Controlling Trapping, Release, and Exchange Dynamics of Micellar Core Components.

Area of Science:

• Supramolecular Chemistry
• Materials Science
• Biophysics

Background:

• Hierarchically organized self-assembled supramolecular structures are well-studied for formation and stability.
• Mechanistic aspects of subcomponent dynamics in these structures are often poorly understood.
• Polyamidoamine (PAMAM) dendrimer-based micelles represent a class of such structures with potential applications.

Purpose of the Study:

• To investigate and manipulate the subcomponent dynamics of PAMAM dendrimer-based micelles.
• To understand how dendrimer generation, pH, and stoichiometry influence micelle dynamics.
• To control the exchange and release kinetics of dendrimers within micelles.

Main Methods:

• Utilized Förster Resonance Energy Transfer (FRET) with fluorescein (donor) and rhodamine (acceptor) labeled PAMAM dendrimers.
• Employed high-resolution Nuclear Magnetic Resonance (NMR) spectroscopy, including Diffusion Ordered Spectroscopy (DOSY).
• Varied dendrimer generation (G4, G5, G6), pH (7.0, 7.8), and stoichiometry.

Main Results:

• Dendrimicelles from G4 and G5 PAMAM dendrimers showed dynamic exchange, evidenced by increased FRET.
• G6 PAMAM dendrimicelles appeared kinetically trapped at pH 7.0.
• At pH 7.8, G6 dendrimicelles exhibited exchange dynamics due to reduced charge, and pH change to 7.0 triggered activated release.

Conclusions:

• Dendrimer generation, charge density, and stoichiometry are critical for controlling complex coacervate core micelle dynamics.
• Micelle behavior can be tuned between kinetically trapped and dynamic states.
• This control enables tailored exchange and release speeds for applications in material science, sensors, and drug delivery.