Binding assay for cholera toxin based on sequestration electrochemistry using lactose labeled with an electroactive compound

Bio-Receptors Functionalized Nanoparticles: A Resourceful Sensing and Colorimetric Detection Tool for Pathogenic Bacteria and Microbial Biomolecules

Pathogenic bacteria and several biomolecules produced by cells and living organisms are common biological components posing a harmful threat to global health. Several studies have devised methods for the detection of varying pathogenic bacteria and biomolecules in different settings such as food, water, soil, among others. Some of the detection studies highlighting target pathogenic bacteria and biomolecules, mechanisms of detection, colorimetric outputs, and detection limits have been summarized in this review. In the last 2 decades, studies have harnessed various nanotechnology-based methods for the detection of pathogenic bacteria and biomolecules with much attention on functionalization techniques. This review considers the detection mechanisms, colorimetric prowess of bio-receptors and compares the reported detection efficiency for some bio-receptor functionalized nanoparticles. Some studies reported visual, rapid, and high-intensity colorimetric detection of pathogenic bacteria and biomolecules at a very low concentration of the analyte. Other studies reported slight colorimetric detection only with a large concentration of an analyte. The effectiveness of bio-receptor functionalized nanoparticles as detection component varies depending on their selectivity, specificity, and the binding interaction exhibited by nanoparticles, bio-receptor, and analytes to form a bio-sensing complex. It is however important to note that the colorimetric properties of some bio-receptor functionalized nanoparticles have shown strong and brilliant potential for real-time and visual-aided diagnostic results, not only to assess food and water quality but also for environmental monitoring of pathogenic bacteria and a wide array of biomolecules.

Recent developments in antibody-based assays for the detection of bacterial toxins

Considering the urgent demand for rapid and accurate determination of bacterial toxins and the recent promising developments in nanotechnology and microfluidics, this review summarizes new achievements of the past five years. Firstly, bacterial toxins will be categorized according to their antibody binding properties into low and high molecular weight compounds. Secondly, the types of antibodies and new techniques for producing antibodies are discussed, including poly- and mono-clonal antibodies, single-chain variable fragments (scFv), as well as heavy-chain and recombinant antibodies. Thirdly, the use of different nanomaterials, such as gold nanoparticles (AuNPs), magnetic nanoparticles (MNPs), quantum dots (QDs) and carbon nanomaterials (graphene and carbon nanotube), for labeling antibodies and toxins or for readout techniques will be summarized. Fourthly, microscale analysis or minimized devices, for example microfluidics or lab-on-a-chip (LOC), which have attracted increasing attention in combination with immunoassays for the robust detection or point-of-care testing (POCT), will be reviewed. Finally, some new materials and analytical strategies, which might be promising for analyzing toxins in the near future, will be shortly introduced.

Quantitative detection of Vibrio cholera toxin by real-time and dynamic cytotoxicity monitoring

We report here the quantitative detection of Vibrio cholerae toxin (CT) in isolates and stool specimens by dynamic monitoring of the full course of CT-mediated cytotoxicity in a real-time cell analysis (RTCA) system. Four cell lines, including Y-1 mouse adrenal tumor cells, Chinese hamster ovary (CHO) cells, small intestine epithelial (FHs74Int) cells, and mouse adrenal gland (PC12-Adh) cells, were evaluated for their suitability for CT-induced cytotoxicity testing. Among them, the Y-1 line was demonstrated to be the most sensitive for CT-mediated cytotoxicity, with limits of detection of 7.0 pg/ml for purified CT and 0.11 ng/ml for spiked CT in pooled negative stool specimens. No CT-mediated cytotoxicity was observed for nontoxigenic V. cholerae, non-V. cholerae species, or non-V. cholerae enterotoxins. The CT-RTCA assay was further validated with 100 stool specimens consecutively collected from patients with diarrhea and 200 V. cholerae isolates recovered from patients and the environment, in comparison to a reference using three detection methods. The CT-RTCA assay had sensitivities and specificities of 97.5% and 100.0%, respectively, for V. cholerae isolates and 90.0% and 97.2% for stool specimens. For stool specimens spiked with CT concentrations ranging from 3.5 pg/ml to 1.8 ng/ml, the inoculation-to-detection time was 1.12 ± 0.38 h, and the values were inversely correlated with CT concentrations (ρ = -1; P = 0.01). The results indicate that the CT-RTCA assay with the Y-1 cell line provides a rapid and sensitive tool for the quantitative detection of CT activities in clinical specimens.