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Ion pairing and hydration in polyelectrolyte multilayer films containing polysaccharides
Thomas Crouzier1, Catherine Picart
1Université de Montpellier 2, CNRS UMR 5539, Place Eugène Bataillon, 34095 Montpellier Cedex 5, France.
Biomacromolecules
|February 10, 2009
Summary
This study investigated thin films made of poly(L-lysine) and various polysaccharides. Hydration, ion pairing, and diffusion properties were found to be interconnected and dependent on the specific biomacromolecules used in the film construction.
Area of Science:
- Biomaterials Science
- Polymer Chemistry
- Surface Science
Background:
- Thin films composed of polycations and polyanions are crucial in various biomedical applications.
- Understanding the internal structure, hydration, and ion pairing of these films is essential for optimizing their performance.
Purpose of the Study:
- To investigate the internal structure, water content, and ion pairing in thin films of poly(L-lysine) (PLL) with different anionic polysaccharides: hyaluronan (HA), chondroitin sulfate (CSA), and heparin (HEP).
- To correlate film properties with the specific structures of the constituent biomacromolecules.
Main Methods:
- In situ monitoring of film buildup using quartz crystal microbalance with dissipation monitoring (QCM-D).
- Attenuated total internal reflectance infrared spectroscopy (ATR-FTIR) for quantifying chemical groups (sulfate, carboxylate, ammonium).
- Carbodiimide chemistry for selective cross-linking to determine ion pairing (COO-/NH3+ and SO3-/NH3+).
- Fluorescence recovery after photobleaching (FRAP) for assessing poly(L-lysine) diffusion.
Main Results:
- Hyaluronan- and chondroitin sulfate-based films exhibited the highest water content.
- The monomer ratio of disaccharide to lysine approached a plateau of approximately 0.5 in all films.
- A significant percentage of ammonium groups remained unpaired in HA (46%) and CSA (21%) films, with none in HEP films.
- The ratio of sulfate to carboxylate pairing with ammonium groups reflected the stoichiometry of the polysaccharides (2:1 for HEP, 1:1 for CSA).
Conclusions:
- Hydration, ion pairing, and poly(L-lysine) diffusion are interconnected properties within these polyelectrolyte multilayer films.
- The specific structure of the anionic polysaccharide significantly influences the internal film properties and ion coordination.
- These findings provide insights into the design and application of functional biomacromolecular films.
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