Fluorimetric and impedimetric sensors for the detection of pathogenic bacteria using carbon dots

Abstract

Over the last decade, the need for rapid testing of pathogens such as bacteria has spiked to curb mortalities in the least possible time. The quick spread of infection with antimicrobial resistant bacteria in the densely populated regions has made the situation even worse. Despite advancements in the detection of pathogenic bacteria, the time-consuming assays, low accuracy, high cost and manual intervention reduces the credibility of current detection techniques. The nanotechnology revolution has made a great stride in rapid and accurate bacterial detection. Recently, fluorescent carbon nanoparticle such as carbon dots has emerged as a promising tool for the detection of pathogenic bacteria. These carbon dots can be used to develop fluorimetric and impedimetric sensors for the detection of pathogenic bacteria with improved turn-around time, sensitivity and selectivity. newlineThis thesis explains the development of fluorimetric and impedimetric biosensors based on carbon dots for bio-imaging and selective identification of pathogenic bacteria such as Escherichia coli, Staphylococcus aurues, Pseudomonas aeurginosa, Bacillus subtilis, Proteus vulgaris and Klebsiella pneumoniae. For the bacterial cell imaging, different variants of bright fluorescent nitrogen/sulphur carbon dots were used to achieve multicolour fluorescence imaging. A unique pH-sensitive nitrogen doped carbon dots was also synthesized for the cell imaging applications and the NtCD was able to tag bacterial cells at specific pH. Also, colistin functionalized carbon dots were used to develop fluorimetric and impedimetric sensors for the sensitive and selective detection of Gram-negative bacteria. Nitrogen and sulfur co-doped carbon dots (N/SCD) were synthesized using microwave-assisted method from two different precursor combinations namely, thiourea and cysteamine with 50X TAE (Tris-acetate-ethylenediamine) buffer. The synergistic presence of nitrogen and sulfur as a dopant enhanced fluorescence with higher quantum yield (57% and 13.2%). N/SCD was found..