title: Atomic force microscopy reveals hydroxyapatite-citrate interfacial structure at the atomic level.
abstract: An approach to organic-inorganic interfacial structure at the atomic level is a great challenge in the studies of biomineralization. We demonstrate that atomic force microscopy (AFM) is powerful tool to discover the biomineral interface in detail. By using a model system of (100) hydroxyapatite (HAP) face and citrate, it reveals experimentally that only a side carboxylate and a surface calcium ion are involved in the binding effect during the citrate adsorption, which is against the previous understandings by using Langmuir adsorption and computer simulation. Furthermore, the adsorbed citrate molecules can use their free carboxylate and hydroxyl groups to be self-assembled on the HAP surface. AFM examination also finds that the presence of citrate molecules on the HAP crystal faces can enhance the adhesion force of the HAP surface. We suggest that the established AFM method can be used for a precise and direct understanding of biointerfaces at the atomic level.
authors.affiliation: Center for Biomaterials and Biopathways and Department of Chemistry, Zhejiang University, Hangzhou, Zhejiang 310027, China.
authors.forename: Wenge
authors.initials: W
authors.lastname: Jiang
authors.forename: Haihua
authors.initials: H
authors.lastname: Pan
authors.forename: Yurong
authors.initials: Y
authors.lastname: Cai
authors.forename: Jinhui
authors.initials: J
authors.lastname: Tao
authors.forename: Peng
authors.initials: P
authors.lastname: Liu
authors.forename: Xurong
authors.initials: X
authors.lastname: Xu
authors.forename: Ruikang
authors.initials: R
authors.lastname: Tang
mesh_terms: D019343:Citric Acid / Q000737:chemistry*; D017886:Durapatite / Q000737:chemistry*; D018625:Microscopy, Atomic Force / Q000379:methods*; D015394:Molecular Structure; D017550:Spectroscopy, Fourier Transform Infrared
chemical_list: D019343:Citric Acid; D017886:Durapatite