Optical and biological properties of transparent nanocrystalline hydroxyapatite obtained through spark plasma sintering.
Transparent bioceramics have attracted a large amount of research interest as they facilitate direct observation of biointerfacial reactions. Thus far, attempts to achieve transparent hydroxyapatite have been focused on augmenting the sintering pressure and/or extending the sintering duration. This study aims at fabricating transparent HA using a direct and fast spark plasma sintering process with appropriate starting powder and moderate sintering pressure. Three types of raw powder, namely micro-spheres, nano-rods and nano-spheres, were sintered to investigate the optical and biological properties of the compacted pellets. It was found that in terms of transparency, the micro-sphere pellet sintered at 1000°C stood out with an in-line transmittance as high as 84% achieved at 1300nm for a 2mm thick sample. In addition, pellets fabricated from micro-spheres demonstrated the highest cell viability in in vitro biological tests with L929 cells. Living cells cultured on a transparent micro-sphere pellet could be directly and clearly observed by light microscopy. It is thus concluded that the micro-sphere powder is the most desirable raw material to manufacture transparent hydroxyapatite because it could enable dense pellets with notably high transparency and outstanding in vitro biocompatibility to be readily obtained.
School of Mechanical & Aerospace Engineering, Nanyang Technological University, 50 Nanyang Avenue, 639798, Singapore.
Zhong
Z
Li
School of Mechanical & Aerospace Engineering, Nanyang Technological University, 50 Nanyang Avenue, 639798, Singapore.
Brianna C
BC
Thompson
School of Materials Science & Engineering, Nanyang Technological University, 50 Nanyang Avenue, 639798, Singapore.
Zhili
Z
Dong
School of Mechanical & Aerospace Engineering, Nanyang Technological University, 50 Nanyang Avenue, 639798, Singapore. Electronic address: mkakhor@ntu.edu.sg.
Khiam Aik
KA
Khor
D000818:Animals; D002452:Cell Count; D002454:Cell Differentiation / Q000187:drug effects; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D017886:Durapatite / Q000737:chemistry / Q000494:pharmacology*; D006801:Humans; D008422:Materials Testing / Q000379:methods*; D051379:Mice; D053758:Nanoparticles / Q000737:chemistry* / Q000648:ultrastructure; D061848:Optical Imaging; D055620:Optical Phenomena; D056951:Photoelectron Spectroscopy; D012542:Scattering, Radiation; D013696:Temperature; D014961:X-Ray Diffraction
D017886:Durapatite
Bioceramic; Biocompatibility; Cell observation; Hydroxyapatite; Spark plasma sintering; Transparency