Microstructure and composition of biosynthetically synthesised hydroxyapatite.
Biosynthetic hydroxyapatite (HA) manufactured utilising the bacterium Serratia sp. NCIMB40259 was characterised using X-ray diffraction (XRD), Fourier transform infra-red spectroscopy (FTIR), energy dispersive X-ray analysis (EDX) scanning electron microscopy (SEM), transmission electron microscopy (TEM) and electron diffraction (ED). SEM/EDX showed that the non-sintered material consisted mainly of calcium-deficient HA (CDHA) with a Ca/P ratio of 1.61 +/- 0.06 and crystal size (from TEM) of 50 +/- 10 nm. ED analysis of non-sintered powder showed resolvable ring patterns ascribed to (0002), (1122) and (0006) planes of crystalline HA. The crystallinity of the samples improved with heat treatment from approximately 9.4% (non-sintered) to 53% (1,200 degrees C). Samples heated at 600 degrees C and sintered at 1,200 degrees C were identified by XRD and FTIR as mainly CDHA with some sodium calcium phosphate in the sintered samples. Ca/P ratios (SEM/EDX) were 1.62 and 1.52, respectively. Single crystal spot patterns characteristic of HA were seen with commercial HA and Serratia HA heated at 600 degrees C. After sintering at 1,200 degrees C the material consisted of needle-like crystals with a length between 86 and 323 nm (from TEM) or 54-111 nm (from XRD) and lattice parameters of a = 9.441 A and c = 6.875 A. This study indicated that the material produced by Serratia bacteria was initially mainly nanophase calcium deficient hydroxyapatite, which sintered to a more highly crystalline form. With further refinements the method could be used as an inexpensive route for hydroxyapatite production for biomaterials applications.
Medina Ledo
Hilda
H
School of Engineering, Metallurgy and Materials, University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK.
Thackray
Ania C
AC
Jones
Ian P
IP
Marquis
Peter M
PM
Macaskie
Lynne E
LE
Sammons
Rachel L
RL
D002118:Calcium / Q000032:analysis / Q000737:chemistry; D002130:Calcium Phosphates / Q000737:chemistry; D017886:Durapatite / Q000737:chemistry*; D006358:Hot Temperature; D046529:Microscopy, Electron, Transmission; D036103:Nanotechnology; D012705:Serratia / Q000378:metabolism; D017550:Spectroscopy, Fourier Transform Infrared; D014961:X-Ray Diffraction
D002130:Calcium Phosphates; D017886:Durapatite; C020243:calcium phosphate; D002118:Calcium