Impedimetric\nGram-Positive Bacteria Biosensor Using\nVancomycin-Coated Silica Nanoparticles with a Gold Nanocluster-Deposited\nElectrode

We introduce a swift, label-free electrochemical biosensor\ndesigned\nfor the precise on-site detection of Gram-positive bacteria via electrochemical\nimpedance spectroscopy. The biosensor was prepared by electroplating\nthe electrode surface with gold nanoclusters (AuNCs) on the gold-interdigitated\nwave-shaped electrode with a printed circuit board (Au-PCB) electrode,\nwhich plays a role in cost-effective and promising lab-on-a-chip microsystems\nand integrated biosensing systems. This was followed by the application\nof silica nanoparticle-modified vancomycin (SiNPs-VAN) that binds\nto Gram-positive bacteria and facilitates their detection on the AuNC-coated\nsurface. The biosensor demonstrated remarkable sensitivity and specificity.\nIt could detect as few as 10<sup>2</sup> colony-forming units (CFU)/mL\nof Staphylococcus aureus, 10<sup>1</sup> CFU/mL of Bacillus cereus, and 10<sup>2</sup> CFU/mL of Micrococcus luteus within 20 min. Additionally, SiNPs-VAN is also known for its high\nstability, low cost, and ease of preparation. It is effective in identifying\nGram-positive bacteria in water samples across a concentration range\nof 10<sup>2</sup>–10<sup>5</sup> CFU/mL and shows selective\nidentification of Gram-positive bacteria with minimal interference\nfrom Gram-negative bacteria like Escherichia coli. The ability of the biosensor to quantify Gram-positive bacteria\naligns well with the results obtained from the quantitative real-time\npolymerase chain reaction (qRT-PCR). These findings highlight the\npotential of electrochemical biosensors for the detection of pathogens\nand other biological entities, marking a significant advancement in\nthis field.