PubMed · 5223203
The source did not provide an abstract. Follow the original record for more information.
Explore connections, maps & timelines
J G Helmcke, G Neubauer, R Rau. 1966-09-01. [Enamel structure and caries process].. https://pubmed.ncbi.nlm.nih.gov/5223203/
Cite the original work for its findings. Save a collection to share your selection of sources.
KEEP EXPLORING
Two kinds of methods combining a biomimetic process and transcription of resist pattern were conducted to form an apatite micropattern. For method 1, apatite nuclei were formed on a resist pattern printed substrate by setting it in contact with CaO-SiO(2)-based glass in a simulated body fluid (SBF) with inorganic ion concentrations nearly equal to those of human blood plasma. Next, apatite was grown from the nuclei by soaking the substrate in an aqueous solution with ion concentrations 1.5 times those of SBF (1.5 SBF). Then, the resist material was dissolved off by organic solvent with the apatite just formed on it. Apatite micropattern transcribing the resist pattern was obtained. For method 2, apatite nuclei were formed on a resist pattern printed substrate by setting it in contact with CaO-SiO(2)-based glass in SBF. Next, the resist material was dissolved off with the apatite nuclei just formed on it. Then, the substrate was soaked in 1.5 SBF to grow the remaining nuclei and an apatite micropattern transcribing the resist pattern was obtained. For both methods, minute apatite patterns with various shapes as straight lines, bending lines, and blocks were clearly formed. The minimum line width of the obtained pattern was 2 microm. These methods are promising for producing multifunctional materials with bioaffinity.
Three gel glasses containing 25 mol % of CaO and SiO(2) + P(2)O(5) contents (in mol %): 75 + 0 (S75); 72.5 + 2.5 (S72.5P2.5); and 70 + 5 (S70P5), respectively, were obtained, characterized, and studied when soaked in a simulated body fluid (SBF). The influence of composition in both textural properties (surface area and porosity) and in vitro behavior of glasses was studied. In as prepared S72.5P2.5 and S70P5 glasses, crystalline phosphate nuclei were detected through XRD and FTIR. In addition, N(2) adsorption and Hg porosimetry measurements showed that the surface area increased, whereas the pore volume and the pore diameter decreased as P(2)O(5) in glasses increased. These variations were explained on the basis of the withdrawal of calcium from the glass silica network, due to the calcium-phosphorous bonding. In vitro studies showed that the three compositions were bioactive, because an apatite layer was formed after soaking in SBF. S75 presented the highest initial reactivity but the lowest crystallization rate of the apatite-like phase. For S72.5P2.5, and S70P5 the amorphous calcium phosphate formation was slower than for S75, but the crystallization of apatite was observed after shorter periods in SBF. Furthermore, after 7 days of soaking, the layer thickness decreased as P(2)O(5) in glasses increased.
X-ray absorption spectroscopy was used to determine the local structure of U(VI) within synthetic fluorapatite at a concentration of 2.3 wt %. Extended X-ray absorption fine structure indicates that U(VI) substitutes into the Ca1 site. To accommodate this substitution the apatite structure significantly distorts such that the Ca1 site approximates octahedral coordination, with six uniform U-0 distances of 2.06A. An X-ray adsorption edge structure, with two inflection points, and optical emission spectra are consistent with 6d orbital crystal field splitting. These results indicate that significant amounts of U(VI) can be accommodated in the apatite structure but with an unexpected coordination, which may bear on the ultimate development of apatite-hosted nuclear-waste forms.