Measurement of Protein Synthesis: In Vitro Comparison of 68Ga-DOTA-Puromycin, [3H]Tyrosine, and 2-Fluoro-[3H]tyrosine

Aim: Puromycin has played an important role in our understanding of the eukaryotic ribosome and protein synthesis. It has been known for more than 40 years that this antibiotic is a universal protein synthesis inhibitor that acts as a structural analog of an aminoacyl-transfer RNA (aa-tRNA) in eukaryotic ribosomes. Due to the role of enzymes and their synthesis in situations of need (DNA damage, e.g., after chemo- or radiation therapy), determination of protein synthesis is important for control of antitumor therapy, to enhance long-term survival of tumor patients, and to minimize side-effects of therapy. Multiple attempts to reach this goal have been made through the last decades, mostly u…

44Sc-DOTA-BN[2-14]NH2 in comparison to 68Ga-DOTA-BN[2-14]NH2 in pre-clinical investigation. Is 44Sc a potential radionuclide for PET?

In the present study we demonstrate the in vitro and in vivo comparison of the (44)Sc and (68)Ga labeled DOTA-BN[2-14]NH(2). (44)Sc is a positron emitter with a half life of 3.92 h. Hence it could be used for PET imaging with ligands requiring longer observation time than in the case of (68)Ga.The binding affinity of (nat)Sc-DOTA-BN[2-14]NH(2) and (nat)Ga-DOTA-BN[2-14]NH(2) to GRP receptors was studied in competition to [(125)I-Tyr(4)]-Bombesin in the human prostate cancer cell line PC-3. A preliminary biodistribution in normal rats was performed, while first microPET images were assessed in male Copenhagen rats bearing the androgen-independent Dunning R-3327-AT-1 prostate cancer tumor.The …

Post-elution processing of 44Ti/44Sc generator-derived 44Sc for clinical application

The (44)Ti/(44)Sc (T(1/2)(44)Ti=60a) generator provides cyclotron-independent access to positron-emitting (44)Sc (T(1/2)=3.97d) for PET imaging. This work aims to post-elution processing of initial (44)Sc generator eluates in order to reduce its volume, HCl concentration and remove the oxalate anions. The on-line adsorption of (44)Sc on cationic resin AG 50W-X8 (200-400 mesh, H(+)-form) is achieved with >98% efficacy. Subsequently, the purified (44)Sc is desorbed by using 3ml of 0.25M ammonium acetate (pH=4.0). The post-processing takes 10min. The overall yield of the post-processing reached 90%, which is referred to the (44)Sc obtained from the (44)Ti/(44)Sc generator. In addition to the c…

Radiolabeling of DOTATOC with the long-lived positron emitter 44Sc.

Abstract The positron-emitting radionuclide 44 Sc with a half-life of 3.97 h and a β + branching of 94.3% is of potential interest for clinical PET. As so far it is available from a 44 Ti/ 44 Sc generator in Mainz, where long-lived 44 Ti decays to no-carrier-added (nca) 44 Sc. The 44 Sc is a trivalent metal cation and should be suitable for complexation with many well established bifunctional chelators conjugated to peptides or other molecular targeting vectors. Thus, the aim of this work was to investigate the potential of 44 Sc for labeling of DOTA-conjugated peptides. DOTA-D-Phe 1 -Tyr 3 -octreotide (DOTATOC) was used as a model molecule to study and optimize labeling procedure. Reaction…

Comparison of different phosphorus-containing ligands complexing 68Ga for PET-imaging of bone metabolism

Abstract 99mTc-phosphonate structures are well established tracers for bone tumour imaging. Our objective was to investigate different 68Ga-labelled phosphonate ligands concerning labelling kinetics, binding to hydroxyapatite and bone imaging using μ-PET. Seven macrocyclic phosphorus-containing ligands and EDTMP were labelled in nanomolar scale with n.c.a. 68Ga in Na-HEPES buffer at pH∼4. Except for DOTP, all ligands were labelled with >92% yield. Binding of the 68Ga-ligand complexes on hydroxyapatite was analysed to evaluate the effect of the number of the phosphorus acid groups on adsorption parameters. Adsorption of 68Ga-EDTMP and 68Ga-DOTP was >83%. For the 68Ga-NOTA-phosphonates …

68Ge content quality control of 68Ge/68Ga-generator eluates and 68Ga radiopharmaceuticals – A protocol for determining the 68Ge content using thin-layer chromatography

(68)Ge breakthrough from a (68)Ge/(68)Ga-generator appears to be one of the most critical parameters for the routine clinical application of this generator and (68)Ga-radiopharmaceuticals. We report a TLC-based (thin-layer chromatography) protocol which allows the (68)Ge breakthrough of a generator to be determined within 1 h post-initial elution. The protocol can also be adapted to allow the (68)Ge content of a (68)Ga-radiopharmaceutical preparation to be determined prior to in vivo application.

44Ti/44Sc Generator and synthesis of 44Sc-DOTA-TOC

Improved column-based radiochemical processing of the generator produced 68Ga.

An improved chemical strategy for processing of the generator produced (68)Ga was developed based on processing of the original (68)Ge/(68)Ga generator eluate on a micro-column. Direct pre-concentration and purification of the eluted (68)Ga is performed on a cation-exchange resin in hydrochloric acid/acetone media. A supplementary step based on a second micro-column filled with a second resin allows direct re-adsorption of (68)Ga eluted from the cation exchanger. (68)Ga is finally striped from the second resin with a small volume of pure water. For this purpose a strong anion exchanger and a novel extraction chromatographic resin based on tetraalkyldiglycolamides are characterized. The stra…

Quantitative online isolation of 68Ge from 68Ge/68Ga generator eluates for purification and immediate quality control of breakthrough

The breakthrough of ⁶⁸Ge from a ⁶⁸Ge/⁶⁸Ga-generator is one of the most sensitive parameters in the context of the clinical application of ⁶⁸Ga-radiopharmaceuticals. The difficulty in its determination lies in the "spectroscopic invisibility" of ⁶⁸Ge within an excess of ⁶⁸Ga. The introduced method for determining the ⁶⁸Ge content of the ⁶⁸Ge/⁶⁸Ga-generator eluate involves the quantitative separation of ⁶⁸Ga from ⁶⁸Ge, using a cation-exchanger. The eluate contains ⁶⁸Ga free of ⁶⁸Ge, which can be determined immediately, i.e. prior to the application of the ⁶⁸Ga-radiopharmaceutical.