Time-course quantitative mapping of caffeine within the epidermis, using high-contrast pump-probe stimulated Raman...

Area of Science:

• Dermatology and Cosmetology
• Biomedical Imaging
• Pharmacokinetics

Background:

• Assessing drug penetration in skin is crucial for dermatology and cosmetology.
• Label-free imaging offers high-resolution detection but struggles with quantitative, time-course distribution mapping in complex tissues.
• Developing advanced imaging techniques is essential for understanding topical drug delivery.

Purpose of the Study:

• To establish real-time, quantitative skin penetration profiles of topically applied caffeine.
• To evaluate the efficacy of pump-probe phase-modulated stimulated Raman scattering (PM-SRS) microscopy combined with confocal reflection microscopy for this purpose.
• To compare caffeine penetration from different topical formulations.

Main Methods:

• Utilized reconstructed human skin epidermis models.
• Employed a combination of PM-SRS and confocal reflection microscopy.
• Analyzed caffeine penetration from aqueous solution, oil-in-water gel, and water-in-oil gel formulations.

Main Results:

• Successfully detected the characteristic Raman signal of caffeine in the skin model using PM-SRS.
• Generated real-time concentration maps of caffeine within the skin model from various formulations.
• PM-SRS demonstrated reduced background signals and provided high-contrast images compared to conventional Raman methods.

Conclusions:

• Real-time skin penetration profiles of caffeine from different formulations were successfully established.
• PM-SRS microscopy proved to be a powerful, non-invasive, and real-time depth-profile imaging technique.
• This method is highly suitable for quantitative studies of topically applied drugs.