title: Adhesion of mussel foot protein-3 to TiO2 surfaces: the effect of pH.
abstract: The underwater adhesion of marine mussels relies on mussel foot proteins (mfps) rich in the catecholic amino acid 3,4-dihydroxyphenylalanine (Dopa). As a side chain, Dopa is capable of strong bidentate interactions with a variety of surfaces, including many minerals and metal oxides. Titanium is among the most widely used medical implant material and quickly forms a TiO2 passivation layer under physiological conditions. Understanding the binding mechanism of Dopa to TiO2 surfaces is therefore of considerable theoretical and practical interest. Using a surface forces apparatus, we explored the force-distance profiles and adhesion energies of mussel foot protein 3 (mfp-3) to TiO2 surfaces at three different pHs (pH 3, 5.5 and 7.5). At pH 3, mfp-3 showed the strongest adhesion force on TiO2, with an adhesion energy of ∼-7.0 mJ/m(2). Increasing the pH gives rise to two opposing effects: (1) increased oxidation of Dopa, thus, decreasing availability for the Dopa-mediated adhesion, and (2) increased bidentate Dopa-Ti coordination, leading to the further stabilization of the Dopa group and, thus, an increase in adhesion force. Both effects were reflected in the resonance-enhanced Raman spectra obtained at the three deposition pHs. The two competing effects give rise to a higher adhesion force of mfp-3 on the TiO2 surface at pH 7.5 than at pH 5.5. Our results suggest that Dopa-containing proteins and synthetic polymers have great potential as coating materials for medical implant materials, particularly if redox activity can be controlled.
authors: Department of Chemical Engineering, University of California, Santa Barbara, California 93106, USA.
authors: Jing
authors: J
authors: Yu
authors: Wei
authors: W
authors: Wei
authors: Matthew S
authors: MS
authors: Menyo
authors: Admir
authors: A
authors: Masic
authors: J Herbert
authors: JH
authors: Waite
authors: Jacob N
authors: JN
authors: Israelachvili
mesh_terms: D000268:Adhesiveness; D000818:Animals; D049872:Bivalvia; D004295:Dihydroxyphenylalanine / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D010084:Oxidation-Reduction; D019736:Prostheses and Implants; D011506:Proteins / Q000737:chemistry*; D013059:Spectrum Analysis, Raman; D014025:Titanium / Q000737:chemistry*
chemical_list: C100750:Mgfp-3 protein, Mytilus galloprovincialis; D011506:Proteins; C009495:titanium dioxide; D004295:Dihydroxyphenylalanine; D014025:Titanium