Supramolecular Encapsulation of Small-Ultra Red Fluorescent Proteins in Virus-Like Nanoparticles for Non-Invasive In Vivo Imaging Agents

Icosahedral virus-like particles (VLPs) derived from bacteriophages Qβ and PP7 encapsulating small-ultra red fluorescent protein (smURFP) were produced using a versatile supramolecualr capsid dissassemble-reassemble approach. The generated fluorescent VLPs display identical structural properties to their non-fluorescent analogs. Encapsulated smURFP shows indistinguishable photochemical properties to its unencapsulated counterpart, exhibits outstanding stability towards pH, and produces bright in vitro images following phagocytosis by macrophages. In vivo imaging allows biodistribution to be imaged at different time points. Ex vivo imaging of intravenously administered encapsulated smURFP reveleas localization in the liver and

kidneys after 2 h blood circulation and substantial elimination constructs as non-invasive in vivo imaging agents.