One of the main approaches of design and manipulation of the quantum emitters’ radiative properties is based on proper control of optical modes of the surrounding quantum emitter environment, leading to, in its ultimate case, to a strong regime of the emitter - environment interaction. In this Letter, we present the realization of a mesoscopic physical system (Au SPASER nanoparticle with polydopamine shell containing dye molecules Cy 7.5) in which the strong optical coupling regime allows: (i) to get rid of dye molecules quenching, (ii) to suppress photobleaching of dye molecules and (iii) to get a great enhancement of dye molecules fluorescence. We have reduced the rate of fluorescence quenching of dye molecules in PDA by 1000 times and increased the fluorescence emission rate of dye molecules by 30 time, thus preparing bright, nanoscale and biocompatible fluorescent probes suitable for bio-sensing applications. As an example of practical use of the probe, we demonstrate direct detection of single SARS-CoV-2 viral particle via fluorescence measurements of the probes attached to the viral particle through the antibodies.