Structural Study of (Hydroxypropyl)Methyl Cellulose Microemulsion-Based Gels Used for Biocompatible Encapsulations

Area of Science:

• Materials Science
• Colloid and Surface Chemistry
• Biotechnology

Background:

• (Hydroxypropyl)methyl cellulose (HPMC) forms gels incorporating water-in-oil (w/o) microemulsions.
• These microemulsion-based gels (MBGs) are utilized as carriers for biocompatible ingredients.
• The internal structure of these MBGs remains poorly understood.

Purpose of the Study:

• To elucidate the structural organization of HPMC-based microemulsion gels.
• To investigate the fate of microemulsion droplets upon incorporation into the HPMC matrix.
• To determine the localization of enzymes within the gel structure.

Main Methods:

• Scanning Electron Microscopy (SEM) for morphology.
• Small-Angle X-ray Scattering (SAXS) for structural analysis and detection of reverse micelles.
• Electron Paramagnetic Resonance (EPR) spectroscopy with spin probes for investigating polar/non-polar regions.
• Enzyme-labelling technique for enzyme localization.

Main Results:

• SEM revealed the bulk morphology of the microemulsion-based gels.
• SAXS and EPR provided insights into the gel's structure and microenvironment.
• No distinct microemulsion droplets were detected within the HPMC matrix post-incorporation.
• A structural model proposes oil channels coated by surfactant and water layers, capable of hosting enzymes.

Conclusions:

• The HPMC matrix undergoes structural rearrangement upon microemulsion incorporation.
• While w/o microemulsions are crucial for gel formation, they are not present as discrete droplets in the final structure.
• The HPMC gel forms a channeled network suitable for hosting active enzymes, suggesting potential applications in drug delivery and biomaterials.