Vancomycin functionalized WO thin film-based impedance sensor for efficient capture and highly selective detection of Gram-positive bacteria.

In this study, we report a facile, reusable, and highly sensitive label-free impedance sensor for discriminating Gram-positive and Gram-negative bacteria. The impedance sensor was fabricated using gold interdigitated electrodes onto a tungsten oxide thin film. X-Ray diffraction confirmed the formation of polycrystalline tungsten oxide. Field emission scanning electron microscopy and atomic force microscopy revealed that tungsten oxide has a porous structure. Tungsten oxide was functionalized with vancomycin, a glycopeptide antibiotic known to have a specific interaction with the peptidoglycan layer of Gram-positive bacteria. Fourier transform infrared microscopy and scanning electron microscopy were employed to test the morphological coating of vancomycin on interdigitated electrodes/tungsten oxide sensor. The functionalized tungsten oxide sensor was highly efficient in the capture of Gram-positive bacteria. The impedance measurement was also sensitive to differentiate between viable and non-viable Gram-positive bacteria. Limit of detection 10 colony forming unit/ml, linear dynamic range 10-10 colony forming unit/ml under physiological conditions and reusable nature of this vancomycin coated impedance sensor provide a label-free strategy for quick, sensitive and highly selective detection of Gram-positive bacteria.