Technetium-99m labelled liposomes to image experimental arthritis

Area of Science:

• Nuclear medicine
• Radiopharmaceutical development
• Inflammatory disease imaging

Background:

• Adjuvant arthritis is a model for inflammatory joint disease.
• Liposomes are potential drug delivery vehicles.
• Technetium-99m (99mTc) is a common radioisotope for medical imaging.

Purpose of the Study:

• To evaluate 99mTc-labeled polyethylene glycol (PEG)-liposomes for imaging adjuvant arthritis in a rat model.
• To compare PEG-liposomes with non-PEG-liposomes and 99mTc-IgG for arthritis imaging.

Main Methods:

• Adjuvant arthritis was induced in rats.
• Rats were injected with 99mTc-labeled non-PEG-liposomes, PEG-liposomes, or 99mTc-IgG.
• In vivo distribution and tissue uptake of radiopharmaceuticals were assessed using scintigraphy and tissue counting at 2, 8, and 24 hours post-injection.

Main Results:

• PEG-liposomes exhibited significantly longer blood circulation half-life (18 hours) compared to non-PEG-liposomes (1 hour) and 99mTc-IgG (3 hours).
• Inflamed ankle uptake of radiopharmaceuticals correlated with blood residence time, with PEG-liposomes showing the highest uptake (1.15% injected dose/g).
• PEG-liposomes achieved the highest inflamed ankle to background ratio (7.5 at 24 hours), indicating superior image quality.

Conclusions:

• 99mTc-labeled PEG-liposomes are effective agents for visualizing arthritis due to their prolonged circulation.
• Enhanced uptake in inflamed joints and improved target-to-background ratios make PEG-liposomes advantageous for scintigraphic imaging of arthritis.
• PEG-liposomes show potential not only for imaging but also for site-specific delivery of antirheumatic drugs.