Journal of Wuhan University of
Technology-Mater. Sci. Ed.
Apr.2013
215
DOI 10.1007/s11595-013-0667-8
Preparation and Characterization of Hydroxyapatite/ -Fe2O3 Hybrid Nanostructure
SUN Ruixue, CHEN Kezheng*, XU Lei
(College of Materials Science and Engineering, Qingdao University of Science and Technology, Qingdao 266042, China) Abstract: The hybrid particles composed of hydroxyapatite (HAp) and ferrite (γ-Fe2O3) were synthesized by two-step precipitation method. The effect of reaction temperature on the morphology of the hybrids was also studied. The resultant hybrids were characterized by transmission electron microscopy (TEM) and X-ray diffraction analysis(XRD). It was found that γ-Fe2O3 nanoparticles dispersed within the HAp matrix and these hybrids had a feather-like or spherical morphology when synthesized at 90 ℃ or room temperature, respectively. The magnetic properties of the hybrid showed good superparamagnetic feature, and they could be controlled by the external magnetic field. Key words: hydroxyapatite; γ-Fe2O3; hybrid nanostructure; superparamagnetism
1 Introduction Hydroxyapatite (Ca 10(PO 4) 6(OH) 2, HAp) is a well-known biomaterial due to its excellent bioactivity and biocompatibility, and has been widely used as bone substitutes and tooth implants in clinical applications [1-3]. Particular adsorbability for various ions and organic molecules of HAp nanoparticles (NPs) makes them good candidates as delivery vehicles of anticancer drugs as well as growth factors and enzymes for controlled release[4-7]. Drug release and catalytic behavior of HAp have been also reported by many researchers. In these practical applications, HAp exhibits an obvious drawback, namely difficulty in targeting and recycling[8]. On the other hand, magnetic nanopowders of Fe 3O 4 and γ-Fe 2O 3 have been extensively used in targeted delivery of drugs, magnetic resonance imaging (MRI) reagent, hyperthermia treatment, and many other fields [9-12]. In recent years, various nanostructures of them, such
©Wuhan University of Technology and SpringerVerlag Berlin Heidelberg 2013 (Received: Feb. 19, 2012; Accepted: Apr. 8, 2012) SUN Ruixue(孙瑞雪): Assoc.Prof.; E-mail:
[email protected] *Corresponding author:CHEN Kezheng(陈克正): E-mail: kzchen@qust. edu.cn Funded by the Project of Shandong Province Higher Educational Science and Technology Program (No. J09LC13) and the Promotive Research Fund for Excellent Young and Middle-Aged Scientists of the Shandong Province (No. BS2010CL018)
as nanowires, nanoneedles, and nanospheres, have been successfully fabricated by many researchers[13,14]. However, pure magnetic nanoparticles are prone to aggregation and rapid biodegradation when they are directly exposed to a biological system[11,15]. For biological applications, magnetic nanoparticles shall be prepared or loaded with other materials, such as silica, polymer, and HAp vesicles to enhance their other desirable properties such as colloid dispersion, drug loading, and biocompatibility[16]. Among these, HAp encapsulated ferrite nanoparticle is one of the most promising materials because of the merits of these two kinds of materials mentioned above. Webster and co-workers [17] reported the synthesis of HApcoated Fe3O4 nanoparticles by using a wet chemical method. The Fe3O4 nanoparticles were embedded in the rod-shaped HAp particles with the average size of 170 nm. Wakiya et al[18] reported the synthesis of HAp-ferrite composite particles by the combination of co-precipitation and ultrasonic spray pyrolysis. The composite particles have round shape with some dimples with the average particle size of around 1.8 m. Xia et al[19] prepared HAp coated ultrafine and uniform γ-Fe2O3 core-shell particles by co-precipitation method for selective oxidation of alkene with H2O2 in the presence of acetonitrile. Liu et al[8] prepared Fe3O4/ HAp nanoparticles with magnetism and photocatalytic property by homogeneous precipitation. These particles are almost spherical in shape with well-defined coreshell structure, rather monodisperse and have a unique
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size of about 25 nm in diameter. Heydari et al [20] prepared hydroxyapatite-encapsulated-γ-Fe2O3 by the same method as reference[8], and studied its potential application in the formylation of amines and amine derivatives. In this work, HAp/γ-Fe2O3 hybrid particles with two different morphologies were synthesized by twostep precipitation synethsis. First step was to synthesize γ-Fe2O3 nanoparticles by coprecipitation method, and second step was the synthesis of HAp/γ-Fe2O3 hybrid particles by wet chemical precipitation method. These magnetic apatite nanoparticles can be employed as reusable catalysts as well as targeted delivery vehicles of drugs.
2 Experimental 2.1 Materials Diammonium hydrogen phosphate [(NH4)2HPO4] and calcium nitrate tetrahydrate [Ca(NO3)2•4H2O] were supplied by Sinopharm Chemical Reagent Corporation (Shanghai, China). Iron (Ⅱ) sulfate heptahydrate (FeSO 4•7H 2O), ferric chloride (FeCl 3•6H 2O), and sodium hydroxide (NaOH) were purchased from Shanghai Chemical Corporation (Shanghai, China). All the reagents were of analytical grade. All glassware used were cleaned with acetone, followed by copious rinsing with deionized water under ultrasonication before drying in an oven at 120 ℃. 2.2 Synthesis of -Fe2O3 nanoparticles The aqueous γ-Fe2O3 suspension was synthesized by precipitation from iron chlorides. Briefly, the Fe3O4 precipitate was firstly obtained by alkalinization of the FeCl3 and FeSO4 (Fe2+/Fe3+ = 1/2) aqueous mixture. Then, it was successively oxidized with 1 M HNO3 (50 mL) and 0.17 M Fe(NO 3)3•9H2O solutions (50 mL) at 100 ℃. The brown dispersion was washed with a 0.5 M HNO3 solution for four times. After that, 0.1 M sodium citrate (15 mL) was added into the brown precipitate at 90 ℃ under vigorous stirring for 15 mins in order to make the prepared particles disperse steadily in water through surface modification. N2 was bubbled throughout the reaction. The final precipitate product was washed with acetone for several times, and dispersed in water for use. 2 . 3 S y n t h e s i s o f H A p / - F e 2O 3 h y b r i d nanostructure The hybrid nanoparticles of HAp/γ-Fe2O3 were prepared by a well-established wet chemical process. Briefly, a 0.5 M Ca(NO3)2•4H2O solution was added
dropwise to a 0.3 M (NH4)2HPO4 solution containing the prepared iron oxide nanoparticles whose pH was adjusted to 11. The reaction was conducted at room temperature or at 90 ℃ in water bath with vigorous mechanical stirring. After 2 h, the mixture was cooled to room temperature and aged overnight. The resultant brown hybrid were separated magnetically and washed with deionized water and ethanol several times. 2.4 Characterization X-ray diffraction (XRD) studies were conducted on a Rigaku D/max-2500 X-ray powder diffractometer using Cu K radiation ( = 1.5406 Å), with a scan speed of 4°/min between 10 and 70° (2θ angle), operated at 40 kV and 100 mA. The morphologies of the products were examined in a field-emission scanning electron microscope (FESEM, JEOL JSM6700F) and a transmission electron microscope (TEM, JEOL JSM-2000EX). The samples were ultrasonically dispersed before the analysis. The particle size distribution and mean particle size were measured using the dynamic light scattering (DLS) by a nanoparticle size analyzer (Nano ZS, Malvern) and distilled water was employed as the dispersion medium. The magnetic properties were measured on a superconducting quantum interference device (SQUID) magnetometer (Quantum Design, MPMS XL-5) at 300 K.
3 Results and discussion The crystalline phase of HAp/γ-Fe 2O 3 hybrid nanoparticles prepared at 90 ℃, together with that of the original HAp as reference sample were examined by the XRD as shown in Fig.1. It indicates that predominant phase of the resultant hybrid nanoparticles is HAp, and small amount of ferrite is also found (Fig.1(b)). The peaks marked by triangles (at around 30.2°, 35.6°and 57.3°) can be indexed as γ-Fe 2O 3
Journal of Wuhan University of
Technology-Mater. Sci. Ed.
(JCPDS No. 39-1346). Other iron oxide phases are apparently not involved. The XRD result reveals the coexistence of the γ-Fe2O3 phase and HAp phase in the hybrid products. The relative low crystallinity of the products is due to the low temperature used in the whole process of preparation.
T E M i m a g e o f t h e a s p r e p a r e d γ - F e 2O 3 nanoparticles is shown in Fig.2. It can be seen that the prepared γ-Fe2O3 has a spherical-like morphology with a diameter of 10-20 nm. Figs.3(a) and 3(b) show
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TEM images with different magnification of the hybrid HAp/γ-Fe2O3 prepared at 90 ℃ in water bath. The assynthesized hybrid HAp/γ-Fe2O3 has a special spindleshaped morphology, with a long axis of about 500 nm and a short axis of about 100 nm. Interestingly, the hybrid HAp/γ-Fe2O3 also has a loosen feather-like structure after magnification as shown in Fig.3(b). In fact, it is an oriented array of bundled nanosheets with about 20 nm in width, which can be further identified by SEM observations in Fig.4. γ-Fe2O3 nanoparticles are not observed in the TEM image, which is possibly due to the smaller size of the nanocrystallites. In Fig.4(b), some spherical particles of about 10 nm are found dispersed between the nanosheets, probably magnetic nanoparticles of γ-Fe2O3. The EDS spectrum (Fig.4(c)) of HAp/γ-Fe 2 O 3 hybrids confirms the presence of calcium (Ca), phosphor (P), oxygen (O), and ferrum (Fe) in the HAp/γ-Fe 2O 3 sample. Fig.5 shows the particle size distribution curve of the HAp/ γ-Fe2O3 hybrids by DLS. The mean particle size of the HAp/γ-Fe2O3 hybrids is about 600 nm, which is corresponded to the TEM results.
In order to test whether this growth mode of HAp is related to the addition of magnetic nanoparticles, we also conducted the same experiment without γ-Fe2O3. TEM images (Fig.6) demonstrate the same spindleshaped morphology of HAp, however, the structure of the single HAp is not so loose as the HAp/γ-Fe2O3 composite with feather-like structure, and the size of
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HAP is smaller than that of HAp/γ-Fe2O3 hybrids. For comparison, the same experiments with and without γ-Fe 2 O 3 were also repeated at room temperature. It can be seen from Fig.7 that the HAp/ γ-Fe2O3 and single HAp prepared at room temperature both have spherical morphology with the particle size of 60-80 nm and 30-40 nm, respectively. Moreover, some small spherical particles of about 10 nm dispersed between large nanospheres can be seen in Fig.7(a), which may be the γ-Fe2O3 nanoparticles.
thermodynamically stable phase. At high temperature, HAp will grow along its c direction and thus has a onedimensional morphology such as nano needles and nano sheets. While at room temperature, HAp will grow isotropically and has a spherical morphology. At the same time, γ-Fe 2 O 3 nanoparticles will be encapsulated into HAp matrix. The magnetic properties of as-prepared HAp/ γ-Fe2O3 hybrid nanostructure were investigated using a SQUID magnetometer at 300 K. As shown in Fig.8, the isothermal magnetization curves of the HAp/ γ-Fe2O3 display a rapid increase with increasing applied magnetic field due to superparamagnetic relaxation. Hysteresis is absent with zero remanence and coercivity, and the satruation magnetization (Ms) reached up to 2.6 emu・g1 for the HAp/γ-Fe2O3 hybrids with spherical morophology, which is smaller than the theoretical Ms for bulk γ-Fe2O3 at room temperature. This difference can be explained by the defined size effects responsible for the degradation of magnetic properties in iron oxide nanoparticles [22]. Fig.8b shows a photograph of an aqueous dispersion of the HAp/γ-Fe2O3 and illustrates the magnetic manipulation ability. When an external magnetic field is placed by the side of the glass vial, the composite nanoparticles can be directed near to the magnet (Fig.8(c)). These magnetic properties of HAp/ γ-Fe2O3 suggest its potential applications for targeting and separation.
4 Conclusions I n c o n c l u s i o n , t h e H A p / γ - F e 2O 3 h y b r i d nanostructure with feather-like and spherical morphology were fabricated through a simple method without any organic template. The analyses of SEM and XRD revealed that the obtained nanoparticles were composed of γ-Fe 2 O 3 and HAp. These two kinds of HAp/γ-Fe 2O 3 hybrids both exhibit good superparamagnetic property. These magnetic apatite nanoparticles can be employed as reusable catalysts as well as targeted delivery vehicles of drugs. As well recognized, HAp can be fabricated to different morphologies, such as nanospheres, nanorods, and nanofibers by using organic surfactant as soft template[9,21]. However, no organic template was added in our experiment. Many researches have shown that the unstable amorphous calcium phosphates (ACP) forms rapidly in the initial stage of the reaction. Then, ACP will transform into HAp, a more
References [1].
Dorozhkin SV. Calcium Orthophosphate Based Biocomposites and Hybrid Biomaterials[J]. J. Mater. Sci., 2009, 44: 2 343-2 387
[2].
Uota M, Arakawa H, Kitamura N, et al. Synthesis of High Surface Area Hydroxyapatite Nanoparticles by Mixed Surfactant-mediated Approach[J]. Langmuir, 2005, 21: 4 724-4 728
[3].
Jevtic M, Mitric M, Skapin SB. et al. Crystal Structure of Hydroxyapatite Nanorods Synthesized by Sonochemical Homogeneous Precipitation [J]. Crystal Growth & Design, 2008, 8: 2 217-2 222
Journal of Wuhan University of [4]
Technology-Mater. Sci. Ed.
[6]
[14] Cao SW, Zhu YJ. Surfactant-free Preparation and Drug Release
Controlled Release Carrier of Protein[J]. Biomaterials, 2004, 25: 3 807-
Property of Magnetic Hollow Core/shell Hierarchical Nanostructures
Mizushima Y, Ikoma T, Tanaka J, et al. Injectalbe Porous Hydroxyapatite Microparticles as A New Carrier for Protein and
Encapsulating Upconversion Fluorescent and Superparamagnetic
Lipophilic Drugs[J]. J. Control. Release, 2006, 110: 260-265
Nanocrystals [J]. Chem. Commun., 2008, 694: 694-696
Kumta PN, Sfeir C, Lee DH, et al. Nanostructured Calcium Phosphates
[16] Yi DK, Selvan ST, Lee SS, et al. Silica-coated Nanocomposites of
for Biomedical Applications: Novel Synthesis and Characterization[J].
Magnetic Nanoparticles and Quantum Dots [J]. J. Am. Chem. Soc.,
Motskin M, Wright DM, Muller K, et al. Hydroxyapatite Nano and Microparticles: Correlation of Particle Properties with Cytotoxicity and Biostability [J]. Biomaterials, 2009, 30: 3 307-3 317
[8]
Liu YC, Zhong H, Li LF, et al. Temperature Dependence of Magnetic Property and Photocatalytic Activity of Fe 3 O 4 /Hydroxyapatite Nanoparticles[J]. Materials Research Bulletin, 2010, 45: 2 036-2 039
[9]
Yang PP, Quan ZW, Li CX, et al. Bioactive, Luminescent and Mesoporous Europium-doped Hydroxyapatite as Drug Carrier[J]. Biomaterials, 2008, 29: 4 341-4 347
[10] Mornet S, Vasseur S, Grasnet F, et al. Magnetic Nanoparticle Design for Medical Diagnosis Therapy[J]. J. Mater. Chem., 2004, 14: 2 1612 175 [11]
[J]. J. Phys. Chem. C, 2008, 112: 12 149-12 156 [15] Liu ZY, Yi GS, Zhang HT, et al. Monodisperse Silica Nanoparticles
Acta Biomater., 2005, 1: 65- 83 [7]
219
Matsumoto T, Okazaki M, Inoue M, et al. Hydroxyapatite Particles as A 3 812
[5]
Apr.2013
Chang Q, Zhu LH, Yu C, et al. Synthesis and Properties of Magnetic and Luminescent Fe3O4/SiO2/Dye/SiO2 Nanoparticles[J]. Journal of Luminescence, 2008, 128: 1 890-1 895
[12] Hou CH, Hou SM, Hsueh YS, et al. The in vivo Performance of Biomagnetic Hydroxyapatite Nanoparticles in Cancer Hyperthermia Therapy[J]. Biomaterials, 2009, 30: 3 956-3 960
2005, 127: 4 990-4 991 [17] Tran N, T. Webster J. Gene Expression and Nanoparticle Uptake by Osteoblasts Exposed to Hydroxyapatite Coated Superparamagnetic Nanoparticles[J]. Acta Biomaterialia, 2011, 7: 1 298-1 306 [18] Wakiya N, Yamasai M, Adachi T, et al. Preparation of Hydroxyapatiteferrite Composite Particles by Ultrasonic Spray Pyrolysis[J]. Materials Science and Engineering B, 2010, 173: 195-198 [19] Zhang Y, Li Z, Sun W, et al. A Magnetically Recyclable Heterogeneous Catalyst: Cobalt Nano-oxide Supported on Hydroxyapatite -encapsulated γ-Fe2O3 Nanocrystallites for Highly Efficient Olefin Oxidation with H2O2 [J]. Catalysis Communications, 2008, 10: 237-242 [20] Mamani L, Sheykhan M, Heydari A, et al. Sulfonic acid Supported on Hydroxyapatite-encapsulated γ-Fe 2 O 3 Nanocrystallites as a Magnetically Bronsted Acid for N-formylation of Amines[J]. Applied Catalysis A:General, 2010, 377: 64-69 [21] Cai YR, Pan HH, Xu XR, et al. Ultrasonic Controlled Morphology Transformation of Hollow Calcium Phosphate Nanosphers: A Smart Biocompatible Drug Release System[J]. Chem. Mater., 2007, 19: 3 0813 083 [22] Mori K, Kanai S, Hara T, et al. Development of Ruthenium-
[13] Lu J, Jiao XL, Chen DR, et al. Solvothermal Synthesis and
H y d r o x y a p a t i t e - e n c a p s u l a t e d S u p e r p a r a m a g n e t i c γ - F e 2O 3
Characterization of Fe3O4 and γ-Fe2O3[J]. J. Phys. Chem. C, 2009, 113:
Nanocrystallites and an Efficient Oxidation Catalyst by Molecular
4 012-4 017
Oxygen[J]. Chem. Mater., 2007, 19: 1 249-1 256
