Influence of Ethylene Glycol on the Formation of Calcium Phosphate Nanocrystals Influence of Ethylene Glycol on the Formation of Calcium Phosphate Nanocrystals

Influence of Ethylene Glycol on the Formation of Calcium Phosphate Nanocrystals

  • 期刊名字:材料科学技术学报(英文版)
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  • 论文作者:Yi ZUO,Yubao LI,Jie WEI,Yongga
  • 作者单位:Research Center for Nano-Biomaterials
  • 更新时间:2020-12-22
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628J. Mater. Sci. Technol, Vol.19 No.6, 2003Infuence of Ethylene Glycol on the Formationof Calcium Phosphate NanocrystalsYi ZUO, Yubao LIt, Jie WEI and Yonggang YANResearch Center for Nano Biomaterials, Analytical and Testing Center, Sichuan University, Chengdu 610064, China[ Manuscript received July 3, 2002, in revised form October 30, 2002]A synthesis route of using calcium hydroxide Ca(OH)2 with ethylene glycol solvent and orthophosphoric acid (H3PO4)as reagents is described. Three ratios of ethylene glycol to distilled water 1:0, 1:1 and 0:1 are used as diluting mediafor Ca(OH)2. Crystals of different morphology and composition are formed under weak alkaline circumstance atpH 7.0~8.0. Acicular calcium phosphate nanocrystals are prepared in pure ethylene glycol while rod-like calciumphosphate nanocrystals form in pure distilled water. The nanograde size of the former is smaller than that of thelatter. Calcium-deficient apatite (CDAP) is obtained with a Ca/P molar ratio of 1.66. Therefore, it was deducedthat the usage of ethylene glycol solvent could influence the formation of calcium phosphate crystal lattice.KEY WORDS: Acicular nanocrystals, Calcium phosphate, Ethylene glycol solvent, Weak alkaline circumstance1. IntroductionDue to its similarity of the component to the mineral ofcalcifed tissues, e.g. bones, teeth and calcified cartilagel1,2.and the ability to form chemical bonding with host tissues(3,4,calcium apatite has received much attention in orthopedicsand plastic surgery in recent years. Pure bydroxyapatite (HACa1o(PO4)e(OH)2) crystals consisting of calcium, phosphate,and hydroxyl ions are stoichiometric with high crytalityt,while biocrystals isolated from bone or calcified cartilage aresmall thin needles of about 5~20 nm in diameter by 60 nm inlength, with poor crystallinity and non-stoichiometric in thecollagen fber matrix! 8。The nano-scale acicular shape bybiocrystals makes them metabolically active with high surfacereactivityl. The surface makes it beneficial to be coveredwith highly reactive labile ions of CO?-,PO43- ,HPO4where organic conslituents or cells can be attached to forma cell-structured interfaceltop. These properties caused byhigh surface reactivity are not expected from highly crys-talline apatite crystals used clinically, but only from low crys-talline bone-like apatite crystals or n1o-apeatite crystals.Calciun phosphate prepared by wet precipitation has thefeature of small size, low crystallinity and high surface activa-synthesis route where calcium hydroxide Ca(OH)2 with ethy-lene glycol solvent and orthophosphoric acid (H3PO4) wereused as reagents is investigated. Three ratios of ethylene gly-col to distilled water (1:0, 1:1 and 0:1) were used as dilut-ing media for Ca(OH)2. The method offers a molecular levelmixing of the calcium and phosphorus precursors, which is一1COncapable of improving chemical homogeneity of the resultingcalcium phosphate to a significant extent, in comparison withlow aqueous solubility of calcium hydroxidel4.ts.Fig.1 TEM micrographs of nano scale calcium phosphatecrystals (a) sample I: acicular crystals, (b) sample II:2. Experimentalmixture of rod-like and acicular crystals, (c) sampleIl: rod-like crystals10Ca(OH)2 + 6HgPO4 + Cano(PO4)e(OH)2+ 18H2O (1)respectively. The preparation procedure was identical to that1000 ml of 0.5 mol/L calcium hydroxide dissolved in puredescribed above,The calcium phosphate precipitates (dried at 1009C andethylene glycol (1:0) and 1000 ml of 0.3 mol/L orthophosphothen heating at 800°C for 2 h) were detected using an X-ric acid dissolved in distilled water were prepared to maintainthe molar ratio of Ca/P to be 1.67. All the chemical reagentsray difractometer (XRD, Philips XRD analyzer) and in-used in this work were of analytic reagent (AR) level. Thenfrared spectroscopy (IR, Nicolet 170SX FI-IR spectrometer).the phosphorous solution was titrated into the calcium solu-Transmission electron microscopy (TEM, JEM-100CX) wasused for microstructural examination. The ratios of Ca/Pof 0.5 mol/L ammonium solution was added to adjust pHwere measured by chemical titration. The contents of Cavalue at 7.0~8.0. Reaction temperature was controlled atnd P were measured by the methocof ethylenediaminetetraacetir acid (FPT'A 1 rholat.nmatru[17.18] and molybdate-In addition to the above synthetic scheme, processes forchinol中国煤化工1:1 of ethylene glycol to distilled water and pure distilled wa-3. Re!YCNMHGter (0:1) as the solvent of calcium hydroxide were employed,3.1 TEM pbotographs↑Prof, to whom correspondence should be addressed,Figure 1 shows the TEM micrographs of the nano-scaleE-mail: nic75040scu.edu.cn.J. Mater. Sci. Technol, Vol.19 No.6, 2003629江(D)wmhWwMy Lw il50 205020/deg.26/deg30 2/1e201deg.Fig.2 XRD patterns of the nano scale calcium phosphate crystals (a) sample 1 dried at 100°C, (b) sample 1heated at 800°C, (c) sarmple II heated at 800°C, (d) sample III heated at 800°Ccalcium phosphate crystals, where rig. 1(a) is for crystals frompure ethylene glycol solvent (sample I), Fig, 1(b) is for crystalsfrom 1:1 of ethylene glycol to distilled water (sarmple II), andFig.1(c) is for crystals from pure distilled water solvent (sam-ple II.. From these micrographs it can be seen that sample Ihas a fine acicular shape with a length from 30 nm to 50 nmand a diameter of 5~15 nm. Samnple III has an irregular rod-like shape with a mean size of about 40~60 nm in lengthand 10~20 nm in diameter. Comparison of Fig.1(a) and (c)leads to a conclusion that the use of ethylene glycol solvent isbeneficial to the formation of thin acicular nano-scale calciumphosphate crystal.3.2 XRD patternsFigure 2 shows the relevant XRD patterns, in which 2(a)is that for sample 1 dried at 100°C, 2(b) is the same sam-ple heated at 800°C for 2 h in a tubular furnace, 2(c) isthat for sample II heated at 800°C for 2 h and Fig.2(d) is40003000200015001000 400for sample 1II heated at 800°C for 2 h. The powders (irTemp./CFig.2(a)) have a poorly crystallized apatite structure. Af-ter heated at 800°C, a well crystallized structure of apatiteFig.3 IR spectra of nano-scale calciun phosphate crystalsmaterial containing nearly 96% hydlroxyapatite (HA) and 4% ,(a) sample I dried at 100°C, (b) sample I heated atbeta-tricalcium phosphate (B-TCP) was obtained. This indi-800°C, (c) sample II heated at 800°C, {d) sample IIcates that the acicular crystals in Fig.2(a) have a Ca/P mo-heated at 800°Clar ratio lower than 1.67, corresponding to non-stoichiometricapatite structure and composition. Because CDAP is decom-reaction took place during the dissolving process. The chem-posed into a mixture of HA and TCP after heating at highical formula would be the fllowing (2):temperaturel20), the sample I would be a calcium deficientapatite. Figure 2(d) exhibits a pure hydroxyapatite structurewith higber crystallinity than that in Fig.2(b) and (c). This,CH2- OHCH2-0means that sample I has a smaller crystal size than that of+ Ca(OH)2一Ca+ 2H2O (2)sample II, which coincides with the TEM micrographs. ThCH2- - QHCa/P molar ratio of the acicular crystals (sample I) was esti-mated from the XRD pattern to be 1.66, which is coincidentThe ethylene glycol solvent is indicated as chelating agentwith result of the chemical analysis.in the reaction, which is useful to calcium bydroxide dissolu-tion. After the reaction, calcium could exist as ionic phase in3.3 IR spectrasolution other than suspending granules. This method ofers aThe IR spectrum in Fig.3(a) indicates the presence ofmixing of the calcium and phosphorus precursors on molecu-OH~ , CO3”-, H2O, HPO42- as wellas PO43- in the powderlar scale, which is capable of improving chemical homogeneityof sample I. The peaks at 3571 cm-1 and 633 cm-1 were re-of the resulting calcium phosphate to a signifcant extent andsulted from OH~ ionsl21~23. The peak near 875 cm-1 couldnanocrystals could be smaller and hold on thin acicular shape,possibly represent the excessive amount of HPO4- ions inAs a result, the apatite crystals formation was infuenced bysuch case. The broad bands from 3700 to 2500 cm-1 an.the ethylene glycol solvent. Because the (CH2-O- )2 ion hasaround 1599 cm-1 arise from water. The 1451 and 1420 cm-'strong nucleophilie property, it is very easy to absorb the hy-, CO:2一 ions in the apatite crystal lattice.drogen ions (H+ ) of phosphorous acid to form intermolecularpeaksaresomeOther peaks are due to PqO:3-Th meanhydrogen bond.scale calcium phosphate crystals have a hydroxyapatite crys-tal structure.CH-0"+H*-- +H3)CH2--0*CH2-0/4. DiscussionIn reaction (3) the hvdroven ions of phosphorous acid canDuring the process of calcium hydroxide dissolved in purebe omparable neutral cir-ethylene glycol, the tompecrature increased from room tem- cumst中国煤化工1m ions to adiust thepetature 26Cto 40~45°C while Ssolution temperatureinthe DH V; to release phosphaticperature260 to40~45~C, while solution 'mperature in thepHl VaYHC N M H Gto release phosphaticdissolved process of other two solvents were lower than it. Insuch case, calcium hydroxide suspension turned into trans-This is diferent from other commonly used apatite prepara-parent solution. These phenomena indicated that chemical tion method, in which the addition of ammonium hydroxide,...630J. Mater. Sci. Technol.,. Val.19 No.6, 2003NH4OH is required to keep the reaction very alkaline (pH at[3] K.de Groot: Bioceramics of Calcium Phosphate, CRC Press,11~12) to ensure the formation of HA[24~26].On the other hand, the strong nucleophilic (CH2- -O- )2[4 ] P.Ducheyne and W.Hasting: Metal and Ceranic Biomaterials,CRO Press, Vol.lI, 1984.ions can absorb calciumn ions strongly as well.The rele-[5] J.Cllott: Studies in Inorganic Chemistry, Elsevier, Amster-vant XRD patterns shown in Fig.2 indicate that sample I arepoorly crystallized non- stoichiometric apatite crystals. This[6] J.L.Katz and RA.Harper: Eneyclopedia of Materials Sciencmeans the nano-apatite is calcium deficient apatite (CDAP).and EEngineering, ed. M.B.Bever, Pergamon Press, NY, 1986,474.However, calcium ions are found to be absent in the filtered[7] J.B.Park. and RS.Lakes: Biomaterials: An introduction,solution of sample I by chemical analysis after the reactionfinished. That is to say, some calciurn ions are still chelat-|Plenun Press. New York and London, 1992, 19Yubao Li, J.De Wijn, C.PA.T.Klein, S.Vam de Meer and K.deing by ethylene glycol, and the metal chelates are absorbedGrool: J. Mater. Seil: Mater. Med, 1994, 5, 252.on the apatite lattice because of the high surface activity of[9] A.S.Posner, F.Betts and N.C.Blurpenthal: Skeleta! research:nanocrystals. These phenomena give an explanation t如o thean experimental approach, eds: D.J .Simons and A.S.Kunin,CDAP formation in sample 1. It can be obviously seen from[10] S.L.Lees, T.Glonek and M.J.Glimcher: Calcif Tissue Int, 1983,Fig.3(b), (c) and (d) that the quantity of the OH- increaseswith the increasing use of ethylene glycol solvent. Therefore,, 35,815.C.Rey and MJ.Glimcher: Chemistry and Biology of Mineralthe existing chelate induces the strengthening of the peaks ofized Tsses eds. H.Slavkin and P.Price, North Hlland; EOH~ group in apatite crystals.As we know, the mineral of natural bone is chieAy com.2] Dean-Mo Liu, T.Troczynski and J.Wenjea: Tseng: Biomateri-posed of non-stoichiometric apatite. crystals, which contain aals, 2001, 22, 1721.Certain arnount of CO32- ions(21,27~29. Sample I shows. a[13] Ming-Fa Hsieh, Li-Hsiang Perng, Tsung-Shune Chin andHuann-Guang Perng: Biomaterials, 2001, 22, 2601.small CO3- peak in IR spetra. CO32-. ions took into the [141 A.Osala, Y.Miura, K Takeuchi, M.Asada and K.Takahash; J.apatite lattice when reaction occurred in air atmosphere. AndMater. Sci: Mater. Med, 1991, 2, 51.the CO:- ions decomposed into carbon dioxide (CO2) after iPierre Laytolle and Albert Lebugle: Chem. Mater, 1994, B,heating at 800°C.[16] Yubao Li: Synthesis and Characterization of Bone _like Min-erals: Macroscopic Approach and Microscopic Emulation.5. ConclusionsPreparation and characterization of nanograde calcium phos-(1) Non- stoichiometric apatite has been found to play animportant role in bone remodeling and bone formation, as7] Changsheng LIU and Yue HUANG: Biomaterials, 2001, 22,01.well as in apatite inducing precipitation(30,31]. Artificial car-[18] Jiaxing Zhang: Analytical Chemistry Experiments, East Chinabonated apatite has also shown itself to be biologically moreInatitute of Chemical Technology Press, Shanghai, 1989, 65.reactive than pure hydroxyapaptite2.33). The use of ethy-(in Chinese)lene glycol solvent can prepare the acicular nano-scale cal- [L9] W JWilliani Handbook of Anion Determination, Beijing Met-cium phosphate crystals, whose morphology and componentsallurgical Industry Press, Beijing, 1987, 582.[20] H.Monma, s.Ueno and T.Kanazawa: J Chem. Technol.are similar to bone apatite.(2) The ethylene glycol solvent was indicated as chelatingBiotechnol, 1981, 31, 15.[21] Yubao Li, K.de Groot, J.de Wijn, C.P.A.T.Klein andageat in the reaction. This method offers the mixing of theS V.D.Meeri.deMater Seil: Mater, Med 1994,5, 36calcium and phosphorus precursors。on molecular scale, whichis capable of improving chemical homogeneity of the resultingB.O FowerJ.C. Helehebarrt. G H Nancola pYesinowskicalcium phosphate to a significant extent and nanocrystalsand SJZawacki: J. Cryst. Growth, 1987, 84, 515.could be smaller and hold on thin acicular shape. Thus, the[23] Jiming ZHOU, Xingdong ZHANG, Jiyong CHEN, ShaoxianZENG and K.de Groot: J. Mater. Sci: Mater. Med, 1993, 4,ethylene glycol solvent can affect the apatite crystals forma-83tion.[24} Larry L.Hench and June Wilson: An Introduction to Bioce-(3) The preparation provides a novel method under weakramics, World Scientifc Publishing Co. Pte. Ltd., Singapore,akxaline circumstance to gynthesize mimic bone apatite cry8-New Jersey, London and Hongkong, 1993, 149.tals to meet the increasing needs.[26] H.Aoki: Science and Medical Applications of Hydroxyapatite,JAAS, Takayama Press System Center Co., Tokyo, 1991.27] P.Ducheyne: J. of Biomed. Mater. Res, 1987, 21(A2), 219.AcknowledgementG.Montel, G. Bonel, J.C.Heughebaert, J.C.Trombe and C.Rey:We would like to acknowledge the support from the Ministry29] K.de Groot, C.PA.T.Klein, J.G.C.Wolke and J.M.A.de Blieck-of Science and Technology of China (2001BA310A).Hogervorst: CRC Handbook of Bioactive Ceramic, V.II, CRCPress, Boca Raton, 1990 3.REFERENCES[30] AS.Posner: Physiol. Rev, 1969, 49, 760.[31] S.R.Radin and P.Ducheyne: J. Biomed. Mater. Res., 1993,27; 35.[1] A.S.Posner: Bull. Hosp. Joint Dis, 1978, 39, 126.[32] YLi, X.Zhang and K.de Groot: Biomaterials, 1997, 18(10),[2j R.A.Harper and A.s.Posner: Proc. Sco. Exp. Biol. Med,,1966, 122, 137s.[33) D.G .A.Nelson: J. Dent. Res, 1981, 60C, 1621.中国煤化工MYHCNMHG

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