Synthetic probe development for measuring single or few-cell activity and efflux

Studying the single cell protein secretome offers the opportunity to understand how a phenotypically heterogeneous population of individual cells contribute to ensemble physiology and signaling. Polarized secretion events such as neurotransmitter release and cytokine signaling necessitates spatiotemporal information to elucidate structure-function relationships. Polymer functionalized single-walled carbon nanotube protein sensor arrays allow microscopic imaging of secreted protein footprints and enable the study of the spatiotemporal heterogeneity of protein secretion at the single-cell level. The protocols for carbon nanotube sensor creation, sensor array preparation, and imaging secreted proteins in both prokaryotic and mammalian cells are presented in this chapter. Secreted RAP1 and HIV-1 integrase proteins were used as proof-of-concept examples. Additionally, we discuss potential variety of protein and non-protein analyte effluxes that can be imaged using this platform, as well as current and future perspectives related to sensor development and deployment.