Fast fluorescent screening assay and dual electrochemical sensing of bacterial infection agent (Streptococcus agalactiae) based on a fluorescent-immune nanofibers

In this study, detection and determination of Streptococcus agalactiae, the cause of pneumonia and meningitis in infants, were done in two steps using electrochemical sensor modified with fluorescent-immune nanofibers. In a layer by layer design, fluorescent nanofibers containing quantum dots (QDs) were electrospinned on the surface of gold electrode and functionalized by specific anti-Streptococcus agalactiae antibody. While the nanofibers were transparent to the emission of QDs, the appearance of a dark spot in the fluorescent view of the immune-sensor, qualitatively confirmed the existence of different concentrations of bacteria in the tested sample. Furthermore, the continuous electron-charge transfer system through gold-QDs-polymer chains ensured quantitative electrochemical recognition of bacteria with a high signal-to-noise ratio. Consequently, real time detection of Streptococcus agalactiae was introduced by providing a detection limit of 6 CFU/mL, dynamic range of 6 order of magnetite and high specificity in clinical samples in the presence of interfering agents using fluorescent-immune sensor.