Immunosensor assembly The immunosensor was assembled on a 5-MHz AT-cut quartz crystal. Before assembly, the gold electrode was triple cleaned in piranha, and then received a final ethanol or acetone rinse and dried in a stream of N 2 (grams). The quartz crystal was then mounted in a flow cell holder, rinsed with phosphate buffer (PB, 50 mM phosphate, pH 7.2), and brought to resonant frequency at room temperature. For the work described herein, a Stanford Research Systems quartz crystal microbalance model 200, which measures both frequency and resistance, was used. Solutions were passed through the cell at a flow rate of 28 μL/min controlled by a Masterflex peristaltic pump. The sequence for biosensor assembly was protein G (20 μg/mL, 10 min), BSA (1 mg/mL, 5 min), antibody (20 μg/mL, 16 min), and viral simulant (500 μg/mL, 11 min) all in PB. The nanoparticles were filtered prior to use with a 0.22-μm filter from Millipore. The crystal was washed for a minimum of 10 min with PB between each step. Deposition of protein G allowed for the immobilization of the Fc region of anti-HA and anti-FLAG antibodies. The binding of non-functionalized Autiop nanoparticles (500 μg/mL, 11 min) with anti-HA antibodies was used as a negative control and as a test for nonspecific binding. Positive control was established utilizing anti-HA's recognition of recombinant H5 HA protein (5 μg/mL, 10 min).