Crystallization of hydroxyapatite on polymers

Abstract

Four copolymers were prepared through the reaction of NN-bis[ (diethoxyphosphinyl)methyl]-1,4benzenediamine with 1,4-or 1,3-benzenediamine and terephthaloyl or isophthaloyl or sebacoyl dichloride at varying molar ratios. A fifth copolymer was prepared by copolymerization of bis(3-aminopheny1)phoephinic acid and 1,3-benzenediamine with ieophthaloyl dichloride in dimethylamine. All five copolymers contained phosphinyl groups and upon introduction in calcium phosphate aqueous solutions, supersaturated only with respect to 8-tricalcium phosphate and hydroxyapatite, three of them induced the precipitation of stoichiometric hydroxyapatite, (Caa(PO&OH, HAP). The investigation of the crystal growth process was done at constant supersaturation, which enabled us to measure even very low rates of crystallization. The apparent growthorder was found to be 1.25 f 0.18, avalue found for the crystallization of HAP on various substrates. The surface energy estimate of 92 mJ m-? from the kinetic data was of the same order of magnitude for the overgrowth of HAP on both inorganic and polymeric substrates. The rates of precipitation showed a linear dependence on the phosphate content of each copolymer, while their structure played b o a decisive role. Thus, "open" structured copolymers yielded high rates of precipitation while copolymers in which the phosphorus-containing groups were "buried", not being accessible to the Ca2+ ions in solution, failed to induce hydroxyapatite formation. It is suggested that the phosphoruscontaining groups act as the active centers for nucleation of the inorganic phase. (34) Glimcher, M. J. In The Chemistry and Biology of Mineralized Cinnetuue Tissues; Vein, A,, Ed.; Ehvier: Amstardam, 1981; pp 617-675. (35) Glimcher, M.

The nucleation and growth of calcium phosphate by amelogenin

“…Although gel systems are interesting models for studying nucleation, solution systems can have some advantages. Solutions systems can be used for in situ, real-time nucleation kinetic studies using the constant composition [32][33][34] and QCM approaches [22], there are fewer diffusional effects, the starting solution supersaturations are known, and it is possible to unambiguously determine nanosphere structures within solutions.…”

Surface functional group dependence on apatite formation on self-assembled monolayers in a simulated body fluid

“…Extensive studies on the mechanisms of biomineraliBiomineralization such as apatite formation occurs zation 6,7 and related processes in the calcification of in normal hard tissue such as bone and dentine, in soft tissue have been conducted over the last 10 years. 8 diseased or atherosclerosed vessel walls, 1 and at bloodApatite formation is a complex process that involves contacting surfaces of long-term implanted cardiovasthe controlled nucleation and growth of it from aquecular devices such as artificial valves, artificial grafts, ous solution.…”

Growth of calcium phosphate on surface-modified cotton

“…Research into the stimulation of calcium hydroxyapatite growth on various substrates has employed a number of techniques including special procedures for raising the ionic activity product of calcium hydroxyapatite in the solution containing the substrate to be coated so stimulating precipitation and the creation of apatite nucleation sites [2], and surface modification (e.g. phosphorylation) giving surface sites which have a crystallographic arrangement similar to that of hydroxyapatite so allowing possible epitaxial growth [3]. In this laboratory, a study of the deposition of calcium phosphate compounds on cationic and anionic (DOWEX and AM-BERLITE) ion-exchange resins pre-saturated with Ca 2÷ or HPO]-ions respectively was recently reported [4].…”