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Int. J. Engg. Res. & Sci. & Tech. 2014 A Ragu et al., 2014

SYNTHESIS AND CHARACTERIZATION OF NANOHYDROXYAPATITE WITH POLY VINYL ACETATE

NANOCOMPOSITE FOR BONE TISSUEENGINEERING

A Ragu1*, K Senthilarasan1 and P Sakthivel1

Synthetic hydroxyapatite (HAp) nano particle were synthesized by a wet chemical precipitationtechnique using calcium hydroxide and ammonium dihydrogen phosphate at room temperaturecondition. Nano hydroxyapatite (nHAp) materials consisting of biocompatible polymers havebeen widely used in orthopedic, dental, hard human tissue and nano filler applications. Syntheticbone graft substitute based on polymer have been largely studied during the past decade. In thiswork, hydroxyapatite (HAp)/Poly vinyl acetate (PVAc) nano composite were synthesized andcharacterized physical-chemically by X-ray diffraction (XRD), Fourier Transform Infraredspectroscopy (FTIR), Transmission Electron Microscopy (TEM), Energy Dispersive Analysis ofX-rays techniques (EDAX) and Micro Hardness test.

Keywords: XRD, FT-IR, TEM, EDAX, Hardness

*Corresponding Author: A Ragu [email protected]

INTRODUCTIONIn this paper, Hydroxyapatite (HAp) has received

considerable attention as a bone substitute due

to its similar biocompatibility, bioactivity,

osteoconductivity and tunable degradability to

bone (Legeros, 1991). The use of bioactive filler

such as hydroxyapatite (HAp), ceramic or

bioglass particle to reinforce a polymer may

improve both the mechanical properties and the

bone bonding properties (LIU, 1997). Bone is an

active, hard and strong living tissue that not only

supports and protects our internal organs, but is

1 Research Scholar, Department of Physics, Urumu Dhanalakshmi College, Kattur, Tiruchirappalli, India.

Int. J. Engg. Res. & Sci. & Tech. 2014

ISSN 2319-5991 www.ijerst.comVol. 3, No. 4, November 2014

© 2014 IJERST. All Rights Reserved

Research Paper

also essential for however; it is susceptible to

fracture as results of traumatic or non-traumatic

events (Turner, 2002). When there is a change in

external stimuli (or) stress, the bone either

remodels itself to sustain such forces or it

fractures ‘breaks’ when the energy from the

impact exceeds the energy the bone can absorb

(Turner, 2002). The conventional treatment for

fracture healing involves immobilization of the

bone/ joint with a cast, brace, split or a sling, while

the bone repair itself to resolve the fracture.

Bone tissue engineering aims to restore

37



skeleton function in the field of orthopedic and

oral maxillofacial surgery, augmentation of

fracture healing, and reconstruction of bone

defects resulting from ageing, osteoporosis,

trauma tumor, infections, biochemical disorder,

or abnormal skeletal development. It facilitates

the repair and remodeling of bone tissue biological

and synthetic substitutes to restore regenerate

and improve bone function ((Bock A K et al., 2003;

Meijer et al., 2007). Bone graft are the second

most common transplantation tissue, where

more than 2.2 million bone grafting procedures

occur worldwide to repair bone defect worldwide

(Giannoudis et al., 2005). Current therapies in

bone tissue engineering, classified as naturally

or synthetically derived biocompatible bone graft,

have drawbacks which limit their potential use.

Natural bone grafts are used for autologous and

allologous transplants, while synthetic bone

grafts, such as permanent artificial bone

substitute, are fabricated with biocompatible

materials. Bone consists of two major structural

components: cortical bone and cancellous bone.

Cortical bone forms the hard, outer, compact layer

of the bone while the cancellous bone form an

inner, porous network containing bone marrow

(Seeley et al., 2005).

Poly Vinyl Acetate (PVAc) is one of the most

widely used biodegradable polymers in synthetic

bone tissue scaffolds. Poly Vinyl acetate (PVAc),

a biocompatible and biodegradable (owing to the

hydrolyzable groups in the side chain) polymer,

has also been used in biomedical applications,

including drug, cell carriers and tissue engineering

(Silvalingam, 2003; Novoa et al., 2005). The

polymers commonly used in these applications

are poly(glycolic acid), poly(lactic acid) (PLA) and

their copolymer poly(lactide-co-glycoide),

polydioxanone, poly(ethylene oxide) and

poly(trimethylene carbonate) (James et al., 2011;

Pielchowska et al., 2010). In addition, poly(€-

caprolactoone) (PCL), polyanhydrides, poly (vinyl

alcohol) (PVA) and polyurethane have also been

investigated for bone regeneration (Pielchowska

et al., 2010). However, out of these polymers,

PLA, poly(glycolic acid) and poly(lactide-co-

glycoide) have received the highest interest

because the architectures and properties of these

polymers can be easily controlled. Various

materials of biological and synthetic origins, such

as metals, ceramic and polymers have been

used for bone tissue regeneration. Moreover, it’s

known that natural polymers including properties

such as collagen and alginate, chitosan are also

attractive, since they exhibit superior

biocompatibility and can facilities cell growth.

Several reports have indicated blood compatibility

of PVAc. PVAc has also been applied in many

medical fields because of its biocompatibility.

MATERIALS AND METHODS

Chemicals

All chemicals used were of analytical grade.

Calcium hydroxide Ca(OH)2 (99%), Ammonium

dihydrogen phosphate (NH4) H2PO4 (99%) and

Poly vinyl acetate (mol.wt 190.000) were procured

from Sigma Aldrich. Deionized water, ethanol,

toluene were used as the solvent.

Methods

Preparation of nHAp

Nano hydroxyapatite powder was synthesized

by wet chemical precipitation method through

microwave accelerated in room temperature

condition. Calcium hydroxide solution was

dissolved in 100 mL volume of an ethanol-water

mixture (50:50%, v/v) and was stirred for 3 h. A

solution of Ammonium dihydrogen phosphate was

38



(b)

dissolved in 100ml volume of water and then

added to the Ca (OH)2 solution over a period of

24 h. The amount of reagents in the solution was

calculated to obtain a Ca/P molar ratio value equal

1.67, corresponding to a stoichiometric HAp. The

PH of the slurry was measured digitally during

the precipitation reaction, reaction a final value of

PH11.

Synthesis of nHAp/PVAc

The nHAp powder was prepared by wet chemical

precipitation method in an aqueous medium. At

first the PVAc was dissolved in toluene, and then

nHAp was added slowly with help of magnetic

stirrer. After addition of the entire nHAp powder to

the polymer solution, the milky white coloration

was observed almost instantaneously. The

solution was dried using micro wave exposure at

900C.

RESULTS AND DISCUSSION

XRD

The XRD patterns of nHAp/PVAc nano

composites were taken. The pattern indicates the

presence of amorphous nHAp. The broad peaks

reveal that the particles size is very small in the

range 5 nm to 9 nm. The reflection planes

corresponding to the characteristic XRD spectral

peaks of pure nano HAp and PVAc nano

composites as shown in Figure 1. The observed

diffraction peaks are identified by standard

JCPDS file no. 09-0432 and are arranged as

crystalline nHAp. The main (h k l) indices for

nanometer sized HAp: (211),(300), and (200) are

indicated in Figure 1. The crystalline size, t(hkl), of

the synthesized nano HAp powder is calculated

using the Debye-Scherrer equation.

)(

9.0)( hklBCOS

t hkl

Figure 1: XRD Pattern of nHAp /PVAc

10 20 30 40 50 60 70 80 90

0

50

100

150

200

250

300

350

Inte

nsi

ty (

a.u

)

( 2 Theta )

HAp-PVAc

( 1

1 0

)

( 2

2 0

)(

1 0

2)

( 2

1 1

)(

3 0

0 )

( 2

0 0

)

( 2

2 2

)(

1 3

0 )

( 3

2 1

)(

1 0

4 )

( 5

0 2

)(

3 0

4 )

( 4

3 1

)(

4 0

4 )

where, is the wavelength of the monochromatic

X-ray beam, B is the Full Width at Half Maximum

(FWHM) intensity, (hkl) is the peak diffraction angle

that satisfies Bragg's law for the (hkl) plane and

t(hkl) is the crystalline size. The XRD patterns show

diffraction peaks with high intensities, which

confirm the nano size with crystalline nature.

FTIR

The FTIR spectrums of pure HAp/PVAc

nanocomposites are shown in Figure 2. The FTIR

spectrum investigation was carried out using

PERKIN ELEMER spectrometer in the range of

400 cm-1 to 4000 cm-1. The functional groups were

identified using peak assignments. A absorption

at 3642.47 cm-1 and 3416.17 cm-1 indicates the

presence of alcohol O-H group. The strong band

at 2934.18 cm-1 was assigned the C-H stretching

in alkane. The frequency at 1741.02 cm-1 shows

stretching of aliphatic carbonyl group. The

medium peak appeared at 1435.08 cm-1 indicates

the presences of C-C stretching of aromatic

group. A strong peak at 1246.08 cm-1 exhibits the

C-O stretching of aliphatic group. The presences

of strong peak at 1035.52 cm-1 indicate the

presence of C-O stretching of aliphatic amines.

39



Figure 2: FTIR Spectrum of nHAp/PVAc

ACIC

St.Joseph's College ( Autonomous)

Trichy-2Spectrum Name: NHAP-PVAc.sp

4000.0 3600 3200 2800 2400 2000 1800 1600 1400 1200 1000 800 600 400.0

0.0

5

10

15

20

25

30

35

40

45

50

55

60

65

70

75

80

85

90

95

100.0

cm-1

%T

3642.47

3416.17

2934.18

2472 .59

1741 .02

1561.96

1435.08

1377.12

1246.08

1035.52

949 .99

872 .20

797.57

606 .27568.58

469.75

The strong band at 949.99 cm-1 was assigned to

carboxylic acid group. The peak at 606.27 cm-1

indicates the presence of phosphate group in

nHAp.

TEM

The Transmission Electron Microscopy (TEM)

showed a nHAp/PVAc as shown in Figure 3 with

average grain size 5 nm to 9 nm. TEM microscopy

depicted the precipitation of hydroxyapatite

aggregates in porous poly vinyl acetate. TEM

studies showed a distribution of nanoHAp with self

assembled and aggregates of uniform sized. The

morphology due to the very f ine size of

precipitated particles present in the aggregates

could not be ascertained through selected area.

The different size of nano HAp particle with

homogeneous dispersion are well identified in

case of the nHAp/PVAc nanocomposite Figure 3

(a), (b) The particle size of nHAp is controlled by

the polymer (PVAc) in the composite as depicted

in the TEM image. The Selected Area Electron

Diffraction (SAED) Figure 3(c) results of nano HAp

and PVAc are good agreement with the lattice

structure of hydroxyapatite and exhibit excellent

crystallinity. In addition to this, there is almost no

Figure 3: (a), (b) TEM Image of nHAp/PVAc

Figure 3: (c) Selected Electron AreaDiffraction (SAED) of HAp/PVAc

Nano Composite

40



agglomeration, which may be due to reduction of

surface energy.

EDAX

The Energy Dispersive Analysis of X-rays (EDAX)

of nHAp/PVAc is shown in Figure 4. The mineral

composition of Ca, O, P and organic content C

present in both nano composite are tested. The

EDAX results confirmed the existence of the

elements such as Ca, P and O Figure 4. The Ca/

P value of synthesized HAp with PVAc

nanocomposite to be 1.72 which is closer to the

Ca/P ratio of human bone (Trommer et al., 2007).

implanted HAp were used to measure the

hardness of bone by means of an indentation test

(Micro hardness MVHT; Wilson Wolpert-

Germany). Brief measurements of micro

hardness were made tangential to the interface

with a Vickers indenter applied to the bone at a

load of 50 g. For the load of 10 g, 25 g, 50 g and

100 g the harness number was in the range 20.1,

21.0, 35.0 and 16.9. The hardness of the

specimens used in this study increase with the

increasing test load and is comparable with other

having reported. The tendency of hardness of

materials decrease with the increasing test load

above 50 g.Figure 4: EDAX of HAp/PVAc Nano Composite

Micro Hardness Test

The micro hardness tests are used to determine

the resistance of a deformation. This test can be

performed on a macroscopic or microscopic

scale. The pellet indentation hardness correlates

linearly with tensile strength. With the controlled

test force, the specimen is pressed by using the

indenter with a dwell time of 10 to 15 s. Micro

hardness of pure nHAp/PVAc based composites

(HAp/PVAc-10 g to 100 g) is shown in Figure 5. A

maximum increasing of the peak value (35 HV

50 g) is observed for the composition. The same

blocks containing the residual part of the

Figure 5: Micro Hardness Test of nHAp/PVAc

CONCLUSIONPVAc is a synthetic polymer that has been used

for the past 30 years in several medical and

nonmedical devices Nano Hydroxyapatite has

been successfully synthesized using the wet

chemical precipitation techniques. This process

showed that high purity product of nano

hydroxyapatite powders could be obtained at room

temperature. Hydroxyapatite with polymer

nanocomposites offers a robust system to

engineer synthetic bone substitute for orthopedic

implant fixation, synthetic bone graft substitute

41



and tissue because of their biocompatibility and

osteoconductivity properties. The formation of

hydroxyapatite nanoparticle was confirmed by X-

Ray Diffraction (XRD) and functional groups of

the compound are identif ied using Fourier

Transforms Infrared Spectroscopy (FTIR). The

elemental compositions were examined using

the EDAX analysis. The size and morphology of

the sample characterized using Transmission

Electron Microscopy (TEM) analysis confirms the

presence of HAp/PVAc nano particles with the

particle size of around 5 nm to 9 nm. Many aspects

of the composite structure can be tailored in order

to design for specific mechanical, biological and

surgical functions. Nano hydroxyapatite with

polymer will remain a fruitful and active area of

biomaterials research for the foreseeable future.

ACKNOWLEDGMENTThe management of Urumu Dhanalakshmi

College, Tiruchirappalli for providing research

facilities in the campus.

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3. James R, Derg M, Laurencin C and

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8. Pielichowska K and Blazewicz S (2010),

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