A method of detecting a target biological entity in a biofluid using a sensor, wherein the biofluid comprises a plurality of the target biological entities and nanoparticles, the sensor comprising a substrate bearing a pair of electrodes having an affinity with the nanoparticles, and wherein a region between the electrodes defines a sensing region. The method comprises: treating the biofluid with a suspension comprising a plurality of nanoparticles to obtain a treated mixture comprising bound nanoparticle-entity assemblies; introducing the treated mixture to the sensor; conditioning the sensor in the presence of the treated mixture by applying an activation voltage between the electrodes to increase a degree of connection between a surface of the pair of electrodes and at least one bound nanoparticle-entity assembly in contact with the surface of the pair of electrodes; and detecting the presence of target biological entities by using the pair of electrodes to detect a current through the at least one bound nanoparticle-entity assembly.