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Page 1: Preparation and characterization of nano hydroxyapatite/polymeric composites materials. Part I

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Materials Chemistry and Physics 130 (2011) 561– 568

Contents lists available at ScienceDirect

Materials Chemistry and Physics

j ourna l ho me pag e: www.elsev ier .com/ locate /matchemphys

reparation and characterization of nano hydroxyapatite/polymeric compositesaterials. Part I

haled R. Mohameda,∗, Zenab M. El-Rashidya, Aida A. Salamab

Biomaterials Dept., National Research Centre, Dokki, Cairo, EgyptBiophysics Dept., Faulty of Science, El-Azhar Univ., Cairo, Egypt

r t i c l e i n f o

rticle history:eceived 20 November 2010eceived in revised form 24 June 2011ccepted 8 July 2011

eywords:omposite materials

a b s t r a c t

The present study is focused on preparation of nano composite materials and the effect of citric acidon their different properties. The formation of nano HA and its interaction with chitosan (C), gelatin (G)polymers and citric acid (CA) materials were studied. The Fourier Transformed Infrared Spectroscopy(FT-IR), X-ray diffraction (XRD), thermo-gravimetric analysis (TGA), transmission electron microscope(TEM), and scanning electron microscope (SEM) were used to characterize these composite materials.The compressive strength (CS) was also measured to know the reinforcement of the prepared composites.

olymersEMT-IR

The results show that carboxylic and amino groups play crucial role for HA formation on chitosan–gelatinpolymeric matrix in the presence of citric acid (CA). The formation of nano HA particles and its averagesize of crystallite is increased with increase of CG content and decreased with addition of CA. Also, theHA formation and binding strength between its particles are improved into the composites especiallywith CA. The nano-composites containing the best ratio of nHA (70%) with CA (0.2 M) are promising for

e fut

medical applications in th

. Introduction

Calcium phosphates, especially hydroxyapatite (HA), are excel-ent candidates for bone repair and regeneration and have beensed in bone tissue engineering for two decades. For example, it haseen shown that HA and its composites are suitable for attachment,roliferation and differentiation of mesenchymal stem cells (MSCs),wing to their structure and chemical compositions [1]. HA has anique capability of binding to the natural bone through biochem-

cal bonding, which promotes the interaction between host bonend grafted material [2]. Although HA is bioactive and osteocon-uctive, its mechanical properties are inadequate, making it unableo be used as a load bearing implant [3]. The stoichiometric HA has

chemical composition of Ca10(PO4)6(OH)2 with Ca/P ratio of 1.67.arbonate apatite has been used as a biocompatible and osteocon-uctive substitute in the field of hard tissue repair and regenerationecause of its similarity to inorganic component of hard tissues,specially carbonate apatite at nano level has an important impactn cell-biomaterial interaction because of its better resorption andlose surface contact with the surrounding tissue [4].

Chitosan is a co-polymer of glucosamine and N-cetylglucosamine, deacetylated from the natural polymerhitin which is the main component of the shells of crustacean,

∗ Corresponding author.E-mail address: kh [email protected] (K.R. Mohamed).

254-0584/$ – see front matter © 2011 Elsevier B.V. All rights reserved.oi:10.1016/j.matchemphys.2011.07.024

ure.© 2011 Elsevier B.V. All rights reserved.

and is known to be biodegradable and non-toxic [5]. Chitosan hasthree types of reactive functional groups, an amino group as wellas both primary and secondary hydroxyl groups at the C(2), C(3),and C(6) positions, respectively. These groups allow modificationof chitosan like graft copolymerization for specific applications,such as scaffolds for tissue engineering applications [6].

Gelatin is a polymer of polypeptide and its structural for-mula is (NH2COOH–CH–R), where R is amino acid of glycine,proline and hydroxyproline. Gelatin is a biodegradable polymerwith many attractive properties, such as excellent biocompatibil-ity, non-antigenicity, plasticity and adhesiveness, and it is widelyused in biomedical and pharmaceutical fields. Thus, gelatin wasselected as a suitable candidate blended with chitosan [7]. Gelatin isan amphoteric polyelectrolyte because gelatin chain contains bothanionic and cationic groups which can absorb ions. The adsorptioncould be driven by electrostatic and/or by hydrophobic interaction,depending on the nature of surface and the medium. Moreover,gelatin chains can strongly interact with each other in water byhydrogen bond [8]. Citric acid (C6H8O7) (CA) has a hydroxyl andthree carboxyl groups in its molecule [9]. Citric acid was used as anucleating agent for HA crystals on cellulose [10].

The composites of carbonate apatite and chitosan polymer cancompensate the weak mechanical properties of pure HA [11].

The nano-hydroxyapatite (nHA) crystallites can be nucleated onthe surfaces of chitosan–gelatin network films when they areimmersed in Ca(NO3)2–Na3PO4 solution. This nucleation dependson the charged functional groups that existed on the surfaces of
Page 2: Preparation and characterization of nano hydroxyapatite/polymeric composites materials. Part I

562 K.R. Mohamed et al. / Materials Chemistry and Physics 130 (2011) 561– 568

Table 1Preparation of HA/chitosan–gelatin composites (CG composites).

Samples HA/chitosan–gelatin (wt%) Ca(OH)2 (g) H3PO4 (g) Chitosan (g) Gelatin (g) Citric acid (%)

HA sample 100/0 14.76 11.71 – – –

cocCtc

tCwT

2

2

i(8(pa

2

22aeeNr2pa

2eicwrdaitdcada

2csp

2

dEpCTch

appeared in the two composites with reducing in its intensity prov-

C1G1 comp. 80/20 11.81

C2G2 comp. 70/30 10.33

C3G3 comp. 60/40 8.86

hitosan–gelatin (CG) films, e.g. negatively charged COO− groupsf gelatin and C O groups of chitosan or gelatin and positivelyharged amino groups of chitosan and gelatin. That is to say theOO−, C O and amino groups offer the nucleation sites for crys-alline HA through binding or chelating oppositely charged ions,alcium and phosphate [12].

The objective of the present study is to prepare and characterizehe nHA/chitosan–gelatin composites in the presence or absence ofA. The hydroxyapatite and its composites with polymeric matrixere characterized by different techniques such as FT-IR, TGA, XRD,

EM, SEM and mechanical testing.

. Materials and methods

.1. Materials

The starting materials for preparing hydroxyapatite (HA) is calcium hydrox-de (Ca(OH)2) (98%) that was purchased from BDH and orthophosphoric acidH3PO4) (85%) was purchased from Laboratory Rasayan. Chitosan polymer (viscosity00,000 cps) with high molecular weight (Mr = 600,000) and deacetylation content85%) was purchased from Aldrich. Gelatin polymer from porcine skin with highurity 99% was purchased from HAS HMRZEL Laboratories LTD., Netherlands. Citriccid (CA) (anhydrous 99%) was purchased from Morgan Chemical Ind. Co., Egypt.

.2. Methods

.2.1. Preparation

.2.1.1. Preparation of HA powder. HA is prepared according to the following stepsnd is shown in Table 1. Calcium hydroxide (14.76 g) was dissolved in 100 mlthanol. Then the mixed H3PO4 solution (11.71%) was dropped slowly into thethanol solution of Ca(OH)2 with vigorous stirring and pH was adjusted with 10%aOH solution at around 10–11. The dropping speed was near 4 ml min−1 and the

eaction was carried out in ambient condition. After that, the stirring was kept for4 h after dropping and then the precipitate was aged for another 24 h. Finally, therecipitate was filtered, washed with distilled water to remove the excess of NaOHnd dried in a vacuum oven at 70 ◦C.

.2.1.2. Preparation of HA/chitosan–gelatin (CG composites). The composites withqual ratio of chitosan and gelatin (1:1) were prepared as the following and shownn Table 1. Preparation of C1G1 composites with weight ratio of composition [(HA:hitosan–gelatin) (80:20)]. The chitosan–gelatin solution with a concentration of 4%as prepared by dissolving chitosan (2 g) into 2% acetic acid (AA) (50 ml) with stir-

ing for 5 h to get a perfectly transparent solution and dissolving gelatin (2 g) intoistilled water (50 ml). The chitosan and gelatin solutions were mixed together,nd then mixed with 9.37% solution of H3PO4. This solution was dropped slowlynto 11.81% ethanol solution of Ca(OH)2 with vigorous stirring. The pH of the mix-ure was adjusted with NaOH solution up to 10. The stirring was kept for 24 h afterropping, and then the obtained paste was aged for another 24 h. Finally, the pre-ipitate was filtered, and washed with distilled water to remove the excess NaOHnd dried in a vacuum oven at 70 ◦C. Preparation of different CG composites withifferent weight ratios of HA powder and chitosan–gelatin polymers were preparedccording to Table 1.

.2.1.3. Preparation of HA/chitosan–gelatin·CA (CG·CA composites). Dissolve each ofhitosan and gelatin biopolymer in 0.2 M citric acid solution (CA% = 3.84). The aboveteps of CG composites preparation were repeated to prepare different CG·CA com-osites with different weight ratios of HA and chitosan–gelatin mixture.

.2.2. CharacterizationThe FT-IR spectra were measured using KBr pellets made from mixture of pow-

er for each sample and was assessed from 400 to 4000 cm−1 using Jasco, FT/IR 300, Fourier Transform Infrared Spectrometer, Serial No. 4140109, Japan. The phase

urity of samples was examined by X-ray diffract meter (Philips P.W: 1730) withu K� target, C S−1 1000 or 400, Ni filter and (� = 1.54 A, T (◦C) = 2, 40 kV, 25 mA).he thermal analysis, thermo-gravimetric analysis of the prepared samples wasarried out using (Shimadu TGA-50 H) under N2 flow over rate 30 ml min−1 witheating rate (10◦ min−1). The particle size of the prepared HA and HA particles into

9.37 2.00 2.00 3.848.20 3.00 3.00 3.847.30 4.00 4.00 3.84

the composite were measured using Transmission Electron Microscope Unit, TEM-1230 (Japan), resolution 0.2 nm, magnification 600k×, up to 120 kV high tension,on steps starting from 40 kV. The composites were also tested by for compres-sive strength (CS) to determine the effect of polymer on mechanical propertiesof the composites. Compressive strength was measured using an Instron 5500 RUniversal Testing Machine, USA, at a cross-head speed of 1 mm min−1 using a loadcell 10 kN. The test samples were made by compressing in a mould, dried in airfor two weeks and then dried in oven at 80 ◦C for 48 h. The average value wastaken for three samples to ensure the results. The morphology of the preparedsamples was examined with SEM, JXA 840A Electron Probe Microanalyzer (JEOL,Japan).

3. Results and discussion

3.1. FT-IR analysis

3.1.1. C1G1 and C1G1·CA compositesThe FT-IR of C1G1 & C1G1·CA polymers, HA and C1G1 &

C1G1·CA composites are shown in Fig. 1. The OH group recordedat 3437 cm−1 in the C1G1 polymer shifted to higher value at3480 cm−1 in C1G1·CA polymer with lower intensity proving inter-action. This result may be due to possible interaction of the OHand three COOH groups of ‘CA’ with OH group of chitosan andNH2 of chitosan or gelatin. The CH band at 1412 cm−1 in theC1G1 polymer shifted to 1401 cm−1 in the C1G1·CA polymer withlower intensity denoting interaction. The amide I and II appearingat 1640 and 1550 cm−1 in C1G1 appeared in C1G1·CA polymericmatrix with decreased intensities due to effect of CA. The C–Oband at 1091 cm−1 in the C1G1 polymer shifted to 1079 cm−1

in the C1G1 CA polymer with lower intensity proving interac-tion. The C O band appeared at 1730 cm−1 in the C1G1·CA as aresult of the effect of CA but it did not appear in the C1G1 poly-mer.

The OH bands were recorded at 3641 and 3563 cm−1 in HApowder and the first band was shifted to lower wavelength at3625 cm−1 in C1G1 composite proving interaction and disappearedcompletely in C1G1·CA composite proving coating. The secondband at 3563 cm−1 disappeared in the two composites denotingcomplete coating. New OH band appeared in the two compositesat 3420 cm−1 due to the presence of chitosan and CA containingOH groups in their structure. Amide I band appeared at 1650 cm−1

in the two composites with higher intensity in the first compositethan in the second composite. Also, the amide II band appeared at1556 and 1537 cm−1 in the first composite but they disappeared inthe second composite due to coating effect proving the presence ofCA which results in HA formation [13].

The two bands of CO32− group at 1457 cm−1 and 877 cm−1 in HA

sample decreased their intensity in the two composites with shiftof the second band to lower wavelength at 858 cm−1 in the sec-ond composite proving interaction. Also, there are new bands forCO3

2− group appeared at 1470 and 1423 cm−1 in C1G1 compositeand appeared at 1417 cm−1 C1G1·CA composite proving carbon-ate formation as a result of introducing CO2 from atmosphere.The stretching PO4

3− band at 1030 cm−1 recorded in HA powder

ing effect of coating. The bending PO43− bands at 602 and 566 cm−1

appeared in the first composite while in the second composite, thefirst band disappeared denoting coating and second band is shiftedto 550 cm−1 denoting interaction due to effect of CA.

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K.R. Mohamed et al. / Materials Chemistry and Physics 130 (2011) 561– 568 563

0 500 1000 1500 2000 2500 3000 3500 40000

1020304050

PO43- CO3

2-H2O

OHHA

0 500 1000 1500 2000 2500 3000 3500 4000

60

80

100

PO43- Amide I

C1G1 composite

0 500 1000 1500 2000 2500 3000 3500 4000

60

80

100

C1G1.CA composite

0 500 1000 1500 2000 2500 3000 3500 4000

406080

100

Amide gr.C-O

C1G1 polymer

0 500 1000 1500 2000 2500 3000 3500 4000

5060708090

100110

CH/C-OCH C-O

Amide gr.

C=O

Tran

ssm

issi

on (%

)

C1G1.CA polymer

umbe

G1 an

3

cCitaCaCaaCC

iceiaibAiope

apcct

Waven

Fig. 1. The FT-IR of HA powder, C1

.1.2. C2G2 and C2G2·CA compositesThe FT-IR of C2G2 & C2G2·CA polymers, HA and C2G2 & C2G2·CA

omposites are shown in Fig. 2. The OH group at 3437 cm−1 in2G2 polymer shifted to 3447 cm−1 in the C2G2·CA polymer prov-

ng interaction. The CH band at 1408 cm−1 in C2G2 polymer shiftedo 1400 cm−1 in C2G2·CA polymer due to interaction. New CH bandsppeared at 1337 cm−1, 934 cm−1, 877 cm−1 and 789 cm−1 in the2G2·CA due to effect of CA. The amide I band at 1638 cm−1 andmide II band at 1570 cm−1 recorded in the two polymers but the2G2·CA had lower intensities due to interaction between OH of CAnd amino groups through peptide bond. The carbonyl band (C–O)ppeared at 1085 cm−1 in the C2G2 with increased intensity in the2G2·CA. The carbonyl band (C O) appeared at 1728 cm−1 in the2G2·CA and do not appear in the C2G2 proving effect of CA.

The band of OH group at 3641 cm−1 in HA powder appearedn the two composites and its intensity is significantly reducedompared to the C2G2 and C2G2·CA composites due to coatingffect. Another OH band in HA powder at 3563 cm−1 disappearedn the two composites proving complete coating. New bands of OHppeared in the two composites, at 3742 cm−1 in the C2G2 compos-te and the other at 3423 cm−1 in the C2G2·CA composite becauseoth composites have high content of OH group in their structure.mide I band appeared at 1644 cm−1 in the two composites and its

ntensity decreased in the second composite compared to the firstne. The amide II band appeared at 1580 cm−1 in the first com-osite while it does not appear in the second composite due tonhancement of coating proving increase of HA formation.

The CO32− bands recorded at 1457 and 877 cm−1 in HA powder

ppeared in the two composites and their intensity decreased com-

ared to HA powder denoting coating especially in the compositesontaining CA. New CO3

2− band appears at 1420 cm−1 in the twoomposites and its intensity is high in the first composite comparedo the second one proving carbonate formation. Chu et al. proved

r (Cm-1 )

d C1G1·CA and their composites.

that the addition of citric acid during the preparation of hydroxya-patite by sol–gel method makes more carbonate groups that enterthe HA crystal as substitutes for phosphate groups [14]. The PO4

3−

bands at 1030, 602, and 566 cm−1 previously recorded in HA pow-der appeared in the two composites but their intensities in both thecomposites reduced compared to HA powder due to high coatingon HA particles.

3.1.3. C3G3 and C3G3·CA compositesThe FT-IR of C3G3 & C3G3·CA polymers, HA and C3G3 & C3G3·CA

composites are shown in Fig. 3. The OH group at 3437 cm−1 inC3G3 polymer shifted to 3447 cm−1 in the C3G3·CA polymer prov-ing interaction. The CH band at 1408 cm−1 in C3G3 polymer shiftedto 1400 cm−1 in C3G3·CA polymer due to interaction. New CH bandsappeared at 1337 cm−1, 934 cm−1, 877 cm−1 and 789 cm−1 in theC3G3·CA due to effect of CA. The amide I band at 1638 cm−1 andamide II band at 1570 cm−1 recorded in the two polymers but theC3G3·CA had lower intensities due to interaction between OH ofCA and amino groups through peptide bond. The carbonyl band(C–O) appeared at 1085 cm−1 in the C3G3 polymer with increasedintensity in the C3G3·CA. The carbonyl band (C O) appeared at1728 cm−1 in the C3G3·CA and do not appear in the C3G3 provingeffect of CA.

The OH band at 3641 cm−1 recorded in HA powder appearedin C3G3 and C3G3·CA composites but its intensity decreasedcompared to HA powder proving coating. Another OH band at3563 cm−1 in HA powder slightly reduced in the two compositesproving coating. The degree of coating increased in the presence of

CA because of formation of calcium citrate complexes [15]. AmideI band at 1650 cm−1 in the two composites, however its intensitydecreased in the second composite compared to the first one. Theamide II band was recorded at 1569 cm−1 in the first composite
Page 4: Preparation and characterization of nano hydroxyapatite/polymeric composites materials. Part I

564 K.R. Mohamed et al. / Materials Chemistry and Physics 130 (2011) 561– 568

0 500 1000 1500 2000 2500 3000 3500 40000

1020304050

HA powder

0 500 1000 1500 2000 2500 3000 3500 4000

20406080

100

C2G2 composite

0 500 1000 1500 2000 2500 3000 3500 4000

20406080

100

C2G2.CA composite

0 500 1000 1500 2000 2500 3000 3500 4000

40

60

80

100

C2G2 polymer

0 500 1000 1500 2000 2500 3000 3500 400040

60

80

100

C2G2.CA polymer

Tran

smis

sion

(%)

Wavenumber (Cm-1 )

Fig. 2. The FT-IR of HA powder, C2G2 and C2G2·CA and their composites.

0 500 1000 1500 2000 2500 3000 3500 4000 45000

1020304050

HA powder

Wavenumber (Cm-1 )

Tran

smis

sion

(%)

0 500 1000 1500 2000 2500 3000 3500 4000 450020406080

100

C3G3 composite

0 500 1000 1500 2000 2500 3000 3500 4000 450020406080

100

C3G3.CA composite

0 500 1000 1500 2000 2500 3000 3500 4000 4500

8090

100110

C3G3 polymer

0 500 1000 1500 2000 2500 3000 3500 4000 4500

8090

100110

C3G3.CA polymer

Fig. 3. The FT-IR of HA powder, C3G3 and C3G3·CA polymers and their composites.

Page 5: Preparation and characterization of nano hydroxyapatite/polymeric composites materials. Part I

K.R. Mohamed et al. / Materials Chemistry and Physics 130 (2011) 561– 568 565

Table 2The weight loss (%) and the attached polymer of the samples.

HA C1G1 comp. C2G2 comp. C3G3 comp.

wv

8bcreeidp

3

sscdpi(pTt

auvtta

ptga

3

Tpawttdciwtpo

par

Table 3The compressive strength (MPa) of the samples.

HA:CG ratio HA CG comp. CG·CA comp.

100/0 9.66 – –80/20 – 2.44 3.0070/30 – 9.12 12.7660/40 – 13.53 16.00

Table 4The TEM results of the prepared samples.

Sample HA C2G2 comp. C2G2·CA comp.

Weight loss (%) 12.598 10.183 16.468 25.793Attached polymer (%) – 2.415 3.87 13.195

hile it is not recorded in the second one because of its maskingia HA formation.

Two bands for CO32− group previously recorded at 1457 and

77 cm−1 in original HA powder appeared in the two compositesut their intensities decreased compared to the HA denoting highoating. The PO4

3− bands at 1030, 602 and 566 cm−1 previouslyecorded in HA powder appeared in the two composites; how-ver their intensities decreased compared to HA indicating coatingffect. It has been reported that the increase of coating is highn the C3G3·CA composite [13] compared to the C3G3 compositeue to effect of CA that enhanced binding interaction between HAarticles.

.2. Phase analysis

The XRD patterns of HA, chitosan and their CG composites arehown in Figs. 4 and 5. All the peak intensities of the HA and Ca(OH)2lightly reduced in the C1G1 composite and highly reduced in C2G2omposite compared to HA powder proving high coating processue to increase of polymeric matrix content. Some of the sameeaks in the C3G3 composite reappeared with slightly decreased

ntensities compared to HA powder denoting coating reductionFig. 4). Several experimental studies have shown that Ca(OH)2 mayossess antimicrobial [16] and anti-inflammatory properties [17].herefore, its presence in HA powder is vital for some bioapplica-ions.

For CG·CA composites, all the peaks of the HA and Ca(OH)2ppeared in C1G1·CA composite and their intensities were grad-ally reduced compared to the HA powder to reach the minimumalue in C3G3·CA composite denoting high coating process. Addi-ionally, the intensity of the main peak of HA at d-spacing 2.8 inhe three composites was enhanced compared to HA powder as CAccelerates HA nucleation (Fig. 5).

By comparing Figs. 4 and 5, it was noted that the intensity of HAeaks in the three CG·CA composites are highly reduced comparedo CG composites. The result was due to CA containing functionalroups combining with chitosan and gelatin through peptide bondnd with HA through hydrogen bond [18].

.3. TGA analysis

The TGA of HA and CG composites are shown in Fig. 6 and Table 2.he prepared HA powder has three endothermic peaks. The firsteak at 95 ◦C with weight loss (WL) (2.683%) is due to release ofbsorbed water molecules. The second peak from 95 to 380 ◦C witheight loss (3.866%) recorded with release of structural water due

o de-hydroxylation of HA and un-reacted calcium hydroxide. Thehird peak at 380–600 ◦C with weight loss (6.049%) is a result ofissociation of carbonate ions proving that the prepared HA formsarbonated hydroxyapatite (CHA) and the presence of carbonateons in HA to mimic the biological apatite [19]. Therefore, the total

eight loss of HA powder is about 12.598. Fig. 6 also shows thathe decomposition of Ca(OH)2 with release of structural water takeslace at ∼510 ◦C in TGA of HA powder which contains small amountf Ca(OH)2.

The C1G1 composite had three endothermic peaks. The firsteak at 238 ◦C with weight loss (0.748%) was due to release ofbsorbed water molecules. The second peak at range 238–430 ◦Cecorded weight loss (6.523%) due to destruction of polymeric com-

Length (nm) 7 35.15 30Width (nm) 2.8 6 5

posite accompanied with release of structural water and organicmatter. The third peak at 430 ◦C with weight loss (2.899%) recordedwith release of the rest CO2 and NH3 gases as well as dissociationof carbonate ions. The total weight loss of C1G1 composite was(10.183%). The C2G2 composite had two weight losses, the firstwas (5.0245%) at 250 ◦C due to absorbed water and the secondweight loss was (11.3975%) at 250 ◦C until 600 ◦C due to release ofall CO2 and NH3 gases as well as dissociation of carbonate ions. Thetotal weight loss of C2G2 composite was (16.468%). For C3G3 com-posite, it possesses three endothermic peaks recorded at 220 ◦C,400 ◦C and 600 ◦C. These peaks were corresponding to weight lossof 4.607%, 13.420% and 7.729%, respectively. The total weight lossof C3G3 composite was 25.793%. The attached polymeric layer ontoHA particles for C3G3 composite was very high compared to C1G1and C2G2 composites confirming high content of polymeric matrixwithin the composite.

3.4. Mechanical testing

Table 3 shows the compressive strength (CS) of the preparedsamples. It is found that the CS of all CG composites enhanced withincrease of polymeric content until reached to a maximum value(13.53 MPa) in C3G3 composite. Also, the CS of all CG·CA compos-ites after addition of CA increased compared to all CG compositeswithout CA. This result is due to the presence of CA which increasedbonding strength between HA particles via its functional group [20].

3.5. TEM analysis

The TEM of the prepared samples are shown in Fig. 7. For HApowder, the HA crystallites were envisioned as needle and sphere-like in shape, the mean of needle size is 7 nm in length and about2.8 nm in width. For the nano-composites, the n-HA in the com-posite exhibited short rod type crystals with a mean size of about35.15 nm in length and 6 nm in width in the C2G2 composite, themean size decreased to 30 nm in length and 5 nm in width for theC2G2·CA nano-composite (Table 4). These results were due to thevital role of CA in reducing the size of HA particles although it accel-erated and increased its formation. It is concluded that the presenceof COO− groups in the composite increased the formation of n-HAand enhanced the growth of crystalline n-HA that reduced in theirsizes because of high acceleration of its formation in the presenceof CA [12].

3.6. SEM analysis

The SEM images of HA sample and the prepared nano-

composites are shown in Fig. 8. HA composed of many whiterod crystals with few needle shaped ones proving CHA formation,which fused together forming clusters (Fig. 8a). In the C2G2 com-posite, the presence of rough surface with many deposited particles
Page 6: Preparation and characterization of nano hydroxyapatite/polymeric composites materials. Part I

566 K.R. Mohamed et al. / Materials Chemistry and Physics 130 (2011) 561– 568

0 10 20 30 40 50 60 70 80

0100200300400

Chitosan

0 10 20 30 40 50 60 70 80

0100020003000

HA powder

0 10 20 30 40 50 60 70 80

0100020003000

C1G1 composite

0 10 20 30 40 50 60 70 80

0100020003000

C2G2 composite

0 10 20 30 40 50 60 70 80

0100020003000

C3G3 composite

Inte

nsity

(a.u

)

Fig. 4. The XRD of HA, chitosan and their CG composites.

0 10 20 30 40 50 60 70 800

100200300400

Chitosan

0 10 20 30 40 50 60 70 80

0

1000

2000

3000HA powder

0 10 20 30 40 50 60 70 80

0

1000

2000

3000

C1G1.CA composite

0 10 20 30 40 50 60 70 80

0

1000

2000

3000C2G2.CA composite

0 10 20 30 40 50 60 70 80

0

1000

2000

3000

Inte

nsity

(a.u

)

C3G3.CA composite

chitos

oms(b

Fig. 5. The XRD of HA powder,

nto the surface indicating enhanced coating by the polymeric

atrix (Fig. 8b). For the C2G2·CA, the surface of the composite had

pherical particles of HA which were embedded into the compositeFig. 7c). It is noted high dispersion and narrow particle size distri-ution within C2G2·CA composite caused by the effect of CA that

an and their CG·CA composites.

led to the enhancement of HA formation into the polymeric matrix.

Shen et al. [18] reported that CA has a strongly chelating ability ofcalcium ions to its carboxylate groups, furthermore, the presenceof CA with chitosan, enhances nucleation center for HA formationvia OH− & COO− of CA and OH− & NH3

+ of chitosan.

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K.R. Mohamed et al. / Materials Chemistry and Physics 130 (2011) 561– 568 567

0 100 200 300 400 500 600

1.651.701.751.801.851.90

Wei

ght (

mg)

sample

12.598 %WL=

HA

Temperature (ºC)

0 100 200 300 400 500 6003.053.103.153.203.253.303.353.403.453.50

10.183 %WL=

C1G1 composite

0 100 200 300 400 500 600

2.62.72.82.93.03.13.2

16.468 %WL=

C2G2 composite

0 100 200 300 400 500 6001.41.51.61.71.81.92.0

25.793 %WL=

C3G3 composite

Fig. 6. The TGA of HA and CG composites.

Fig. 7. The TEM images of (a) HA powder, (b) C2G2 composite and (c) C2G2·CA composite.

Page 8: Preparation and characterization of nano hydroxyapatite/polymeric composites materials. Part I

568 K.R. Mohamed et al. / Materials Chemistry and Physics 130 (2011) 561– 568

(b) C2

4

nCfsgaitnwcmo

R

[[

[[[[[

[

Fig. 8. The SEM images of (a) HA powder,

. Conclusion

The characterization of the samples proved that HA formedano-carbonated hydroxyapatite. The formation and coating ofHA increased by increasing chitosan–gelatin concentration whichurther increased significantly after addition of CA, which bindstrongly with calcium ions, chitosan and gelatin through hydro-en bonds. The compressive strength of these CG composites afterddition of CA was enhanced compared to CG composites due toncrease of bonding strength between HA particles. In addition,he results revealed that the size of the prepared CHA is withinano-range and is increased in C2G2 composite while decreasedith CA addition that accelerated the HA formation as in C2G2·CA

omposite resulting in the reduction of the HA crystallite size. Theorphology of the composites proved homogeneity and formation

f CHA within polymeric matrix.

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