## Abstract Peptides are known as receptor‐specific molecules that play an important role not only in diagnosis and therapy of neoplastic diseases, but also in the pathogenesis of other diseases. In an effort to develop a peptide‐based radiopharmaceutical for scintigraphic studies, a small peptide
Synthesis and preliminary biological evaluation of a 99mTc-labeled hypericin derivative as a necrosis avid imaging agent
✍ Scribed by Humphrey Fonge; Lixin Jin; Huaijun Wang; Guy Bormans; Yicheng Ni; Alfons Verbruggen
- Publisher
- John Wiley and Sons
- Year
- 2008
- Tongue
- French
- Weight
- 275 KB
- Volume
- 51
- Category
- Article
- ISSN
- 0022-2135
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✦ Synopsis
Abstract
Mono‐[^123^I]iodohypericin and mono‐[^123^I]iodohypericin monocarboxylic acid are iodine‐123‐labeled hypericin derivatives which have shown great promise in preclinical studies as necrosis avid imaging agents in animal models of infarction. In view of the more attractive properties of a ^99m^Tc‐labeled hypericin derivative, we have synthesized a conjugate of protohypericin monocarboxylic acid with S‐benzoylmercaptoacetyldiglycyl‐diaminopentane in an overall yield of 15%. The conjugate was labeled with technetium‐99m by exchange labeling at pH 10 in a labeling yield of 95% followed by photocyclization to yield ^99m^Tc‐mercaptoacetyldiglycyl‐1,5‐diaminopentylene hypericincarboxamide (^99m^Tc‐13). The negatively charged ^99m^Tc‐13 complex was purified by reversed phase high‐pressure liquid chromatography and the log P~7.4~ was determined to be 2.36. In normal NMRI mice, the complex showed slow hepatobiliary clearance while plasma clearance was rapid. The tracer was evaluated in rats with reperfused hepatic infarction by ex vivo autoradiography, gamma counting and histochemical techniques. Unlike the radioiodinated hypericin derivatives, the new tracer agent did not show preferential uptake in necrotic tissue on autoradiography and gamma counting techniques. Conjugation of hypericin with a ^99m^Tc‐chelate, resulting in a change in size, charge and lipophilicity, had a profound effect on the necrosis avidity of the tracer agent. The results show that ^99m^Tc‐13 is not suitable for imaging necrosis. Copyright © 2008 John Wiley & Sons, Ltd.
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