title: Nanoscale variation in surface charge of synthetic hydroxyapatite detected by chemically and spatially specific high-resolution force spectroscopy.
abstract: The normal intersurface forces between nanosized probe tips functionalized with COO-- and NH3+-terminated alkanethiol self-assembling monolayers and dense polycrystalline phase pure synthetic hydroxyapatite (HA) were measured via a powerful nanomechanical technique called chemically specific high-resolution force spectroscopy. The data taken on approach of the probe tip to the HA surface was compared to the nonlinear Poisson-Boltzmann-based electrostatic double layer theory to predict the surface charge per unit area of the HA, sigmaHA (C/m2), as a function of ionic strength, position within a variety of grains, and across grain boundaries. The average sigmaHA was found to be approximately -0.02 C/m2 and to vary from -0.0037 to -0.072 C/m2 with nanoscale position in relation to grain boundaries and crystal planes up to -0.19 C/m2/microm. Positional measurement of nanoscale surface properties holds great promise in elucidating the molecular origins of physicochemical processes occurring at the biomaterial interface.
authors.affiliation: Departments of Materials Science and Engineering, RM13-4022, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Vandiver
authors.forename: Delphine
authors.initials: D
authors.lastname: Dean
authors.forename: Nelesh
authors.initials: N
authors.lastname: Patel
authors.forename: William
authors.initials: W
authors.lastname: Bonfield
authors.forename: Christine
authors.initials: C
authors.lastname: Ortiz
mesh_terms: D001672:Biocompatible Materials / Q000032:analysis / Q000737:chemistry*; D003198:Computer Simulation; D017886:Durapatite / Q000032:analysis / Q000737:chemistry*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008422:Materials Testing / Q000379:methods*; D008956:Models, Chemical; D008968:Molecular Conformation; D036103:Nanotechnology / Q000379:methods*; D055672:Static Electricity; D013499:Surface Properties
chemical_list: D001672:Biocompatible Materials; D017886:Durapatite