Electrochemical Deposition of Octacalcium Phosphate Micro-fiberchitosan

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Electrochemical deposition of octacalcium phosphate micro-fiber/chitosancomposite coatings on titanium substrates

Xiong Lu a,b,, Yang Leng b , Qiyi Zhang b ,c

aKey Lab of Advanced Technologies of Materials, Ministry of Education, School of Materials Science and Engineering,

Southwest Jiaotong University, Chengdu 610031, Chinab Department of Mechanical Engineering, Hong Kong University of Science and Technology, Kowloon, Hong Kong, China

c The College of Chemical Engineering, Sichuan University, Chengdu 610065, China

Received 13 July 2007; accepted in revised form 19 November 2007Available online 4 December 2007

Abstract

Calcium phosphate/chitosan composites have been extensively studied as bone substitutes, tissue engineering scaffolds, or bone cements. Inthe present study, we have prepared octacalcium phosphate (OCP) micro-fiber/chitosan composite coatings through an electrochemical depositionmethod. OCP coatings with microporous structure, which are woven by micro-fibers with 2030 m in length and 0.11 m in width, have agood ability to incorporate chitosan. This novel OCP micro-fiber/chitosan composite coating could have broad applications in the biomedicalengineering. 2007 Elsevier B.V. All rights reserved.

PACS:81.15.Pq; 87.68.+zKeywords:Electrochemical deposition; Composite coatings; Octacalcium phosphate; Chitosan

1. Introduction

Titanium is the most widely used metallic biomedicalmaterials used in orthopedics due to its good mechanical

properties. Various techniques have been developed to depositbioceramic coatings on titanium substrates to improve theirsurface bioactivity as reviewed by de Groot et al. [1]. Amongthem, electrochemical deposition (ED) is one of the mostcommonly used methods. Ease of processing control, variabilityof the coating composition, the possibility of protein delivery

and the suitability for complex implant geometries have madethe ED method increasingly popular [2]. Different types ofcalcium phosphate (Ca-P) bioceramic coatings have beenachieved with the ED method, such as dicalcium phosphatedehydrate (DCPD, CaHPO42H2O) [3], dicalcium phosphate

anhydrous (DCPA, CaHPO4)[4], octacalcium phosphate (OCP,Ca8(HPO4)2(PO4)45H2O) [5], and hydroxyapatite (HA, Ca10(OH)2(PO4)6)[6,7].

In recent years, there is a tendency to develop organicmaterials/Ca-P composite coatings, such as protein/Ca-P,collagen/Ca-P, on Ti substrates in order to obtain new typesof coatings that are more biocompatible and bioactive [8,9].Chitosan/Ca-P coatings also attract much research interesting[1015]. Chitosan is the copolymer of glucosamine and N-acetyl glucosamine that derives from partially deacetylated

chitin and the idealized chemical structure of chitosan is shownin Fig. 1 [16]. In the past twenty years, chitosan has drawnconsiderable attention in the biomedical areas because it hasmany important properties such as good biocompatibility,minimal foreign body reaction, excellent antimicrobial activity,the ability to be molded in various geometries, and thesuitability for cell ingrowth and osteoconduction [17]. Nowa-days chitosan become one of the most promising biopolymersfor tissue engineering and orthopedic applications and con-siderable attention has been given to chitosan-based materials.Chitosan/CaP composites have also been widely studied as

bone substitute, tissue engineering scaffolds, and bone cements,

Available online at www.sciencedirect.com

Surface & Coatings Technology 202 (2008) 31423147www.elsevier.com/locate/surfcoat

Corresponding author. Key Lab of Advanced Technologies of Materials,Ministry of Education, School of Materials Science and Engineering, SouthwestJiaotong University, Chengdu 610031, China. Tel.: +86 28 87634023; fax: +8628 87601371.

E-mail addresses: [email protected](X. Lu),[email protected](Y. Leng), [email protected](Q. Zhang).

0257-8972/$ - see front matter 2007 Elsevier B.V. All rights reserved.doi:10.1016/j.surfcoat.2007.11.024
mailto:[email protected]:[email protected]:[email protected]://dx.doi.org/10.1016/j.surfcoat.2007.11.024http://dx.doi.org/10.1016/j.surfcoat.2007.11.024mailto:[email protected]:[email protected]:[email protected]


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which demonstrates increased bioactivity and biodegradationtogether with sufficient mechanical strength[1822].

Heretofore there are several reports about Ca-P/Chitosancomposite coatings prepared by ED method. Redepenning et al.

prepared composite coatings containing DCPD/chitosan by EDand the composites were converted to HA/chitosan compositesthrough bathing the samples in 0.1 M NaOH for 7 days at roomtemperature[12]. Wang et al. developed a hybrid Ca-P/chitosancoating through ED and this hybrid coating showed animproved bone marrow stromal cell attachment[10,11]. Note

that the Ca-P phase in the hybrid coatings was a mixture of OCPand HA. Pang et al. employed electrophoretic approach todeposit chemically precipitated HA nanoparticles and chitosantogether to obtain composite coatings with pure HA phase [14].OCP is one important type of Ca-P bioceramics that has beenregarded as the precursor of biological apatite and recent studieshas described the positive role of OCP in osteoconduction andosteoinduction because it is more resorbable and enhances more

bone formation than HA does [23,24]. To the author'sknowledge, although there were several reports about control-ling OCP growth under various condition[25,26], the study of

pure OCP micro-fiber/chitosan composite coatings on titaniumsubstrates is still missing. The objective of this study is to

prepare pure OCP micro-fiber/chitosan coatings on Ti substrateusing ED method. In this paper, experimental results on thefabrication and characterization of OCP/chitosan compositecoatings were reported and the electrochemical depositionmechanism was also discussed.

2. Experimental

Titanium specimens used in this work were commercial puretitanium (Grade 4, CP Ti) obtained from Baoji Special Iron andSteel Co. LTD., China. Before ED processing, the titanium wascut to make plate specimens of 10 mm10 mm1 mm in

dimensions. The specimens were etched in an acidic mixture toremove the natural oxide layer and increase the surfaceroughness. The acidic etching was conducted in a mixedsolution of 98% H2SO4 and 36% HCl and deionized water(volume ratio of H2SO4: HCl: H2O=1:1:1) at 60 C for 1 h.After etching, the specimens were cleaned by ultrasound indeionized water for 15 min.

ED was conducted in the cell that had three electrodes: atitanium plate as the working electrode, a platinum plate as thecounter electrode and a saturated calomel electrode (SCE) as thereference electrode. The titanium plate was welded to connectcopper wire by an electric resistance welder. The weld spot andthe copper wire were sealed with silicone gel. Ca-P/chitosancoating were prepared on cathodic Ti plates in the electrolyte of

an aqueous solution of 12.5 mM Ca(NO3)2 and 5 mMNH4H2PO4 and 4 wt.% chitosan. According to theoreticalanalysis, high Ca-P concentrations help OCP crystal growth,which guide us to use high concentration Ca-P solution [27].The pH value of the electrolyte was buffered by HClTris at

pH = 5. Pure Ca-P coating without chitosan also was prepared as

a comparison. The ED was conducted one hour for eachspecimen at room temperature using a potentiostat/galvanostat(PGP201 Radiometer, Denmark) with the current maintained at1.0 mA/cm2. During the process, the electrolyte was kept staticwithout any stirring so as to obtain well crystalline OCP. Thetitanium plates with coatings were then rinsed with deionizedwater and dried at 50 C overnight.

Scanning electron microscopy (SEM) (JSM 6300, JEOL,Japan), transmission electron microscopy (TEM) (PhilipsCM20, Philips Analytic, The Netherlands) and High ResolutionTEM (HRTEM) (JSM 2010, JEOL, Japan) were used to examinethe morphology and crystal structures of the calcium phosphate

deposits. The TEM samples were extracted from the substrate byan ultrasonic vibration method [28]. The coatings on thetitanium surfaces were also examined using a thin film X-raydiffractometer (TF-XRD) (X'pert pro-MPD, PANalytical, The

Netherlands). The TF-XRD measurements were performed on astage using a Cu-K (wavelength=1.54056 ) X-ray sourcewith a step rate of 0.01 per second. Fourier transform-infraredspectroscopy (FTIR) (FTS 6000, Bio-Rad, USA) was used todetermine the chemical composition of the deposited coatings.

The tensile adhesion strength of the as-prepared coating wasevaluated using a universal mechanical testing machine (Model5567, Instron, USA). The sample was fixed on the stage of thetesting machine and the coating was glued a titanium stub

(diameter 10 mm) that was connected to the crosshead through agrip. The glue was cured for 48 h at room temperature beforetensile testing. A tensile load at the crosshead speed of 1 mm/min was applied to the coating/substrate interface until failureoccurred. The adhesion strength was calculated as the load atfailure divided by the coated area bonded to the stub. Thereported adhesion strength of the coatings was calculated byaveraging measurements of five specimens.

In order to evaluate bioactivity of the coatings, the coatingswere immersed in 200 ml of an acellular simulated body fluid(SBF) with ion concentrations close to that of human blood

plasma at 36.5 C for 7 days. The SBF recipe followed that of

Kokubo [29] and was prepared by dissolving reagent gradeNa Cl (8 .035 g) , Na HCO3(0.355 g), KCl (0.225 g),K2HPO43H2O(0.230 g), MgCl26H2O (0.311 g), CaCl2(0.293 g), and Na2SO4 (0.072 g) into 1 l double-distilledwater and buffering at pH 7.4 with tris-hydroxymethylamino-methane [(CH2OH)3CNH2] and 1 M hydrochloric acid (HCl).The SBF was refreshed every two days in order to keep the ionconcentration stable.

3. Results

Both the OCP/Chitosan and pure OCP coatings areuniformly deposited across the surfaces of titanium substrate.The morphology of coatings under different conditions is totally

Fig. 1. The chemical structure of idealized chitosan.

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different. In OCP/chitosan coatings formed at pH=5, crystallineOCP micro-fibers were observed (Fig. 2a, b) while large flakyOCP crystals were found in pure OCP coatings (Fig. 2c).However, the OCP/chitosan coatings formed at pH=4.5 havemorphologies similar to those of the pure OCP coatings. SEMobservations (Fig. 2a, b) revealed that the OCP fibers are around

2030 m in length while the widths range from 0.1 to 1 m.The aspect ratio of as-synthesized fibers could be as large as100. The variety of length and width of fibers may be due to thedifference of the rate of crystal growth of fibers during synthesis

process. Note that the morphology of OCP fibers are similar to

those obtained by Iijima et al., which might suggest thatchitosan has similar function to amelogenin that controls theoriented and elongated growth of OCP crystals[26].Fig. 1a and

b demonstrated that OCP micro-fibers were woven together to

form porous structures. Chitosan was entrapped in the recessesand covered on the fibers as observed by SEM. On the otherhand, the pure OCP coatings were mainly composed of largeflake-like crystals with the sized around 500 nm in width asrevealed by SEM (Fig. 2c) and TEM micrographs (Fig. 5c).

The TF-XRD spectra showed that the deposits crystals wereOCP. in spite of flake-like or fiber-like crystals. The pure OCPcoatings exhibited distinct diffraction peaks at 2=4.7, 26.0,31.6 corresponding to the (100), (002), (402) crystal plane ofOCP (seeFig. 3). These peaks were the characteristic peaks ofwell-crystallized OCP as listed in JCPDS card #79-0423. Fiber-like OCP/chitosan coatings also had all the typical OCPdiffraction peaks which demonstrated that the micro-fibers were

OCP. Besides, the XRD pattern of fiber-like OCP/chitosancoatings also revealed a weak and broad band at 2ranged from10 to 20 that was the contribution from the chitosan content inthe composite coatings.

The clear evidence of chitosan existence in the fiber-likeOCP/chitosan coatings was from FT-IR investigation (Fig. 4).All the characteristic peaks of OCP were observed in the

Fig. 2. SEM micrographs of OCP/chitosan coatings and pure OCP coatings: (a)

Fiber-like OCP reinforced chitosan coatings; (b) Amplified image of (a); (c)Flake-like pure OCP coatings.

Fig. 3. TF-XRD spectra of different samples: (a) Ti substrate; (b) Pure OCPcoatings; (c) fiber-like OCP/chitosan coatings.

Fig. 4. FTIR spectra of different samples: (a) Pure OCP coatings; (b) Flake-likeOCP/chitosan coatings.

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spectra. A broad band related to the OH stretching vibration ofthe hydrate water in OCP was noticed at 3400 cm1. Thespectral range 9501200 cm1 contains the symmetric and theasymmetric PO stretching modes of the phosphate groups.The spectral range 550700 cm1 contains the bending mode ofthe phosphate group[30,31]. In addition, the unique peaks ofOCP are the stretching mode of HPP4

2 (867 and 917 cm1) andthe hydrogen bending modes of waters of crystallization in OCPcrystal (~1640 cm1)[2]. Additional distinct peaks due to thechemical functional groups of chitosan appeared only in thespectrum of fiber-like OCP/chitosan coatings, which supportedthat chitosan well incorporated in the composite coatings. The

peaks at 2966, 2932, 2869 cm1

caused by aliphatic CHstretching band of CH2 and CH3 [32] and 1458 cm1 were

assigned to CH2 [33]. Another major peak at wave number1730 cm1 was assign to carbonyl group due to the presence ofacetyl group which confirms that the used chitosan is a partiallydeacetylated product [34]. Besides these, the weak band at1380 cm1 was assigned to CH bending and CH stretchingof CH3[35]; the weak band at 1243 cm

1 represented the freeprimary amino group (NH2) at C2 position of glucosamine,which is the major functional group of chitosan. A peak at1400 cm1 represented CO stretching mode of primaryalcoholic group (CH2OH)[36]. Note that there were severalregions that the bands of OCP overlapped with that of chitosan:the significant band of amide group at 1655 cm1 due to the

C_O stretching (amide I) overlapped with that of OCP1640 cm1; the broad band in the region 35503350 cm1

due to the OH stretching vibration of hydrate water in the OCP

Fig. 5. TEM micrographs of individual OCP fiber and flake: (a) bright field image of OCP fiber; (b) SAD of (a); (c) Bright field image of OCP flake; (d) SAD of (c).

Fig. 6. High resolution TEM micrograph of the interface between OCP andchitosan.



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crystal overlapped with the broad band caused by the NHstretching vibration [37]. Apart from above mentioned, noextraneous functional group was detected for the compositecoatings. The FTIR results confirmed that chitosan macro-molecules were intact well in the composites and did notstimulate any unwanted impurity phases.

The orientation and crystal structure of an individual OCPfiber and flake, the interface of OCP/chitosan were furtherexamined by TEM, selected area diffraction (SAD) andHRTEM. Fig. 5 presented the typical bright field image andSAD results of single crystal OCP fibers and flakes. Both thediffraction patterns of the flake-like and fiber-like crystals wereindexed as that of OCP with B =[110], in which the (110)spacing of 0.938 nm revealed the unique OCP structure [2].HRTEM showed the lattice fringe of crystalline OCP graduallytransited to amorphous chitosan, which proved that OCP andchitosan had a smooth interface (Fig. 6). The correspondingFast-Fourier Transformation (FFT) pattern (Fig. 6, inset) of the

HRTEM fringes indicated the diffraction pattern of the OCPstructure with the [110] zone axis, which was in excellentagreement with the SAD patterns inFig. 5.

The tensile test showed that the adhesion strength of the pureOCP coatings was 1.310.33 MPa while the OCP/Chitosan

composite coatings showed the adhesion strength of 7.131.99 MPa. It is well known that the adhesion strength forcoatings formed by deposition is usually rather low, which isalso proved by our results. The adhesion strength was improved

by adding the chitosan into the composite coatings. Thisincrease in adhesion strength could be attributed to the crosslink

effects of chitosan formed during the electrodeposition.Bioactivity is defined as the property of the material to developa direct, adherent, and strong bonding with the bone tissue[38].It has been already confirmed that the bioactivity of orthopedicmaterials can be examined by their capability of forming a

bone-like apatite on their surfaces in SBF with ion concentra-tions nearly equal to those of human blood plasma [3941].Currently, SBF has been widely used for the assessment of the

bioactivity of various materials and for the formation of boneapatite on various implants in vitro. In the present study, SEMobservation showed that a layer of calcium phosphate (Ca-P)deposited on both the pure OCP and OCP/chitosan coatings

after 7 days SBF immersion, which indicated the goodbioactivity of these coatings (seeFig. 7).

4. Discussion

The results of this work demonstrated the possibility of thefabrication of OCP/chitosan composite coatings in acidicchitosan/supersaturated Ca-P mixing solution through an EDmethod. Generally chitosan is insoluble in alkaline conditions.However, it can dissolve easily in acid solution and takes a

positive charge and becomes a cationic polyelectrolyte throughthe following equation[14]:

ChitNH2H2OChitNH3 H2O 1

Then, in the electrochemical cell, electric field enables themotion of the charged chitosan macromolecules towards thecathode surface. On the cathode, the following reaction happenswhich generate hydroxyl ion (OH), resulting in an increasing

pH at the electrode surface:

2H2O2e

H22OH 2

Then OCP precipitates are formed on the cathodic titaniumsurface with all the reactants needed for Ca-P formation [27]:

OH H2PO

4

HPO2

4

H2O 3

OH HPO24 PO34 H2O 4

8Ca2 2HPO24 4PO34 5H2O

Ca8HPO24 2PO

34 4 5H2O 5

At the same time, the chitosan loses its charge and forms aninsoluble deposit on the cathode surface:

ChitNH3 OH

ChitNH2H2O 6

Therefore, it can be speculated that two events will take placeat the cathode surface: OCP will precipitate on the substrate dueto locally increased pH; and positively charged chitosan will

Fig. 7. SEM micrographs show the Ca-P formation on the as-prepared coatings

immersed in SBF after 7 days: (a) Pure OCP coatings; (b) OCP/chitosancoatings.

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also move to the cathode by electric attraction [11]. Finally, aCa-P/chitosan composite coating will be formed on the cathodicsubstrate through ED process from the theoretical point of view.

The most interesting finding of this research is that chitosanmay have the ability to modulate the morphology of OCPcrystals. SEM and TEM micrographs revealed that chitosan was

tightly entrapped within OCP micro-fibers. These results werefurther verified by XRD and FTIR analysis. However, it is stillnot clear how chitosan interact with OCP during the crystal-lization process. One explanation might be that chitosan prefersto be deposited on the microporous coatings woven by OCPfibers with the high aspect ratio due to the large specific surfacearea of the micro-fibers. In the presence of an electric field, theionized chitosan is more easily deposited at the cathode surfaceand then chitosan itself may also modulate Ca-P precipitationand help to form OCP micro-fibers. It was hypothesized that themodulation action of chitosan to some extent is comparablewith that of some proteins, such as amelogenin proteins[25,26].

The modulating action leading to more fibers formation is apositive feedback and helps to attract more chitosan deposition.Considering the two independent processes, i.e. OCP andchitosan deposition, both of them contribute to the formation ofOCP micro-fiber reinforced chitosan composite coatingssimultaneously and synergistically.

5. Conclusions

Composites of chitosan and calcium phosphate have beenstudied widely as bone substitute, tissue engineering scaffolds,or bone cements. This report presented the first stageexperiment results of the OCP micro-fiber reinforced chitosan

composite coatings on titanium substrates synthesized throughan electrodeposition method. OCP has good osteoconductivityand even can enhance more bone formation than HA can.Chitosan helps to enhance osteoblast attachment and prolifera-tion and inhibit fibroblast proliferation. The as-prepared OCP/chitosan coatings combine both the advantages of OCP andchitosan and the microporous structures of the coatings woven

by OCP fibers is in favor of osteoblast adhesion and tissueingrowth. This novel OCP micro-fiber/chitosan compositecoating could be used to increase the bioactivity of titaniumand have broad applications in the biomedical engineering.

Acknowledgement

This project was financially supported by the NationalNatural Science Foundation of China (no. 30700172).

References

[1] K. de Groot, J.G.C. Wolke, J.A. Jansen, Proc. Inst. Mech. Eng. 212 (1998)137.

[2] X. Lu, Z.F. Zhao, Y. Leng, J. Cryst. Growth 284 (2005) 506.[3] M. Kumar, H. Dasarathy, C. Riley, J. Biomed. Mater. Res. 45 (1999) 302.[4] M.H. Prado Da Silva, J.H.C. Lima, G.A. Soares, C.N. Elias, M.C.

de Andrade, S.M. Best, I.R. Gibson, Surf. Coat. Technol. 137 (2001) 270.[5] S. Lin, R.Z. LeGeros, J.P. LeGeros, J. Biomed. Mater. Res. 66A (2003)

819.[6] M. Shirkhanzadeh, J. Mater. Sci., Mater. Med. 9 (1998) 67.

[7] H.B. Hu, C.J. Lin, P.P.Y. Lui, Y. Leng, J. Biomed. Mater. Res. 65A (2003)24.

[8] X.L. Cheng, M. Filiaggi, S.G. Roscoe, Biomaterials. 25 (2004) 5395.[9] Y. Liu, E.B. Hunzikerc, N.X. Randalld, K. de Groot, P. Layrolle,

Biomaterials. 24 (2003) 65.[10] J. Wang, A. van Apeldoorn, K. de Groot, J. Biomed. Mater. Res. 76A

(2006) 503.[11] J. Wang, J. de Boer, K. de Groot, J. Dent. Res. 83 (2004) 296.[12] J. Redepenning, G. Venkataraman, J. Chen, N. Stafford, J. Biomed. Mater.

Res. 66 (2003) 411.[13] J. Pena, I. Izquierdo-Barba, M. Garca, M. Vallet-Reg, J. Eur. Ceram. Soc.

26 (2006) 3631.[14] X. Pang, I. Zhitomirsky, Mater. Chem. Phys. 94 (2005) 245.[15] R.A.A. Muzzarelli, G. Biagini, A. DeBenedittis, P. Mengucci, G. Majni, G.

Tosi, Carbohydr. Polym. 45 (2001) 35.

[16] K. Okuyama, K. Noguchi, M. Kanenari, T. Egawa, K. Osawa, K. Ogawa,Carbohydr. Polym. 41 (2000) 237.

[17] A.D. Martino, M. Sittinger, M.V. Risbud, Biomaterials 26 (2005) 5983.[18] Y. Yokogawa, K. Nishizawa, F. Nagata, T. Kameyama, J. Sol-Gel. Sci.

Technol. 21 (2001) 105.[19] Y. Zhang, M. Zhang, J. Biomed. Mater. Res. 62 (2002) 378.[20] H.K. Xua, C.G. Simon, Biomaterials 26 (2005) 1337.[21] Y. Zhang, M. Zhang, J. Biomed. Mater. Res. 55 (2001) 304.[22] S. Takagia, L. Chow, S. Hirayama, F. Eichmiller, Dent. Mater. 19 (2003)

797.[23] S. Kamakura, Y. Sasano, T. Shimizu, K. Hatori, O. Suzuki, M. Kagayama,

K. Motegi, J. Biomed. Mater. Res. 59 (2002) 29.[24] P. Habibovic, C.M. van der Valk, C.A. van Blitterswijk, K. de Groot,

G. Meijer, J. Mater. Sci. Mater. Med. 15 (2004) 373.[25] M. Iijima, J. Moradian-Oldak, J. Mater. Chem. 14 (2004) 2189.

[26] M. Iijima, Y. Moriwaki, H.B. Wen, A.G. Fincham, J. Moradian-Oldak,J. Dent. Res. 81 (2002) 69.

[27] X. Lu, Y. Leng, Biomaterials 26 (2005) 1097.[28] X. Lu, Y. Leng, Biomaterials 25 (2004) 1779.[29] A. Oyane, H. Kim, T. Furuya, T. Kokubo, T. Miyazaki, T. Nakamura,

J Biomed Mater Res. 65A (2003) 188.[30] A. Stoch, A. Brozek, S. Bazewicz, W. Jastrzebski, J. Stoch, A. Adamczyk,

I. Roj, J. Mol. Struct. 651653 (2003) 389.[31] B.O. Fowler, E.C. Moreno, W.E. Brown, Arch. Oral Biol. 11 (1966)

477.[32] N. Shanmugasundaram, P. Ravichandran, P. Reddy, N. Ramamurty, S. Pal,

K. Panduranga Rao, Biomaterials 22 (2001) 1943.[33] Y.X. Xu, K.M. Kim, M.A. Hanna, D. Nag, Ind. Crops Prod. 21 (2005)

185.[34] A. Pawlak, M. Mucha, Thermochim. Acta 396 (2003) 153.

[35] S. Wang, Q. Huang, Q. Wang, Carbohydr. Res. 340 (2005) 1143.[36] R. Murugan, S. Ramakrishna, Biomaterials 25 (2004) 3829.[37] K. van de Velde, P. Kiekens, Carbohydr. Polym. 58 (2004) 409.[38] L.L. Hench, J. Am. Ceram. Soc. 74 (1991) 1487.[39] T. Kokubo, H.M. Kim, M. Kawashita, Biomaterials 24 (2003) 2161.[40] T. Kokubo, H.M. Kim, M. Kawashita, T. Nakamura, J. Mater. Sci., Mater.

Med. 12 (2004) 99.[41] T. Kokubo, H. Takadama, Biomaterials 27 (2006) 2907.


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Electrochemical Deposition of Octacalcium Phosphate Micro-fiberchitosan