Radiolabeled vitamins as the potential diagnostic probes for targeted tumor imaging.

Nuclear medicine like single-photon emission computed tomography (SPECT) and positron emission tomography (PET) is one of the most sensitive methods for diagnostic imaging and radionuclide therapy which could lead to higher efficacy and reduced toxicity. There is enormous incentive to develop probes that detect lesions at earliest stages. Vitamins are biomolecules that play an important role in a variety of biological processes in animals and humans. The development of vitamin based radiopharmaceuticals for use in the detection and treatment of malignancies is increasing. In this review article we focus on recent studies that employ radiolabeled vitamins for targeted tumor imaging.

The utility of radiolabeled PSMA ligands for tumor imaging.

Prostate-specific membrane antigen (PSMA) is a glycosylated type-II transmembrane protein expressed in prostatic tissue and significantly overexpressed in several prostate cancer cells. Despite its name, PSMA has also been reported to be overexpressed in endothelial cells of benign and malignant non-prostate disease. So its clinical use was extended to detection, staging, and therapy of various tumor types. Recently small molecules targeting PSMA have been developed as imaging probes for diagnosis of several malignancies. Preliminary studies are emerging improved diagnostic sensitivity and specificity of PSMA imaging, leading to a change in patient management. In this review, we evaluated the first preclinical and clinical studies on PSMA ligands resulting future perspectives radiolabeled PSMA in staging and molecular characterization, based on histopathologic examinations of PSMA expression.

Synthesis, characterization, and in vitro and in vivo 68Ga radiolabeling of thiosemicarbazone Schiff base derived from dialdehyde dextran as a promising blood pool imaging agent.

To be used as a carrier of 68Ga radioisotope for possible blood pool imaging studies, dialdehyde dextran thiosemicarbazone (DADTSC) Schiff base polymer with different thiosemicarbazone contents (TSCC) = 0.93, 2.43, and 3.4 mmol/g were synthesized and characterized by FT-IR, GPC, and CHNS. Although they were successfully radiolabeled at room temperature, stable radio-complexes were prepared at 60 °C. Effect of thiosemicarbazone content on the dissolution rate, cytotoxicity, coagulation and hemolysis activities, and radiolabeling efficiency of Schiff bases as well as on the in-vitro radio-complexes stability was investigated. DADTSC1 (TSCC = 0.93 mmol/g) showed a less cytotoxicity (cell viability, CV50 = 490 µg/ml), a better solubility, suitable coagulation and hemolytic activities, and a sufficient radiolabeling efficiency (Radiochemical purity (RCP) > 95%) and formed a stable (RCP > 90%) radio-complex, which be chosen for in-vivo biodistribution study in healthy rats through tissue sampling and counting for radioactivity. Like blood pool imaging agents, 68Ga-DADTSC1 presented a retention profile in blood circulation, though more studies, including imaging in larger mammals, are required.