title: Long-term conversion of 45S5 bioactive glass-ceramic microspheres in aqueous phosphate solution.
abstract: The conversion of 45S5 glass and glass-ceramics to a hydroxyapatite (HA)-like material in vitro has been studied extensively, but only for short reaction times (typically <3 months). In this paper, we report for the first time on the long-term conversion of 45S5 glass-ceramic microspheres (designated 45S5c) in an aqueous phosphate solution. Microspheres of 45S5c (75-150 μm) were immersed for 10 years at room temperature (~25 °C) in K(2)HPO(4) solution with a concentration of 0.01 M or 1.0 M, and with a starting pH of 7.0 or 9.5. The reacted 45S5c microspheres and solutions were analyzed using structural and analytical techniques. Only 25-45 vol% of the 45S5c microspheres were converted to an HA-like material after the 10 year reaction. In solutions with a starting pH of 9.5, an increase in the K(2)HPO(4) concentration from 0.01 to 1.0 M resulted in a doubling of the volume of the microspheres converted to an HA-like material but had little effect on the composition of the HA-like product. In comparison, reaction of the 45S5c microspheres in the solution with a starting pH of 7.0 resulted in an HA-like product in the 0.01 M K(2)HPO(4) solution but a calcium pyrophosphate product, Ca(10)K(4)(P(2)O(7))(6).9H(2)O, in the 1.0 M solution. The consequences of these results for the long-term use of 45S5 glass-ceramics in biomedical applications are discussed.
authors.affiliation: Department of Materials Science and Engineering, Center for Bone and Tissue Repair and Regeneration, Missouri University of Science and Technology, Rolla, MO 65409, USA.
authors.forename: Hailuo
authors.initials: H
authors.lastname: Fu
authors.forename: Mohamed N
authors.initials: MN
authors.lastname: Rahaman
authors.forename: Delbert E
authors.initials: DE
authors.lastname: Day
authors.forename: Wenhai
authors.initials: W
authors.lastname: Huang
mesh_terms: D002516:Ceramics / Q000737:chemistry*; D004058:Diffusion; D004355:Drug Stability; D005898:Glass / Q000737:chemistry*; D008832:Microchemistry; D008855:Microscopy, Electron, Scanning; D008863:Microspheres; D009994:Osmolar Concentration; D044367:Phase Transition; D010710:Phosphates / Q000737:chemistry / Q000494:pharmacology*; D017680:Potassium Compounds / Q000737:chemistry / Q000494:pharmacology; D012996:Solutions / Q000737:chemistry / Q000494:pharmacology; D017550:Spectroscopy, Fourier Transform Infrared; D013997:Time Factors; D014867:Water / Q000737:chemistry / Q000494:pharmacology*; D014961:X-Ray Diffraction
chemical_list: D010710:Phosphates; D017680:Potassium Compounds; D012996:Solutions; C425330:bioactive glass 45S5; D014867:Water; C023506:Glass ceramics; C013216:potassium phosphate