title: Polyion complex micelle MRI contrast agents from poly(ethylene glycol)-b-poly(l-lysine) block copolymers having Gd-DOTA; preparations and their control of T(1)-relaxivities and blood circulation characteristics.
abstract: The current study synthesized macromolecular magnetic resonance imaging (MRI) contrast agents constituted of the poly(ethylene glycol)-b-poly(L-lysine) block copolymer (PEG-P(Lys)). A chelate group, 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA), was attached to the primary amino group of the block copolymer in desired contents. Gd-DOTA-based macromolecular contrast agents were prepared from PEG-P(Lys) having DOTA (PEG-P(Lys-DOTA) and Gd(III) ions. All of the PEG-P(Lys) block copolymers having gadolinium ions (PEG-P(Lys-DOTA-Gd)) showed higher T(1) relaxivity (per gadolinium), r(1)=5.6-7.3mM(-1)s(-1), than that of a low-molecular-weight gadolinium-chelate, diethylenetriaminepentaacetic acid-gadolinium(III) (Gd-DTPA) at 9.4T. The study prepared the polyion complex (PIC) micelles from the amino groups of the lysine units and an oppositely charged polyanion, poly(methacrylic acid) or dextran sulfate, in an aqueous medium. In contrast, the fully DOTA-attached PEG-P(Lys-DOTA-Gd) formed a PIC with a polycation. Compared with partially DOTA-attached cationic PEG-P(Lys-DOTA-Gd), this PIC micelle yielded a forty percent decrease of r(1). This r(1) decrease was considered to result from a change in the accessibility of water molecules to gadolinium ions in the micelles' inner core. The r(1) was decreased upon formation of the PIC micelle, and this change proved that our concept worked in vitro. Blood-circulation characteristics of PIC micelles were controlled by means of changing the molecular weight of the counter anion. The PIC micelles accumulated in tumor tissues, and MRI study showed T1W image of axial slice of tumor area was significantly enhanced at 24h after the injection.
authors.affiliation: Kanagawa Academy of Science and Technology, Yokoyama Nano-medical Polymer Project, KSP East 404, Sakado 3-2-1, Takatsu-ku, Kawasaki, Kanagawa 213-0012, Japan.
authors.forename: Kouichi
authors.initials: K
authors.lastname: Shiraishi
authors.forename: Kumi
authors.initials: K
authors.lastname: Kawano
authors.forename: Yoshie
authors.initials: Y
authors.lastname: Maitani
authors.forename: Masayuki
authors.initials: M
authors.lastname: Yokoyama
mesh_terms: D000818:Animals; D003110:Colonic Neoplasms / Q000378:metabolism / Q000473:pathology*; D003287:Contrast Media / Q000008:administration & dosage / Q000138:chemical synthesis / Q000493:pharmacokinetics; D016264:Dextran Sulfate / Q000737:chemistry; D005260:Female; D006571:Heterocyclic Compounds / Q000008:administration & dosage / Q000097:blood / Q000138:chemical synthesis / Q000493:pharmacokinetics; D007275:Injections, Intravenous; D008239:Lysine / Q000031:analogs & derivatives* / Q000138:chemical synthesis; D008279:Magnetic Resonance Imaging / Q000295:instrumentation; D051379:Mice; D008823:Micelles; D008970:Molecular Weight; D009942:Organometallic Compounds / Q000008:administration & dosage / Q000097:blood / Q000138:chemical synthesis / Q000493:pharmacokinetics; D019047:Phantoms, Imaging; D011073:Polyamines; D000071228:Polyelectrolytes; D011092:Polyethylene Glycols / Q000138:chemical synthesis*; D011108:Polymers; D014018:Tissue Distribution
chemical_list: D003287:Contrast Media; D016264:Dextran Sulfate; D006571:Heterocyclic Compounds; D008239:Lysine; D008823:Micelles; D009942:Organometallic Compounds; D011073:Polyamines; D000071228:Polyelectrolytes; D011092:Polyethylene Glycols; D011108:Polymers; C092361:poly(ethylene glycol) lysine copolymer; C050823:gadolinium 1,4,7,10-tetraazacyclododecane-N,N',N'',N'''-tetraacetate