title: Synthesis of positively charged calcium hydroxyapatite nano-crystals and their adsorption behavior of proteins.
abstract: Positively charged Hap nano-crystals were prepared by using beta-alanine and clarified the adsorption affinity of these surface amide functionalized Hap nano-crystals to proteins. Colloidal surface amide functionalized Hap nano-crystals were prepared by wet method in the presence of various amounts of beta-alanine by changing molar ratio of beta-alanine/Ca (beta/Ca ratio) in the solution. The rod-like nano-crystals were lengthened with addition of beta-alanine though their width did not vary; carboxyl groups of beta-alanine are strongly coordinated to Ca2+ ions exposed on ac and/or bc faces to inhibit particle growth to a- and/or b-axis directions and enhance the particle growth along to the c-axis. No difference can be recognized on the crystal structure among the synthesized Hap nano-crystals by XRD measurements. However, the large difference was recognized by TG-DTA and FTIR measurements. Those measurements revealed that beta-alanine is incorporated on the Hap nano-crystal surface up to the beta/Ca ratio of 1.0, though they are absent in the nano-crystals synthesized at beta/Ca ratio > or = 2.0. The zeta potential (zp) of beta-alanine-Hap nano-crystals prepared at beta/Ca = 0.4 and 1.0 of those incorporating beta-alanine exhibited positive charge at pH < or = 5.9. The saturated amounts of adsorbed BSA for the positively charged beta-alanine-Hap nano-crystals were increased 2.3-2.4-fold by their electrostatic attraction force between positively charged beta-alanine-Hap nano-crystals and negatively charged BSA molecules. We were able to control the adsorption affinity of Hap nano-crystal by changing their surface charge.
authors.affiliation: School of Chemistry, Osaka University of Education, Asahigaoka 4-698-1, Kashiwara-shi, Osaka 582-8582, Japan. kandori@cc.osaka-kyoiku.ac.jp
authors.forename: Kazuhiko
authors.initials: K
authors.lastname: Kandori
authors.forename: Shohei
authors.initials: S
authors.lastname: Oda
authors.forename: Masao
authors.initials: M
authors.lastname: Fukusumi
authors.forename: Yoshiaki
authors.initials: Y
authors.lastname: Morisada
mesh_terms: D000327:Adsorption; D000818:Animals; D001672:Biocompatible Materials / Q000737:chemistry; D002118:Calcium / Q000737:chemistry; D002417:Cattle; D003102:Colloids / Q000737:chemistry; D003460:Crystallization; D017886:Durapatite / Q000737:chemistry*; D046529:Microscopy, Electron, Transmission; D008956:Models, Chemical; D015394:Molecular Structure; D053758:Nanoparticles / Q000737:chemistry* / Q000648:ultrastructure; D010316:Particle Size; D011506:Proteins / Q000737:chemistry*; D012710:Serum Albumin, Bovine / Q000737:chemistry; D017550:Spectroscopy, Fourier Transform Infrared; D014961:X-Ray Diffraction; D015091:beta-Alanine / Q000737:chemistry
chemical_list: D001672:Biocompatible Materials; D003102:Colloids; D011506:Proteins; D015091:beta-Alanine; D012710:Serum Albumin, Bovine; D017886:Durapatite; D002118:Calcium