite for Salmonella enterica serovar Typhimurium detection

To improve sensitivity of S. enterica serovar Typhimurium detection, multiwalled carbon nanotubes (MWCNTs) and gold nanoparticles (AuNPs) were combined and used as a label to amplify signal in a scanometric based assay. In this study, the MWCNTs/AuNPs nanocomposite was fabricated by directly assemble of Au(3+) to MWCNTs and allowed growing of AuNPs along the MWCNTs surface. This MWCNTs/AuNPs nanocomposite was then attached to anti-S. typhimurium antibody (MWCNTs/AuNPs/Ab(1)) and used as a detecting molecule. Upon binding to Salmonella, they were pre-concentrated by magenetic beads/antibody (MBs/Ab(2)) forming a sandwich immuno-complex which is later spotted on a nitrocellulose membrane coated slide. Silver reduction was applied to amplify signal. The detection limit of 42CFU/ml was achieved when 2% BSA was used as a blocking agent. Given different types of real samples testing, chicken broth was found to give lowest detection limit, followed by orange juice low fat and whole milk. Selectivity testing was performed by using Escherichia coli as interference and found slightly cross-reactivity which could be due to specificity of the Ab used. By virtue of using a slide for multi-samples spotting and a flatbed scanner for signal-read out acquisition, this scano-magneto immunoassay could enable low-cost detection as well as high throughput screening.