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Silicon addition to hydroxyapatite increases nanoscale electrostatic, van der Waals, and adhesive interactions
Author(s) -
Vandiver Jennifer,
Dean Delphine,
Patel Nelesh,
Botelho Claudia,
Best Serena,
Santos José D.,
Lopes Maria A.,
Bonfield William,
Ortiz Christine
Publication year - 2006
Publication title -
journal of biomedical materials research part a
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.849
H-Index - 150
eISSN - 1552-4965
pISSN - 1549-3296
DOI - 10.1002/jbm.a.30737
Subject(s) - van der waals force , materials science , hamaker constant , monolayer , adhesion , surface charge , silicon , nanoscopic scale , nanotechnology , force spectroscopy , chemical engineering , van der waals radius , chemistry , composite material , organic chemistry , atomic force microscopy , molecule , engineering , metallurgy
The normal intersurface forces between nanosized probe tips functionalized with COO − ‐terminated alkanethiol self‐assembling monolayers and dense, polycrystalline silicon‐substituted synthetic hydroxyapatite (SiHA) and phase pure hydroxyapatite (HA) were measured via a nanomechanical technique called chemically specific high‐resolution force spectroscopy. A significantly larger van der Waals interaction was observed for the SiHA compared to HA; Hamaker constants ( A ) were found to be A SiHA = 35 ± 27 zJ and A HA = 13 ± 12 zJ. Using the Derjaguin–Landau–Verwey–Overbeek approximation, which assumes linear additivity of the electrostatic double layer and van der Waals components, and the nonlinear Poisson–Boltzmann surface charge model for electrostatic double‐layer forces, the surface charge per unit area, σ (C/m 2 ), was calculated as a function of position for specific nanosized areas within individual grains. SiHA was observed to be more negatively charged than HA with σ SiHA = −0.024 ± 0.013 C/m 2 , two times greater than σ HA = −0.011 ± 0.006 C/m 2 . Additionally, SiHA was found to have increased surface adhesion (0.7 ± 0.3 nN) compared to HA (0.5 ± 0.3 nN). The characterization of the nanoscale variations in surface forces of SiHA and HA will enable an improved understanding of the initial stages of bone–biomaterial bonding. © 2006 Wiley Periodicals, Inc. J Biomed Mater Res, 2006