Flow Injection Analysis System Using Magnetic Beads, Screen Printed Electrodes and Magnets

Disposable Voltammetric Immunosensors Integrated with Microfluidic Platforms for Biomedical, Agricultural and Food Analyses: A Review

Disposable immunosensors are analytical devices used for the quantification of a broad variety of analytes in different areas such as clinical, environmental, agricultural and food quality management. They detect the analytes by means of the strong interactions between antibodies and antigens, which provide concentration-dependent signals. For the herein highlighted voltammetric immunosensors, the analytical measurements are due to changes in the electrical signals on the surface of the transducers. The possibility of using disposable and miniaturized immunoassays is a very interesting alternative for voltammetric analyses, mainly, when associated with screen-printing technologies (screen-printed electrodes, SPEs), and microfluidic platforms. The aim of this paper is to discuss a carefully selected literature about different examples of SPEs-based immunosensors associated with microfluidic technologies for diseases, food, agricultural and environmental analysis. Technological aspects of the development of the voltammetric immunoassays such as the signal amplification, construction of paper-based microfluidic platforms and the utilization of microfluidic devices for point-of-care testing will be presented as well.

Potentiometric Detection of Listeria monocytogenes via a Short Antimicrobial Peptide Pair-Based Sandwich Assay

Peptide-based sandwich assays are promising tools in molecular detection, but may be restricted by the availability of "pairs" of affinity peptides. Herein, a new potentiometric sandwich assay for bacteria based on peptide pairs derived from an antimicrobial peptide (AMP) ligand is demonstrated. As a model, the original AMP with a well-defined structure for  Listeria monocytogenes (LM) can be split into two fragments to serve as the peptide pairs for the sandwich assay. The recognition and binding of the short peptide pairs to the target can be verified by circular dichroism, flow cytometry, fluorometry, and optical microscopy. The potentiometric magnetic bead-based sandwich assay is designed by using horseradish peroxidase as a label. The enzyme can catalyze the oxidation of 3,3',5,5'-tetramethylbenzidine with H₂O₂ to induce a potential change on a polymeric membrane ion-selective electrode. Under optimal conditions, the concentration of LM can be determined potentiometrically in a linear range of 1.0 × 10² to 1.0 × 10⁶ CFU mL^-1 with a detection limit of 10 CFU mL^-1 (3σ). The proposed sensing strategy expands the applications of peptides in the field of bioassays.

Recent advances in flow injection analysis

A dynamic development of methodologies of analytical flow injection measurements during four decades since their invention has reinforced the solid position of flow analysis in the arsenal of techniques and instrumentation of contemporary chemical analysis.