title: Nanoparticles containing octreotide peptides and gadolinium complexes for MRI applications.
abstract: New mixed nanoparticles were obtained by self-aggregation of two amphiplic monomers. The first monomer (C18)(2) L5-Oct contains two C18 hydrophobic moieties bound to the N-terminus of the cyclic peptide octreotide, and spaced from the bioactive peptide by five units of dioxoethylene linkers. The second monomer, (C18)(2) DTPAGlu, (C18)(2) DTPA or (C18)(2) DOTA, and the corresponding Gd(III) complexes, contains two C18 hydrophobic moieties bound through a lysine residue to different polyamino-polycarboxy ligands: DTPAGlu, DTPA or DOTA. Mixed aggregates have been obtained and structurally characterized by small angle neutron scattering (SANS) techniques and for their relaxometric behavior. According to a decrease of negative charges in the surfactant head-group, a total or a partial micelle-to-vesicle transition is observed by passing from (C18)(2) DTPAGlu to (C18)(2) DOTA. The thicknesses of the bilayers are substantially constant, around 50 Å, in the analyzed systems. Moreover, the mixed aggregates, in which a small amount of amphiphilic octreotide monomer (C18)(2) L5-Oct (10% mol/mol) was inserted, do not differ significantly from the respective self-assembled systems. Fluorescence emission of tryptophan residue at 340 nm indicates low mobility of water molecules at the peptide surface. The proton relaxivity of mixed aggregates based on (C18)(2) DTPAGlu(Gd), (C18)(2) DTPA(Gd) and (C18)(2) DOTA(Gd) resulted to be 17.6, 15.2 and 10.0 mM(-1) s(-1) (at 20 MHz and 298K), respectively. The decrease in the relaxivity values can be ascribed to the increase in τ(M) (81, 205 and 750 ns). The presence of amphiphilic octreotide monomer exposed on mixed aggregate surface gives the entire nanoparticles a potential binding selectivity toward somatostatin sstr2 receptor subtype, and these systems could act as MRI target-specific contrast agent.
authors.affiliation: Department of Biological Sciences, CIRPeB, University of Naples Federico II, & IBB CNR, Via Mezzocannone 16, 80134 Naples, Italy.
authors.forename: Antonella
authors.initials: A
authors.lastname: Accardo
authors.forename: Anna
authors.initials: A
authors.lastname: Morisco
authors.forename: Eliana
authors.initials: E
authors.lastname: Gianolio
authors.forename: Diego
authors.initials: D
authors.lastname: Tesauro
authors.forename: Gaetano
authors.initials: G
authors.lastname: Mangiapia
authors.forename: Aurel
authors.initials: A
authors.lastname: Radulescu
authors.forename: Astrid
authors.initials: A
authors.lastname: Brandt
authors.forename: Giancarlo
authors.initials: G
authors.lastname: Morelli
mesh_terms: D003287:Contrast Media / Q000737:chemistry*; D005682:Gadolinium / Q000737:chemistry*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D053758:Nanoparticles / Q000737:chemistry*; D015282:Octreotide / Q000737:chemistry*
chemical_list: D003287:Contrast Media; D005682:Gadolinium; D015282:Octreotide