Photo-Responsive Phase-Separating Fluorescent Molecules for Intracellular Protein Delivery

Cellular membranes, including the plasma and endosome membranes, are barriers to outside proteins. Various vehicles have been devised to deliver proteins across the plasma membrane, but in many cases, the payload gets trapped in the endosome. Here we designed a photo-responsive phase-separating fluorescent molecule (PPFM) with a molecular weight of 666.8 daltons. The PPFM compound condensates as fluorescent droplets in the aqueous solution by liquid-liquid phase separation (LLPS), which disintegrate upon photoirradiation with a 405 nm light-emitting diode (LED) lamp within 20 min or a 405 nm laser within 3 min. The PPFM coacervates recruit a wide range of peptides and proteins and deliver them into mammalian cells. Photolysis disperses the payload from condensates into the cytosolic space. Altogether, a type of small molecules that are photo-responsive and phase separating are discovered; their coacervates can serve as transmembrane vehicles for intracellular delivery of proteins, whereas photo illumination triggers the cytosolic distribution of the payload. Here, we designed a low-molecular-weight compound that forms molecular coacervates based on liquid-liquid phase separation in the aqueous solution. The molecular coacervates deliver proteins into mammalian cells and disperse the payload within the cytosol upon photoillumination. This work showcases a small-molecule coacervation system and photoresponsive cytosolic protein delivery.+image

Automated summary

The article describes a new fluorescent molecule that can deliver proteins into mammalian cells and release the payload into the cytosol through photoinduced disintegration.