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68 Ga-DOTA-peptides are a promising PET radiotracers used in the detection of different tumours types due to their ability for binding specifically receptors overexpressed in these. Furthermore, 68 Ga can be produced by a 68 Ge/ 68 Ga generator on site which is a very good alternative to cyclotron-based PET isotopes. Here, we describe a manual labelling approach for the synthesis of 68 Ga-labelled DOTA-peptides based on concentration and purification of the commercial 68 Ga/ 68 Ga generator eluate using an anion exchange-cartridge. 68 Ga-DOTA-TATE was used to image a pheochromocytoma xenograft mouse model by a microPET/CT scanner. The method described provides satisfactory results, allowing the subsequent 68 Ga use to label DOTA-peptides. The simplicity of the method along with its implementation reduced cost, makes it useful in preclinical PET studies. [ABSTRACT FROM AUTHOR]

Abstract: A scaled-up radiolabelling and improved post-labelling purification procedure for [68Ga]DOTATATE is reported, using a more than 1 year old SnO2-based 1850MBq 68Ge/68Ga generator (initially double-loaded with 3700MBq 68Ge) as a source of ionic 68Ga. The elution method of choice comprised elution with 0.6M HCl in a single 4mL fraction, containing up to 95% of the total eluted 68Ga activity. The unpurified fraction was directly used for labelling after pH adjustment with 2.5M sodium acetate. Labelling efficiencies were determined at 90–95°C at various reaction times and reaction volumes of up to 5.7mL, using either 30μg or 50μg DOTATATE. Only the latter amount resulted in consistently high labelling efficiency in excess of 95%. Post-labelling purification, carried out on Sep-Pak C18, showed that 50% ethanol in saline was a superior desorption eluant than 100% ethanol. The highest and most consistent decay-corrected radiochemical yields (89%) were obtained using 50μg DOTATATE and a 20min reaction time. [Copyright &y& Elsevier]

Abstract: Objectives: PET scintigraphy with 68Ga-labelled analogs is of increasing interest in Nuclear Medicine and performed all over the world. Here we report the characteristics of the eluate of SnO2-based 68Ge/68Ga generators prepared by iThemba LABS (Somerset West, South Africa). Three purification and concentration techniques of the eluate for labelling DOTA-TATE and concordant SPE purifications were investigated. Methods: Characteristics of 4 SnO2-based generators (range 0.4–1GBq 68Ga in the eluate) and several concentration techniques of the eluate (HCl) were evaluated. The elution profiles of SnO2-based 68Ge/68Ga generators were monitored, while [HCl] of the eluens was varied from 0.3–1.0M. Metal ions and sterility of the eluate were determined by ICP. Fractionated elution and concentration of the 68Ga eluate were performed using anion and cation exchange. Concentrated 68Ga eluate, using all three concentration techniques, was used for labelling of DOTA-TATE. 68Ga-DOTA-TATE-containing solution was purified and RNP increased by SPE, therefore also 11 commercially available SPE columns were investigated. Results: The amount of elutable 68Ga activity varies when the concentration of the eluens, HCl, was varied, while 68Ge activity remains virtually constant. SnO2-based 68Ge/68Ga generator elutes at 0.6M HCl >100% of the 68Ga activity at calibration time and ±75% after 300 days. Eluate at discharge was sterile and Endotoxins were <0.5EU/mL, RNP was always <0.01%. Metal ions in the eluate were <10ppm (in total). Highest desorption for anion purification was obtained with the 30mg Oasis WAX column (>80%). Highest desorption for cation purification was obtained using a solution containing 90% acetone at increasing molarity of HCl, resulted in a 68Ga desorption of 68±8%. With all 68Ge/68Ga generators and for all 3 purification methods a SA up to 50MBq/nmol with >95% incorporation (ITLC) and RCP (radiochemical purity) by HPLC ±90% could be achieved. Purification and concentration of the eluate with anion exchange has the benefit of more elutable 68Ga with 1M HCl as eluens. The additional washing step of the anion column with NaCl and ethanol, resulted in a lower and less variable [H+] in the eluate, and, as a result the pH in the reaction vial is better controlled, more constant, and less addition of buffer is required and concordant smaller reaction volumes. Desorption of 68Ga-DOTA-TATE of SPE columns varied, highest desorption was obtained with Baker C18 100mg (84%). Purification of 68Ga-DOTA-TATE by SPE resulted in an RNP of <10−4%. Conclusions: Eluate of SnO2-based 68Ge/68Ga generator, either by fractionated elution as by ion exchange can be used for labelling DOTA-peptides with 68Ga at a SA of 50MBq/nmol at >95% incorporation and a RCP of ±90%. SPE columns are very effective to increase RNP. [Copyright &y& Elsevier]

Abstract: Peptide receptor radionuclide therapy (PRRT) has recently expanded due to radiolabelling of DOTA-peptides, such as the somatostatin analogues [DOTA0, Tyr3]octreotate (DOTATATE). The achievement of high specific activities during procedures has been indicated as the critical factor to consent effective therapy. Several radiochemical factors may negatively impact reaction procedures such as pH, temperature and time of reaction. Our study was undertaken to explore the influence of radiochemical parameters, such as time of incubation, on reaction kinetics during the radiolabelling of DOTATATE with 90Y. Methods: Forty-five radiolabelling procedures were carried out using small volumes of yttrium-90, typically 60–78μL. At nearly constant pH and temperature two different settings of radiolabelling procedures were implemented, removing the products from the heating water bath approximately after 30min (group E, early; n=20) and after 39min (group L, later; n=25). Quality controls were performed by means of both high-performance liquid chromatography (HPLC) and thin-layer chromatography (TLC). Results: Reaction kinetics for 90Y were found to a provide suitable percentage of incorporation at pH 4.5 for both groups. Reaction temperature was not different between groups E and L. A significant difference was found between the two groups in radiochemical yield, which was 95.6%±0.8 for group E and 98.2%±1.1 for group L (p<0.0001). The specific activity of the final product was 46.9MBq/nmol. Conclusion: In order to achieve optimal specific activities, pH, temperature and time of reaction necessitate careful evaluation and setting. A statistically significant difference in labelling yield was found between a set of procedures completed at 39min as compared to that executed at 30min, keep the reaction pH and temperature constant. [Copyright &y& Elsevier]

Abstract: For the first time, natural and synthetic humic substances were radiolabelled by azo coupling [U-14C]phenyldiazonium ions onto the aromatic fragments of their macromolecules under mild reaction conditions. The radiolabelling procedure was optimized with respect to pH, reaction temperature and the molar ratio of the humic substance to the labelling compound. The labelled humic substances were purified by precipitation or ultrafiltration. The chemical yields were in the range between 23% and 95%, and the specific radioactivities varied between 68 and 206MBq 14C per gram of the humic substance, depending on the origin of the humic substance and the purification method. With the 14C-labelled humic compounds thus obtained, we were able to detect humic substances at concentrations as low as 5μg/L. These radiolabelled compounds can be used in long-term studies because, according to size exclusion chromatography data, there are no signs of their decomposition even after 5 months of storage. [Copyright &y& Elsevier]

Abstract: This work describes the synthesis and tumor affinity testing of 8-[123I]iodo-l-1,2,3,4-tetrahydro-7-hydroxyisoquinoline-3-carboxylic acid [ITIC(OH)], a cyclic non-naturally occurring amino acid as an imaging probe for prostate cancer. Parameters for labelling were optimized with regard to the amount of precursor, the temperature and time. Thereafter, ITIC(OH) was evaluated in terms of its uptake in primary human PC-3 and DU-145 prostate cancer cells, followed by analysis of the underlying mechanisms of the radioactivity accumulation in tumor cells. No-carrier-added ITIC(OH) was obtained in 80±15% radiochemical yield and >98% radiochemical purity by a one-step radioiodination, using IODO-GEN as oxidant. The total synthesis time was less than 30min, and compatible with a clinical routine production. ITIC(OH) accumulated intensively in primary human prostate cancer cells. The radioactivity incorporation in tumor following a 10-min incubation at 37°C/pH 7.4 varied from 35% to 58% of the total loaded activity per 106 tumor cells (355–540 cpm/1000 cells). Inhibition experiments revealed that ITIC(OH) was taken up into tumor by an active transport different from the common amino acid carrier systems, including the sodium-dependent system A and B+,0, and the sodium-independent L- and ASC-type transporter. In contrast, the cellular incorporation was dependent on the membrane potential and correlated with the activity of the mitochondria. In conclusion, the specific and high-level accumulation of ITIC(OH) in human prostate carcinoma cells, indicates that the new radiopharmaceutical is a good candidate for further in vivo investigations to ascertain its potential as an imaging probe for prostate cancer by SPET. [Copyright &y& Elsevier]

Formation and growth of metastases require a new vascular network. Angiogenesis plays an essential role in the expansion and progression of most malignancies. A high number of molecular pathways regulate angiogenesis, including vascular endothelial growth factor (VEGF), α v β 3 integrin, matrix metalloproteinases (MMPs), or aminopeptidase N. The aim of this study is to involve new, easily accessible peptide sequences into the of neo-angiogenesis in malignant processes. Labelling of these peptide ligands with 68Ga enable PET imaging of neo-vascularization. • Receptor selective peptides can play an important role in PET imaging • VEGFR-1, α v β 3 integrin, or APN can be a target to visualize neo-angiogenesis • Properties of the biological vector determines the behaviour of the probe • The 68Ga-labelled peptides showed accumulation on the examined B16F10 cell line [ABSTRACT FROM AUTHOR]

Biologically stable 90Y-labelled albumin microspheres (AMS) were developed by optimizing the process of their preparation. Three formulations of 90Y-AMS were initially prepared with high radiolabelling yield but depending on the step when the radionuclide 90Y and DTPA chelator were added, radiolabelled microspheres with different i n vitro and in vivo stability were obtained. DTPA was proved as a useful chelating agent that tightly links radionuclide 90Y to albumin. Also, AMS radiolabelled via DTPA during preparation and before microspheres stabilization, showed significant in vitro and in vivo stability ready for the potential use in selective internal radiation therapy. • Three formulations of hard, less porous and degradable AMS were prepared by emulsification technique using HSA or HSA-DTPA. • Direct labelling of AMS with 90Y, resulted in high yield, but significantly lower in vitro/in vivo stability of AMS-90Y. • Indirect 90Y-labelling of AMS via DTPA during microspheres preparation significantly increased their in vitro/in vivo stability. [ABSTRACT FROM AUTHOR]