Comprehensive Study of the Chemistry behind the Stability of Carboxylic SWCNT Dispersions in the Development of a Transparent Electrode

DNAzyme-based colorimetric biosensor for rapid detection of Shigella flexneri

Shigella flexneri, a formidable gram-negative bacterium, that triggers the most contagious form of shigellosis through bloody diarrhea, presenting a significant threat. As a severe foodborne pathogen, it underscores the need for intensified research into more effective prevention strategies and heightened public health awareness. The traditional methods used to detect S. flexneri are time-consuming and inconvenient. As a result, there is a need for accurate and rapid diagnostics in food and water samples. The experimental methods involved modifying S. flexneri-specific HGD-aptamer and employing single-walled carbon nanotubes to develop a colorimetric detection assay exploiting DNAzyme. The HGD-aptamer-SWCNT complex binds specifically to S. flexneri cells, resulting in a detectable colorimetric response in a test sample involving enzymatic reactions. The assay's efficacy was validated through sensitivity and specificity evaluations, which demonstrated a detection limit of 51 CFU/mL and selective detection of the target with no signal in different bacterial environments. Comparative analysis with PCR-based methods confirmed the assay's performance, highlighting its potential as a rapid, cost-effective, and user-friendly diagnostic tool. This study introduces an innovative approach to identifying S. flexneri, which has the potential to improve food safety, environmental monitoring, and public health.

Single-Walled Carbon Nanotube-Modified Gold Leaf Immunosensor for Escherichia coli Detection

The requirement to prevent foodborne illnesses underscores the need for reliable detection tools, stimulating biosensor technology with practical solutions for in-field applications. This study introduces a low-cost immunosensor based on a single-walled carbon nanotube (SWCNT)-modified gold leaf electrode (GLE) for the sensitive detection of Escherichia coli. The immunosensor is realized with a layer-by-layer (LbL) assembly technique, creating an electrostatic bond between positively charged polyethylenimine (PEI) and negatively charged carboxyl-functionalized SWCNTs on the GLE. The structural and functional characterization of the PEI-SWCNT film was performed with Raman spectroscopy, high-resolution scanning electron microscopy (HRSEM), and electrical measurements. The PEI-SWCNT film was used as a substrate for antibody immobilization, and the electrochemical sensing potential was validated using electrochemical impedance spectroscopy (EIS). The results showed a wide dynamic range of E. coli detection, 101-108 cfu/mL, with a limit of detection (LOD) of 1.6 cfu/mL in buffer and 15 cfu/mL in the aqueous solution used for cleansing fresh lettuce leaves, affirming its efficiency as a practical and affordable tool in enhancing food safety.

Editorial for Special Issue: "Preparation of Nanomaterial Modified Electrode and Its Sensing Application"

Electrochemical sensors have attracted enormous attention for their precision, high sensitivity, rapid response, and ease-of-use for analysis [...].