Development of an optical biosensor utilizing gold nanoparticles to detect porcine reproductive and respiratory syndrome virus

Porcine Reproductive and Respiratory Syndrome virus (PRRSv) is a highly contagious disease that causes dramatic losses in swine production. Some common symptoms of infection can include anorexia, fever, reproduction failure, and difficult breathing. These problems accompanied with some swine showing no signs of infection have created a desperate need for serologic tests in PRRS detection. We are utilizing the transduction method of fluorescence resonance energy transfer (FRET) to detect the PRRS virus. Two different techniques were examined: (1) a FRET method which utilized two fluorophores, termed the donor and acceptor and (2) a FRET method which utilized a donor fluorophore with an acceptor gold nanoparticle. Energy transfer occurs between the donor and acceptor when they are in close proximity In our experiments, SDOW-1 7 antibodies, specific to PRRS virus, were labeled with a donor fluorophore, Alexa Fluor 546, while protein A was labeled to either the acceptor fluorophore, Alexa Fluor 594 or 20 nm gold nanoparticles (AuNP). Protein A preferentially binds to the Fc region of the antibody, thus creating the FRET bioprobes. The bioprobes were immobilized onto silica optical fibers via silanization. The biosensors were exposed to different concentrations of the virus. Upon exposure, the antibodies would undergo a conformational change, resulting in a change in fluorescence. The AuNP bioprobes showed the greatest response with a detection limit of < 25 particles/ml while the fluorophore bioprobes displayed a detection limit of similar to 12,700 particles/ml. It was concluded the AuNP bioprobes provided greater sensitivity with fast detection, within 10 minutes.