Indocyanine Green as a Marker for Nose-to-Brain Delivery Pathways, Brain Distribution, and PLGA Nanoparticle...

Area of Science:

• Neuroscience
• Biomedical Engineering
• Pharmacology

Background:

• Intranasal drug delivery offers a direct route to the brain, bypassing the blood-brain barrier.
• Indocyanine green (ICG) is a near-infrared fluorescent dye with potential applications in neuroimaging and drug delivery.

Purpose of the Study:

• To evaluate the retention rate and duration of indocyanine green (ICG) in the rat brain after intranasal administration.
• To compare the brain retention of ICG in aqueous solution versus encapsulated in poly(D,L-lactide-co-glycolide) (PLGA) nanoparticles.

Main Methods:

• Rats received a single intranasal dose of ICG (aqueous or PLGA nanoparticles).
• Near-infrared fluorescence of ICG was measured in brain and visceral organs at multiple time points (1h to 2 weeks).

Main Results:

• Both ICG formulations stained olfactory bulbs and brainstem.
• ICG fluorescence was detectable in the brain up to 14 days post-administration.
• ICG-loaded PLGA nanoparticles exhibited significantly higher brain emission on day 14 compared to the aqueous solution.

Conclusions:

• ICG is transported to the brain via olfactory and trigeminal nerve pathways.
• ICG is a viable in vivo dye due to its sustained emission and low toxicity.
• ICG-encapsulated PLGA nanoparticles show promise for brain delivery of therapeutics.