In situ forming collagen-hyaluronic acid membrane structures: Mechanism of self-assembly and applications in regenerative medicine

Bioactive, in situ forming materials have the potential to complement minimally invasive surgical procedures and enhance tissue healing. For such biomaterials to be adopted in the clinic, they must be cost-effective, easily handled by the surgeon and have a history of biocompatibility. To this end, we report a novel and facile self-assembling strategy to create membranes and encapsulating structures using collagen and hyaluronic acid (HA). Unlike membranes built by layer-by-layer deposition of oppositely charged biomolecules, the collagen-HA membranes described here form a diffusion barrier upon electrostatic interaction of the oppositely charged biomolecules, which is further driven by osmotic pressure imbalances. The resulting membranes have a nanofibrous architecture, a thicknesses of 130 mu m and a tensile modulus (0.59 +/- 0.06 MPa) that can increase 7-fold using carbodiimide chemistry (4.42 +/- 1.46 MPa). Collagen-HA membranes support mesenchymal stem cell proliferation and have a slow and steady protein release profile (7% at day 28), offering opportunities for targeted tissue regeneration. We demonstrate the capacity to encapsulate cells by injecting HA into the collagen solution, and enhance allograft and implant biocompatibility through a coating technique. This study describes a novel mechanism of collagen-HA membrane formation and provides the groundwork to apply these membranes in a variety of tissue engineering applications. (C) 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.