【正文】 23:2249–2254.27. Matsumoto T, Okazaki M, Inoue M, Hamada Y, Taira M, Takahashi J. Crystallinity and solubility characteristics of hydroxyapatite adsorbed amino acid. Biomaterials 2020。7:3008–3011.11. Chang MC, Douglas WH, Tanaka J. Organic–inorganic interaction and the growth mechanism of hydroxyapatite crystalsin gelatin matrices between 37 and 808C. J Mater Sci MaterMed 2020。 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。 revised 12 September 2020。and PO43–were diffused into the fibrin gel fromopposite sides to facilitate mineralization in the gel. (B)Fibrin gel size, 8 mm 3 mm (diameter 3 thickness): (a)Fibrin gel, (b) 4 h postmineralization, (c) 3 days postmineralization.BIOMIMETIC FABRICATION OF FIBRIN/APATITE COMPOSITE MATERIAL 223Journal of Biomedical Materials Research Part Ain the gel mineralization systems。181:232–240.8. Rees SG, Hughes Wassell DT, Wanddington RJ, Embery G.Interaction of bone proteoglyacans and proteoglycan ponents with hydroxyapatite. Biochim Biophys Acta 2020。57:735–742.24. Liu C, Huang Y, Shen W, Cui J. Kiics of hydroxyapatiteprecipitation at pH 10 to 11. Biomaterials 2020。10:73–80.30. Martin RI, Brown PW. Phase equilibria among acid calciumphosphates. J Am Ceram Soc 1997。75:494–501.14. Boskey AL, Boyan BD, Schwartz Z. Matrix vesicles promotemineralization in a gelatin gel. Calcif Tissue Int 1997。 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 fluoride ions,the minerals obtained in the gel diffusion systemwere DCPD under the noncontrolled pH conditions,the DCPD and OCP mixture at pH , and the OCPand HAp mixture at pH . Previous reports havesuggested that the pH condition suitable for DCPDsynthesis is acidic,30for OCP, it is neutral to mildlyacidic,31and for HAp, it is neutral to weakly alkaline.32The decrease in local pH during mineralization in the gel system may be responsible for thepresent results.Figure 3. (A) Xray diffraction patterns of the mineralproducts obtained using a variety of fluoride concentrations at pH . (B) Expanded (300) Xray reflections ofthe mineral products. (a) F2free, (b) 2 ppm, (c) 20 ppm,(d) 50 ppm, (e) 100 ppm, (f) 200 ppm, (g) 500 ppm,(h) 1000 ppm, (i) 2020 ppm.Figure 4. Crystallinity (n) and solubility (l) of the minerals obtained in the fibrin gel using a variety of fluorideconcentrations at pH . Crystallinity was defined as theinverse of the hal