Optimized Skin Optical Clearing for Optical Coherence Tomography Monitoring of Encapsulated Drug Delivery Through the Hair Follicles

The study evaluated the effectiveness of various optical clearing agents (OCAs) in enhancing the optical probing depth (OPD) and optical detection depth (ODD) for monitoring drug delivery through hair follicles using optical coherence tomography (OCT). Conducted ex vivo on rats, the research found that all tested OCAs increased OPD, but hyperosmotic agents caused skin dehydration, reducing OCT contrast in the dermis and thus decreasing ODD. Lipophilic agents improved epidermal optical clearing without dehydration. The highest ODD was achieved with a PEG-400/oleic acid mixture, which was also tested in vivo, showing significant enhancement in both ODD and OPD.