Materials Chemistry and Physicsphysics.utsa.edu/laserlab/publications/papers/2017/Karthi 2017.pdf · 1. Introduction The unique physical and chemical properties exhibited by nanoparticles

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Materials Chemistry and Physics 193 (2017) 356e363

Contents lists avai

Materials Chemistry and Physics

journal homepage: www.elsevier .com/locate/matchemphys

Fluorapatite coated iron oxide nanostructure for biomedicalapplications

S. Karthi a, G.A. Kumar b, D.K. Sardar b, G.C. Dannangoda c, K.S. Martirosyan c, E.K. Girija a, *

a Department of Physics, Periyar University, Salem 636 011, Tamil Nadu, Indiab Department of Physics and Astronomy, University of Texas at San Antonio, San Antonio, TX 78249, USAc Department of Physics, University of Texas at Rio Grande Valley, Brownsville, TX 78520, USA

h i g h l i g h t s

* Corresponding author.E-mail address: [email protected] (E.K.

http://dx.doi.org/10.1016/j.matchemphys.2017.02.0470254-0584/© 2017 Elsevier B.V. All rights reserved.

g r a p h i c a l a b s t r a c t

� Surface modification of Fe3O4 nano-particles is achieved with FAPcoating.

� FAP coated Fe3O4 nanoparticles ex-hibits superparamagnetic nature at300 K.

� Prepared nanoparticles can be a po-tential contrast agent for MRI.

a r t i c l e i n f o

Article history:Received 5 October 2016Received in revised form20 February 2017Accepted 23 February 2017Available online 23 February 2017

Keywords:Iron oxideFluorapatiteBiocompatible coatingNanoparticlesSuperparamagnetic

a b s t r a c t

In the present work, surface modification of iron oxide (Fe3O4) nanoparticles with biocompatible fluo-rapatite (FAP) coating achieved by a simple method and their characterizations using XRD, TEM, FT-IR,DSC and VSM are reported. TEM images revealed the spherical morphology of Fe3O4 nanoparticle androd-like FAP coated Fe3O4 nanoparticles with size of about 12 and 30 nm, respectively. Magnetic mea-surements (M-H) of both the samples exhibited superparamagnetic behavior at 300 K. FAP coated Fe3O4

nanoparticles enhance the cell viability and colloidal stability when compared to Fe3O4 nanoparticles.These results demonstrate that FAP coated Fe3O4 nanoparticles could be a suitable candidate forbiomedical applications.

© 2017 Elsevier B.V. All rights reserved.

1. Introduction

The unique physical and chemical properties exhibited bynanoparticles make them attractive materials for applications in

Girija).

various fields including magnetic separation, magnetic resonancetechnology, low friction seals, damping and cooling agents, etc.[1e4]. The interesting magnetic properties, biocompatibility andstability of nanoscale Fe3O4 exploited it for various biomedicalapplications like magnetic resonance imaging (MRI), drug delivery,tissue engineering, bioseparation, hyperthermia, etc. [5,6]. Thereare several methods based on both top down and bottom up

S. Karthi et al. / Materials Chemistry and Physics 193 (2017) 356e363 357

approaches for Fe3O4 nanoparticle synthesis [5e7]. Among them,co-precipitation is a less expensive bottom up approach to syn-thesize monodispersed, size and shape controlled nanoparticlesand it is the widely used method for the synthesis of Fe3O4 nano-particles [8].

Surface modification of Fe3O4 nanoparticles is important inbioapplications for improving their effective biodistribuion, hy-drophilicity, colloidal stability, biocompatibility, and conjugation ofbioactive functional groups [9]. Surface modification of Fe3O4 usingorganic materials such as capping agents, polymers, etc. and inor-ganic ceramic materials are reported widely [6,10e18]. The harshin vivo conditions may lead to the disappearance of the organicsurface coatings and also the utilization of organic solvent as re-agents for generating the organic coatings is a concern from thetoxicity point of view. Hence surface modification using inorganicmatrix may be more effective [19e21].

Hydroxyapatite [Ca10(PO4)6(OH)2, HAP], a calcium phosphatephase with Ca/P ratio 1.67 is a biomaterial due to its excellentproperties such as biocompatibility, bioactivity and osteoinductiveand osteoconductive nature [22]. HAP basedmagnetic materials aredeveloped for hyperthermia applications but the saturationmagnetization was less and was found to be difficult to reach thehyperthermia temperature [23e28]. Fluorapatite [Ca10(PO4)6(F)2,FAP], have gained greater attention from researchers because oftheir potential use as biomedical materials, for applications such ascoating material for metallic implants, dental implants, drug de-livery and deep tissue bioimaging due to its excellent biocompati-bility and similarity to the component of human bones [29,30]. FAPmaterials are also identified as potential candidates for cell tar-geting [31]. FAP contains four nonequivalent ions such as F�, PO4

3�,Ca2þ (I) and Ca2þ (II) and it crystallizes in hexagonal system withP63/m space group [32]. FAP exhibits better physicochemicalproperties such as thermal stability, chemical stability, crystallinity,corrosion resistance, cell proliferation and osteointegration whencompared to HAP [33,34].

There are several reports on the investigations of HAP-magneticnanoparticle based systems for magnetic property based biomed-ical applications. Likewise, employing FAP as a coating over Fe3O4nanoparticles may also be an appropriate approach to improve thebioapplications of Fe3O4. This paper aims to investigate a simplemethod for the synthesis of FAP coated Fe3O4 nanoparticles and toanalyze the physico-chemical and magnetic characteristics of it forbiomedical applications.

2. Experimental procedure

2.1. Materials

Analytical grade ferric chloride hexahydrate (FeCl3$6H2O, 99%),ferrous sulphate heptahydrate (FeSO4$7H2O, 98%), calcium nitratetetrahydrate (Ca(NO3)2$4H2O, 98%), di-ammonium hydrogenphosphate ((NH4)2HPO4, 99%), ammonium fluoride (NH4F, 95%),trisodium citrate dihydrate (Na3C6H5O7$2H2O, 99%) and ammoniasolution (NH4OH, 25%) purchased from Merck were used for theexperiments without any further purification. Double distilledwater was employed as the solvent.

2.2. Synthesis of Fe3O4 nanoparticles

Nanoparticles of Fe3O4 was prepared by co-precipitationmethod [35]. In brief, FeSO4$7H2O and FeCl3$6H2O were mixed ina molar ratio 1: 2 to which NH4OH (12 M) was added drop by dropwith continuous stirring. This resulted in the formation of a blackprecipitate which was aged for 24 h. The precipitate was thenwashed 3 times with double distilled water to remove the

byproducts and the product was dried over night at 100 �C. Thissample will be referred hereafter as K1.

2.3. Preparation of FAP coated Fe3O4 nanoparticles

0.5 M Ca(NO3)2$4H2O solution was mixed with 0.167 M ofNa3C6H5O7$2H2O to form Ca-citrate complex. 0.5 g of Fe3O4 syn-thesized using the above mentioned procedure was added to itunder vigorous stirring. To this mixture 0.3 M (NH4)2HPO4 and0.1 M NH4F solution was added dropwise followed by vigorousstirring for 1 h, while maintaining the pH of the mixture above 10by adding NH4OH solution. The suspension was aged for 24 h atroom temperature then the precipitate was removed by centri-fuging at 5000 rpm and subsequently washed thrice with doubledistilled water. The obtained precipitate was dried using freezedryer (Boyikang Laboratory Instruments, China) and the samplewill be further referred as K2.

2.4. Characterizations

The powder X-ray diffraction (XRD) measurements of Fe3O4 andFAP coated Fe3O4 nanoparticles were done using a Rigaku MiniFlexII powder X-ray diffractometer in the 20e70� range with CuKa(l¼ 1.5406Å) to determine the phase and structure of the particles.The morphology of the samples was examined using high-resolution transmission electron microscopy (HRTEM, JEOL JEM-2010, Japan). The sample was dispersed in ethanol and drop cas-ted onto carbon coated Cu grids of 200 mesh and used for TEManalysis. Fourier transform infrared (FT-IR) spectra of Fe3O4 and FAPcoated Fe3O4 were recorded in the region of 4000e400 cm�1 with a4 cm�1 resolution using a Perkin Elmer RX I FT-IR spectrometer byKBr pellet technique. The zeta potentials of K1 and K2 samples weredetermined in aqueous solution by using a Malvern zetasizer nanoZS system. Thermo-gravimetric analyses (TGA) were performed byDifferential Scanning Calorimeter (Q-600, TA instrument) to esti-mate weight loss percentage in the sample and pre-calibrated forheat flow curve integration. The sensitivity of DSC-Q600 is 0.1 mg. InDSC/TGA measurement, samples were heated from ambient tem-perature to 750 �C with a heating rate of 20 �C/min under airatmosphere.

Magnetic characterization was conducted by using PhysicalProperty Measurement System (PPMS Evercool-2, QuantumDesign, Inc.) with vibrating sample magnetometer (VSM). Hyster-esis loops (M-H) were measured under a maximum applied field of9 T at 5 K and 300 K. Coercivity (HC) and saturation magnetization(MS) were evaluated using M (H) curves. Temperature dependenceof magnetization measurement, Zero-field-cooling (ZFC) and Field-Cooling (FC) curves were measured in the temperature range from2 K to 300 K using field of 100 Oe. K1 and K2 samples weredispersed in distilled water at different concentrations for T2weighted MR imaging. MR imaging experiments were performedwith a 1.5 T MRI health scanner (Acheiva, Philips). T2-weightedimages were recorded in spin echo pulse sequence with thefollowing parameters: repetition time (TR) 6000ms; echo time (TE)120ms; field of view (FOV) 20� 20 cm;matrix size 256� 256; slicethickness 5 mm.

The cytocompatibility of K1 and K2 samples were tested withhuman osteoblast like MG-63 cells using by MTT assay. The cellswere grown in Eagles Minimum Essential Medium containing 10%fetal bovine serum (FBS) with 100 U per ml penicillin-streptomycinat 37 �C under humidified atmosphere of 95% air and 5% CO2.Maintained cultures were passaged every week and the culturemedium was changed twice a week. The monolayer cells weredetached with trypsin-ethylenediaminetetraacetic acid (EDTA) tomake single cell suspensions and viable cells were counted using a

Fig. 2. TEM images and SAED pattern of (a, b) K1 and (c, d) K2 samples.

S. Karthi et al. / Materials Chemistry and Physics 193 (2017) 356e363358

hemocytometer and diluted with a medium containing 5% FBS togive a final density of 1 � 105 cells per ml. 100 ml per well of cellsuspension were seeded into 96 well plates at a plating density of10000 cells per well and incubated at 37 �C in 5% CO2, 95% air and100% relative humidity. After 24 h incubation, samples K1 and K2were added to the culture medium at different dosages (25, 50, 100,250 and 500 mgml�1). The plates were further incubated for 48 h at37 �C in 5% CO2, 95% air and 100% relative humidity.

After 48 h incubation, 15 ml of 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) solution (5 mgml�1 in phos-phate buffer saline (PBS)) was added into each well and the platewas further incubated for 4 h in the incubator. After discarding thesupernatants, the dark blue formazan crystals were dissolved in100 ml dimethyl sulfoxide (DMSO) and the optical density wasmeasured using a Synergy H4 micro plate reader at 570 nm. Themean and the standard deviationwere obtained from sums of threedifferent experiments. The cell viability was calculated by using thefollowing equation

Cell viabilityð%Þ ¼�ODsampleODcontrol

�� 100

where ODsample and ODcontrol represent the optical density (OD)values of cells cultured with the sample and without the sample,respectively.

3. Results and discussion

Powder XRD patterns of K1 and K2 samples (Fe3O4 and FAPcoated Fe3O4 nanoparticles) are shown in Fig. 1. The peaks (220),(311), (400), (333) and (440) observed in the XRD pattern of Fe3O4are well in agreement with the face-centered cubic pattern of Fe3O4(JCPDS card no. 82-1533). The XRD pattern of FAP coated Fe3O4

Fig. 1. XRD pattern of K

nanoparticles revealed the diffraction peaks of both FAP (JCPDScard no. 15-0876) and Fe3O4. The diffraction peaks from FAP aremore intense but the intensity of the Fe3O4 phase reduced signifi-cantly after coating with FAP. The crystallite size calculated fromXRD data using the Debye-Scherrer approximation is 26 and 41 nmfor K1 and K2 samples, respectively.

Fig. 2(a) and (c) shows the TEM images of K1 and K2 nano-particles. Fe3O4 nanoparticles exhibits spherical morphology withaverage particle size of about 12 nm but are agglomerated. While,FAP coated Fe3O4 nanoparticles are found to be surrounded by rodlike FAP nanoparticles and the average size of these nanostructures

1 and K2 samples.

Fig. 4. Zeta potential of K1 and K2 samples.

Fig. 5. FTIR spectra of K1 and K2 samples.

S. Karthi et al. / Materials Chemistry and Physics 193 (2017) 356e363 359

are about 30 nm. Selected Area Electron diffraction (SAED) patternof K1 and K2 nanoparticles are given in Fig. 2(b) and (d). Adiffraction spot pattern is observed for Fe3O4 nanoparticles indi-cating the single crystalline nature of sample. FAP coated Fe3O4nanoparticles exhibits continuous ring around bright spot revealingthe polycrystalline nature. Particle size distributions (PSD) of thesamples are obtained using the image analysis program ImageJ andthe results of particle size distribution of K1 and K2 samples areshown in Fig. 3.

Colloidal stability of nanoparticles is a key factor of biomedicalapplications. The zeta potential of K1 and K2 nanoparticles sus-pension inwater are shown in Fig. 4.The Zeta potential of K1 and K2are �9.08 and �11.7 mV, respectively, the value for K2 nano-particles is more negative than K1. The aggregation of sample K2 inwater is less as compared to K1, which improves colloidal stabilitywith increasing zeta potential values. This result indicates that theK2 nanoparticles can be considered as a potential candidate forbiomedical applications such as hyperthermia, MRI and drugdelivery.

Fig. 5 illustrates the FT-IR spectra of K1 and K2 samples. Thepeak present at 547 cm�1 in the K1 spectrum is attributed to FeeOstretching vibration [35]. The peaks corresponding to the watermolecules associated with Fe3O4 are seen at 3425 cm�1 and1627 cm�1. The characteristic PO4

3- (y4) vibrations of FAP appearedat 570 and 601 cm�1 alongwith other phosphate peaks at 470 cm�1

(y1), 972 cm�1 (y2), and 1064 cm�1 (y3). The broad band envelopebetween 2000 and 3750 cm�1 could be assigned to H2O molecules.The HeOeH bending mode of lattice water molecules appears at1627 cm�1 [36,37]. The absorption band observed at 1411 and1589 cm�1 correspond to antisymmetric and symmetric modes ofthe carboxylic group yas (OeCeO) and ys (OeCeO) respectively[38].

Fig. 6 shows the thermo-gravimetric analysis for the K2 sample.DSC curves show initial weight loss up to 225 �C with endothermiceffect of 272 J/g with peak value around 70 �C due to the desorptionof adsorbed water and additional weight loss from 250 �C to 400 �Cis due to the loss of lattice water with the exothermic effect of 249 J/g with the peak value at 313 �C. The total weight lost accounted was14 wt %, which is in a good agreement with published data [39].

Figs. 7 and 8 show the magnetic field dependence of magneti-zation (M-H) of K1 and K2 measured at 5 K and 300 K withexpanded scale of the low field in the insets. It can be seen clearlyfrom Fig. 7, at 5 K the K1 shows ferromagnetic behavior with adistinct coercivity (17.9 mT), while the coercive field becomesalmost zero (1.5 mT) at 300 K where K1 is close to become super-paramagnetic state. At 300 K, K2 sample also exhibits super-paramagnetic behavior with no noticeable remanence and

Fig. 3. Particle size distribution o

coercivity (1.6 mT), whereas exhibits a ferromagnetic behavior witha coercivity of 17.8 mT at 5 K (Fig. 8).

f (a) K1 and (b) K2 samples.

Fig. 6. Heat flow and weight change dependence on the temperature for of K2 sample.

Fig. 7. M-H curve of K1 at 5 K and 300 K (Insets are the expanded scale of the low fieldregion).

Fig. 8. M e H curve of K2 at 5 K and 300 K (Insets are the expanded scale of the lowfield region).

Table 1Comparison of coercivity and saturation magnetization.

Materials Temperature(K)

Coercivity(mT)

Saturationmagnetization(emu/g)

Reference

Fe3O4 100 16.08 55.74 [37]300 1.68 51.68 [37]10 34.9 57.1 [38]

HA-Ferrite Composite 300 12.0 0.83 [39]Magnetic-HAP

composite300 7.9 7.40 [40]

K1 5 17.9 79.2 Presentstudy300 1.5 71.7

K2 5 17.8 11.6300 1.6 9.7

S. Karthi et al. / Materials Chemistry and Physics 193 (2017) 356e363360

Saturation magnetization was obtained from the relationshipM(H) ¼ MS(1 � b/H), where b is a field independent parameter,extrapolating to zero field the experimental M(H) curve from thehigh magnetic field range where the magnetization varies linearlywith H. Calculated values of coercivity and saturation magnetiza-tion of K1 and K2 are summarized in Table 1. Saturation magneti-zation gets reduced drastically in the case of K2 sample for both 5 Kand 300 K when compared to K1. The calculated saturationmagnetization and coercivity values reported for similar sizedFe3O4 and Fe3O4-HAP composite materials are given in Table 1[40e43].

The reduction of saturated magnetization and coercivity of K2sample when compared to Fe3O4 is due to the diamagneticcontribution of the FAP surrounding the Fe3O4 nanoparticles.NiFe2O4 embedded in a HAP-tricalcium phosphate (TCP) matrixwith saturated magnetization value 1.15 emu/g was able togenerate temperature of about 90 �C in less than 2 min [44]. Theseresults indicate that the K2 sample may be a potential candidate forhyperthermia applications.

Variation of magnetization (M) with magnetic field (H) can beestimated by using simple Langevin function [45],

M ¼ M0LðbÞ ¼ M0½cothðbÞ � 1=b�;

where b ¼ mH/kbT, m (¼MsV) is magnetic moment of the particle, Vis the particle volume, Ms is the saturation magnetization of thebulkmaterial andM0 is the saturationmagnetization of the sample.kb and T are Boltzmann constant and temperature, respectively.Fig. 9 shows the experimental and theoretical curves of sample K1and K2 at 300 K. The calculated values using Langevin function maydeviate from the experimental values due to the facts such asparticle size distribution, anisotropy (inhomogeneous particles)and interparticle interaction (exchange and dipole coupling). Byassuming uniform particle size and negligible anisotropy andinterparticle interaction, average magnetic moments per particleswere calculated for K1 and K2 as 20823mB and 24030mB, respec-tively. Average particle diameter was calculated by assuming all theparticles have spherical shape and they were 10.3 nm and 21.1 nmfor K1 and K2 samples, respectively. These values are in goodagreement with the values obtained from the TEM measurements.

Fig. 10 shows the ZFC and FC curves of K1 and K2 samples.Temperature dependence of magnetization measurements wereperformed by cooling down the sample from 300 K to 2 K withoutapplying any magnetic field so that particles will be blockedrandomly. After reaching 2 K, by applying a small field of 10 mT

Fig. 9. Experimental M-H and theoretical (Langevin) fits of K1 and K2 samples at300 K.

Fig. 10. Temperature variation of MZFC and MFC of K1 and K2, B ¼ 10 mT.

Fig. 12. Cell viability of K1 and K2 samples with human osteoblast MG-63 Cells.

S. Karthi et al. / Materials Chemistry and Physics 193 (2017) 356e363 361

sample was heated up to 300 K while measuring the magnetizationto obtain the ZFC curve. FC curve is obtained by cooling down thesample from 300 K to 2 K while the field is applied.

The information about particle size distribution, blocking tem-perature and dipole interparticle interaction can be extracted fromthe ZFC/FC curves. When temperature increases with applied

Fig. 11. T2-weight MR images of K1 and K2 samples at different concentrations.

magnetic field, particles tend to block along its easy magnetizationdirection and reach themaximum at a temperature, which dependson the particle volume, anisotropy and orientation.

Since the blocking temperature depends on the size of thecrystallites, each crystallite with specific volume distributionblocked at a different temperature creates broad peak in the ZFCcurve. Peak temperature in ZFC curve is a representation of averageblocking temperature of all the different particle sizes. Furtherincreasing the temperature will upraise the thermal energycompared to the anisotropy energy of the particle. This will makethe particle to be unblocked and behave as superparamagnetic.When the ZFC/FC curves of K1 and K2 are compared, missing peaksin ZFC and non-overlapping ZFC/FC curves make it difficult todetermine the blocking temperature clearly. Also, it suggests thatparticles may not behave as superparamagnetic below 300 K [46].Fig. 11 shows the T2 weighted images of K1 and K2 samples atvarious concentrations ranging from 0 to 100 mg/ml. As the con-centration of K1 and K2 samples increased, MRI signal intensitycontinuously decreased, resulting in darker images. This resultsuggests that K1 and K2 samples have a potential application as aMRI contrast agent.

In vitro cytotoxicity assays is the primary biocompatibilityscreening tests for materials used in vivo biomedical applications.Fig. 12 shows the viability effects of varying concentrations(12.5e500 mg/ml) of K1 and K2 nanoparticles on human osteoblastlike MG-63 cells using MTT assay. From the cytotoxicity data, it isfound that the cell viability gradually decreases with increasingconcentration in both the samples. Sample K2 did not exhibit anysignificant toxicity up to 500 mg/ml whereas sample K1 is not toxicupto the cell concentration of 200 mg/ml. According to biologicalevaluation of medical devices-Part 5: tests for in vitro cytotoxicity(ISO 10993-5: 2009), if cell viability of the material is less than 70%then it has a cytotoxic potential [47,48]. Optical images of osteoblastMG-63 cells and cells containing different dosages of the K1 and K2nanoparticles for 48 h incubation are shown in Fig. 13. The obtainedresults demonstrate the good biocompatibility and cell prolifera-tion of the K2 nanoparticles compared to K1 nanoparticles. Thedecreased toxic effect of K2 may be due to the FAP coated on Fe3O4nanoparticles. The result shows that the K2 nanoparticles can beideal candidate for use in hyperthermia applications.

Fig. 13. Optical microscope image of different dosages of K1 and K2 samples with MG-63 cells.

S. Karthi et al. / Materials Chemistry and Physics 193 (2017) 356e363362

4. Conclusions

In summary, we report that the surface modified Fe3O4 nano-particles with FAP nanorods. TEM image showed 12 nm sized ironoxide nanoparticles covered by FAP with average size of 30 nm. FT-IR and TGA-DSC analysis confirmed the coating of fluorapatite onthe surface of iron oxide nanoparticles. The nanoparticles weresuperparamagnetic in nature at room temperature with saturatedmagnetization values of 71.7 and 9.7 emu/g for Fe3O4 and FAPcoated Fe3O4 nanoparticles, respectively. Zero field cooling andfield cooling results suggest that particles may not behave assuperparamagnetic below 300 K. FAP coated Fe3O4 nanoparticlescan be considered as a potential material for drug delivery appli-cations, hyperthermia and as an inorganic MRI contrast agent.

Acknowledgements

Author EKG acknowledges University Grants Commission, Indiathrough project (Project Ref. no. 41-1013/2012 SR). Author SKthanks to Periyar University for providing fellowship under URF.Authors GAK, DKS and KSM would like to acknowledge the finan-cial support from the National Science Foundation Partnerships forResearch and Education in Materials (NSF-PREM) grants DMR-0934218 and DMR-1523577.

References

[1] Y.M. Huh, Y.W. Jun, H.T. Song, S.W. Kim, J.S. Choi, J.H. Lee, S. Yoon, K.S. Kim,J.S. Shin, J.S. Suh, J. Cheon, In vivo magnetic resonance detection of cancer byusing multifunctional magnetic nanocrystals, J. Am. Chem. Soc. 127 (2005)12387e12391.

[2] J.M. Perez, F.J. Simeone, Y. Saeki, L. Josephson, R. Weissleder, Viral-inducedself-assembly of magnetic nanoparticles allows the detection of viral particlesin biological media, J. Am. Chem. Soc. 125 (2003) 10192e10193.

[3] B.M. Berkovsky, V.F. Medvedev, M.S. Krakov, Magnetic Fluids (in Russian),Moskva “Himia”, 1989, pp. 132e171. Ch. 4.

[4] K. Raj, Magnetic fluids and devices: a commercial survey, in: B. Berkovsky,V. bashtovoi (Eds.), Magnetic Fluids and Applications Handbook, Begell House,New York, 1996, pp. 657e751.

[5] S. Laurent, D. Forge, M. Port, A. Roch, C. Robic, L.V. Elst, R.N. Muller, Magneticiron oxide nanoparticles: synthesis, stabilization, vectorization, physico-chemical characterizations, and biological applications, Chem. Rev. 108 (2008)2064e2110.

[6] M. Mahmoudi, S. Sant, B. Wang, S. Laurent, T. Sen, Superparamagnetic ironoxide nanoparticles (SPIONs): development, surface modification and appli-cations in chemotherapy, Adv. Drug Deliv. Rev. 63 (2011) 24e46.

[7] T.D. Schladt, K. Schneider, H. Schild, W. Tremel, Synthesis and bio-functionalization of magnetic nanoparticles for medical diagnosis and treat-ment, Dalton Trans. 40 (2011) 6315e6343.

[8] M. Sairam, B.V.K. Naidu, S.K. Nataraj, B. Sreedhar, T.M. Aminabhavi, Poly(vinylalcohol)-iron oxide nanocomposite membranes for pervaporation dehydra-tion of isopropanol, 1,4-dioxane and tetrahydrofuran, J. Membr. Sci. 283(2006) 65e73.

[9] D.B. Shieh, F.Y. Cheng, C.H. Su, C.S. Yeh, M.T. Wu, Y.N. Wu, C.Y. Tsai, C.L. Wu,D.H. Chen, C.H. Chou, Aqueous dispersions of magnetite nanoparticles withNH3þ surfaces for magnetic manipulations of biomolecules and MRI contrastagents, Biomaterials 26 (2005) 7183e7191.

[10] J.I. Simkiene, M. Treideris, G. Niauraa, R. Szymczak, P. Aleshkevych, A. Reza,I. Kasalynas, V. Bukauskas, G.J. Babonas, Multifunctional iron and iron oxidenanoparticles in silica, Mater. Chem. Phys. 130 (2011) 1026e1032.

[11] A.K. Hauser, R. Mathias, K.W. Anderson, J.Z. Hilt, The effects of synthesismethod on the physical and chemical properties of dextran coated iron oxidenanoparticles, Mater. Chem. Phys. 160 (2015) 177e186.

[12] E. Amstad, M. Textor, E. Reimhult, Stabilization and functionalization of ironoxide nanoparticles for biomedical applications, Nanoscale 3 (2011)2819e2843.

[13] L. Bronstein, X. Huang, J. Retrum, A. Schmucker, M. Pink, B. Stein, B. Dragnea,Influence of iron oleate complex structure on iron oxide nanoparticle for-mation, Chem. Mater. 19 (2007) 3624e3632.

[14] Z.Ü. Akal, L. Alpsoya, A. Baykal, Biomedical applications of SPION@APTES@PEG- folic acid@ carboxylated quercetin nanodrug on various cancer cells,Appl. Surf. Sci. 378 (2016) 572e581.

[15] Z.Ü. Akal, L. Alpsoy, A. Baykal, Superparamagnetic iron oxide conjugated withfolic acid and carboxylated quercetin for chemotherapy applications, Ceram.Int. 42 (2016) 9065e9072.

[16] N. Kemikli, H. Kavas, S. Kazan, A. Baykal, R. Ozturk, Synthesis of protopor-phyrin coated SPION via dopamine anchor, J. Alloys Compd. 502 (2010)439e444.

[17] R.A. Pareta, E. Taylor, T.J. Webster, Increased osteoblast density in the pres-ence of novel calcium phosphate coated magnetic nanoparticles, Nanotech-nology 19 (2008) 265101.

[18] N. Tran, Thomas J. Webster, Increased osteoblast functions in the presence ofhydroxyapatite-coated iron oxide nanoparticles, Acta Biomater. 7 (2011)1298e1306.

[19] Y. Zhang, N. Kohler, M. Zhang, Surface modification of superparamagneticmagnetite nanoparticles and their intracellular uptake, Biomaterials 23 (2002)1553e1561.

[20] S.M. Moghimi, A.C. Hunter, J.C. Murray, Long-circulating and target-specificnanoparticles: theory to practice, Pharmacol. Rev. 53 (2001) 283e318.

[21] E.M. Moreno, M. Zayat, M.P. Morales, C.J. Serna, A. Roig, D. Levy, Preparation ofnarrow size distribution superparamagnetic g-Fe2O3 nanoparticles in a sol-�gel transparent SiO2 matrix, Langmuir 18 (2002) 4972e4978.

[22] M. Vallet-Reg, J.M. Gonzlez-Calbet, Calcium phosphates as substitution ofbone tissues, Prog. Solid State Chem. 32 (2004) 1e31.

[23] A. Tampieri, T. D’Alessandro, M. Sandri, S. Sprio, E. Landi, L. Bertinetti,S. Panseri, G. Pepponi, J. Goettlicher, M. Banobre-Lopez, J. Rivas, Intrinsicmagnetism and hyperthermia in bioactive Fe-doped hydroxyapatite, ActaBiomater. 8 (2012) 843e851.

[24] C. Hou, S. Hou, Y. Hsueh, J. Lin, H. Wu, F. Lin, The in vivo performance ofbiomagnetic hydroxyapatite nanoparticles in cancer hyperthermia therapy,

S. Karthi et al. / Materials Chemistry and Physics 193 (2017) 356e363 363

Biomaterials 30 (2009) 3956e3960.[25] S. Murakami, T. Hosono, B. Jeyadevan, M. Kamitakahara, K. Ioku, Hydrother-

mal synthesis of magnetite/hydroxyapatite composite material for hyper-thermia therapy for bone cancer, J. Ceram. Soc. Jpn. 116 (2008) 950e954.

[26] E. Andronescu, M. Ficai, G. Voicu, D. Ficai, M. Maganu, A. Ficai, Synthesis andcharacterization of collagen/hydroxyapatite: magnetite composite materialfor bone cancer treatment, J. Mater. Sci. Mater. Med. 21 (2010) 2237e2242.

[27] E.M. Muzquiz-Ramos, D.A. Cortes-Hernandez, J. Escobedo-Bocardo, Bio-mimetic apatite coating on magnetite particles, Mater. Lett. 64 (2010)1117e1119.

[28] H. Wu, T. Wang, J. Sun, W. Wang, F. Lin, A novel biomagnetic nanoparticlebased on hydroxyapatite, Nanotechnology 18 (2007) 165601.

[29] V.J. Shirtliff, L.L. Hench, Bioactive materials for tissue engineering, regenera-tion and repair, J. Mater. Sci. 38 (2003) 4697e4707.

[30] M. Mazaheri, M. Haghighatzadeh, A.M. Zahedi, S.K. Sadrnezhaad, Effect of anovel sintering process on mechanical properties of hydroxyapatite ceramics,J. Alloys Compd. 471 (2009) 180e184.

[31] S. Karthi, G.S. Kumar, G.A. Kumar, D.K. Sardar, C. Santhosh, E.K. Girija, Mi-crowave assisted synthesis and characterizations of near infrared emitting Yb/Er doped fluorapatite nanoparticles, J. Alloys Compd. 689 (2016) 525e532.

[32] N. Leroy, E. Bres, Structure and substitutions in fluorapatite, Eur. Cells Mater 2(2001) 36e48.

[33] D. Lexa, Preparation and physical characteristics of a lithium-beryllium-substituted fluorapatite, Metal. Mater. Trans. A 30 (1999) 147e153.

[34] C.J. Tredwin, A.M. Young, E.A.A. Neel, G. Georgiou, J.C. Knowles, Hydroxyap-atite, fluor-hydroxyapatite and fluorapatite produced via the sol-gel method:dissolution behaviour and biological properties after crystallization, J. Mater.Sci. Mater. Med. 25 (2014) 47e53.

[35] N.V. Jadhav, A.I. Prasad, Amit Kumar, R. Mishra, S. Dhara, K.R. Babu,C.L. Prajapat, N.L. Misra, R.S. Ningthoujam, B.N. Pandey, R.K. Vatsa, Synthesis ofoleic acid functionalized Fe3O4 magnetic nanoparticles and studying theirinteraction with tumor cells for potential hyperthermia applications, ColloidsSurf. B 108 (2013) 158e168.

[36] M.H. Fathi, E.M. Zahrani, Fabrication and characterization of fluoridated hy-droxyapatite nanopowders via mechanical alloying, J. Alloys Compd. 475(2009) 408e414.

[37] N. Johari, M.H. Fathi, M.A. Golozar, The effect of fluorine content on the me-chanical properties of poly ( 3-caprolactone)/nano-fluoridated hydroxyapatite

scaffold for bone-tissue engineering, Ceram. Int. 37 (2011) 3247e3251.[38] C. Zhang, S. Huang, D. Yang, X. Kang, M. Shang, C. Peng, J. Lin, Tunable

luminescence in Ce3þ, Mn2þ-codoped calcium fluorapatite through combiningemissions and modulation of excitation: a novel strategy to white lightemission, J. Mater. Chem. 20 (2010) 6674e6680.

[39] T. Iwasaki, R. Nakatsuka, K. Murase, H. Takata, H. Nakamura, S. Watano,Simple and rapid synthesis of magnetite/hydroxyapatite composites for hy-perthermia treatments via a mechanochemical route, Int. J. Mol. Sci. 14 (2013)9365e9378.

[40] P.B. Shete, R.M. Patil, N.D. Thorat, A. Prasad, R.S. Ningthoujam, S.J. Ghosh,S.H. Pawar, Magnetic chitosan nanocomposite for hyperthermia therapyapplication: preparation, characterization and in vitro experiments, Appl.Surf. Sci. 288 (2014) 149e157.

[41] F. Dilnawaz, A. Singh, C. Mohanty, S.K. Sahoo, Dual drug loaded super-paramagnetic iron oxide nanoparticles for targeted cancer therapy, Bio-materials 31 (2010) 3694e3706.

[42] N. Wakiya, M. Yamasaki, T. Adachi, A. Inukai, N. Sakamoto, D. Fu, O. Sakurai,K. Shinozaki, H. Suzuki, Preparation of hydroxyapatite-ferrite compositeparticles by ultrasonic spray pyrolysis, Mate. Sci. Eng. B 173 (2010) 195e198.

[43] D. Gopi, M.T. Ansari, E. Shinyjoy, L. Kavitha, Synthesis and spectroscopiccharacterization of magnetic hydroxyapatite nanocomposite using ultrasonicirradiation, Spectrochim. Acta Part A 87 (2012) 245e250.

[44] R. Karunamoorthi, G. Suresh Kumar, A.I. Prasad, R.K. Vatsa, A. Thamizhavel,E.K. Girija, Fabrication of a novel biocompatible magnetic biomaterial withhyperthermia potential, J. Am. Ceram. Soc. 97 (2014) 1115e1122.

[45] R.W. Chantrell, J. Popplewell, S.W. Charles, Measurements of particle sizedistribution parameters in ferrofluids, IEEE Trans. Magn. MAG 14 (1978)975e977.

[46] A. Gloria, T. Russo, U. D’Amora, S. Zeppetelli, T. D’Alessandro, M. Sandri,M. Ba~nobre-L�opez, Y. Pi~neiro-Redondo, M. Uhlarz, A. Tampieri, J. Rivas,T. Herrmannsd€orfer, V.A. Dediu, L. Ambrosio, R. De Santis, Magnetic poly(ε-caprolactone)/iron-doped hydroxyapatite nanocomposite substrates foradvanced bone tissue engineering, J. R. Soc. Interface 10 (2013) 20120833.

[47] http://www.iso.org/iso/home.html.[48] G.S. Kumar, R. Govindan, E.K. Girija, In situ synthesis, characterization and

in vitro studies of ciprofloxacin loaded hydroxyapatite nanoparticles for thetreatment of osteomyelitis, J. Mater. Chem. B 2 (2014) 5052e5060.