Modeling apatite nucleation in the human body and in the geochemical environment

Abstract

ABSTRACT. This paper serves to show that under similar physicochemical conditions, universal chemical reaction pathways can be involved in the interactions of fluids, biomolecules and minerals, whether in the human body or in the geochemical environment. The concept is illustrated by comparing heterogeneous apatite nucleation at bone sialoprotein (BSP) surfaces, bioceramic implant surfaces and on marine, diatomaceous sediments where phosphorite deposits are formed. The present approach combines crystallographic considerations, experimental NMR data and ab initio molecular orbital calculations of NMR parameters to elucidate reactive site geometry, mineral nucleation and inhibition reaction pathways. This technique may be applicable in future investigations of biomineralization mechanisms.The peptide sequence, S(P)EE, is proposed to constitute an active site on BSP, where the three acidic groups are arranged at 60°from each other. The equilateral triangle provides a stereochemical match for Ca 2؉ on the (001) face of apatite. The analogous active site on silicate bioceramics is the cyclic silicate trimer or three-ring containing surface silanol groups. One possible reaction pathway for calcium phosphate (CaP) nucleation consistent with experimental 31 P NMR data involves the following steps: Ca 2؉ sorption at the active site and HPO 4 2؊ attachment resulting in the critical nucleus, followed by nucleus growth and phase transformation to apatite. The present ab initio calculations cannot provide information on which CaP phase is nucleated, so we assume that the CaP nucleus is amorphous. Magnesium inhibits nucleation by adsorbing faster than calcium, as an outer-sphere surface complex, at the active site.

Principles of demineralization: Modern strategies for the isolation of organic frameworks

“…In conclusion, demineralization is an ongoing, challenging group of mechanisms and aspects applicable and used by different scientific disciplines with their diverse directions including the following: evolutionary paleontology (Gould, 1970); astrobiology (McLoughlin et al, 2007); biomolecular deterioration and survival of organic matter (Collins et al, 2002); geomycology (Gadd, 2007); paleoclimatology (Schöne and Giere, 2005); seawater chemistry (Porter, 2007); material chemistry (Dujardin and Mann, 2002); geomedicine (Sahai, 2005); paleobathymetry (Wisshak and Rüggeberg, 2006); exobiology (Onofri et al, 2004); osteoarchaeology (Davis, 1997); archaeology and bioarcheology (Larsen, 2002); histology and histotechnology (Callis and Sterchi, 1998); forensic dentistry and forensic science (Rogers, 1988); demineralized bone allografts (Herold et al, 2002); dental anthropology (Alt et al, 1998); mineral dissolution (Nancollas, 1982;Wang et al, 2005bWang et al, , 2006a; bio-and chemical weathering (Benzerara et al, 2005); medical geology (Skinner and Berger, 2003); calcibiocavitology and endolithic microborings (Carriker and Smith, 1969); bioerosion (Lazar and Loya, 1991;Garcia-Pichel, 2006); remineralization of biomaterials ; shell repair and regeneration (Meenakshi et al, 1974;Palmer, 1983); sclerochronological studies ; bioremediation (Singh and Ward, 2004); bone diseases, osteoporosis, osteopenia, osteoclasia (Skinner, 2000); biodeterioration (Morton, 1987); taphonomy (Child, 1995); archeological bone chemistry (Pate, 1994); paleohistory, paleoecology, paleontology (Pate, 1994;…”

Small molecule‐mediated control of hydroxyapatite growth: Free energy calculations benchmarked to density functional theory

“…It is believed that nucleation and/or growth of bone crystals is regulated by acidic functional macromolecules, such as bone sialoprotein (BSP) and osteopontin (OPN), as well as small acidic molecules, such as citric acid . However, the detailed role of these molecules in bone formation is not known at the molecular level, despite many experimental studies and a few computational studies using ab initio cluster calculations or molecular dynamics (MD) simulations . The development of treatments for bone diseases and disorders as well as biomimetic synthesis of bone fillers and mineral components for composite scaffolds in tissue engineering requires a knowledge of how the crystal is templated by the organic molecules.…”

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“…These results www.scienceasia.org contradict those reported previously, indicating that the formation of bone apatite on fully sintered HA and TCP ceramics has been hardly detectable 31,32 . Indeed, the nature and crystallinity of apatite forming phases depend on various parameters, including concentrations of phosphate/carbonate sources, ionic strength and pH of the soaked solution, and the kinetics of the nucleation and growth processes 33 . Because the porosity of the scaffolds was not compromised by the formed apatite layers and the initial porous morphology was maintained, the composites produced in this study are potential candidates to be used as new biomaterials for hard tissue repair.…”