Radiolabeling/radiolabeled process

It is imperative that the radiolabeling process be sufficiently validated before the aerosols are administered to human subjects. This includes identifying the purity and form of the radiolabel if complex extractions are performed. As mentioned previously, it is important to ensure that the particle size distribution of the radiolabeled aerosol is similar to that of the unlabeled aerosol, which is most commonly accessed using an... 

Cons Prone to artifacts. The radiolabeling process can mask or denature epitopes recognized by antibodies. 

The actual time required for poly-L-lactide implants to be completely absorbed is relatively long, and depends on polymer purity, processing conditions, implant site, and physical dimensions of the implant. For instance, 50—90 mg samples of radiolabeled poly-DL-lactide implanted in the abdominal walls of rats had an absorption time of 1.5 years with metaboHsm resulting primarily from respiratory excretion (24). In contrast, pure poly-L-lactide bone plates attached to sheep femora showed mechanical deterioration, but Httie evidence of significant mass loss even after four years (25). 

The use of microbial siderophores by dicotyledonous plants appears to involve uptake of the entire metallated chelate (42-44), or an indirect process in which the siderophore undergoes degradation to release iron (45). As demonstrated in initial studies examining this question, there was concern that iron uptake from microbial siderophores may be an artifact of microbial iron uptake in which radiolabeled iron is accumulated by root-colonizing microorganisms (46). Consequently, evidence for direct uptake of iron from microbial siderophores has required the use of axenic plants. In experiments with cucumber, it was shown that the microbial siderophore ferrioxamine B could be used as an iron source at concentrations as low as 5 pM and that the siderophore itself entered the plant (42). 

The following procedure describes the iodination process for the Bolton-Hunter reagent and its subsequent use for the radiolabeling of protein molecules. Modification of other macromolecules can be done using the same general method. For particular labeling applications, optimization of the level of iodine incorporation may have to be done to obtain the best specific radioactivity with retention of biological activity. 

A similar strategy is adopted when undertaking DNA clearance studies. The starting material is spiked with radiolabelled DNA and then subjected to downstream processing. The level of residual DNA remaining in the product stream after each step can easily be determined by monitoring for radioacbvity. 

Aromatic fluorination can be carried out by a regiospecific destannylation process shown in reaction 69. This is an effective method for producing fluorinated m-tyrosine and other radiopharmaceuticals, as shown in reaction 70. The process can be applied for radiolabelling with 18F, denoted as F in these reactions, and the products used as radioactive tracers for clinical and fundamental investigations318-321. 

---