Electrochemical detection of a single cytomegalovirus at an ultramicroelectrode and its antibody anchoring

Significance The need for rapid, dependable, and sensitive detection of biological threats is ever increasing. Relatively arduous techniques, with varying degrees of sensitivity, exist for the detection of pathogens, including ELISA, electrogenerated chemiluminescence methods, sensitive PCR techniques, culturing, and microscopy. Here, we extend the observation of particle collisions on ultramicroelectrodes to murine cytomegalovirus. We further present an electrochemical technique for the specific detection of low concentrations of a virus by observing the effect of virus and antibody-specific polystyrene bead binding. This work, in principle, provides a framework for the detection of any biologically relevant antigen. We report observations of stochastic collisions of murine cytomegalovirus (MCMV) on ultramicroelectrodes (UMEs), extending the observation of discrete collision events on UMEs to biologically relevant analytes. Adsorption of an antibody specific for a virion surface glycoprotein allowed differentiation of MCMV from MCMV bound by antibody from the collision frequency decrease and current magnitudes in the electrochemical collision experiments, which shows the efficacy of the method to size viral samples. To add selectivity to the technique, interactions between MCMV, a glycoprotein-specific primary antibody to MCMV, and polystyrene bead “anchors,” which were functionalized with a secondary antibody specific to the Fc region of the primary antibody, were used to affect virus mobility. Bead aggregation was observed, and the extent of aggregation was measured using the electrochemical collision technique. Scanning electron microscopy and optical microscopy further supported aggregate shape and extent of aggregation with and without MCMV. This work extends the field of collisions to biologically relevant antigens and provides a novel foundation upon which qualitative sensor technology might be built for selective detection of viruses and other biologically relevant analytes.