(510l) Nanostructured Glycosaminoglycan-Based Polyelectrolyte Multilayers Using The Polyanion Heparin And The Polycation Chitosan

The layer-by-layer (LBL) technique for fabricating polyelectrolyte multilayer (PEM) films is based on the alternate adsorption of a polycation and a polyanion from solution onto a charged surface. During each adsorption step, the surface charge is inverted, resulting in electrostatic repulsion that can limit the layer thickness. Thus, individual layer thickness is limited to the nanometer length scale, and films are stabilized by strong electrostatic interactions. Polyelectrolyte adsorption can be a strong function of pH, ionic strength, polymer charge density, and the presence of monovalent or divalent salts in the deposition solutions. Controlling these parameters can therefore provide precise control over LBL assembly of polymer thin films at the nanoscale, with respect to thickness, composition, and layer interpenetration. The goal of this work is to demonstrate the use of LBL to generate nanostructured polysaccharide thin films and obtain control over the composition at the nanoscale by varying simple processing parameters. Here we use the LBL technique to assemble PEM of heparin (strong polyanion) and chitosan (weak polycation) and characterize the PEM composition and layer thickness as functions of suitable processing parameters (e.g. pH, ionic strength). A combination of Fourier transform surface plasmon resonance and spectroscopic ellipsometry provide details on the layer thickness, and vibrational spectroscopy and X-ray photoelectron spectroscopy provide details of the chemistry (i.e. composition) of the PEM. This work will contribute to understanding the physical chemistry and polyelectrolyte behavior of an important class of biological macromolecules. These glycosaminoglycans were chosen based on their biocompatibility and biological functionality. Future applications might include activation of biofunctional tissue engineering scaffolds with heparin, which binds and enhances many growth factors, and chitosan which has demonstrated antimicrobial activity.