Diffusion exchange NMR spectroscopic study of dextran exchange through polyelectrolyte multilayer capsules

Area of Science:

• Materials Science
• Polymer Chemistry
• Biophysics

Background:

• Polyelectrolyte multilayer (PEM) hollow capsules are promising for drug delivery applications.
• Understanding molecule diffusion through these capsules is key to optimizing their design.
• Dextran molecules of varying sizes are often used to probe transport phenomena.

Purpose of the Study:

• To investigate the diffusion and exchange dynamics of dextran molecules with different molecular weights through PEM hollow capsules.
• To elucidate the influence of capsule confinement on dextran diffusion.
• To provide quantitative data for the design of PEM capsules as drug carriers.

Main Methods:

• Utilized two-dimensional nuclear-magnetic-resonance (2D-NMR) spectroscopy techniques.
• Employed diffusion-diffusion exchange spectroscopy (DEXSY) to study molecular exchange.
• Applied diffusion-relaxation correlation spectroscopy (DRCOSY) to analyze diffusion behavior under confinement.

Main Results:

• Dextran 77 kDa diffusion showed time dependence, indicating confinement effects within the capsules.
• Significant partitioning of dextran 77 kDa into capsule states was observed, exceeding volume fraction predictions.
• Dextran 77 kDa exhibited diffusive exchange through capsules with an exchange time of approximately 1 second.
• Dextran 4.4 kDa diffusion was not detectably influenced by the PEM capsules.

Conclusions:

• PEM hollow capsules demonstrate size-selective permeability, hindering larger molecules like 77 kDa dextran.
• The observed diffusion behavior of 77 kDa dextran suggests effective interaction and transport across the capsule walls.
• The study provides valuable insights into the transport mechanisms within PEM capsules, aiding in their development for targeted drug delivery.