Biocompatible, detachable, and free-standing polyelectrolyte multilayer films

Self-assembled polyelectrolyte multilayers have gained tremendous popularity over the past decade and have been incorporated in diverse applications. However, the fabrication of detachable and free-standing polyelectrolyte multilayers (PEMs) has proven to be difficult. We report the design of detachable, free-standing, and biocompatible PEMs comprised of hyaluronic acid (anionic PE) and chitosan (cationic PE). These PEMs can be detached from an underlying inert substrate without any postprocessing steps. Our approach enables the fabrication of detachable PEMs from a wide range of polyelectrolytes. Cross-linked PEMs exhibited greater than 95% weight retention when maintained in phosphate buffered saline at 37 °C over a seven day period. The PEM thickness was approximately 3 μm for dried films and increased 2-fold under hydration. A unique feature of the detachable, free-standing PEMs is their optical transparency in the 400-900 nm range under hydrated conditions. The Young's modulus of the cross-linked films ranged from 300-400 MPa, rendering these detachable free-standing multilayers ideal for biomaterial applications. BALB/c 3T3 fibroblasts adhered on the PEMs and colonized the entire surface over a six day period. The cellular responses, as well as the physical properties, demonstrate that the detachable PEM films exhibit tremendous potential for applications in biomaterials and tissue engineering.