title: Assembly of amorphous clusters under floating monolayers: a comparison of in situ and ex situ techniques.
abstract: We report synchrotron X-ray scattering studies of biomimetic crystallization of hydroxyapatite (the primary constituent of bone), using monolayers of fatty acid molecules floating on simulated body fluid (SBF) as well as aqueous solutions of calcium phosphate. A ∼10 Å thick film of amorphous material is observed to form immediately at the molecular monolayer, consistent with the proposed formation of "Posner clusters". This layer becomes denser but not significantly thicker as the subphase concentration and the temperature approach physiological conditions. The amorphous films do not crystallize within 24 h, in contrast to prior reports of more rapid crystallization using electron microscopy on ex situ samples. However, crystallization occurs almost immediately after our films are transferred onto solid substrates. These results illustrate the importance of in situ measurements for model biomineralization experiments.
authors.affiliation: Department of Physics and Astronomy, Northwestern University , Evanston, Illinois 60208, United States.
authors.forename: Ahmet
authors.initials: A
authors.lastname: Uysal
authors.forename: Benjamin
authors.initials: B
authors.lastname: Stripe
authors.forename: Binhua
authors.initials: B
authors.lastname: Lin
authors.forename: Mati
authors.initials: M
authors.lastname: Meron
authors.forename: Pulak
authors.initials: P
authors.lastname: Dutta
mesh_terms: D002130:Calcium Phosphates / Q000737:chemistry; D003460:Crystallization; D017886:Durapatite / Q000737:chemistry*; D005227:Fatty Acids / Q000737:chemistry*; D008854:Microscopy, Electron; D010316:Particle Size; D013499:Surface Properties; D017356:Synchrotrons; D013696:Temperature; D014961:X-Ray Diffraction
chemical_list: D002130:Calcium Phosphates; D005227:Fatty Acids; D017886:Durapatite; C020243:calcium phosphate