How useful is SBF in predicting in vivo bone bioactivity

We have used the pH-induced self-assembly of a peptide-amphiphile to make a nanostructured fibrous scaffold reminiscent of extracellular matrix. The design of this peptide-amphiphile allows the nanofibers to be reversibly cross-linked to enhance or decrease their structural integrity. After cross-linking, the fibers are able to direct mineralization of hydroxyapatite to form a composite material in which the crystallographic c axes of hydroxyapatite are aligned with the long axes of the fibers. This alignment is the same as that observed between collagen fibrils and hydroxyapatite crystals in bone.

http://science.sciencemag.org/content/sci/294/5547/1684.full.pdf

Self-assembly and mineralization of peptide-amphiphile nanofibers

A review of the biological response to ionic dissolution products from bioactive glasses and glass-ceramics

Novel bioactive materials with different mechanical properties.

Surface modification of inorganic nanoparticles for development of organic–inorganic nanocomposites—A review

Bioactive titanium metal, which forms a bonelike apatite layer on its surface in the body and bonds to the bone through the apatite layer, can be prepared by NaOH and heat treatments to form an amorphous sodium titanate layer on the metal. In the present study, the mechanism of apatite formation on the bioactive titanium metal has been investigated in vitro. The metal surface was examined using transmission electron microscopy and energy dispersive X-ray spectrometry as a function of the soaking time in a simulated body fluid (SBF) and complemented with atomic emission spectroscopy analysis of the fluid. It was found that, immediately after immersion in the SBF, the metal exchanged Na(+) ions from the surface sodium titanate with H(3)O(+) ions in the fluid to form Ti-OH groups on its surface. The Ti-OH groups, immediately after they were formed, incorporated the calcium ions in the fluid to form an amorphous calcium titanate. After a long soaking time, the amorphous calcium titanate incorporated the phosphate ions in the fluid to form an amorphous calcium phosphate with a low Ca/P atomic ratio of 1.40. The amorphous calcium phosphate thereafter converted into bonelike crystalline apatite with a Ca/P ratio of 1.65, which is equal to the value of bone mineral. The initial formation of the amorphous calcium titanate is proposed to be a consequence of the electrostatic interaction of negatively charged units of titania, which are dissociated from the Ti-OH groups, with the positively charged calcium ions in the fluid. The amorphous calcium titanate is speculated to gain a positive charge and to interact with the negatively charged phosphate ions in the fluid to form the amorphous calcium phosphate, which eventually stabilizes into bonelike crystalline apatite.

TEM-EDX study of mechanism of bonelike apatite formation on bioactive titanium metal in simulated body fluid.

Bioactive titanium metal, prepared by treatment with NaOH followed by an annealing stage to form a sodium titanate layer with a graded structure on its surface, forms a biologically active bone-like apatite layer on its surface in the body, and bonds to bone through this apatite layer. In this study, process of apatite formation on the bioactive titanium metal in a simulated body fluid was investigated using X-ray photoelectron spectroscopy. The bioactive titanium metal formed Ti-OH groups soon after soaking in the simulated body fluid, via the exchange of the Na(+) ions in the sodium titanate on its surface with H(3)O(+) ions in the fluid. The Ti-OH groups on the metal combined with the calcium ions in the fluid immediately to form a calcium titanate. After a long period, the calcium titanate on the metal took the phosphate ions as well as the calcium ions in the fluid to form the apatite nuclei. The apatite nuclei then proceeded to grow by consuming the calcium and phosphate ions in the fluid. These results indicate that the Ti-OH groups formed on the metal induce the apatite nucleation indirectly, by forming a calcium titanate. The initial formation mechanism of the calcium titanate may be attributable to the electrostatic interaction of the negatively charged Ti-OH groups with the positively charged calcium ions.

An X-ray photoelectron spectroscopy study of the process of apatite formation on bioactive titanium metal.

The mechanism of biomineralization of apatite on a Na2O−SiO2 glass was investigated in vitro, in which the glass surface was surveyed by transmission electron microscopy and energy-dispersive X-ray spectrometry as a function of soaking time in simulated body fluid (SBF), complemented with Fourier transform infrared reflection spectroscopy of the glass surface and atomic emission spectroscopy of the fluid. The glass was found to exchange Na+ ions with H3O+ ions in the SBF to form silanol (Si−OH) groups on its surface at an early stage of soaking. Immediately after they were formed, the Si−OH groups incorporated calcium ions in the fluid to form an amorphous calcium silicate. After a long soaking time, the calcium silicate incorporated phosphate ions and further calcium ions in the fluid to form an amorphous calcium phosphate with a low Ca/P atomic ratio of 1.43. The amorphous calcium phosphate was eventually converted into crystalline apatite, which contained small amounts of Na, Mg, and Cl and had a Ca/P ...

Mechanism of biomineralization of apatite on a sodium silicate glass: TEM-EDX study in vitro

http://iopscience.iop.org/article/10.1016/S1468-6996(01)00007-9/pdf

Hiroaki Takadama

Papers

How useful is SBF in predicting in vivo bone bioactivity

TEM-EDX study of mechanism of bonelike apatite formation on bioactive titanium metal in simulated body fluid.

An X-ray photoelectron spectroscopy study of the process of apatite formation on bioactive titanium metal.

Mechanism of biomineralization of apatite on a sodium silicate glass: TEM-EDX study in vitro

XPS study of the process of apatite formation on bioactive Ti—6Al—4V alloy in simulated body fluid