Accepted Manuscript

Mg-doped fluorapatite nanoparticles-poly(ε-caprolactone) electrospun nano-

composite: Microstructure and mechanical properties

Zeinab Fereshteh, Mohammad hossein Fathi, Reza Mozaffarinia

PII: S0749-6036(14)00241-9

DOI: http://dx.doi.org/10.1016/j.spmi.2014.07.011

Reference: YSPMI 3328

To appear in: Superlattices and Microstructures

Received Date: 1 July 2014

Accepted Date: 3 July 2014

Please cite this article as: Z. Fereshteh, M.h. Fathi, R. Mozaffarinia, Mg-doped fluorapatite nanoparticles-poly(ε-

caprolactone) electrospun nanocomposite: Microstructure and mechanical properties, Superlattices and

Microstructures (2014), doi: http://dx.doi.org/10.1016/j.spmi.2014.07.011

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Mg-doped fluorapatite nanoparticles-poly(ε-caprolactone) electrospun nanocomposite

: microstructure and mechanical properties

Zeinab Fereshteh*,1, Mohammad hossein Fathi 1, Reza Mozaffarinia1

1 Biomaterials Research Group, Department of Materials Engineering, University of

Technology, 8415683111, IRAN

* Correspondence to: Tel.: +98 311 3915708; fax: +98 311 3912752. E-mail addresses:

zeinabfereshteh57@gmail.com.

abstract

The aim of this study was to prepare and characterize the poly (ε-caprolactone)/Mg-doped

fluorapatite nanoparticles (PCL/nMg-FA) nanocomposite electrospun scaffolds. The effect

of solvent type on distribution of nanoparticles and mechanical properties of the scaffolds

was also investigated. The optimized nanofibrous scaffold was obtained by 5 wt. % nMg-

FA while its tensile strength and elastic modules were significantly enhanced compered to

PCL scaffolds. It is noteworthy that no surfactant was used in present study. The Mg-FA

nanoparticles were homogeneously dispersed in the nanofibers and prepared scaffolds

without any agglomeration.

Key words: Nanocomposites, Apatite; Mechanical properties; Biomedical applications;

Mg-doped fluorapatite nanoparticle.

1. Introduction

Several inorganic biomaterials such as bioactive ceramics including silicate glasses,

forstrite, tricalcium phosphate, hydroxyapatite (HA), and selected compositions of apatite

have been widely used for bone regeneration applications.1,2 The biocompatibility of HA is

due to its compositional and structural similarities to the mineral phase of bone.3 Because

of its noble bioactivity, biocompatibility and osteoconductivity with human body

components, HA and other modified apatites such as Fluorine-substituted HA, Fluorapatite

(FA), Mg-substituted HA and so on, have received increasing attentions in the field of

biomedical applications. Among them, Mg2+ substituted FA provides greater

biocompatibility and biological properties than pure FA or HA.4 On the other hand, fluorine

ions are known to affect the mineralization and bone formation in vivo, resulting from their

antibacterial effect. Also, the osteoblast responses are improved through fluoride

incorporation.5

The macro-porous bioceramics are considered as brittle materials; additionally, polymeric

materials are unable to bear the applied loads in many applications.5 Therefore, the

polymeric materials are generally combined with bioactive ceramics to form composite

scaffolds. The obtained composite systems present several advantages such as controllable

scaffold degradation rate, enhanced bioactivity and mechanical properties, and improved

scaffold structural integrity.6 Based on the aforementioned advantages, the composite

materials containing bioactive ceramics and biodegradable polymers have emerged as ideal

candidates for bone regeneration and tissue engineering scaffolds. 5,7

Electrospinning is an efficient method for developing fibrous structures with controllable

diameters ranging from nano to micrometer; hence, electrospinning is regarded as a suitable

choice for bone tissue preparation; for instance, it has been already shown that electrospun

scaffolds have the potential to promote osteoblastic cell function and bone proliferation.8

One of the most studied biodegradable polymers for this purpose is poly (ε-caprolactone)

(PCL). This polymer is aliphatic polyester, biocompatible and bioresorbable which is

hydrolytically devoid of toxic by-product. PCL has numerous applications as medical

scaffold, screw bones for sutures and staples, fracture fixation, drug delivery vehicles to

mats or porous structures for tissue engineering.5, 7-10 In the ceramic/ polymer composite, it

is remarkable that the behavior of the ceramic particles inside the polymer matrix. They

should distributed homogenous and evenly. To date, researchers used various ways to

achieve this aim, such as: modification of ceramic surface and using ultrasonic.11-13

The objective of this paper is to develop a novel nanocomposite scaffold by Mg-doped

fluorapatite (nMg-FA) nanoparticles and biodegradable PCL fibers using electrospinning

process for guided bone regeneration. Moreover, the effects of solvent, polymer

concentration, applied voltage, nozzle to collector distance and content of ceramic are

evaluated in order to obtain optimized process parameters. Our hypothesis is that PCL is a

suitable biomaterial to fabricate scaffold, and the addition of nMg-FA nanoparticle

improves the biomedical properties of the polymeric scaffold. Also, by choosing binary

solvent system can be achieved a homogenous ceramic/polymer composites scaffold.

2. Experimental

2.1. Materials and methods

Poly (ε-caprolactone) (PCL, Mw = 80,000, m.p. 60� ) (Sigma-Aldrich), and solvents

including 99.8 v% chloroform (Ch), 99.8 v% methanol (MeOH) and 99.8 wt. % ethanol

(EtOH) (Merck Co) were used as starting materials. Also, Mg-doped fluorapatite (nMg-FA)

nanoparticles were prepared by sol-gel method according to Ref [4].

2.2. Preparation of scaffold

The electrospinning solutions were prepared by dispersing a certain amount of nMg-FA

into ethanol or methanol. Subsequently, chloroform was added into the solution and mixed

for another 15 min using an ultrasonic bath. Finally, PCL pellets were added into the

solution. To achieve complete dispersion, the prepared solutions were magnetically stirred

at room temperature for 24 h. Fibers were electrospun from polymer solutions containing 8,

10, 12 and 14 % w/v PCL. The parameters used for solution preparation are summarized in

Table 1. The parameters modified in this study include the type of solvent system, and the

amounts of ceramic and polymer. The scheme for fabrication of pure PCL and nMg-

FA/PCL composite nanofibers is presented in Fig. 1.

The solution was fed through a 23 G needle with a feed rate of 1 ml/h and electrospun onto

a grounded collector placed at a distance of 20 cm. The prepared electrospun nanofibers

were collected on a flat aluminum sheet. The electrospinning process was carried out at

humidity of 20% and temperature of 25� . The electrospun fibers were subsequently

desiccator to remove any residual solvent.

2.3. Measurements and characterization

The morphology and size of nanoparticles and nanofibers were assessed using transmission

electron microscopy (TEM) (Philips EM208 accelerating voltage of 100kV) and scanning

electron microscopy (SEM) (Phillips XL 30). The SEM and TEM images of scaffolds were

digitized and analyzed using an image analysis software (NIH Image J) to determine the

size of nanofibers and nanoparticles (n=100). A Philips X-ray diffractometer (XRD) (40

kV) with Cu Kα radiation (λ=0.15406 nm) was used to investigate the structural changes

and phase analysis of the Mg-FA nanoparticles and nanocomposite scaffolds. The XRD

patterns were recorded in 2θ range of 5-60° (step size of 0.02° and time per step of 1s). The

functional groups of the samples were identified by Fourier transform infrared spectroscopy

(FT-IR) (Bruker-Tensor 27) in the range of 400–4000 cm-1. The compositional analysis and

elemental X-ray mapping were executed using energy dispersive X-ray (EDAX) (SERON

TECHNOLOGY A15- 2100). Thermogravimetric analysis (TGA) (Rheometric scientific

1998, USA) was carried out to measure the real weight percent of nanoparticles in the

fibrous scaffolds. The mechanical properties of samples were measured in terms of

Young’s modulus, stress/strain at yield point and stress/strain at break by an Instron-type

machine (Zwick, United Kingdom) with load capacity of 10 N and strain rate of 10

mm/min. All samples were prepared in rectangular shape with dimensions of 50×10 mm

from the electrospun membranes. To take the repeatability into account, six samples were

tested for each type of electrospun nanofibrous membranes and the average of test results

was reported. The mechanical testing was conducted at relative humidity and temperature

of 20 ± 5% and 25�, respectively.

3. Results and discussion

3.1. Mg-FA nanoparticles characterization

The SEM micrograph, TEM images, XRD pattern, and EDX spectrum of the prepared pure

Mg-doped fluorapatite, with formula of Ca9.5Mg0.5(PO4)6F2, is shown in Fig. 2. The size

distribution curve is also shown in the image inserted in Fig. 2b. It is observed that Mg-FA

is made up of quasi spherical particles with diameter of ~ 12 nm.

3.2. Electrospinning Process

The solvent has a significant influence on electrospinning since at the first step of this

process, dissolution of the polymer into a suitable solvent takes place. The selection of a

proper solvent is done based on various properties such as boiling point, vapor pressure and

volatility. The intermolecular interaction between a polymer and the solvent molecules

(attractive or repulsive) depends solely on the type of the solvent.14 The most important

parameters of the prepared solution include its conductivity and viscosity.10,15,16 A solution

with high conductivity possesses a high surface charge density. The elongational force on

the jet is increased in electric field due to self-repulsion of the excess charges on the

surface.17 This inhibits the Rayleigh instability, enhances whipping, and leads to the finer

fibers. It has been shown that, for a given material and specified processing parameters, the

relative dominance of two instabilities is a function of surface charge density. Therefore,

uniform fibers without bead could be obtained in optimal condition. 18

Increasing the solution viscosity results in the higher resistance to flow; hence, at a constant

applied load, the fibers become thicker as the viscosity rises, in agreement with data

reported in the literature.18-20 It is worth exploring the optimum solution viscosity for

electrospinning process, since very high viscosity requires extremely high operating

voltage, and very low viscosity causes the defects like beads to be appeared in the fibers.

In order to obtain an optimum solvent for electrospinning of nMg-FA/PCL, different single

and binary solvent systems were studied. At this stage, the polymer and bioceramic

concentrations were fixed at 12 and 1 wt. %, respectively. PCL was completely soluble in

chloroform (Ch) but Mg-FA nanoparticles were not well-dispersed in this solvent and other

organic solvents. This arises from hydrophilic surfaces of the ceramic nanoparticles which

require polar solvent for dispersion; thus, ethanol and methanol proposed as the polar

solvents for dispersion of nMg-FA. SEM images from pure chloroform (Ch) nanofibers,

ethanol/chloroform (Et/Ch) nanofibers and methanol/chloroform (Me/Ch) nanofibers are

shown in Fig. 3. In the case of pure chloroform system, the presence of non-uniform and

thick fibers (2.787(1.203) μm) together with agglomerated nanoparticles is evident (Fig.

3b). This feature, which results from the interaction between nanoparticles and organic

systems (Ch/PCL), is not appropriate for fiber preparation, in agreement with data given in

the literature.19,22 As for Ch/Me system, although the fibers diameter was lower than that

observed for pure Ch system, the uniformity of the fibers was decreased (Fig. 3c). In

contrast, very thin and uniform fibers were achieved in the Et/Ch system, as indicated in

Fig. 3d. Beads are observed in all the systems except for the Me/Ch. The binary system of

methanol or ethanol/chloroform results in the fibers smaller than 600 nm. On the other

hand, utilizing the Me/Ch system yields to fibers in the nanoscale range with a few beads,

but nanofibers are non-uniform (0.548 (0.342) μm). Electrospun nanofibers prepared using

Et/Ch system are more uniform (0.692 (0.0783) μm) and several times smaller than those

obtained by pure Ch (0.692 (0.0783) μm). Several properties of different solvents are

presented in Table 2, chloroform as the main solvent is more consistent with ethanol in

terms of solubility and dielectric constant. Based on the outcomes of solvent optimization,

the binary Et/Ch solvent system was chosen for further investigations.

The viscosity and conductivity of solution are considered as competing parameters since

they both are increased with increasing the percentage of ethanol. According to Fig. 4 and

Table 3, the Et/Ch solvent system with ratio of 20/80 presents the optimum condition so

that nanofibers in this system are very small with narrow size distribution. Fig. 4 shows the

SEM images from the binary Et/Ch solvent system containing different volumes of ethanol.

The size of fibers prepared using different solvent systems and their symbols are listed in

Table 3. The fibers diameter and size distribution are initially decreased with increasing the

ethanol volume to 20 % (v/v), after which the fibers become thicker with further ethanol

addition. It is suggested that the ethanol addition at the early stages increases the solution

conductivity to a larger extent than its viscosity, leading to the primary fiber size reduction.

This effect becomes weakened with further increasing the ethanol volume resulting in the

subsequent fibers thickening. Consequently, the binary Et/Ch (20/80) was selected as the

optimum solvent constituent for subsequent experiments.

To further improve the electrospinning process, the effect of different polymer

concentrations ranging from 8-14 wt. % was examined, while other parameters remained

constant. Fig. 4b shows the SEM image of 12 wt. %. Also, SEM images of 10 and 14 wt. %

PCL are presented in Fig. 5. Since the solution containing low polymer concentration

reveals very low viscosity, a minimum polymer concentration is necessary for

electrospinning process. At low concentrations (8 wt. %), the entanglements of the polymer

chains are not able to provide a stable jet and droplets. On the other hand, at high polymer

concentration viscosity of the solution becomes so high that electrospinning is no longer

possible; this is caused by the extremely rapid solidification of the polymer which leads to

blocking the needle outlet in some cases.19 There are some beads at the polymer

concentration of 8 wt. %. By increasing the polymer concentration, beads disappear but the

average diameter of fibers is increased. It appears that minimum polymer concentration of

10 wt. % is required; otherwise, the solution viscosity becomes too low. Therefore,

optimum solution concentration for the electrospinning process was found to be 12 wt. %,

because uniform and non-beaded nanofibers were formed at this conditions.

In electrospinning process, the applied voltage is a key factor since the fibers can be only

formed when a threshold voltage is achieved. It is believed that at high voltages, higher

stretching of solution takes place owing to the stronger electric field and greater columbic

forces in the jet. This yields to the reduction of fiber diameter as well as rapid evaporation

of solvent from the fibers. There is also a greater probability of beads formation at higher

voltages.14 The level of significance varies with the distance between the tip and the

collector.23 It should be noted that an appropriate distance is required to fabricate uniform

fibers; otherwise beads are formed.21 In this research, diameter of PCL/nMg-FA fibers

decreased from 1019 (191) nm to 427 (411) nm with increasing the electric potential from

15 to 25 kV. By increasing the applied voltage, standard deviation changes as the jet fluid

reaches unsteady state. It is known that the average diameter of fibers increases with

decreasing nozzle to collector distance. However, variation of standard deviation is not

significant by increasing distance. According to Table 4, voltage of 25 kV and distance of

20 cm were selected as optimum parameters since they resulted in the minimum average

fibers diameter with maximum uniformity together with the maximum steady state area.

Consequently, other samples were fabricated by the optimum conditions, i. e. Et /Ch

(20/80), 12 wt. % polymer, 25 kV and 20 cm.

Different ceramic concentrations including 1, 5, 10, 15 and 20 wt. % were examined. Fig.

6. demonstrates the SEM images of the nanofibers and their diameter distribution.

Regarding the diameters of the nanofibers, it is observed that the diameter of the nanofibers

is decreased by increasing the ceramic concentration, probably due to the enhanced

dielectric properties of solution. The solution conductivity affects the morphology of

fibers.15 Solutions with high conductivity have high surface charge density, increasing the

elongational force on the jet under a fixed electric field. It is caused by the self-repulsion of

the excess charges on the surface. Then, it inhibits the Rayleigh instability, increases

whipping and forms finer fibers.18 Therefore, it is noted that the fiber diameter is decreased

with increasing the conductivity. Up to a certain concentration (15 wt. % nMg-FA),

standard deviation rises owing to generation of an instable Taylor cone. On the other hand,

multi jets are formed by incorporation of nMg-FA nanoparticles, leading to the fiber

diameter distribution to be increased.

According to Fig. 6, it seems that nMg-FA is not agglomerated in the PCL nanofibers at 15

wt. %. This originates from the appropriate dispersion of nanoparticles in ethanol (protic

polar solvent). The protic polar solvents can donate a proton and have high dielectric

constants. The nMg-FA is highly hydrophilic which consequences the improved dispersion

of nanoparticles in the PCL solution. It seems that when ethanol releases protons, its

oxygen ions are able to interact with the surface of nMg-FA; hence, the dispersion of nMg-

FA in polymer solution is improved. In biomedical applications and using the

biodegradation scaffolds, the dispersion, distribution and capture of the nMg-FA inside the

nanofibers will be effective on biological properties such as bioactivities, rate of

biodegradation and the growth kinetics of the cells.9 In the samples containing 15 and 20

wt. %, nanoparticles were agglomerated, as evidenced by blue arrows in Fig. 6.

3.3. Nanocomposite scaffolds characterization

Phase analysis of the PCL scaffolds containing nMg-FA at different levels (pure PCL, 1, 5,

10, 15 wt. %) was carried out using XRD, as shown in Fig. 7. The pure PCL scaffold

pattern consists only of PCL characteristic peaks at ~2θ = 21.4882º and 23.8277º. The XRD

pattern of the nanocomposite scaffold exhibits peaks from both materials (Fig. 7e: 15 wt %

of nMg-FA). There are no extra peaks and/or peak shift on the XRD patterns of scaffolds,

since no chemical reaction occurs between polymeric solution components. This is also

confirmed by FTIR spectra in which the intensity corresponding to PCL peaks decreases by

increasing the nanoparticles content, in agreement with results reported by other

researches.5,7,24

The structure of the nanocomposite was analyzed using FT-IR spectroscopy (Fig. 8). As

seen, characteristic structural bands of both nMg-FA and PCL are observed for all PCL-

nMg-FA ratios. Pure PCL spectrum reveals the peaks corresponding to PCL including -

CH2- group within 3000–2850 cm-1 and 1250–1450 cm-1 regions (symmetric C-H

stretching and C-C stretching, respectively), C=O bonds around the region centered at 1750

cm-1 (stretching vibrations of the carboxyl) and C-O groups within 1150–1250 cm-1 region

(stretching vibrations of the ether groups (C-O-C), C-O stretching vibrations and

asymmetric C-O-C stretching).5 In the spectra of nanocomposites, in addition to PCL

bands, the characteristic absorption bands of nMg-FA are observed. A major peak of

phosphate group is noticed in the region between 1100 and 1000 cm-1. In fact, it is observed

that the PO4-3 absorbance emerges within the range of 950–1100 (symmetric P-O stretching

vibration) and 550–620 cm-1 (vibration mode of phosphate group).25 No band shifts are

observed in the FT-IR spectroscopy, confirming that no chemical reaction occurs in the

mixed components. Compared to FTIR spectrum of pure PCL, the spectra of scaffolds

indicate a number of PCL bands shifted to lower wavenumbers which might be due to the

formation of hydrogen bonds between the specific groups of nMg-FA and PCL.

Fig. 9 shows the X-ray maps related to the scaffolds containing 5 and 10 wt. % nMg-FA

nanoparticles. The mapping of calcium, phosphorus, magnesium and fluorine elements

reveals that the nanoparticles are distributed throughout the mat and also inside the fiber.

Furthermore, the nMg-FA particles are homogeneously dispersed within the nanofibers

without any agglomeration. The higher the nanoparticles content, the higher the intensity is

achieved for all elements in the maps, as illustrated in Fig. 9a, b. It is known that the

relative intensity is decreased with decreasing atomic number. Then, independent of the

element concentration, light elements have a low relative intensity.26 This is why the

relative intensity of phosphorus is higher than calcium while its concentration is lower.

In addition to the X-ray maps, distribution of the nanoparticles in polymer matrix was

investigated by TEM. The TEM images of scaffolds demonstrate that the nMg-FA particles

were sufficiently dispersed in the polymer fibers (Fig. 10). The size of all nanoparticles

attached to nanofibers was found to be less than 10 nm, especially in the case of samples

containing 1 and 5 wt. % nanoparticles (Fig. 10c-f). The nanoparticles were distributed

evenly through the material. Further TEM observations prove that the most of particles are

embedded in the fibers (samples with 1 and 5 wt. % nanoparticles), while some of them

appear to be located on the fiber surface (sample with 10 wt. % nanoparticles).

TGA experiments were performed to analyze the weight loss nMg-FA nanoparticles, pure

PCL and PCL-5 % nMg-FA (Fig. 11). The weight loss of single phase nMg-FA

nanoparticles was 5.67 wt. % within the temperature range of ~ 65-120�, due to the loss of

water molecules from the product. The TGA results show that pure PCL and PCL-5 %

nMg-FA nanofibers undergo single step decomposition. According to the TGA curve,

thermal decomposition of pure PCL and PCL-5 % nMg-FA nanofibers occurs in the

temperature ranges of 310-470 � and 325-600�, respectively. Moreover, the values of

weight loss for pure PCL and PCL-nMg-FA composite nanofibers are 92.32 and

88.26 wt. %, respectively. This originates from decomposition and oxidation of the

polymer nanofibers. It can be observed that the onset of the thermal degradation occurs at

higher temperatures for PCL-5% nMg-FA as compared to pure PCL nanofibers (about 5�).

This is due to the presence of ceramic nanoparticles which enhances thermal stability of

nanocomposite. Furthermore, according to the TGA results, it can be concluded that the

electrospinning process allows the all solvents to be evaporated during the nanofibers

production. As a result, no pre-drying treatment is required for cell viability and cell

attachment tests.

Mechanical properties of the scaffolds are of great importance since they should support

cell growth and proliferation between the empty spaces and the local environment for tissue

regeneration period. Fig. 12 shows the typical stress–strain curves for the electrospun

scaffolds. They exhibit similar mechanical behavior under tensile force, as it is

characteristic for ductile materials. At the beginning of the curves (strain < 10%), the

membranes obeys the Hooke’s law, showing a proportional increase of stress and strain. As

strain is continuously increased, the curves deviate from the linear proportionality. As listed

in Table 5, different mechanical properties are achieved for scaffolds depending on the

nMg-FA content. With increasing the nMg-FA content up to 5 wt. %, the tensile modulus,

strains at break and energy per volume of the membranes are increased to 10.2±2.6 (MPa),

408.6±12.8 (%) and 2.34±0.45 (MPa), respectively; while, as the nMg-FA nanoparticle

content reached 10 wt. %, strain at break of scaffolds is decreased to 291.7±13.8. Besides,

tensile modulus of fibrous membranes is decreased at 5 wt. % of nanoparticles due to the

nanoparticles agglomeration and heterogeneity of the structures, as observed in Fig. 6 and

Fig. 10. Previous results on PCL-based electrospun scaffolds also reported the reduced

strain at break at higher amount of filler due to a quasi-brittle behavior.9,27

Yang et al. reported the improved mechanical properties for the PCL membrane by addition

of nAp.27 They suggest that the mechanical reinforcement can be ascribed to an additional

energy-dissipating mechanism of the nanoparticles in PCL. In fact, this additional

dissipative mechanism is a result of the mobility of nanoparticles. During this process, the

nanoparticles orient and align under tensile stress, creating temporary cross-links between

polymer chains, in that way generating a local region of enhanced strength.27 Bianco et al.

also demonstrated that mechanical properties are significantly decayed for HAp contents

higher than 3.6 wt. %.9

On the other hand, the modulus and strength of the fibers increase as the fiber diameter is

decreased. For the fibers with diameter of less than ~ 700 nm, the effect of diameter on

tensile stiffness and strength becomes more predominant. The ductility of the fibers is

increased with increasing the fiber diameter.28 Furthermore, the tensile modulus is

increased for the sample containing 15 wt. % nMg-FA nanoparticles. It is suggested that the

effect of fiber diameter on mechanical properties is more pronounced than the ceramic

content. This can be explained by reducing the fiber diameter. The fiber diameter is

decreased from 460 nm to 383 nm for the samples containing nMg-FA 10 wt. % and nMg-

FA 15 wt. %, respectively. In the case of PCL-20 wt. % nMg-FA, this trend continues and

tensile modulus is decreased.

4. Conclusions

The (nMg-FA)/PCL nanocomposite scaffolds containing 1, 5, 10, 15 and 20 wt. % Mg-

doped fluorapatite nanoparticles were successfully produced by solvent electrospinning

method. Investigation of the single and binary solvent systems revealed the major potential

of Ethanol/Chloroform solvent mixture with ratio of 20/80 for electrospinning nMg-

FA/PCL nanoparticles, leading to the formation of very thin nanofibers with narrow size

distribution. The optimum values of polymer concentration, applied voltage and collector to

needle distance were 12 wt. %, 25 kV and 20 cm, respectively. The nMg-FA particles were

homogeneously dispersed in the nanofibers devoid of agglomeration.

Moreover, nMg-FA nanoparticles content influenced the mechanical properties. Tensile

strength of the scaffolds was increased by decreasing the fiber diameter, and decreased by

increasing the ceramic content. The PCL/nMg-FA 5 wt. % nanocomposite scaffold

revealed the maximum tensile strength (2.34±0.45).

Based on the obtained results, one can conclude that the fibrous nanocomposite prepared by

electrospinning is a promising material for guided bone regeneration scaffold. Besides, the

fibrous nanocomposite can be utilized as an appropriate prototype for further development

of a final membrane for in vitro and in vivo experiments. Because of the simplicity of the

method, many opportunities may exist to further control the fibers size. Furthermore, it

would be interesting to study biological properties of nMg-F /PCL nanocomposite

scaffolds. It appears that addition of nMg-FA nanoparticles increased the hydrophilicity,

bioactivity and degradable ability of pure PCL fibrous membranes.

Acknowledgements

The authors are grateful to council of University of Technology for providing financial

support to undertake this work.

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[27] Yang, F., Both, S.K., Yang, X., Walboomers, X. F., Jansen, J.A. Acta Biomaterialia,

2009, 5, 3295–3304.

[28] Wong, S. C., Baji, A., Leng, S., Polymer, 2008, 49, 4713–4722.

Figures captions

Fig. 1. Scheme of the plan for fabrication of nMg-FA/PCL composite nanofibers.

Fig. 2. a) SEM micrograph, b) TEM images, (image inserted is size distribution curve), c)

XRD pattern, and d) EDX spectrum of prepared nanoparticles, nMg-FA.

Fig. 3. SEM micrographs and diameter size distribution of the nanofibers for various

solvent systems a, b) Ch, c) Et/Ch, and d) Me/Ch (1 wt. % ceramic and 12 wt. % polymer

in all of samples).

Fig. 4. SEM images and diameter size distribution of the nanofibers of the binary solvent

system of Et/Ch for different volume of ethanol: a) Et 10, b) Et 20, c) Et 25 and d) Et 30.

Fig. 5. SEM images and diameter size distribution of the nanofibers of a) 10 wt. % PCL b)

14 wt. % PCL in Et/Ch (20/80).

Fig. 6. SEM images and diameter size distribution of the nanofibers a) 1 wt. % nMg-FA, b)

5 wt. % nMg-FA, c) 10 wt. % nMg-FA, d) 15 wt. % nMg-FA, e) 20 wt. % nMg-FA

nanoparticles and f) curve of nanofiber diameter versus content of ceramic.

Fig. 7. XRD patterns of produced PCL–nMg-FA scaffolds with different fractions of

nanoparticles: a) PCL pure, b) 1, c) 5, d) 10 and e) 15 wt.%.

Fig. 8. FTIR spectra of produced PCL–nMg-FA scaffolds with different weight fractions of

nMg-FA.

Fig. 9. The X-ray maps of a) the PCL-5 wt. % and b) the PCL-10 wt. % scaffolds.

Fig. 10. TEM micrographs of the nanofibers of: a, b) Pure PCL; c, d) PCL-nMg-FA 1 %; e,

f) PCL-nMg-FA 5 % and g, h) PCL-nMg-FA 10 %.

Fig. 11. TGA curves of nMg-FA nanoparticle, the electrospun PCL and PCL-5 % nMg-FA.

Fig. 12. Typical tensile stress–strain curves of the electrospun scaffolds.

Table captions

Table 1. Selected factors and their levels.

Table 2. Properties of the solvents.

Table 3. Size of prepared fibers using different solvent systems (single and binary systems).

Table 4. Average fiber diameter size and standard deviation as a function of voltage (kV)

and nozzle to collector distance.

Table 5. Mechanical properties of the electrospun scaffolds.

Table 6. Selected factors and their levels.

EtOH / Ch Polymer (wt./v %) Ceramic (wt.%)

0/100 8 1

10/90 10 5

20/80 12 10

25/75 14 15

30/70 20

Table 7. Properties of the solvents.

Solvent Solubility parameter (MPa-1/2)

Dielectrical constant

Specific density (20 ��

Viscosity (20 / cP)

Boiling temperature ( )

Vapor pressure (20 �/mmHg)

Chloroform 18.84 4.80 1.48 0.58 61.7 160

Methanol 29.20 33.0 0.79 0.6 64.7 96

Ethanol 26.2 24.3 0.79 1.1 78.4 43.7

Table 8. Size of prepared fibers using different solvent systems (single and binary systems).

Solvent system Symbol Size of fiber (nm) S.D

pure chloroform Ch 2787 1203

Methanol/ chloroform Mt/ Ch 548 342

Ethanol/ chloroform Et/ Ch 692 78.3

Binary solvent system of Ethanol/ chloroform (v/v)

Ethanol Chloroform Symbol Size of fiber S.D

10 90 Et 10 872 540

20 80 Et 20 692 78.3

25 75 Et 25 1194 824

30 70 Et 30 1067 566

Table 9. Average fiber diameter size and standard deviation as a function of voltage (kV) and nozzle to

collector distance.

Voltage

Distance 25 cm 20 cm 15 cm

25 kV 427 (411) 490 (73) 646 (189)

20 kV 553 (102) 633 (152) 914 (191)

15 kV 677 (229) 714 (193) 1019 (139)

Table 10. Mechanical properties of the electrospun scaffolds.

Sample Stress (MPa) Strain (%) E-Modulus (MPa)

PCL Pure 2.29±0.13 444.8±46.2 14.9±2.8

PCL-1% 1.87±0.35 319.0±12.1 38.5±4.3

PCL-5% 2.34±0.45 408.6±12.8 10.2±2.6

PCL-10% 1.67±0.34 291.7±13.8 9.8±1.5

PCL-15% 1.83±0.1 155.6±3.9 15.4±2.7

PCL-20% 1.64±0.12 236.6±10.35 11.9±1.4

Figure 1

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