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.

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