Thermosensitive and biocompatible cyclotriphosphazene micelles

Area of Science:

• Polymer Chemistry
• Materials Science
• Nanotechnology

Background:

• Cyclotriphosphazenes offer a versatile scaffold for designing functional materials.
• Amphiphilic polymers are crucial for self-assembly into nanostructures for drug delivery.
• Thermosensitive materials can respond to temperature changes, enabling controlled release.

Purpose of the Study:

• To synthesize and characterize novel thermosensitive micellar cyclotriphosphazenes.
• To investigate the self-assembly behavior and micelle formation of these amphiphilic trimers.
• To evaluate the potential of these micelles for local drug delivery applications.

Main Methods:

• Synthesis via stepwise nucleophilic substitution of hexachlorocyclotriphosphazene.
• Characterization using multinuclear NMR spectroscopy ((1)H, (31)P), elemental analysis, and dynamic light scattering (DLS).
• Assessment of thermosensitive behavior (lower critical solution temperature) and micelle size determination.

Main Results:

• Successfully synthesized amphiphilic cyclotriphosphazene trimers with methoxy poly(ethylene glycol) (MPEG) and oligopeptide side groups.
• Demonstrated self-assembly into stable micelles in aqueous solutions with tunable lower critical solution temperatures (20-48 °C).
• Observed a significant reduction in micelle size (7-8 nm) with longer MPEG chains and hexapeptides, attributed to hydrophobic interactions.

Conclusions:

• The synthesized cyclotriphosphazene trimers form stable, thermosensitive micelles with controllable sizes.
• Excellent biocompatibility was confirmed through local tolerance tests in rabbits.
• Promising in vitro release profiles suggest potential for local delivery of protein drugs like human growth hormone (hGH).