Caffeine delivery in porcine skin: a confocal Raman study

Area of Science:

• Pharmacology
• Biophysics
• Analytical Chemistry

Background:

• Confocal Raman microscopy (CRM) is an emerging optical technique for non-destructive analysis of pro-drug and drug delivery.
• CRM allows for the measurement of drug permeation profiles through biological tissues like skin.
• Current semi-quantitative evaluations typically normalize compound peaks to endogenous skin signals (amino acid, amide I).

Purpose of the Study:

• To optimize a methodology for complete quantitative measurement of active compounds within different skin depths.
• To establish a reliable method for assessing drug penetration and distribution in skin layers.
• To advance CRM from semi-quantitative to fully quantitative analysis for drug delivery applications.

Main Methods:

• Utilized caffeine as a model compound to evaluate skin penetration using CRM.
• Obtained semi-quantitative depth profiles by normalizing Raman intensities.
• Developed an external calibration curve correlating Raman intensity ratios with caffeine concentration in porcine skin samples analyzed by CRM and HPLC.

Main Results:

• Established a correlation between Raman signal intensity and caffeine concentration per skin mass.
• Successfully created a depth profile for caffeine penetration in porcine skin.
• Demonstrated that correlation curves enable full quantification of caffeine in skin based on Raman intensity ratios.

Conclusions:

• The optimized CRM methodology allows for precise, quantitative measurement of drug penetration at various depths.
• This technique overcomes the limitations of semi-quantitative analysis, providing more accurate drug distribution data.
• The developed method holds significant potential for enhancing the study of drug delivery and skin permeation.