Automated preparation of radiopharmaceuticals as a tool of radiation protection optimisation of staff.

Preparation of radiopharmaceuticals means everyday exposure to ionizing radiation for pharmaceutical workers. Manual preparation of positron radio-pharmaceuticals may be a risk in exceeding the legisla-tive limits for radiation workers, in particular in finger dosimetry. Instrumental methods of preparation of radiopharmaceuticals can serve as an effective tool of radiation protection. The present study deals with the evaluation of the results of personal dosimetry in workers preparing the radiopharmaceutical 18F-FDG with the use of instrumental methods of preparation of this radiopharmaceutical. The results of the paper show a clear decrease in the values of finger dosimetry and a minute increase in the values of whole-body dosimetry in the cohort of pharmaceutical personnel. The evaluation thus shows a clear contribution of instrumental methods of preparation of the radiopharmaceutical 18F-FDG to the results of finger dosimetry of pharmaceutical personnel.

Antiangiogenic Human Monoclonal Antibody Ramucirumab Radiolabelling: In Vitro Evaluation on VEGFR2-positive Cell Lines.

Background/Aim: Radiolabelling of monoclonal antibodies (mAbs) could be beneficial in cancer diagnosis and therapy, however it may cause structural changes and consequently deteriorate their immunoreactivity. Materials and Methods: The therapeutic mAb ramucirumab (RAM) was technetium-99m labelled using either a direct or an indirect method with the use of two bifunctional chelating agents (HYNIC, DTPA). The radiochemical purity was assessed using instant thin-layer chromatography (ITLC) and high-performance liquid chromatography (HPLC) technique. The affinity of radiolabelled RAM was tested on human cancer cell lines. Results: The radiolabelling provided the following stable compounds: [ 99m Tc]RAM, [ 99m Tc]HYNIC-RAM and [ 99m Tc]DTPA-RAM. Their radiochemical purity was over 95%. All prepared radiopharmaceuticals showed moderate affinity to the targeted receptor, in vitro. However, their affinity was one order lower compared to that of the natural mAb. Moreover, directly and DTPA-radiolabelled RAM demonstrated less favourable binding kinetics. Conclusion: Radiolabelling negatively affected the affinity of RAM to its targeted receptor.

In vitro evaluation of concentration, labeling effectiveness and stability for 131 I-labeled radioimmunoassay ligand using real-time detection technology.

Radioimmunoassay belongs to the analytical method enabling highly specific and sensitive quantification of molecules. The verification of the real-time radioimmunoassay technology usefulness for ligand-quality characteristics evaluation such as concentration, influence of radiolabeling on binding affinity and stability was estimated. The anti-epidermal growth factor receptor antibody 131 I-cetuximab was employed as the ligand antibody. The concentration of 131 I-cetuximab was derived from the shape of binding curves coming from the ligand-receptor interaction. The binding curves also allowed the estimation of 131 I-cetuximab binding affinity for different radiolabeling procedures (incubation times 1, 5, and 10 minutes) in stability testing up to 96 hours at 4°C. The stability testing also included comparative analysis by size exclusion high-performance liquid chromatography. The assessment of cetuximab concentrations using real-time method showed acceptable accordance between real and calculated values. The real-time method revealed that 1-minute radiolabeling proved to be the optimal incubation time for direct radioiodination of cetuximab. Stability testing showed the significant change in radioligand affinity by one order at the longest incubation times (72 and 96 hours). Characterization of stability and binding behavior of radiolabeled monoclonal antibodies by the verified real-time method before use in other assays may be employed to eliminate variability and suboptimal antibody performance.