Junko Nakao

Apatite deposition on polyamide films containing carboxyl group in a biomimetic solution

The development of organic–inorganic hybrids composed of hydroxyapatite and organic polymers is attractive because of their novelty in being materials that show a bone-bonding ability, i.e. bioactivity, and because they have mechanical properties similar to those of natural bone. The biomimetic process has received much attention for fabricating such a hybrid, where bone-like apatite is deposited under ambient conditions on polymer substrates in a simulated body fluid (SBF) having ion concentrations nearly equal to those of human extracellular fluid or related solutions. It has been shown that the carboxyl group is effective for inducing heterogeneous nucleation of apatite in the body. In the present study, apatite deposition on polyamide films containing various numbers of carboxyl groups was investigated in 1.5 SBF, which had ion concentrations 1.5 times those of a normal SBF. The effect of incorporation of calcium chloride on the formation of apatite was examined. Polyamide films containing ≤33 mol % CaCl2 did not form apatite, even after soaking in 1.5 SBF for 7 days, and even when the polymer film contained 50 mol % carboxyl group. On the other hand, those modified with ≥40 mass % CaCl2 formed apatite on their surfaces in 1.5 SBF. The ability of the modified film to form an apatite layer increased, and the adhesion of the apatite layer bonded to the film improved, with increasing carboxyl group content. It is concluded that novel apatite–polyamide hybrids can be prepared by a biomimetic process.

Preparation and Properties of Sulfonated or Phosphonated Polybenzimidazoles and Polybenzoxazoles

Five series of copolybenzazoles, polybenzimidazoles and polybenzoxazoles, containing sulfonic acid or phosphonic acid were prepared and their basic properties were compared, although the backbone structures were not exactly corresponding each other. The sulfonic acid-containing polybenzimidazoles showed higher thermal stability and hydrolysis resistance than the sulfonic acid-containing polybenzoxazoles. However, Proton conductivity of the sulfonic acid-containing polybenzoxazoles was superior to that of the sulfonic acid-containing polybenzimidazoles. The phosphonic acid-containing polybenzimidazoles showed similar or higher thermal stability and lower proton conductivity than the sulfonic acid-containing correspondents. The characteristics of the polybenzimidazole systems seem to be explained by the salt formation between ionic functional groups and imidazole rings.

Apatite Formation on Polyamide Films Containing Sulfonic Groups by a Biomimetic Process

Fabrication of apatite-polymer hybrids have been attractive o produce novel bone-repairing materials with both bone-bonding ability, i.e. bioactivity , and mechanical properties analogous to natural bone, since natural bone is a kind of organic-inorganic hybrid, composed of collagen fiber and apatite crystals. We previously reported that apa ti e w s deposited on polyamide films containing carboxyl groups in a solution mimicking body fluid, when they were incorporated with calcium salts. To find alternative functional group effective on the apatite formation, in the present study we examined apatite-forming ability on polyamide fil ms containing sulfonic groups in the same solution. It was found that the polyamide film containing sulf onic groups could deposit apatite on the surfaces in the solution when the film was incorpora ted with calcium salts. These results show that sulfonic group also acts as a functional group effe ctive for apatite deposition in body environment as carboxyl group. Introduction Natural bone is a kind of organic-inorganic hybrid composed of collagen f ib r and apatite crystals [1]. Hydroxyapatite fabricated under a mimicking condition of body e nvironment shows high biological affinity to bony tissues. Apatite-polymer hybrids, ther efo e, have been attractive as novel bone-repairing materials with both bone-bonding ability, i.e. bioactivity , and mechanical properties analogous to natural bone. In order to fabricate such a hybrid, Kokubo a nd his colleagues reported a biomimetic process in which hydroxyapatite layer can be coated on organic polymers in solutions mimicking extracellular fluid [2]. In this process, organic substr ate is first placed in the neighborhood of bioactive glass powder in simulated body fluid (SBF) wit h ion concentration nearly equals to those of human extracellular fluid. Apatite depositi on is significantly related to the dissolved silicate and calcium ion (Ca ) from bioactive glass. The dissolved silicate ions provide a heterogeneous nucleation site on the surface of the substrate, whil dissolved Ca 2+ increase degree of supersaturation of fluid in terms of the apatite. Once apatit e nuclei are formed, they can grow spontaneously by consuming Ca 2+ nd phosphate ions from the surrounding fluid. The biomimetic process has been paid much attention on apatite-organic hybrid, because it does not require heat treatment at high temperature and produces the apatite with struc ture and composition similar to Key Engineering Materials Online: 2003-05-15 ISSN: 1662-9795, Vols. 240-242, pp 59-62 doi:10.4028/www.scientific.net/KEM.240-242.59