Preparation of chitosan_PLA blend micro_nanofibers by electrospinning

Preparation of chitosan/PLA blend micro/nano ?bers by electrospinning

Jia Xu,Jinhui Zhang,Weiquan Gao,Hongwei Liang,Hongyan Wang,Junfeng Li ?

College of Chemistry,Jilin University,Changchun,130012,People's Republic of China

a b s t r a c t

a r t i c l e i n f o Article history:

Received 3February 2008Accepted 11December 2008

Available online 25December 2008Keywords:

Electrospinning Nano ?ber Chitosan PLA

The chitosan/PLA blend micro/nano ?bers have been prepared for the ?rst time by electrospinning.Tri ?uoroacetic acid (TFA)was found to be the co-solvent for electrospinning.The chitosan/PLA blend solutions in various ratios were studied for electrospinning into micro/nano ?bers.The morphology of the ?bers was shown by scanning electron microscope (SEM).It was found that the average diameter of the chitosan/PLA blend ?bers became larger,and the morphology of the ?bers became ?ner with the content of PLA increasing.To show the molecular interactions,chitosan/PLA ?bers were characterized by Fourier transform infrared spectroscopy (FTIR).The spun micro/nano ?bers are expected to be used in the native extracellular matrix for tissue engineering.

?2008Elsevier B.V.All rights reserved.

1.Introduction

Electropinning is a simple and low-cost method for manufacturing nanoscale polymer ?bers [1].The micro/nano ?bers produced by electrospinning method have showed amazing characteristics such as very large surface area-to-volume ratio and high porosity with very small pore size [2],so they are used in the biomedical area,including wound dressings [3],drug delivery [4],tissue engineering scaffolds [5],and so on.For the tissue engineering scaffold,a highly porous micro-structure with interconnected pores and large surface area is conducive to tissue ingrowth.The collected non-woven ?bers mats just meet these requirements.The topology of these electrospun scaffolds closely mimics that of native extracellular matrix (ECM)[6].Many materials,including natural macromolecule [7,8],synthetic polymer [9,10]and their mixture [11],were manufactured into tissue engineering scaffold by electrospinning.Among these materials,chitosan (poly-1,4-D-glucosamine),a partially deacetylated derivative from chitin,is chemically similar to glycosaminoglycan (GAG)[12]and has many desirable properties as tissue engineering scaffolds [13].Nevertheless,just as other natural macromolecules,chitosan has a poor mechanical property for supporting tissue cells.With the development of synthetic polymer/natural macromolecule composite material in tissue engineer-ing,the mixing of chitosan and synthetic polymer which has a good mechanical property can improve the mechanical property.In the previous report,chitosan-based nano ?bers have been successfully electrospun from chitosan solutions blended with poly (ethylene oxide)(PEO)[14],poly (vinyl alcohol)(PVA)[15,16].PLA was a biocompatible synthetic polymer which was approved by the Food and Drug Administration for speci ?c human clinical applications,such

as surgical sutures and some implantable devices.Most importantly,PLA has eximious mechanical property [17]and is a perfect material to prepare composite material with chitosan.Many researchers have investigated manufacture of chitosan/PLA composite material by electrospinning.Peesan et al.[18]had successfully prepared hexanoyl chitosan/PLA blend ?bers by electrospinning.A ?y in the ointment was sacri ?cing many amino and hydroxyls in chitosan which were very useful signal to be identi ?ed by cells.Duan et al.[19]had prepared PLGA/chitosan hybrid nano ?ber membranes by collecting PLGA nano ?bers and chitosan nano ?bers on one rotary drum.

In this study,a very convenient method of using a single syringe was introduced for the preparation of chitosan/PLA blend ?bers and tri ?uoroacetic acid was the co-solvent.Chitosan and PLA were blended in at molecular level,which maintained both of their advantages.2.Experimental 2.1.Materials

Chitosan (Mw=8000–20,000,Sinopharm Chemical Reagent Co.,Ltd (China)),Poly(L-lactic acid)(PLA,Mw=5000,Changchun Institute of Applied Chemistry (China)),Tri ?uoroacetic acid (TFA,Tianjin Fuchen Chemical Reagents Factory (China)).2.2.Electrospinning

Different weights of PLA (0.02,0.09,0.18,0.27,0.36and 0.72g)were added into 10g TFA respectively together with 0.18g chitosan,the mixtures were stirred for 24h at room temperature.Then,the spinning solutions with different ratios by weight (chitosan/PLA:9/1,2/1,1/1,1/1.5,1/2and 1/4)were prepared.At room temperature,the polymer solution was placed into a 2ml glass syringe with the tip of inner diameter of 1mm.A clamp connected with high voltage power

Materials Letters 63(2009)658–660

?Corresponding author.Tel.:+86431851684704;fax:+8643185168420.E-mail address:j ?i@https://www.360docs.net/doc/2516234945.html, (J.

Li).0167-577X/$–see front matter ?2008Elsevier B.V.All rights reserved.doi:

10.1016/j.matlet.2008.12.014

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supplier (0–30kV)was attached to the glass syringe.As grounded collector,a piece of aluminum foil was placed towards the tip at the distance of 22cm.The polymer ?bers generated from the tip by high voltage ?ied to the grounded collector and formed the micro/nano ?ber mesh.The apparatus for the electrospinning experiments was similar to previous report [20].2.3.Instruments

The morphology of the electrospun ?bers were observed under a Scanning Electron Microscope (SHIMADZU SSX-550)at an accelerat-ing voltage of 15kV.FT –IR spectra were recorded on a Nicolet Instruments Research series 5PC Fourier Transform Infrared spectro-meter.The transmission electron microscopy (TEM)images were recorded on a JEM-2000EX microscopy.

3.Results and discussion 3.1.Selection of a solution

It is easy to ?nd a solvent which could dissolve chitosan,such as dilute acid,but the solution could not be spun into ?bers by electrospinning.Concentrated acetic acid solution could dissolve and electrospin chitosan [21],but it could not dissolve PLA.So ?nding a proper solvent to dissolve both chitosan and PLA became tough work.That's why the electrospinning of chitosan/PLA blend has never been reported.

TFA was a suitable solvent for chitosan electrospinning [22].Basing on this,we tried to dissolve PLA into TFA,and spun it into ?bers for the ?rst time successfully.The smooth ?bers were obtained between the concentration of 15%and 29%of the solution.Fig.1(F)shows the SEM images of typical PLA micro/nano ?bers.It explains that TFA is a good solvent of PLA for electrospinning.So according to this,TFA was selected as co-solvent of chitosan/PLA.3.2.Electrospinning

For the sake of electrospinning chitosan/PLA,the behavior of chitosan was studied ?rst.It was found that chitosan can be spun into ?bers with the concentration from 1.2

to 2.4wt.%.Comparing with other concentrations,the ?bers spun by the solution of 1.77wt.%(0.18g chitosan,10g TFA)were more homogeneous and smooth.So,this content was used in confecting chitosan/PLA blend solution.Fig.1(A –F)showed SEM micrographs of the micro/nano ?bers which were spun from the chitosan/PLA solutions with different content of PLA.It was observed that the ?ber diameter distribution of each sample was wide.With the increasing content of PLA,the beads were decreasing and the average diameter was increasing (Fig.2).TEM image (Fig.1(I))showed that chitosan and PLA were well blended in the ?ber.It was also found that some branches like Fig.1(B)insert image occurred in each samples.

In Previous report,Zhao et al.[23]attributed this phenomenon to the nonuniform dispersion of charges and low molecular weight.The nonuniform dispersion of charges could cause the electrostatic repulsion forces to overcome the surface tension in some areas,and the lower viscosity of the lower molecular weight polymer may allow for the split of the jet.Jessica D.Schiffman et al.[24]also gave another possible

explanation

Fig.1.SEM image of the chitosan/PLA blend ?bers in different weight ratios.(A)9/1;(B)2/1;(C)1/1;(D)1/1.5;(E)1/2;(F)1/4;(G)1/20;(H)pure PLA.TEM image (I)of the chitosan/PLA blend ?ber in 1/1.5weight

ratio.

Fig.2.The relationship between PLA content and ?ber average diameter.

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that the appearance of branching caused by low percent humidity.In their experiment,the branched ?bers were created in the 20–25%humidity range while the nonbranched ?bers were spun when the humidity was twice as high,40–45%humidity.

In our experiment,both of chitosan (Mw =8000–20,000)and PLA (Mw =5000)were low molecular weight polymer.At the same humidity,the ?bers which contained chitosan had branches,but pure PLA ?bers (Fig.1(H))had no branching.It may be explained that different polymers have different limiting values in humidity and molecular weight for occurring branches.

When the difference between the contents of chitosan and PLA was not very large,the morphology of ?bers had the property of chitosan as well as PLA,so the branched ?bers were created.When the content of PLA was inundatory,the morphology of ?bers was mainly contributed by PLA.Fig.1(G)showed SEM micrograph of the chitosan/PLA blend ?bers which were spun from 17.4wt.%(the weight ratio of chitosan and PLA is 1:20)blend solution.Obviously,the ?bers were homogeneous and smooth without any branching.It was just the same as pure PLA ?bers (Fig.1(H)).3.3.Study of Fourier transform infrared spectroscopy

Fig.3(A)displays the Fourier transform infrared spectroscopy (FTIR)spectra of the electrospun pure chitosan and pure PLA ?bers.Chitosan ?bers displayed characteristic absorption bands at 1680and 1540cm ?1which represent the amide I and II characteristic absorption bands respectively.A weak peak at 1324cm ?1is the amide III characteristic absorption band as shown in Fig.3A (a).

The FTIR spectrum of PLA ?bers (Fig.3A (b))depicted characteristic absorption bands at 1759,1185,1130and 1089cm ?1,which represent the backbone ester group of PLA.

Fig.3(B)displays the FTIR spectra of the electrospun chitosan/PLA blend ?bers with different ratios.Obviously,with the increase of PLA,the relative strength of peak at 1759cm ?1which belongs to carbonyl group in PLA was increased,and the relative strength of peak at 1680cm ?1which represent the amide I absorption band of chitosan was decreased.

The peaks position of these spectra almost didn't change.It may be explained that the molecular interaction between chitosan and PLA was weak because PLA does not have enough ?OH groups to form hydrogen bonds with ?OH groups and ?NH 2groups in chitosan.

4.Conclusion

In this study,we succeeded for the ?rst time in preparing chitosan/PLA blended ?bers by an electrospinning technique.We ?nd that tri ?uoroacetic acid is a suitable solvent for the electrospinning of

chitosan/PLA blended ?bers.With the increasing of content of PLA,the beads gradually disappeared and the morphology of ?bers became ?ner.The result of FTIR indicated that the molecular interaction between chitosan and PLA was weak.It was assumed that the production would have a great potential application in the tissue engineering.References

[1]Li D,Xia YN.Adv Mater 2004;16:1151–70.

[2]Park WH,Jeong L,Yoo DI,Hudson S.Polymer 2004;45:7151–7.[3]Kim SH,Nam YS,Lee TS,Park WH.Polym J 2003;35:185–90.

[4]

Zeng J,Xu X,Chen X,Liang Q,Bian X,Yang L,et al.J Control Release 2003;92:227–31.

[5]Zong X,Ran S,Fang D,Hsiao SB,Chu B.Polymer 2003;44:4959–67.

[6]Li WJ,Tuli R,Okafor C,Derfoul A,Danielson KG,Hall DJ,et al.Biomaterials

2005;26:599–609.

[7]Wnek GE,Carr ME,Simpson DG,Bowlin GL.Nano Lett 2003;3:213–6.[8]Chen ZG,Mo XM,Qing FL.Mater Lett 2007;61:3490–4.

[9]Yoshimoto H,Shin YM,Terai H,Vacanti JP.Biomaterials 2003;24:2077–82.[10]Yang F,Murugan R,Wang S,Ramakrishna S.Biomaterials 2005;26:2603–10.[11]Nam J,Huang Y,Agarwal S,Lannutti J.J Appl Polym Sci 2008;107:1547–54.[12]Gajewiak J,Cai SS,Shu XZ,Prestwich GD.Biomacromolecules 2006;7:1781–9.[13]Nettles DL,Elder SH,Gilbert JA.Tissue Eng 2002;8:1009–16.

[14]Bhattarai N,Edmondson D,Veiseh O,Matsen FA,Zhang MQ.Biomaterials

2005;26:6176–84.

[15]Jia YT,Gong J,Gu XH,Kim HY,Dong J,Shen XY.Carbohydr Polym 2007;67:403–9.[16]Zhou YH,Yang DZ,Chen XM,Xu Q,Lu FM,Nie J.Biomacromolecules

2008;9:349–54.

[17]Zhang JF,Sun XZ.Biomacromolecules 2004;5:1446–51.

[18]Peesan M,Rujiravanit R,Supaphol P.J Biomater Sci Polym Ed 2006;17:547–65.[19]Duan B,Wu LL,Yuan XY,Hu Z,Li XL,Zhang Y,et al.J Biomed Mater Res

2007;83A:868–78.

[20]Gupta P,Elkins C,Long TE,Wilkes GL.Polymer 2005;46:4799–810.[21]Geng XY,Kwon O,Jang J.Biomaterials 2005;26:5427–32.

[22]Ohkawa K,Cha D,Kim H,Nishida A,Yamamoto H.Rapid Commun

2004;25:1600–5.

[23]Zhao YY,Yang QB,Lu XF,Wang C,Wei Y.J Polym Sci Part B Polym Phys 2005;43:

2190–5.

[24]Schiffman JD,Schauer CL.Biomacromolecules 2007;8:594–

601.Fig.3.FTIR spectra of chitosan,PLA and chitosan/PLA blend ?bers.(A)chitosan (a)and PLA (b);(B)chitosan/PLA blend ?bers in different weight ratios.(c)9/1;(d)2/1;(e)1/1;(f)1/1.5;(g)1/2;(h)1/4.

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