A point of use sensor assay for detecting purely viral versus viral-bacterial samples

Rapid confirmative categorization of infections in clinical settings as bacterial or viral is frequently challenging due to the vague presentations of diseases and symptomatic similarities. A point of use disposable paper based impedimetric sensor has been developed for generic differentiation of bacteria and virus based on their interaction with chitosan stabilized silver nanoparticles. Decrease in the electrochemical impedance spectra at low frequencies (10 Hz–100 Hz) was observed when a droplet of bacterial suspension, dispensed on polyaniline nanofibers’ modified filter paper substrate, was subjected to chitosan stabilized silver nanoparticles. An increase in the impedance was seen when viruses were subject to the same. Bacterial perforation and viral aggregation were hypothesised to effect these responses, and confirmed with cryo-scanning electron microscopy and transmission electron microscopy respectively. The principle has been demonstrated with E. coli, P. aeruginosa, S. aureus as model bacteria and bacteriophages T4, N4 and MS2 as model viruses suspended in simulated cerebrospinal fluid. Generic differentiation of the two in mixtures was also possible. These characteristic electrical impedance signatures of bacteria and virus, established here, have promising prospects in inexpensive and scalable bedside diagnostic development.