New nanosized biocompatible MR contrast agents based on lysine-dendri-graft macromolecules.
Paramagnetic nanomaterials for use as magnetic resonance imaging (MRI) contrast agents have higher relaxivity than conventional low molecular weight MRI agents. However, the biocompatibility and pharmacokinetics of such nanomaterials will strongly affect the likelihood of clinical approval. We synthesized MRI contrast agents based on biocompatible lysine-dendri-grafts: Gd-BzDTPA-lysineG2 and Gd-BzDTPA-lysineG3. The relaxivity of Gd-BzDTPA-lysineG2 and Gd-BzDTPA-lysineG3 increased with sample temperature, while the relaxivity of Gd-BzDTPA-PAMAMG4 decreased with increasing sample temperature. The increase in relaxivity with increasing temperature may be attributed to accessibility of water to the internal Gd chelates with lysine-dendri-grafts, which does not occur with PAMAM dendrimers. Gd-BzDTPA-lysineG3 had a long intravascular half-life but were largely excreted by the kidneys. Therefore, Gd-BzDTPA-lysineG3 enhanced the blood vessels for longer periods than Gd-BzDTPA-PAMAMG4, but was still excreted through the kidney. Because of their biocompatibility, desirable magneto-physical characteristics and favorable pharmacokinetics, which are derived from different interior structures rather than the physical size, lysine-dendri-graft MR contrast agents may be feasible for clinical use.
Ogawa
Mikako
M
Molecular Imaging Program, Center for Cancer Research, National Cancer Institute, National Institute of Health, Research Technology Program, SAIC-Frederick, Inc., NCI-Frederick, USA.
Regino
Celeste A S
CA
Marcelino
Bernardo
B
Williams
Mark
M
Kosaka
Nobuyuki
N
Bryant
L Henry
LH
Choyke
Peter L
PL
Kobayashi
Hisataka
H
D000818:Animals; D003287:Contrast Media / Q000737:chemistry* / Q000493:pharmacokinetics*; D050091:Dendrimers / Q000737:chemistry* / Q000493:pharmacokinetics; D005260:Female; D019786:Gadolinium DTPA / Q000737:chemistry* / Q000493:pharmacokinetics; D008239:Lysine / Q000737:chemistry* / Q000493:pharmacokinetics; D008279:Magnetic Resonance Imaging / Q000379:methods*; D051379:Mice; D008819:Mice, Nude; D010316:Particle Size; D051598:Whole Body Imaging / Q000379:methods
D003287:Contrast Media; D050091:Dendrimers; C104700:PAMAM Starburst; D019786:Gadolinium DTPA; D008239:Lysine