Initial Study of Electrospinning PCL/PLLA Blends

doi:10.4236/ampc.2011.13016

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Advances in Materials Physics and Chemistry, 2011, 1, 94-98

doi:10.4236/ampc.2011.13016 Published Online December 2011 (http://www.SciRP.org/journal/ampc)

Initial Study of Electrospinning PCL/PLLA Blends

Guinea B. C. Cardoso, Geraldine N. R. Perea, Marcos A. D’Avila, Carmen G. B. T. Dias,

Cecília A. C. Zavaglia, Antonio C. F. Arruda

Materials Engineering Department, Faculty of Mechanical Engineering, State University of Campinas,

Campinas, Brazil

E-mail: [email protected]

Received September 7, 2011; revised October 13, 2011; accepted October 24, 201 1

Abstract

The process of electrospinning is considered one of the most promising methods for the fabrication of poly-

mer nanofibers. This essentially consists of applying a high electric field, which causes stretching of the

polymer which exits through a capillary. Among the numerous applications of this process, electrospinning

allows the fabrication of semiconductor and conductive nanofibers from mixtures or solutions, which have

great potential for applications in sensors and the fabrication of scaffolds for cell growth. The aim of this

work was to analyze the properties of the blend, produces by the electrospinning of the PCL and PLLA solu-

tion, with the focus to generate a promissory scaffold. PCL is a semi-crystalline aliphatic polymer that has a

slower degradation rate 12 - 24 months. It has a low glass transition temperature at –60˚C, a melting tem-

perature at about 60˚C, and a high thermal stability. Properties of PLA depend on the component isomers,

processing temperature, annealing time and molecular weight. Thus were used PCL, from Aldrich, with Mw

of 80,000 g/mol, and PLLA, sintered in laboratory, with Mw of 240,000 g/mol, were dissolved in chloroform

(CHCl3, Merck) and acetone (Synth) by stirring for 6 hours. The solution was electrospinning for 1 hour us-

ing the equipment made in the laboratory, the voltage used was 13 kv, the rate of 0.5 ml/h and an approxi-

mate distance from the tip of the needle to the collector of 12 cm. The morphology of the samples was ob-

served by images made with scanning electron microscopy (SEM) and also was analyzed by FT-IR and

DSC.

Keywords: Polymers, Poly (ε-Caprolactone), Poly (L-Lactic Acid), Electrospinning

1. Introduction

Tissue engineering can be defined by Langer and Va-

canti, as “an interdisciplinary field that applies the prin-

ciples of engineering and the life sciences toward the

development of biological substitutes that restore, main-

tain or improve tissue function” [1].

Tissue engineering strategies aim for mimicking the in

vivo process of bone repair in a laboratory setting. The

three key elements for generating bone tissue, namely

osteogenic progenitor cells, osteoinductive growth fac-

tors and osteoconductive matrices are involved in this

process.

Scaffolds are temporary matrices for bone growth and

provide a specific environment and architecture for tissue

development. The material composition as well the

structural characteristics such as external and internal

design are putatively crucial for the successful outcome

of all scaffold-based bone tissue-engineering strategies.

Recently, the effects of the nano or micro structure

surface features of the various cells have been examined.

Some researchers have found that in the micro structured

surface environment, increasing the surface roughness by

sand-basting can affect the production of growth factors

and the number of osteoblast like MG-63 on a titanium

surface, or promote cell adhesion and migration on a

PMMA surface [2,3].

Some methods to fabricate scaffolds are electrospin-

ning, solvent casting, fiber bonding, phase separation,

gas induced foaming, salt leaching, 3D printing, selective

laser sintering, multi-phase jet solidification and others

[4-8].

Electrospinning, has attracted a lot of attention due to

its relative simplicity regarding the generation of fibrous

scaffolds with nanoscale dimensions. Electrospinning

utilizes electrostatic forces to spin polymer solutions or

melts into whipped jets, producing continuous fibers

with diameters from a few nanometers to micrometers

G. B. C. CARDOSO ET AL.95

after solvent evaporatio n in the spinning process [9,10].

Polymers are organic or inorganic materials, whose

structures are composed of repeating units, the mere

linked by covalent bonds. Among the polymers that are

used for more than two decades in the medical field, are

the poly (α-hydroxy acids), which is considered one of

the most promising family of polymers in the area of

bioresorbable. Its great advantage in this form of degra-

dation occurs by hydrolysis of their ester bonds. As an

example, poly (L-lactic acid) (PLLA), poly (glycolic acid)

(PGA) and poly (ε-caprolactone) (PCL), these sub-

stances obtained approval by the Food and Drug Ad-

ministration (FDA).

The poly (ε-caprolactone) (PCL) has been used in

many researches because of its biodegradable, biocom-

patible properties and also has the approval of US Food

and Administration (FDA). PCL is a semi-crystalline

aliphatic polymer that has a slow degradation rate 12 - 24

months. It has a low glass transition temperature at

–60˚C, a melting temperature at about 60˚C, and a high

thermal stability [11].

Poly (L-lactic acid) (PLLA) has been used in many

researches because the characteristics o f biocompatibilit y,

degradation and absorption in aqueous absorption in

aqueous medium, also has the approval of US Food and

Administration (FDA). PLLA is a semicrystalline poly-

mer with a melting point around 170˚C and a crystallin-

ity around 70%, making it among the poly (lactic), which

has the lowest rate of degradation.

By using only one type of polymer for the fabrication

of scaffolds is often not attained all the necessary char-

acteristics for a given clinical application. Thus, research

has been directed to study blends, copolymers and com-

posites that improve the fundamental properties of scaf-

folds, such as permeability, absorption and elastic prop-

erties [12].

The use of PLLA and PCL display important proper-

ties regarding degradation rates, porosity and resistance

to stress. Also, a critical characteristic is that they can be

molded in different sizes and shapes. In this work the

aim was to produce a blend of polycaprolactone and poly

(L-lactide) using the method of eletrospinning for a pro-

duction of scaffold. The blends were fabricated using

poly (ε-caprolactone) (PCL, from Aldrich), with Mw of

80,000, and poly (L-lactide) (PLLA, sintered in labora-

tory).

2. Materials and Methods

2.1. Preparation of the Solution

The polymer PLLA was synthesized by opening of cy-

clic dimer of lactic acid (lactide), with the objective of

obtaining high molecular weight polymer [13].

The blend was made using poly (ε-caprolactone) (PCL,

from Aldrich), with Mw of 80,000 g/mol, and PLLA,

with Mw of 240,000 g/mol, was dissolved in chloroform

(CHCl3, Merck) and acetone [(CH3)2CO, Synth] with a

rate of 25/75 wt%, respectively. The mixtures were stir-

ring during 6 hours [14].

2.2. Eletrospinning Process

The solution was electrospinning for 1 hour using the

equipment made in the laboratory, the voltage used was

13 kv, the rate of flow of 0.5 ml/h and an approximate

distance from the tip of the needle to the collector of 12

cm. The different percentages of PCL/PLLA were sam-

ple 1 25/75 wt%, sample 2 50 wt% and sample 3 75/25

wt%.

2.3. Instrumental Characterization

The morphology of the samples was observed by images

made with scanning electron microscopy (SEM) using

the equipment Jeol (JXA 840 A, Brazil). The average

were produce by the analysis of 8 wires in each sample,

and also were calculated the standard deviat ion.

The samples were also analyzed by Fourier Transform

Infrared Spectroscopy (FTIR) the blends of PLLA/PCL

were analyzed by infrared spectroscopy of the average

(4000 to 500 cm–1). The transmission spectra of samples

were obtained in the form of KBr pellet using THERMO

SCIENTIFIC NOCOLET IR100 spectrometer.

In the analysis of differential scanning calorimetric

(DSC), the thermal properties of the blends of PLLA/

PCL studied were determined using the equipment MET-

TLER TOLEDO DSC 823e. The samples were weighed

into an aluminum sample port of cylindrical and her-

metically closed. The test for the dynamic method was

performed under nitrogen atmosphere at 45 mL/min and

two scans temperature range:

 First scan of 0˚C to 300˚C at a ra te of 10˚C/min;

 Second scan of 0˚C to 300˚C at a rate of 10˚C/min;

interspersed with a cooling rate of 20˚C/min.

3. Results and Discussion

Biopolymer films are modified to promote cell growth

for tissue engineering can be generally categorized using

two types of approach. First, bioactive components such

as hydroxyapatite particles are incorporated into polyesters

by co-polymerization or blending. Second, the biopo-

lymers with the nano rough surfaces can be fabricated

using various techniques, such as the addition of surfac-

tants (e.g. Span 80, Sigma) and others reagents ( e.g. w at e r)

G. B. C. CARDOSO ET AL.

at the polymeric solution. For example, Mo X et al.,

reported that the emulsion fabricated by the eltrospinning

of poly (L-lactide-co-ε-caprolactone), Span 80 and dis-

tilled water produces samples with a surface that shows

to have influence into the pro liferation an d cells adh esion

[15].

3.1. DSC

The DSC analysis confirmed the blend of those polymers,

in all the heating the peaks showed in the same tempera-

ture, therefore those polymers combined just physically,

showed in the Figure 1.

The red line, sample with more PCL percent, presents

the peak of Tm more defined, when compared with the

sample with more PLLA in your composition, blue line,

which present an exothermically peak, because the in-

teraction of PLLA to PCL. The sample with 50% of PCL

and PLLA showed the peak in the middle of both sam-

ples.

3.2. IF-TR

Figure 2 shows the spectrum of PLLA at green line. All

the samples were dislocated 300 cm–1. Therefore the

peak at 2995 cm–1 corresponds to alkane stretch (C-H).

The C=O peak is at 1750 cm–1 while peak at 1187 cm–1 is

for C-O group. Figure 2 shows spectrum of PCL red line.

The O-H bond is at 3443 cm–1. The peaks appearing at

2943 and 2866 cm–1 are due to the C-H stretching. The

peak at 1724 cm–1 is due to the C=O bonding. The C-O

bending is at 1167 cm–1.

Figure 3 shows the spectrum of the polymer blends

(PLLA/PCL). The peak at 3358 cm–1 corresponds to O-H

bond. The C-H stretching is at 2992 and 2945 cm–1. The

peak at 1747 cm–1 is due to the C=O bonding and at 1184

cm–1 corresponds to the C-O bending. These groups indi-

cate the presence of both polymers (PLLA/PCL) in the

blends.

Figure 1. DSC of the samples: 1-blue; 2-green; and 3-red.

Figure 2. FT-IR of the samples green line—PLLA and red

line—PCL.

Figure 3. FT-IR of the samples: 1—red line; 2—purple; and

3—blue.

3.3. Morphology

The morphology of the different blends was showed in

the Figure 4. It is clear the alteration of the diameter of

the wires. In the Figure 4 (1B) the wires were showed an

average of 1.31 µm, this value showed near the Figure 4

(3B), where the media was 1.37 µm. However, when

produce the blend with equal proportion of PCL and

PLLA, the average showed lower, as 0.79 µm, that’s

possible by the solution presents characteristics indicated

for electrospinning. Also, in the Figure 4 (2B), it is pos-

sible to observe the morphology of the wires when con-

tact with other, in those intercession s present more adhe-

sion of the polymers.

The structural and functional properties of the natural

extracellular matrix (ECM) are crucial for the prolifera-

tion, differentiation and migration of cells. As a cones-

quence, there is an increasing tendency to design scaffold

materials, as applied in tissue regeneration approaches,

according to the characteristics of the ECM. The angle of

contact can be very useful for the adhesion and prolifera-

tion of cells, therefore is very important to study this

aspect, which will be the aim in th e next approach.

4. Conclusions

The use of biomaterials has been regarded as an efficient

alternative to the allograft, since it significantly reduces

the risk of rejection and local inflammation. Also, the

method of preparation of the biopolymer together with it

properties may influence in the degradation rate, flexibil-

G. B. C. CARDOSO ET AL.97

1A 1B

Figure 4. SEM images of the different samples: (1) sample 1;

(2) sample 2; and (3) sample 3; using (A) 1000x and (B)

5000x.

ity and cell adhesion.

The both polymers PCL and PLLA either alone or

combined as blends or co-polymer, are approved by the

Food and Drug Administration, therefore those polymers

have been extensively used in tissue engineering due to

their advantages of wide availability, ease of processing,

adjustable degradatio n and mechanical properties.

In this paper was observed the influence of the blend

composition into the fiber morphology, the fibrous mat

with high porosity were successfully obtained by elec-

trospinning, showing the potential use of electrospinning

to fabricate scaffolds for tissue engineering.

However are necessary others experiments to deter-

mine the effect of the blend composition into the degra-

dation rate and also the initial influence of the surface of

the fibers.

5. Acknowledgements

This work was support mainly by FAPESP project num-

ber 2009/54546 -9. The eq uipment sup por ts were especial

with the grants of CAPES and CNPq.

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