Resonance Imaging Contrast Agents

Four approved Gd(III) complexes are now widely used clinically. Complexes containing DTPA 71 (Magnevist) and DOTA 72 (Dotarem) are ionic, whereas those of DTPA-BMA 73 (Omniscan) and HP-DOTA 74 (Prohance) are neutral their low osmolarity decreases the pain of the injections. All these agents are extracellular and they rapidly diffuse into the interstitial space. Doses are usually in the region of 0.1 mmol kg-1, which means that total injected doses are close to 4 g. 

Both the DTPA- and DOTA-Gd(III) complexes are thermodynamically very stable (Table V), but DOTA complexes have a higher kinetic stability. The stabilities are highly pH dependent. For example, log K for [Gd(DTPA)] falls by a factor of about 4 when the pH drops from 7.4 to 5. This could be significant in some biological compartments, e.g., lysosomes, where the pH can be as low as 5. 

Dendrimer-metal chelate complexes offer the possibility of delivering high concentrations of Gd(III) effectively. Thus adducts of the 

Agent Structure number Tr (ps)6 k298 (106 s-l)b Relaxivity Ri6 (mM 1 s1) log K Reference 

Starburst (TM) dendrimers with DTPA can contain 170 bound Gd(III) ions and have relaxivities (per bound Gd) up to 6 times that of Gd-DTPA (308). Both global and local motion contribute to the overall rotational correlation time. Attempts have been made to increase the re-laxivity of Gd(III) by optimizing the rotational correlation time via binding of Gd(III) to derivatized polysaccharides (309) and by binding lipophilic complexes to albumin in serum (310). The latter approach has achieved relaxivities as high as 44.2 mM l s1 for derivatized 72 (311). 

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Kobayashi, H., Kawamoto, S., Star, R.A., Waldmann, T.A., Tagaya, Y., and Brechbiel, M.W. (2003) Micro-magnetic resonance lymphangiography in mice using a novel dendrimer-based magnetic resonance imaging contrast agent. Can. Res. 63, 271-276. 

Keywords Metallofullerene, endohedral, gadolinium, magnetic resonance imaging, contrast agent, relaxivity, cellular imaging, molecular imaging... 

S.D. Camthers, P.M. Winter, S.A. Wickline, G.M. Lanza, Targeted magnetic resonance imaging contrast agents. Methods Mol. Med. 124 (2006) 387-400. 

Lin YS, Hung Y, Su JK, Lee R, Chang C, Lin ML, Mou YC (2004) Gadolinium(III)-incorporated nanosized mesoporous silica as potential magnetic resonance imaging contrast agents. J Phys Chem B 108 15608-15611... 

Keywords Magnetic resonance imaging, Contrast agent, Smart, Targeting, Chelate... 

Copper has been immobilized on glycylglycine bolaamphiphile peptide nanotubes that display histidine residues, and paramagnetic gadolinium, a magnetic resonance image contrast agent, has been immobilized on nanofibers produced from peptide amphiphiles (see Gazit, 2007 and references therein). 

Woods, M., Kovacs, Z., Zhang, S., and Sherry, A.D. (2003) Towards the rational design of magnetic resonance imaging contrast agents isolation of the two coordination isomers of lanthanide DOTA-type complexes. Angewandte Chemie Interrmtional Edition, 115, 6069-6072. 

Terzi C, Sokmen S. Acute pancreatitis induced by magnetic-resonance-imaging contrast agent. Lancet 1999 354(9192) 1789-90. 

Lin J, Idee JM, Port M, Dial A, Berthommier C, Robert M, Raynal I, Devoldere L, Corot C Interference of magnetic resonance imaging contrast agents with the serum calcium measurement technique using colorimetric reagents. JPharm Biomed Anal21 931-943,1999. 

Several applications have been envisaged for nanocrystals, ranging from simple dyes to magnetic-resonance-imaging contrast agents [160], components of electronic circuitry [33, 161] and magnetic media [115], ingredients in catalyst and sensors, and so on. All the above applications seek to exploit the tunability provided by the size-dependent properties of the nanocrystals [4]. Before we dwell upon collective properties in mesostructures, the case of isolated nanocrystals is briefly discussed. 

Corbin IR, Li H, Chen J, et al. Low-density lipoprotein nanoparticles as magnetic resonance imaging contrast agents. Neoplasia 2006 8 488-498. 

Pascolo, L Cupelli, F, Anelli, P.L., Lorusso, V., Visigalli, M Uggeri, F., and Tiribelli, C. (1999) Molecular mechanisms for the hepatic uptake of magnetic resonance imaging contrast agents. Biochemical and Biophysical Research Communications, 257, 746-752. 

E. C. Wiener, V. V. Narayanan, Magnetic Resonance Imaging Contrast Agents Theory and the Role of Dendrimers, in Advances in Dendritic Macromolecules, G. R. Newkome, Ed., pp. 129-247, Elsevier Science, Kidlington, Oxford, UK, 2002. 

Nuetral templates may not be bound to the zeolite surface but simply trapped. This is the basis of our zeolite synthesis method for the preparation of ship-in-a-bottle metal complexes, ie crystallization of the zeolite around a metal chelate complex. Zeolite encapsulated metal complexes have many applications, ranging from shape selective catalysis [9] to magnetic resonance imaging contrast agents [10]. 

Lu ZR, Mohs AM, Zong Y, Feng Y. Polydisulfide Gd(III) chelates as biodegradable macromolecular magnetic resonance imaging contrast agents. Inti J Nanomed 2006 1 31-40. 

Rongved, P., Fritzell, T. H., Strande, P. and Klaveness, J., 1996, Polysaccharides as carriers for magnetic resonance imaging contrast agents synthesis and stability of a new amino acid linker derivative. Carbohydr. Res., 287 77-89... 

Introduction to Magnetic Resonance Imaging and Magnetic Resonance Imaging Contrast Agents 531... 

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