Companion-Probe & Race platform for interrogating nuclear protein and migration of living cells.

Probing nuclear protein expression while correlating cellular behavior is crucial for deciphering underlying causes of cellular disorders, such as tumor metastasis. Despite efforts to access nuclear proteins by trafficking the double barriers of cell membrane and nuclear membrane, they mostly fall short of the capacity for analyzing various proteins in different cells. Herein, we introduce a Companion-Probe & Race (CPR) platform that enables interrogating nuclear proteins in living cells, while guiding and tracking cellular behaviors (e.g., migration) in real time. The Companion-Probe consists of two polypeptide complexes that were structured with nuclear localization signal (NLS) for entering nucleus, recognition polypeptide for targeting different sites of nuclear proteins, and fragments of green fluorescent protein (GFP) that can recover a whole fluorescent GFP once the two polypeptide complexes combine with a same target protein. The two polypeptide complexes were expressed by two plasmids (named "probe plasmids") that were uniformly and efficiently delivered into cells by nano-electroporation (NEP), a high-performance delivery method for cell focal-poration and accelerated intracellular delivery. To track cell migration, multiple radial microchannels were designed with micro-landmarks on the platform to serve as addressable runways for cells. The proof-of-concept of CPR platform was validated with clinical primary cells that indicated the positive-correlation between nuclear protein murine double minute 2 (MDM2) expression level and cell migration velocity. This platform shows great promises to interrogate nuclear proteins in live cells, and to decode their roles in determining cellular behaviors on a chip.