Previously we developed a method based on the suspended nanochannel resonator (SNR) that is capable of weighing nanometer sized particles with high precision. Here I will describe how we’re using the SNR to quantify the empty:full capsid ratio for a purified Adeno-Associated Virus (AAV) samples in a way that provides a direct readout without the need to calibrate based on serotype. This approach achieves a resolution near 10 zeptograms (corresponding to 1% of the genome holding capacity of the AAV capsid) in a 10-minute sampling window using only a few μL of sample. I will also present recent progress towards using suspended microchannel resonators to provide nondestructive measurements of single-cell biophysical properties (e.g. mass, density and stiffness) with the goal of predicting transfection and vector production yield.