Temperature triggered self-assembly of polypeptides into multivalent spherical micelles.

Area of Science:

• Biomaterials Science
• Polymer Chemistry
• Nanotechnology

Background:

• Elastin-like polypeptides (ELPs) are stimuli-responsive biopolymers with tunable properties.
• Self-assembly of block copolymers into nanostructures is crucial for drug delivery and biomedical applications.
• Developing thermally responsive materials for targeted therapies remains a significant challenge.

Purpose of the Study:

• To genetically synthesize and characterize linear AB diblock elastin-like polypeptides (ELPs) with N-terminal peptide ligands.
• To investigate the temperature-dependent self-assembly of these ELP block copolymers into spherical micelles.
• To explore the potential of these self-assembled micelles for targeted cancer cell delivery.

Main Methods:

• Genetic synthesis of ELP block copolymers using recursive directional ligation.
• Characterization of self-assembly using light scattering, fluorescence spectroscopy, and cryo-transmission electron microscopy (cryo-TEM).
• Determination of critical micelle temperature, micelle size, and critical micelle concentration.

Main Results:

• Ten ELP block copolymers (ELP(BC)'s) were synthesized with varying molecular weights and block ratios.
• ELP(BC)'s exhibited two phase transitions: unimer-to-micelle and micelle-to-bulk aggregate.
• Micelle formation and size were controllable by polymer length and block ratio, with high stability (4-8 microM CMC).
• ELP(BC)'s with peptide ligands formed multivalent micelles in the 37-42°C range, targeting cancer cells.

Conclusions:

• Thermally responsive ELP block copolymers can self-assemble into stable spherical micelles above body temperature.
• The design rules for controlling micelle formation and properties are established.
• ELP-based micelles with peptide ligands show promise for thermally triggered, targeted drug delivery, particularly for cancer therapy.