【文章內(nèi)容簡介】 The minerals produced in the gel system wereDCPD under the noncontrolled pH conditions, theDCPD and OCP mixture at pH , and the OCP andHAp mixture at pH [Fig. 2(A)]. The XRD profilerevealed that the crystallinity of the mineral generatedin the gel diffusion system was higher than that ofmineral generated in the solution system.To understand the effect of the fluoride ions presenton the mineral produced in the gel systems, 200 ppmHF was added to the phosphate solution at varyingpH conditions, and the minerals generated in the fibringel were investigated using XRD analysis. The resultsindicated that the minerals generated in the fibrin gelat each pH condition were HAp/fluorapatite (FAp).Further, the crystallinity was not significantly differentin each sample [Fig. 2(B)]. We selected pH as thecondition for mineralization in further studies, becausethe condition mimicked the biological environment.To obtain varying degrees of the crystallinity andthe solubility for the mineral ponent in the gel,we added different concentration of fluoride ions (2–2020 ppm) to the gel mineralization system. XRDanalysis indicated that in the absence of the fluorideions, the produced mineral was the DCPD and OCPmixture。 in the presence of up to 20 ppm fluorideions, it was the OCP and HAp mixture。 and in thepresence of up to 500 ppm fluoride, it was the typical HAp/FAp mixture. Finally, the XRD patternsindicated that in the presence of more than 500 ppmof fluoride ions, the produced mineral was theHAp/FAp posite and calcium fluoride (CaF2)mixture [Fig. 3(A)]. To estimate the effect of fluorideions on mineral crystallinity, the index of crystallinity was determined as the inverse of the halfvaluebreadths at the (002) peak. Crystallinity increasedconsiderably till the fluoride concentration of 100ppm, and then for fluoride concentrations above 100ppm, it saturated (Fig. 4). The (300) reflection peakposition shifted to higher angle from 0 to 500 ppmfluoride concentration, indicating that the FAp content in the minerals had increased with the increaseof fluoride ion concentration [Fig. 3(B)].TABLE IThe pH Value in the Fibrin Gel 24 hAfter MineralizationCondition pH ValueFibrin gel before mineralization 6 pH noncontrolled 6 pH 6 pH 6 Figure 2. (A) Xray diffraction patterns of the mineralproduced by the gel diffusion and the solution systems atvarious pH conditions。 (a–c) Mineralization in the solutionsystem: (a) noncontrolled pH, (b) pH , (c) pH 。 (d–f)Mineralization in the gel system: (d) noncontrolled pH, (e)pH , (f) pH . (B) Xray diffraction patterns of themineral products in the gel diffusion system by additionof 200 ppm fluoride at various pH conditions: (a) noncontrolled pH, (b) pH , (c) pH .224 YOH ET AL.Journal of Biomedical Materials Research Part ATo understand the process of crystal growth in thefibrin gel, SEM images of the mineralized gel wereobtained in the presence of 20 ppm fluoride ions atvarious timepoints. The results demonstrated thatmineral nucleation on the fibrin fibrils occurred at1 min after mineralization, and granules of the mineralcrystal developed and transformed into needlelikestructures as time progressed (Fig. 5). To appreciatethe effect of the fluoride ions on the crystal morphology, SEM images of crystals that were obtained3 days after mineralization at different fluoride concentrations were observed。 an increase in fluoride ionconcentration resulted in a decrease in the number ofribbonlike OCP crystals. Finally, at fluoride ion concentration of 200 ppm fluoride ions, the entire areawas covered by needlelike FAp crystals (Fig. 6).Solubility experimentThe solubility of each sample was determined asthe ratio of the eluted Ca ions to the initial Ca content in the mineralized gel. As expected, the solubility decreased with an increase in fluoride concentration (Fig. 4).DISCUSSIONOver the past decade, a number of studies havebeen conducted on organic/inorganic positematerials for improving their mechanical properties,biodegradability, and biological affinity.28,29In thisstudy, we established a method for fabricating organic/inorganic material from fibrin and calciumphosphate by using bidirectional diffusion of the Caand PO4solutions into the fibrin gel. We also demonstrated that the characteristics of the mineralphase of this posite material could be controlledby altering the pH and fluoride ion concentration.First, we pared the mineral characteristicsformed in the gel diffusion system with thoseformed in the solution system. The crystallinity ofthe mineral generated in the gel system was higherthan that generated in the solution system. Fibrin gelprises a work of small fibrils, and this structure might attenuate ion diffusion and promote crystal growth in the gel. In the absence of