Analysis on the Difference between Synthetic Hydroxyapatite and Bone Apatite

Vol.20 Suppl.Joumal of Wuhan University of Technology - Mater. Sei. Ed.Dec.2005Analysis on the Difference between Synthetic Hydroxyapatiteand Bone ApatiteSONG Yunjing'LI Musen2LV Yupeng2SHI Wenhua'(1. Shandong Flectric Power Research Institute, Jinan 250002;2. Department of Materials Science and Engineering, Shandong University ,Jinan 250062, China)Abstract: The composition and stnucture of bone apatie and synheic hydroxyapatite pouder prepared byprecipiation method, sol- gel method was studied by FTIR, EMPA, AFM in this paper . The resuts showed thatthe composition and phase structure of apaie pouder prepared by sol gel method uas most similr wih that in thebone . The caciun phosphate ratios of apatite prepared by tuo kinds of uet precipitation was 1.69, and 1.73 re-spectirely . The calciumn phoasphate ratio of apatile prepared by sol-gel method uas 1.66. The apatite pouder pre-pared by sol- gel method was hoped to be more bioactire and biocompatible compared uith apatite poncder preparedby wer preipiatin method . The EMPA results proved that the bone consistedofCa, P, 0, Na, Mg, K, a,ete elements 。The amount of apatite decreased while amount of collagen increased from the outer layer to innerlayer of the bone. AFM resuls showed that HA particle，with the size about 150- 450 nm in length，100- 150 nmin width, 15- 40 nm in tikness, grown layer upon layer regularly. The long axis 1os not aboays parallel tothe collagen fiber. The angle betueen collagen fiber and apatite lamellar uas about 30-45 degree .Key words: bone; bone apatie;synthetic apatite1 Introductiongel method6.? . Although many studies on HA powder prep-aration and bone tsse are carried out respectively, fewBone is the important structural matenial used to carycomparison is performed. The aim of this paper is to find themajor loads of human body. It is a kind of corposite materi-difference between the natural bone apatite and synthetic HAprepared by wet precipatiation method and sol-gel method.al whose components are primarily collagen and hydroxyapa-The results in this paper are hoped to be helpful to the syn-tite'. Bone is a composite material in several ways. First ofthesis of more biocompatible and bioactive HA powder. Atall, it is porous material composed of a solid matrix contain-the same time, it is interesting to study the composition anding voids of varying sizes which are flled with soft tssues.morphology of apatite in the bone.The porosity of bone varies continuously from about 5% toabout 95%. Natural bone exists in two foms: either “com-pact"( with low porosity) or‘spongy” ( with high porosi-50ty)2i . The second way in which bone is a composite maten-d)al stem from its hierarchical level of structural organization.1o8Compact bone is always composed of osteons ( also calledHarversian canal) which are tubular stuctures about 200 pumsof 自秉in diameter. The osteons contains severul lamellae sheetswhich are conposed of ollagen(20 wt%), calcium phos-8)phate(69 wt%) and water(9% ). Calcium phaosphate is al-ways in form of crytallized hydroxyapatitesl . S Talharnmero0f雷and W M Heckl has used atonic force micrnscopy (AFM) tostudy the collagen fibrils and found that AFM figures three-dimensionally the surface of a sample with high resolutiondown to a nanometer scale4. . Stoichiometric hydroxyapatite,Cag(P0,)6 (OH)2, comonly refrered to as HA or HAP,has become an attractive materials for hard tsse implants4000 3000 20001000because it can provide a chermical bond to the bone ankWavenumbers/cmgradually be replaced by bone. HA powers can be preparedFig.1 FIR curves of dfferent powder sintered atby several methods such as wet precipitation methodb.，sol-900 C for 30 min(a)SGHA, (b)CHHA,中国煤化工(Received:Feb. 24 ,2004; Accepted: May 23, 2005)SONG Yunjing(宋云京):soc. Prof. ;Ph D; E-mail:yj - song@2JYHCNMHG;163. com* Funded by Science Development Plan Foundation of ShandongThree kinds of synthetic HA powder are prepared asProvince( No.01 120106)Vol.20 Suppl.SONG Yunjing et al :Analysis on the Diference between Synthetic Hydroxyapatite....171follows: the first HA powder, which is naned as CNHA,about 1 456 cm-' in SCHA and BHA.is prepared using Ca(NO3 )2●4H2O and (NH)2HPO4 asFrom Table 1 it can be seen that the Ca/P molar ra-reagent according to Ca/P molar ratio 1. 67. Thetio of HA prepared by two wet precipitation method is(NH)2 HPO4 aqueous solution is slowly dropped into the1.69,1.73 respectively. The Ca/P molar ratio of BHAstirred Ca( NO3)2●4H2O. The pH values for both solut-and SCHA, which are 1.64 and 1. 66 respectively, areions is adjusted to 10 with anmonium solution. 'The as-similar. The composition of SCHA powder is most similarprepared powder is heated at 900 C for 30 min. The sec-with the apatite in the bone.Table 1 The comparison and Ca/P molar ratioond HA powder, which is named as CHHA，is preparedbetween the BHA and synthetic HA_using Ca(OH)2 and H;PO。as reagent according to Ca/PCalcium content Phosphorus content Ca/P molarmolar ratio 1.67. The H PO4 solution is titrated to stiredSammple/wt%Ca( OH)2 suspension. The as- prepared powder is heatedBHA30.814.61.64at 900 C for 30 min. The third HA powder, which isSCHA39.218.31.66named as SGHA, is prepared using Ca( NO, )2 *4H2O andCHH/18.41.73P2O3 ethanol solution, 'The process is same as publishedCNHA40.618.61.69paper?7. 'The Ca/P ratios of all the three reagents arThe purity of CNHA powder and CHHA powder is1.67. Bone apatite which is named as BHA is preparedlower than that of SGHA powder. Over HPO:~ ions ap-by calcined femoral compact bone powder at 900 C for 30pear from CHHA powder.min. The four kinds of apatite powders are characterizedCross sections of the compact cone are shown inby FTTR and EPMA. Purity of the samples is tested byFig.2. It can be seen that the compact bone is composedFourier transform infrared spectrometry FTIR ( Nicoletof osten, which is arranged in concentric rings aroundNexus470). The composition of synthetic powder ancHarversian canal .bone apatite is analyzed by EPMA(JXA-8800R).Table2 is the composition of compact femoral boneAtomic force microscopy analysis is performed on anwhich is tested by EMPA. It can be seen that the boneAFM(Nanoscope IA) with 100 pum xy-scan range and 10apatite consists of Ca, P, 0, Na, Mg, K, Cl etc ele-nN touch force. The bone samples are supplied by Depar-ment. The bone apatite is not stoichiometric hydroxyapa-tment of Orthpaedics, Shandong University Qilu Hospital.te( Cano(P04 )6(OH)2) .There are many substitutions inThe samples used in present study are performed on femo-bone, for example, K, Mg, Na for Ca; carbonate forral compact bone tissue from a male adult which has beenphosphate; and Cl for OH. The element content in theobtained at autopsy. The man has died from trffc acci-outer and inner layer of the bone is different. The outerdent and no evidence of bone defects is provided. Bone islayer of bone consisted of more Ca，P, K, Na ions whilecut into slice sample along longitudinal and transverse di-the inner layer of bone consisted of more 0 ions. Thisrection. The atomic force microscope( AFM), moves ahows that the amount of apatite decreases while amountvery sharp tip attached to a bone surface. Delections inof collagen increases from the outer layer to inner layer ofthe tip that correspond to surface topography are recorded.the bone.Previous analyses show that normal human femoral3 Results and Discussionbone consists exclusively of collagen. The organic boneIn Fig.1, (a), (b), (c), (d) are the FTIR curvesmatrix show a network of bundles which are mostly ar-of SCHA, CHHA, CNHA, BHA respectively. The peaksranged in parallel fibres, 400 nm in diameter on av-rage'" . The HA crystals, present in the form of plates orat about 1 090,1 046, 962, 602,572 cm-' are attibutedneedles, are about 40-60 nm long, 20 nm wide, andtothe P02-. It is noted that the peaks are sharp, sug-1.5-5 nm thick. They are deposited parallel to the colla-gesting that HA powders are well crystallized. The peaksgen fibers and the larger dimension of crystals is along theat about 3 571,632 cm~' are derived from stretching andaxis of the fiber3].bending modes of 0H~ . The peaks around 3 440, 1 629In the present report， we have applied a novel mi-cm-' are atibuted to the adsorption of H2O. The peakscroscopic technique to the analysis of collagen diameter,of NO3 derived from NH4 NO3 at about 1 384 cm^' appearshape and sie of bone apatite. It can be seen from Fig.3in CNHA. The NO; in CNHA is maybe from ammoniumand Fig.4 that AFM can be applied to identify collagennitrate. In order to eliminate ammonium nitrate and resid-bundles and to determine their diameter. AFM resultsual ammonia, washing and rinsing with a large amount ofshow that HA particles, with the size about 150-450 nmwaler are inevitable. But a small amount of ammonium ni-in length, 100-150 nm in width, 15-40 nm in thickness,trate still exists in HA powder HA powder prepared by Cagrow中国煤化Ilong axis of HA par-(NO3)2 .4H2O and (NH )2HPO4 is from reaction as fol-ticle igen fiber. The anglebetweMHC N M H Gite lamellar is aboutlows:10Ca(NO3)2 + 6(NH)2 HPO, + 8NH,0H→Cag(P04)。3045 degree. This technique is superior to other ul-(OH)2 + 20NH.NO, + 6H20(1)trastructural methods such as SEM or TEM. In addition,this technique is very effective and fast ."The peak around 1 422 cm^ ' is atibuted to HP0?in C号势数uve. The bands of C03~ is detected at172Joumal of Wuhan University of Technology - Mater. Sci. Ed.Dec.2005Table2 The composition of compact femoral boneElement content/wt%PositionP_0MgKOuter layer31.0314.8351.351.350.400.290.43Middle layer30.7814.7151.631.270.390.48Inner layer30.6614.3752.201.290.350.220.49-10.01000.0 nm7.5500.0 nm.00.0 nm100u.m25 5.0 7.5 10.0Fig.3 AFM of logmitudinal section fromFig.2 Cross. section of hunan compact femoral bonecompact femoral boneSection Analysis429.69 m10.045 mmDICpih。,otl] 5.718|Ron25.630mauf| RzCat1.033 μm乳2.00 4.00 _6.00 8.02098mm433.68 mSpectrumHort dsancec 429.69 aVert distance27.468 mngle3.658 mHz01 160948.001DCMinSeteJRMs amp_ 000 mFig.4 AFM of transverse section from compact femoral bone4 ConclusionsReferencesWeiner, H D Wanger. 'The Material Bone: Structure Me-The study on the differences between HA powderchanical Function Relations. Annu . Rev . Mater . Sei., 1998,28:271-298prepared by wet precipitation， sol-gel method and bone[ 2] R B Martin. Bone as a Ceramnie Composite Material. Materi-apatite proves that the composition and phase structure ofals Science Forum , 1999 ,293:5-16apatite powder prepared by sol-gel method are similar with[3] Wojciech Suchanek, Masahiro Yoshimura. Processing andthat in the bone. The apatite powder prepared by sol-gelProperties of Hydroxyapatite-based Biomaterials for Usemethod is hoped to be more bioactive and biocompatibleHard Tissue Replacement Implants. J. Mater . Res., 1998,13compared with apatite powder prepared by wet precipitati-(1):94-117on method.[4] s Talhanmer, W M Heckl. Atonie Force Microsopy forThe EMPA results prove that the bone apatite con-High Resolution Imaging of Collagen Fibrils-a New Techniqueto Investigate Collagen Structure in Historic Bone Tissues .sisted of Ca, P，0, Na，Mg，K, Cl elc element. TheJoumal of Archuelogical Science ,2001 ,28: 1061-1068bone apatite is not stoichiometric hydroxyapatite， Ca[5] A Osaka, Y Miura, K Takeuchi, M Asada, K Takahashi.(P04)6(0H)2, there are many substitutions in bone, K，Calcium Apatite Prepared from Calcium Hydroxide and Or-Mg, Na for Ca; carbonate for phosphate, and Cl for 0H.thophosphoric Acid. J. Mater . Sci . : Mater . Med., 1991 ,2:HA particles, with the size about 150-450 nm in length,[651-55Atarn Itn. Tetanrva Tateishi. Sol-Gel Synthe-100-150 nm in width, 15-40 nm in thickness, grow layer中国煤化工ste and Sintering into Mi-upon layer regularly. The long axis of HA particle is not_ics.J . An. Ceram. Soc.,always parallel to the collagen fiber. The angle betweenYHCNMHGcollagen fiber and most apatite lamellar is about 30-45 de-[7] Yunjing Song, Shulin Wen, Musen Li，et al. Preparationand Phycicochemical Process of Nanosized HydroxyapatitePowders with High Purity. Joumal of Inorganic Materials ，2002, 17(5) :985-991