title: Chitosan adsorption on hydroxyapatite and its role in preventing acid erosion.
abstract: Polymer adsorption onto an artificial saliva (AS) layer is investigated using quartz-crystal microbalance with dissipation (QCM-D) and chitosan as the model polymer. QCM-D is utilized in an innovative manner to monitor in situ adsorption of chitosan (CH) onto a hydroxyapatite (HA) coated crystal and to examine the ability of the adsorbed layer to "protect" the HA upon sequential exposure to acidic solutions. After deposition of a thin AS layer (16 nm), the total thickness on the HA substrate increases to 37 nm upon exposure to CH at pH 5.5 for 10 min. Correspondingly, the surface charge changes from negative (i.e., AS) to positive, consistent with the adsorption the polycationic CH onto or into the AS layer. Upon exposure to an oxidizing agent, the chitosan cross-links and collapses as noted by a decrease in thickness to 10 nm and an increase in the shear modulus by an order of magnitude. Atomic force microscopy (AFM) is used to determine the surface morphology and RMS roughness of the coated and HA surfaces after citric acid challenges. Both physisorbed and cross-linked chitosan are demonstrated to limit and prevent the erosion of HA, respectively.
authors: Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia, PA 19104, United States. Hyun-Su.Lee@uphs.upenn.edu
authors: Hyun-Su
authors: HS
authors: Lee
authors: Shannon
authors: S
authors: Tsai
authors: Chin-Chen
authors: CC
authors: Kuo
authors: Alice W
authors: AW
authors: Bassani
authors: Brian
authors: B
authors: Pepe-Mooney
authors: Davide
authors: D
authors: Miksa
authors: James
authors: J
authors: Masters
authors: Richard
authors: R
authors: Sullivan
authors: Russell J
authors: RJ
authors: Composto
mesh_terms: D048271:Chitosan / Q000737:chemistry*; D019343:Citric Acid / Q000737:chemistry*; D020099:Coated Materials, Biocompatible / Q000737:chemistry*; D017886:Durapatite / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D018625:Microscopy, Atomic Force; D013499:Surface Properties
chemical_list: D020099:Coated Materials, Biocompatible; D019343:Citric Acid; D048271:Chitosan; D017886:Durapatite