Unveiling Supramolecular Structures Formed by Menthol and Xanthan Gum in Oleic Acid-Based Microemulsions

Area of Science:

• Physical Chemistry
• Materials Science
• Pharmaceutical Sciences

Background:

• Microemulsions (MEs) are advanced delivery systems leveraging supramolecular structures to improve drug dissolution rates.
• Excipients like menthol (drug) and xanthan gum (XG, thickening agent) can significantly alter ME nanostructures.

Purpose of the Study:

• To elucidate the mechanistic basis of supramolecular structural changes in oleic acid-based MEs upon addition of XG and menthol.
• To correlate these structural modifications with changes in physical properties for rational formulation design.

Main Methods:

• A multitechnique approach including electron microscopy, dynamic light scattering (DLS), small-angle X-ray scattering (SAXS), rheology, and texture analysis.
• Characterization of MEs with varying concentrations of menthol (0.1-1.0%w/w) and XG (0.1-0.5%w/w).

Main Results:

• Menthol addition modulated droplet size (DLS: 127-157 nm; SAXS: 108-136 nm), indicating drug incorporation.
• XG addition formed a distinct interconnected "pearl-necklace" architecture (DLS: 102-111 nm; SAXS: 102 nm) without altering droplet size.
• Rheological and textural analyses revealed significant changes in consistency, firmness, and adhesiveness, particularly with XG, and enhanced adhesiveness with menthol.

Conclusions:

• Controlled addition of excipients like XG and menthol enables rational design of microemulsion nanostructures.
• The observed "pearl-necklace" architecture and enhanced adhesive properties suggest potential for sustained topical drug delivery.
• Further investigation into skin permeation and therapeutic efficacy is warranted for dermatological applications.