Intravenous technetium-99m labelled PEG-liposomes in horses: a safety and biodistribution study.
Authors: Underwood C, van Eps A W, Ross M W, Laverman P, van Bloois L, Storm G, Schaer T P
Journal: Equine veterinary journal
Summary
# Editorial Summary: PEG-Liposome Safety and Biodistribution in Horses PEG-coated liposomes represent a promising nanotechnology platform for targeted drug delivery and diagnostic imaging in equine medicine, yet their safety profile and behaviour in the equine body required investigation before clinical application. Researchers administered intravenous technetium-99m-labelled PEG-liposomes to ten healthy horses at escalating infusion rates, monitoring clinical parameters, haematological and biochemical markers, complement activation, and organ distribution via scintigraphy and tissue analysis. No adverse reactions occurred during infusion, though transient elevations in heart and respiratory rates at 20–25 minutes post-injection were recorded; notably, complement consumption was negligible despite a non-significant trend towards decreased haemolytic complement activity. Scintigraphic imaging demonstrated prolonged vascular circulation persisting to 21 hours post-injection with consistent organ accumulation patterns, with the lungs, kidneys, liver and spleen showing the highest radioactive concentrations. These findings establish safety parameters and baseline biodistribution data essential for developing liposome-based therapeutics for equine infection, inflammation and neoplasia; the long circulating half-life and reproducible tissue distribution suggest considerable potential for both targeted drug delivery applications and diagnostic imaging of pathological lesions in clinical practice.
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Practical Takeaways
- •PEG-liposomes labeled with technetium-99m offer a safe, non-adverse diagnostic imaging option for detecting infections, inflammatory conditions, and tumors in clinical horse practice.
- •The 21-hour circulating half-life and predictable organ distribution make these liposomes practical for scintigraphic imaging protocols without requiring multiple injections.
- •The temporary elevations in heart and respiratory rates during infusion are clinically insignificant and self-resolving, allowing routine use in conscious horses without sedation complications.
Key Findings
- •Intravenous PEG-liposome administration was safe in all 10 horses with no adverse reactions observed during or after infusion.
- •Significant elevation in heart rate and respiratory rate occurred at 20-25 minutes post-infusion, with no significant complement consumption detected.
- •Scintigraphic imaging showed prolonged vascular phase lasting to 21 hours post-infusion with reproducible organ distribution pattern.
- •Highest radiopharmaceutical concentrations were found in lungs, kidneys, liver, and spleen, demonstrating long-circulating characteristics suitable for diagnostic imaging.