A Possible Percutaneous Penetration Pathway That Should Be Considered.

Area of Science:

• Dermatology
• Materials Science
• Biophysics

Background:

• Intercellular lipids in the stratum corneum are key to skin barrier function.
• These lipids form ordered and disordered (fluid) phases.
• The fluid phase's role in percutaneous penetration is significant but understudied.

Purpose of the Study:

• To accurately quantify the proportion of the fluid phase within stratum corneum intercellular lipids.
• To reassess previous estimations that may have overestimated the fluid phase proportion.
• To understand the implications of the fluid phase proportion for percutaneous penetration.

Main Methods:

• Developed a method using ethanol treatment to selectively dissolve fluid-phase lipids.
• Analyzed the remaining lipid structures to infer the original fluid phase proportion.
• Compared results with previous extraction-based methods.

Main Results:

• Ethanol treatment suggests the fluid phase proportion may exceed 50% of total intercellular lipids.
• This finding challenges previous estimates that suggested up to 80% fluid phase.
• The fluid phase is likely a major component of the intercellular lipid matrix.

Conclusions:

• The fluid phase of intercellular lipids is a substantial component of the stratum corneum.
• Accurate characterization of the fluid phase is essential for understanding and optimizing percutaneous penetration.
• Future research should consider the fluid phase's role in drug delivery and skin barrier function.