Labeling with radionuclides

Since emission tomography requires some type of internal radioactive sources, a large number of radionuclides have been developed and produced specifically for these applications. Gamma emitters are used for SPECT, while positron emitters are used for PET. The chemical form of a radionuclide is tailored specifically for a given target (tissue, bone, or organ). Compounds labeled with radionuclides for administration to patients are known as radiopharmaceuticals. 

The stability of proteins labeled with radionuclides is affected primarily by physical and secondarily by chemical processes Ph cal processes... 

Labeled proteins are used in enzymology especially as substrates for determining the activity of proteolytic enzymes, for studying structural properties of enzyme molecules (7.2), and for some analytical purposes. Here, attention is paid to the determination of proteolytic activities when proteins labeled with radionuclides, chromophores and fluorophores are used as substrates. 

We have given the name nuclisomes to SLT particles which are loaded with DNA interacting compounds labelled with radionuclides or nuclides that become activated upon neutron irradiation. A schematic drawing of a boron containing nuclisome is given in Figure 1. 

The ability of hydroxylapatite to accept foreign ions into its structure and onto the surface has been used to incorporate radionuclides. Radioactive samarium and rhenium have been incorporated into hydroxylapatite microspheres sized at 20-40 pm and injected into knee joints to treat rheumatoid joint synovitis (Chinol et al. 1993). Clinical studies have shown that hydroxylapatite particles are easily labeled with radionuclides, exhibit low leakage of radioactive species, and provide a reduced inflammation of the synovium and restored joint motion to the patient (Clunie et al. 1996). 

Polymer formation of fullerene labeled with radionuclides was also observed. In a multi-tracer study using heavy-ion nuclear reaction of with Au formation of new metallofullerenes (Zr, Hf, and Mb included in fullerene) was also reported. 

Decay products of the principal radionuclides used in tracer technology (see Table 1) are not themselves radioactive. Therefore, the primary decomposition events of isotopes in molecules labeled with only one radionuclide / molecule result in unlabeled impurities at a rate proportional to the half-life of the isotope. Eor and H, impurities arising from the decay process are in relatively small amounts. Eor the shorter half-life isotopes the relative amounts of these impurities caused by primary decomposition are larger, but usually not problematic because they are not radioactive and do not interfere with the application of the tracer compounds. Eor multilabeled tritiated compounds the rate of accumulation of labeled impurities owing to tritium decay can be significant. This increases with the number of radioactive atoms per molecule. 

A specialized application of microwave-assisted organic synthesis involves the preparation of radiopharmaceuticals labeled with short-lived radionuclides, particularly for use in positron emission tomography [70-72]. This represented an excellent application of microwave technology, where the products must be prepared quickly and in high radiochemical yield, on a small scale. 

The development of PET radiopharmaceuticals labeled with generator-produced radionuclides has facilitated greater use of PET in clinical nuclear medicine. The 68Ge/68Ga parent/daughter pair is ideal as a source of PET radiopharmaceuticals as a result of the favorable half-lives of both the parent and daughter radionuclides (43-45). The 271 days half-life of the 68Ge parent... 

A protocol for the light microscope radioautography of Lilium longiflorum pollen tubes labeled with [14C]-proline follows. This protocol, which does not require tissue embedding in paraffin or Paraplast, can be modified for paraffin-embedded tissues see Chapter 2). Thus, by employment of the protocol, together with the preceding introductory information in this chapter, one should be able to derive a protocol applicable to the cells or tissue in question. The performance of the protocol requires approval of an institution s Radiation Safety Officer. An inventory of incoming radionuclides, their presence in secondary containers, and their waste must be carefully recorded. The waste must be further broken down into solid waste, liquid waste, and animal carcasses to aid in its proper disposal. 

Photons with detectable energy differences that are emitted by various radionuclides can be quantified simultaneously, but independently from each other. This allows the use of dual-labeling approaches (4). These experiments will reveal information regarding both the liposomal carrier—labeled with one radionuclide—and the encapsulated compound—labeled with a different radionuclide—after a single injection in the same animal. However,... 

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