Water Dynamics in Dextran-Based Hydrogel Micro/Nanoparticles Studied by NMR Diffusometry and Relaxometry.

Area of Science:

• Materials Science
• Physical Chemistry
• Biophysics

Background:

• Understanding water dynamics in hydrogels is crucial for applications in drug delivery and tissue engineering.
• Mesoporous dextran hydrogels offer unique structural properties for controlled water interaction.

Purpose of the Study:

• To investigate the complex water dynamics within mesoporous dextran hydrogel micro/nanoparticles.
• To elucidate the molecular mechanisms governing water diffusion and relaxation in these systems.

Main Methods:

• High-resolution 1H NMR spectroscopy for detailed spectral analysis.
• Pulsed Field Gradient (PFG) NMR diffusometry to quantify water diffusion coefficients.
• 1H spin-lattice relaxation dispersion profiles using Fast Field Cycling (FFC) NMR and conventional relaxometry.

Main Results:

• Identified distinct water fractions with diffusion coefficients orders of magnitude lower than bulk water.
• Demonstrated that reorientation-mediated translational motions (RMTMs) dominate relaxation at intermediate frequencies.
• Revealed that slow solid-gel dynamics at the pore surface influence relaxation at low frequencies.

Conclusions:

• Water dynamics in dextran hydrogels are heterogeneous, with distinct populations interacting differently with the gel matrix.
• NMR techniques effectively probe water mobility and relaxation mechanisms, correlating with hydrogel structure.
• The study provides insights into the submillisecond correlation time of dextran gel motion and water-gel interactions.