title: Targeting cells with MR imaging probes based on paramagnetic Gd(III) chelates.
abstract: The low sensitivity is the major disadvantage of MRI as compared to PET. Therefore, amplification strategies are necessary for specific pathway labeling. This survey is aimed at exploring different routes to the entrapment of Gd(III) chelates in various type of cells at amounts sufficiently large to allow MRI visualization. Namely, the obtained results have been summarized in terms of internalization via i) pinocytosis; ii) phagocytosis; iii) receptors; iv) receptor mediated endocytosis; v) transporters; vi) transmembrane carrier peptides. MRI visualization of cells appears possible when the number of internalized Gd(III) chelates is of the order of 10(7)-10(8)/cell. Pinocytosis shows to be particularly useful for labeling cells that can be incubated for several hours in the presence of high concentrations of Gd-agent. This approach appears very effective for labeling stem cells. Nanoparticles filled with Gd-chelates can be used for an efficient loading of cells endowed with a good phagocytic activity. Entrapment via receptors most often results in receptor mediated endocytosis. Suitably functionalized monomeric and multimeric Gd-chelates can be considered for being internalized by this route as well as supramolecular systems such as those formed between Avidin and biotinylated Gd-complexes. Exploitation of up-regulated transporters of nutrients in tumor cells appears to be a promising route for their differentiation from healthy cells. Finally, properly designed systems entering the cells by means of penetrin-like peptides deserve great attention.
authors.affiliation: Dipartimento di Chimica Inorganica, Chimica Fisica e Chimica dei materiali - Universita di Torino - Via Pietro Giuria 7, I-10125 Torino - Italy. silvio.aime@unito.it
authors.forename: S
authors.initials: S
authors.lastname: Aime
authors.forename: A
authors.initials: A
authors.lastname: Barge
authors.forename: C
authors.initials: C
authors.lastname: Cabella
authors.forename: S Geninatti
authors.initials: SG
authors.lastname: Crich
authors.forename: E
authors.initials: E
authors.lastname: Gianolio
mesh_terms: D000818:Animals; D001704:Biopolymers / Q000032:analysis / Q000378:metabolism*; D002614:Chelating Agents; D003287:Contrast Media; D016503:Drug Delivery Systems / Q000379:methods*; D005682:Gadolinium; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008280:Magnetics; D008967:Molecular Biology / Q000379:methods; D015336:Molecular Probe Techniques; D015335:Molecular Probes; D043942:Nanotubes / Q000737:chemistry / Q000648:ultrastructure
chemical_list: D001704:Biopolymers; D002614:Chelating Agents; D003287:Contrast Media; D015335:Molecular Probes; D005682:Gadolinium