الفهرس 
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Abstract
Auger electron emitters provide a tool for radiotherapy with low
doses of radiations. The pharmacological effect of these Auger electron
emitters have been proven by many authors as a radiotoxic agents. Auger
emitters produce electrons of low energy deposited near the site of their
origin. This energy was sufficient to produce double strand break and
hence, inhibit DNA synthesis. Their action is restricted to be only
intracellular. Iodine-125 was the famous Auger electron emitter’s
radioisotope and the most used one for in vivo as well in vitro studies. This
work was conducted to study the radiotherapeutic effect of iodine-125 in
vivo on tumor bearing mice and in vitro on EAC cells. The study was also
performed to find a model to deliver Auger electron emitters (125I) to tumor
cells. This was obtained by labeling of folic acid and nimesulide with
iodine-125 to give new therapeutic radiopharmaceuticals that produce their
pharmacological action through high tumor targeting ability.
Radiolabeling of folic acid and nimesulide with iodine should be
performed with high radiochemical yield as to insure that the biological
behavior belongs to the radiolabeled compounds not to the free iodide. This
because these labeled compound have the ability to deliver the radioisotope
to the tumor site to produce the pharmacological effect. It was shown that
folic acid and nimesulide were labeled successfully with iodine-125 via
direct electrophilic substitution using chloramines-T as an oxidizing agent.
It was found that 500 μg and 300 μg of chloramine-T was required
respectively for labeling of folic acid and nimesulide. One mg folic acid
was used to obtain maximum radiochemical yield (97.6%) while two
hundreds μg nimesulide were enough to obtain maximum radiochemical yield (95.1%). The optimum reaction temperature for achieving a
maximum radiochemical yield for folic acid and nimesulide is ambient
temperature. The reaction medium pH should be 9 for folic acid and 7 for
nimesulide. Folic acid radioiodination reaction takes 30 minutes to reach a
maximum radiochemical yield while radioiodination of nimesulide takes
only one minute to give maximum radiochemical yield. The in vitro
stability of both radiolabeled compounds showed that they are stable and
no significant change in radiochemical yield up to 48 h post labeling.