(501d) Modular Biomaterials from Surfactant and Polyelectrolyte Mixtures

Polyelectrolytes (e.g., alginate, chitosan, and hyaluronan) have become ubiquitous in biomaterials science. They exhibit acute sensitivity to external stimuli such as pH and ionic strength, and can form a variety of structures (using either chemical crosslinking or physical association) that range from drug-bearing nanoparticles to macroscopic scaffolds. In many applications it is critical to control their biodegradability. This is usually achieved through synthetic modification. As a simpler alternative, we exploit the associative phase separation in mixtures of bio-derived surfactants and polyelectrolytes. Gel fiber scaffolds are formed via phase inversion, using a homologous series of fatty acid salts (sodium caprate, laurate, and myristate) and a water-soluble chitosan derivative, N-[(2-hydroxy-3-trimethylammonium)propyl]chitosan chloride (HTCC). Their in vitro interactions with neural stem cells indicate them to be cell-adhesive and cytocompatible. Their dissolution times are modulated through the selection of the fatty acid molecule, and range from minutes (for HTCC-caprate), to hours (for HTCC-laurate), to days (for HTCC-myristate). These variations are linked to the surfactant-polyelectrolyte binding strength and scale with the equilibrium binding constants of the fatty acid-HTCC mixtures.