99m Tc-tricarbonyl labeling of paclitaxel as an antimicrotubule agent and its evaluation in B16-F10 melanoma tumor-bearing mice

Preparation, Characterization, and Radiolabeling of Anti-HER2 scFv With Technetium Tricarbonyl and Stability Studies

Breast cancer is the most common diagnosed cancer, and the second cause of cancer death among women, worldwide. HER2 overexpression occurred in approximately 15% to 20% of breast cancers. Invasive biopsy method has been used for detection of HER2 overexpression. HER2-targeted imaging via an appropriate radionuclide is a promising method for sensitive and accurate identification of HER2+ primary and metastatic lesions. 99mTc-anti-HER2 scFv can specifically target malignancies and be used for diagnosis of the cancer type and metastasis as well as treatment of breast cancer. We radiolabeled anti-HER2 scFv that was expressed in Escherichia coli and purified through Ni-NTA resin under native condition with 99mTc-tricarbonyl formed from boranocarbonate. HER2-based ELISA, BCA, TLC, and HPLC were used in this study. In the current study, anti-HER2 scFv was lyophilized before radiolabeling. It was found that freeze-drying did not change the binding activity of anti-HER2 scFv to HER2. Results demonstrated direct anti-HER2 scFv radiolabeling by 99mTc-tricarbonyl to hexahistidine sequence (His-tag) without any changes in biological activity and radiochemical purity of around 98%. Stability analysis revealed that 99mTc-anti-HER2 scFv is stable for at least 24 h in PBS buffer, normal saline, human plasma proteins, and histidine solution.

Synthesis of novel technetium-99m tricarbonyl-HBED-CC complexes and structural prediction in solution by density functional theory calculation

HBED-CC (N,N'-bis[2-hydroxy-5-(carboxyethyl)benzyl]ethylene diamine-N,N'-diacetic acid, L₁ ) is a common bifunctional chelating agent in preparation of ⁶⁸Ga-radiopharmaceuticals. Due to its high stability constant for the Ga³⁺ complex (logK_GaL = 38.5) and its acyclic structure, it is well known for a rapid and efficient radiolabelling at ambient temperature with Gallium-68 and its high in vivo stability. [^99mTc][Tc(CO)₃(H₂O)₃]⁺ is an excellent precursor for radiolabelling of biomolecules. The aim of this study was to develop a novel preparation method of ^99mTc-HBED-CC complexes. In this study, HBED-CC-NI (2,2'-(ethane-1,2-diylbis((2-hydroxy-5-(3-((2-(2-nitro-1H-imidazol-1-yl)ethyl)amino)-3-oxopropyl)benzyl)-azanediyl))-diacetic acid, L₂ ), a derivative of HBED-CC, was designed and synthesized. Both L₁ and L₂ were radiolabelled by [^99mTc][Tc(CO)₃(H₂O)₃]⁺ successfully for the first time. In order to explore the coordination mode of metal and chelates, non-radioactive Re(CO)₃ L₁ and Re(CO)₃ L₂ were synthesized and characterized spectroscopically. Tc(CO)₃ L₁ and Tc(CO)₃ L₂ in solution were calculated by density functional theory and were analysed with radio-HPLC chromatograms. It showed that [^99mTc]Tc(CO)₃ L₂ forms two stable diastereomers in solution, which is similar to those of [⁶⁸Ga]Ga-HBED-CC complexes. Natural bond orbital analysis through the natural population charges revealed a charge transfer between [^99mTc][Tc(CO)₃]⁺ and L₁ or L₂ . The experimental results showed that tricarbonyl technetium might form stable complex with HBED-CC derivatives, which is useful for the future application of using HBED-CC as a bifunctional chelating agent in developing new ^99mTc-radiopharmaceuticals as diagnostic imaging agents.