Temperature-Dependent Complex Coacervation of Engineered Elastin-like Polypeptide and Hyaluronic Acid...

Area of Science:

• Biomaterials Science
• Polymer Chemistry
• Physical Chemistry

Background:

• Coacervates, formed by phase separation of polymers, have broad applications in personal care, pharmaceuticals, and food.
• Traditional coacervate formation relies on pH, ionic strength, or polyelectrolyte concentration changes.
• Biological coacervates are crucial in cellular processes, but their formation mechanisms are complex.

Purpose of the Study:

• To investigate the temperature-induced microphase separation and complex coacervate formation between elastin-like polypeptides (ELPs) and hyaluronic acid (HA).
• To model biological coacervates using these natural polyelectrolytes.
• To explore the potential of ELP/HA coacervates as delivery vehicles for hydrophobic payloads.

Main Methods:

• Utilized temperature as the primary trigger for coacervate formation, bypassing the need for salt or pH adjustments.
• Employed fluorescent imaging and dynamic light scattering (DLS) to characterize particle size and polydispersity.
• Investigated the influence of polyion charge ratios on coacervate structure and size using microscopy techniques.

Main Results:

• ELP/HA complex coacervates formed well-defined spherical particles upon temperature-induced phase transition, unlike pure ELP solutions.
• Coacervate formation was reversible with minimal hysteresis.
• High charge ratios at elevated temperatures yielded particles of 400-600 nm with low polydispersity indices (PDIs) of ~0.1.
• Polyion ratio significantly impacted the size and structure of the ELP/HA coacervates.
• ELP/HA coacervates demonstrated the ability to sequester the hydrophobic molecule pyrene.

Conclusions:

• ELP/HA complex coacervates offer a tunable and reversible system for particle formation driven by temperature.
• The size and structure of these coacervates can be controlled by adjusting the ratio of the constituent polyions.
• The sequestration of hydrophobic molecules highlights the potential of ELP/HA coacervates as effective delivery vehicles.