title: Peptides and Gd complexes containing colloidal assemblies as tumor-specific contrast agents in MRI: physicochemical characterization.
abstract: The aggregation behavior of an amphiphilic supramolecular system, with potential application as a tumor-specific magnetic resonance imaging contrast agent, has been studied in detail by dynamic light scattering, small-angle neutron scattering and cryotransmission electron microscopy. The system was constituted of mixed aggregates formed by an anionic unimer containing the DTPAGlu, a chelating agent for the paramagnetic Gd(3+) ion, and an uncharged unimer containing the bioactive peptide CCK8, capable of directing the assembly toward tumor cells. Mixed aggregates formed by both unimers, and in the case of the DTPAGlu unimer with the chelating agent as free base or as Gd(3+) complex, have been investigated. A number of interesting features of the aggregation behavior were revealed: at physiological pH, micelles and bilayer structures were present, whereas upon decreasing solution pH or increasing ionic strength, the formation of bilayer structures was favored. On the basis of the above observations, the aggregating mechanism has been elucidated by considering the screening effect on intra- and interaggregate electrostatic repulsions.
authors.affiliation: Department of Chemistry, University of Naples Federico II, Naples, Italy.
authors.forename: Mauro
authors.initials: M
authors.lastname: Vaccaro
authors.forename: Antonella
authors.initials: A
authors.lastname: Accardo
authors.forename: Gerardino
authors.initials: G
authors.lastname: D'Errico
authors.forename: Karin
authors.initials: K
authors.lastname: Schillén
authors.forename: Aurel
authors.initials: A
authors.lastname: Radulescu
authors.forename: Diego
authors.initials: D
authors.lastname: Tesauro
authors.forename: Giancarlo
authors.initials: G
authors.lastname: Morelli
authors.forename: Luigi
authors.initials: L
authors.lastname: Paduano
mesh_terms: D003287:Contrast Media / Q000494:pharmacology*; D020285:Cryoelectron Microscopy; D004058:Diffusion; D005682:Gadolinium / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007477:Ions; D008027:Light; D008051:Lipid Bilayers; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008823:Micelles; D046529:Microscopy, Electron, Transmission; D010455:Peptides / Q000737:chemistry*; D012542:Scattering, Radiation; D055672:Static Electricity; D013501:Surface-Active Agents
chemical_list: D003287:Contrast Media; D007477:Ions; D008051:Lipid Bilayers; D008823:Micelles; D010455:Peptides; D013501:Surface-Active Agents; D005682:Gadolinium