Tracking of Individual Cell Populations by 19F MRI using a "Cargo Internalization Receptor (CIR)" System

Magnetic resonance imaging (MRI) is an important key for non-invasive visualization of immigrating cells in in vivo studies. We use Perflourcarbons (PFC) coupled to green fluorescent protein (GFP) for a 1H and 19F MRI detection. To this end, we engineered synthetic cell surface receptors, “Cargo Internalization Receptors” (CIR), which contain a GFP-nanobody and specifically bind GFP, followed by a rapid internalization of the GFP-PFC particles, but without inducing any signaling in the targeted cells. In order to explore the suitability of different uptake mechanisms we constructed three different CIRs, which contain different cytoplasmic domains that have different internalizations motifs and properties to enable the specific uptake of the GFP-PFC cargo in CIR-transfected cells. We show that the CIR approach is working in vitro, and has the potential to specifically track CIR containing cells by 1H and 19F MRI. We used microarrays to detail the overall influence of the constructs to confirm background free action of the CIR receptor constructs.