Aptamer-Based Viability Impedimetric Sensor for Bacteria

The development of an aptamer-based viability impedimetric sensor for bacteria (AptaVISens-B) is presented. Highly specific DNA aptamers to live <i>Salmonella typhimurium</i> were selected via the cell-systematic evolution of ligands by exponential enrichment (SELEX) technique. Twelve rounds of selection were performed; each comprises a positive selection step against viable <i>S. typhimurium</i> and a negative selection step against heat killed <i>S. typhimurium</i> and a mixture of related pathogens, including <i>Salmonella enteritidis</i>, <i>Escherichia coli</i>, <i>Staphylococcus aureus</i>, <i>Pseudomonas aeruginosa</i>, and <i>Citrobacter freundii</i> to ensure the species specificity of the selected aptamers. The DNA sequence showing the highest binding affinity to the bacteria was further integrated into an impedimetric sensor via self-assembly onto a gold nanoparticle-modified screen-printed carbon electrode (GNP-SPCE). Remarkably, this aptasensor is highly selective and can successfully detect <i>S. typhimurium</i> down to 600 CFU mL^–1 (equivalent to 18 live cells in 30 μL of assay volume) and distinguish it from other <i>Salmonella</i> species, including <i>S. enteritidis</i> and <i>S. choleraesuis</i>. This report is envisaged to open a new venue for the aptamer-based viability sensing of a variety of microorganisms, particularly viable but nonculturable (VBNC) bacteria, using a rapid, economic, and label-free electrochemical platform

Aptamer-Based Impedimetric Sensor for Bacterial Typing

The development of an aptamer-based impedimetric sensor for typing of bacteria (AIST-B) is presented. Highly specific DNA aptamers to <i>Salmonella enteritidis</i> were selected via Cell-SELEX technique. Twelve rounds of selection were performed; each comprises a positive selection step against <i>S. enteritidis</i> and a negative selection step against a mixture of related pathogens, including <i>Salmonella typhimurium</i>, <i>Escherichia coli</i>, <i>Staphylococcus aureus</i>, <i>Pseudomonas aeruginosa</i>, and <i>Citrobacter freundii</i>, to ensure the species-specificity of the selected aptamers. After sequencing of the pool showing the highest binding affinity to <i>S. enteritidis</i>, a DNA sequence of high affinity to the bacteria was integrated into an impedimetric sensor via self-assembly onto a gold nanoparticles-modified screen-printed carbon electrode (GNPs-SPCE). Remarkably, this aptasensor is highly selective and can successfully detect <i>S. enteritidis</i> down to 600 CFU mL^–1 (equivalent to 18 CFU in 30 μL assay volume) in 10 min and distinguish it from other Salmonella species, including <i>S. typhimurium</i> and <i>S. choleraesuis</i>. This report is envisaged to open a new venue for the aptamer-based typing of a variety of microorganisms using a rapid, economic, and label-free electrochemical platform

Development of Bacteriostatic DNA Aptamers for Salmonella

<i>Salmonella</i> is one of the most dangerous and common food-borne pathogens. The overuse of antibiotics for disease prevention has led to the development of multidrug resistant <i>Salmonella</i>. Now, more than ever, there is a need for new antimicrobial drugs to combat these resistant bacteria. Aptamers have grown in popularity since their discovery, and their properties make them attractive candidates for therapeutic use. In this work, we describe the selection of highly specific DNA aptamers to <i>S. enteritidis</i> and <i>S. typhimurium</i>. To evolve species-specific aptamers, twelve rounds of selection to live <i>S. enteritidis</i> and <i>S. typhimurium</i> were performed, alternating with a negative selection against a mixture of related pathogens. Studies have shown that synthetic pools combined from individual aptamers have the capacity to inhibit growth of <i>S. enteritidis</i> and <i>S. typhimurium</i> in bacterial cultures; this was the result of a decrease in their membrane potential