We present a protocol for the real-time optical detection of single unlabeled proteins as they are secreted from living cells. This is based on interferometric scattering (iSCAT) microscopy, which can be applied to a variety of different biological systems and configurations.
Gemeinhardt, A., McDonald, M. P., König, K., Aigner, M., Mackensen, A., Sandoghdar, V. Label-Free Imaging of Single Proteins Secreted from Living Cells via iSCAT Microscopy. J. Vis. Exp. (141), e58486, doi:10.3791/58486 (2018).