title: Biomimetic calcium phosphate coatings on Polyactive 1000/70/30.
abstract: Precalcification of Polyactive 1000/70/30 with a biomimetic calcium phosphate coating is expected to enhance the bioactivity of this biodegradable polymer for the application as bone filler or scaffold of bone tissue engineering. This study presents a 1-day one-step incubation method to obtain either amorphous or bone-like apatitic calcium phosphate coating on Polyactive 1000/70/30. Either dense plates or three-dimensional porous blocks of the polymer were incubated in a simplified but concentrated simulated body fluid-derived solution at 37 degrees C. By bubbling CO2 gas, a solution was prepared with calcium and phosphate ion concentrations five times of that of regular simulated body fluid. With controlled stirring, the CO2 was released out of the solution and exchanged by air. The pH of the solution increased to induce coating formation. Adjusting stirring rate and CO2/air exchange rate controlled the process kinetics. The reaction kinetics had little influence on the crystallographic structure of the final coating mineral for a given solution composition as shown by Fourier transform infrared spectroscopy and X-ray diffraction. However, the interface structure between the coating and substrate was kinetics-dependent. A fast precipitation condition resulted in a uniform but superficial calcification pattern at the surface of polymer. A slow process by selecting either a slow stirring or a slow CO2/air exchange, on the contrary, induced a localized but deep inside calcification pattern. A tensile test showed no statistically significant difference in the mechanical properties among uncoated and coated polymers. The cracking behavior of coatings from different kinetics, however, exhibited different manners, as can be attributed to different interface structures and interfacial strengths.
authors.affiliation: IsoTis N V, Professor Bronkhorstlaan 10, 3723 MB Bilthoven, The Netherlands. chang.du@isotis.com
authors.forename: C
authors.initials: C
authors.lastname: Du
authors.forename: P
authors.initials: P
authors.lastname: Klasens
authors.forename: R E
authors.initials: RE
authors.lastname: Haan
authors.forename: J
authors.initials: J
authors.lastname: Bezemer
authors.forename: F Z
authors.initials: FZ
authors.lastname: Cui
authors.forename: K
authors.initials: K
authors.lastname: de Groot
authors.forename: P
authors.initials: P
authors.lastname: Layrolle
mesh_terms: D018786:Bone Substitutes / Q000138:chemical synthesis* / Q000592:standards; D002130:Calcium Phosphates / Q000737:chemistry*; D020099:Coated Materials, Biocompatible / Q000138:chemical synthesis* / Q000592:standards; D003460:Crystallization; D006801:Humans; D019563:Mechanics; D011091:Polyesters / Q000138:chemical synthesis*; D011092:Polyethylene Glycols / Q000138:chemical synthesis*; D017550:Spectroscopy, Fourier Transform Infrared; D013499:Surface Properties; D013718:Tensile Strength; D014961:X-Ray Diffraction
chemical_list: D018786:Bone Substitutes; D002130:Calcium Phosphates; D020099:Coated Materials, Biocompatible; D011091:Polyesters; C485828:alpha-tricalcium phosphate; C072932:polyethylene oxide-polybutylene terephthalate copolymer; C485830:tetracalcium phosphate; D011092:Polyethylene Glycols; C485838:calcium phosphate, monobasic, anhydrous; C020243:calcium phosphate; C485829:calcium phosphate, dibasic, anhydrous