Radiopharmaceutical complexes

A complete understanding of why specific metal complexes target certain tissues has yet to be achieved, but would be extremely valuable for the rational design of new radiopharmaceuticals. Complexes of 99mTc vvilli diphosphonates, e.g. methylenediphosphonate, localize in bone and especially in areas of disturbance of bone metabolism, such as tumours thus they may be used to map the presence and location of bony metastases from various types of cancer. Chelates such as "Tc-DTPA may be used to study differential renal function in the kidneys or to monitor the function of a transplanted kidney. Attachment of chelating groups, often based on DTPA, to antibody proteins permits the formation of Tc- or in-labelled antibodies for tumour localization. 

Despite the many advantages outlined for [ Tc(OH2)3(CO)3] for the development of radiopharmaceuticals, complexes with targeting vectors are stiU at an early stage but their utiHty is recognized [73]. Potential reasons for this have recentiy been discussed extensively [7, 74]. One of the main reasons is the newness of the approach. Reliable kits have only been available for about one year. A new method takes time for adoption and optimization. It should be emphasized at this point... 

There are three general types of radiopharmaceuticals elemental radionucHdes or simple compounds, radionucHde complexes, and radiolabeled biologically active molecules. Among the first type are radionucHdes in their elemental form such as Kr and Xe or Xe, and simple aqueous radionucHde solutions such as or I-iodide, Tl-thaUous chloride, Rb-mbidium(I) chloride [14391-63-0] Sr-strontium(II) chloride, and Tc-pertechnetate. These radiopharmaceuticals are either used as obtained from the manufacturer in a unit dose, ie, one dose for one patient, or dispensed at the hospital from a stock solution that is obtained as needed from a chromatographic generator provided by the manufacturer. 

PET imaging systems are somewhat more complex, and therefore more expensive than are SPECT systems, and the price factor is generally between two and three. The primary cost premium associated with these systems, however, is the need for a cyclotron and its attendant staff combined with the relative complexity of radiopharmaceutical preparation for short half-life isotopes. As of 1996, there are considerable hurdles blocking widespread regulatory approval and full reimbursement of PET studies. 

Werner s coordination theory, 1, 6 Whewellite structure, 6, 849 Wickmanite structure, 6, 849 Wilkinson s catalyst, 6, 239 Wilson s disease, 5, 721 copper, 6,648 removal, 6,769 copper complexes, 2,959 copper metabolism, 6,766 radiopharmaceutical agents, 6,968 Wolfram s red salt, 5,427 Wurzite... 

Ajayaghosh A, George SJ, Schenning APHJ (2005) Hydrogen-Bonded Assemblies of Dyes and Extended jr-Conjugated Systems. 258 83-118 Akai S, Kita Y (2007) Recent Advances in Pummerer Reactions. 274-. 35-76 Albert M, Fensterbank L, l.acote E, Malacria M (2006) Tandem Radical Reactions. 264 1-62 Alberto R (2005) New Organometallic Technetium Complexes for Radiopharmaceutical Imaging. 252 1-44... 

Saladino R, Crestini C, Costanzo G, DiMauro E (2005) On the Prebiotic Synthesis of Nucle-obases, Nucleotides, Oligonucleotides, Pre-RNA and Pre-DNA Molecules. 259 29-68 Santos I, Paulo A, Correia JDG (2005) Rhenium and Technetium Complexes Anchored by Phosphines and Scorpionates for Radiopharmaceutical Applications. 252 45-84 Santos M, see Szathmdry E (2005) 259 167-211... 

The results obtained to date are considerable and show that the chemistry of the TcN group may well be the most varied and interesting of the transition metal nitrido complexes [1,9,10]. The aim of this chapter is to provide a fairly comprehensive review of the literature up to the latter part of 1994. Additional data may be found in two conference volumes [11,12] and a recent review of Tc coordination chemistry [4]. For macroscopic studies with the long-lived "Tc (ti/2 = 2.11 x 10s years) the "Tc radionuclide is denoted simply as Tc. No carrier added studies and radiopharmaceutical applications utilizing the shortlived "mTc radionuclide (ti/2 = 6.01 hours) are denoted as "mTc. 

Acknowledging the important part that 99mTc(V) radiopharmaceuticals are playing in nuclear medicine, advances in their coordination chemistry, as attained by new syntheses and better structural characterization, are discussed with respect to the design of Tc(V) radiotracers. In the light of current interest in making technetium complexes active in vivo, a chapter considering several aspects of reactivity is included. 

The O-donor complexes of Tc(V) exhibit moderate and differential stability in aqueous solution. In the presence of reducing agents, such as stannous chloride, they are reduced to mainly undefined products of Tc in a lower oxidation state. However, at the low technetium concentration of "mTc that is used in nuclear medicine, the rate of the reduction process is very low. This makes it possible to prepare Tc(V) radiopharmaceuticals with O-donor ligands by the usual procedure, in which an excess of reducing agent over technetium is unavoidably used. The Tc(V) complexes also tend either to be easily oxidized or to disproportionate [23],... 

O-donor complexes that are currently used as Tc(V) precursors in the chemical and radiopharmaceutical synthesis are listed in Table 1. 

Table 1. TcOdigand),]" precursors used in the chemical and radiopharmaceutical synthesis of Tc(V) complexes...

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