Intravenous technetium-99m labelled PEG-liposomes in horses: a safety and biodistribution study.

This research introduces a study looking into the safety and biodistribution of polyethyleneglycol (PEG) liposomes in horses. The study found that when injected intravenously, these liposomes appear safe and show a specific pattern of distribution in the horses’ bodies, potentially proving useful for targeted drug delivery and disease detection.

Objective and Methods

• The key aim of this research was to gauge the safety and assess how PEG-liposomes distribute within a horse’s body when administered intravenously.
• To perform this study, the PEG-liposomes were created through a process known as the film hydration method and subsequently labelled with technetium-99m, a common radiopharmaceutical used in medical imaging.
• A combination of technetium-99m labelled PEG-liposomes and unlabelled PEG-liposomes were administered to 10 conscious horses via intravenous infusion. The infusion was given at a rate of 6 µmol/min for the first 15 minutes, and then at a rate of 60 µmol/min afterwards.
• Different parameters such as heart rate, respiratory rate, hematology, plasma biochemistry, and serum complement activity were monitored at various intervals. Scintigraphic (a diagnostic test in nuclear medicine) imaging was performed 1, 12, and 21 hours post intravenous infusion to assess the distribution of the PEG-liposomes in the horses’ bodies.

Results

• No adverse reactions were reported in the horses during or after the infusion of the PEG-liposomes.
• A noticeable raise in heart rate and respiratory rate was observed at the 20 and 25-minute marks post-infusion.
• There were trends indicating decreased total haemolytic complement values (part of the immune response) at 20 minutes post-infusion, but no significant complement consumption was detected otherwise.
• Scintigraphic images showcased a prolonged vascular phase lasting to 21 hours post-infusion, and revealed a clear pattern of organ distribution with a high concentration of radiopharmaceutical within the lung, kidney, liver, and spleen.

Conclusions

• The study concluded that the administration of PEG-liposomes intravenously is safe in horses. The technetium-99m labelled liposomes circulated for a long time in the body and showed reliable organ distribution patterns.
• It was highlighted that these radiolabelled liposomes can potentially be used for identifying infections, inflammations, and tumors in horses.
• The possibility of using PEG-liposomes for targeted drug delivery in horses was also emphasized in the conclusion, making this a potentially significant development in veterinary medicine. This research sets a foundation for interpreting findings and tissue distribution of technetium-99m PEG-liposomes after intravenous administration in healthy horses.