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.
School of Engineering, Metallurgy and Materials, University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK.
Hilda
H
Medina Ledo
Ania C
AC
Thackray
Ian P
IP
Jones
Peter M
PM
Marquis
Lynne E
LE
Macaskie
Rachel L
RL
Sammons
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