Chiang Mai J. Sci. 2014; 41(1) 213

Chiang Mai J. Sci. 2014; 41(1) : 213-223http://epg.science.cmu.ac.th/ejournal/Contributed Paper

Fabrication of Natural Tapioca Starch Fibers by aModified Electrospinning TechniqueKrit Sutjarittangtham [a], Patthanakorn Jaiturong [b], Uriwan Intatha [c],Kamonpan Pengpat [a], Sukum Eitssayeam*[a] and Jakkapan Sirithunyalug [b][a] Department of Physics and Materials Science, Faculty of Science, Chiang Mai University,

Chiang Mai 50200, Thailand.[b] Department of Pharmaceutical Science, Faculty of Pharmacy, Chiang Mai University,

Chiang Mai 50200, Thailand.[c] School of Science, Mae Fah Luang University, Chiang Rai 57100, Thailand.*Author for correspondence; e-mail: sukum99@yahoo.com

Received: 13 October 2012Accepted: 19 March 2013

ABSTRACTWe report the fabrication of high purity natural tapioca starch (NTS) fibers by using

a modified electrospinning technique with a dehydration process using a -20°C ethanol collectorbath to complement the conventional electrospinning technique. Electrospun fibers withdiameters of 1.3-14.5 μm were generated from a simple solution of starch in deionized waterwith starting concentrations of 3.0 to 5.0 wt%. X-ray diffraction and FTIR analyses wereemployed to study the phase and functional groups occurring in the prepared NTS fibers.X-ray diffraction revealed an A crystalline type structure of the starting NTS and FTIR confirmedthat the functional group of the NTS electrospun fibers remained unchanged, indicatingunmodified NTS fiber products. The water swelling ratio was 148 % for the electrospun NTSat solution concentration of 4.5 wt% and 78% for 3 wt%. It has been found that using NTSfiber as a disintegrating excipient in tablet form for pharmaceutical applications was notcomparable with a superdisintegrant. However, by using a combination of NTS powdersand NTS fibers, in particular in lower percentages, there were good results, with a disintegratingtime of about one and half minute. These fibers were found to enhance swelling which showsthat this fiber is a promising candidate for drug release applications.

Keywords: electrospinning, tapioca starch, electrospun fibers, starch fibers

1. INTRODUCTIONNatural starch has been compounded

with other polymers to produce modifiedfibers using the electrospinning technique forapplications in the field of controlled drugrelease [1]. These starches are biodegradablepolymers with excellent biocompatibility and

non-toxicity but often present difficulty whenbeing formed. Additional polymers, forexample synthetic polymers of Poly(lactide);PLA, Poly(caprolactone); PCL and Poly(vinylalcohol); PVA or natural polymers of chitosanand alginate, are added to starch solutions to

214 Chiang Mai J. Sci. 2014; 41(1)

improve the forming properties [1]. The needfor high purity natural starch fibers withoutany additional added polymers requires theuse of an improved electrospinning technique.In this modified process, a simple starch indeionized water solution is modified by useof an ethanol bath collector at -20°C.

In general, starch is the main energystorage resource for all higher plants and hasgained much attention as a naturally occurringconstituent of biodegradable thermoplasticmaterials [1-2]. Such materials are known asnatural biopolymers, and have been widelyused for the entrapment of food ingredients,fillers, binders, and disintegrants in thepharmaceutical field as they are cost effective,non-toxic, biodegradable, edible, and can bemetabolized by the human body [1-3].

Two main components of biopolymersare amylose and amylopectin [4]. Three crystalstructures (A, B, C) have been described,depending on the starch region and the typeof processing of the starch products [4].Differences between these polymorphs arefound in the hydrogen-bonding pattern, thewater content, and in the conformation ofthe polysaccharide chain. A-starches areusually found in grains while B-starches arefound in tuberous plants. C-starches are rarerand found mainly in a few plant sourcesincluding the pea. Single helical V-typestructures have also been observed whenamylose crystals are prepared from complexes[4].

Starches and their derivatives play animportant role in drug delivery as a form ofadjuvants in tablet and capsule formulation[5]. In recent years, polymers based onstarches have shown potential applications inmatrix construction, such as matrix tabletsfor drug delivery applications and have beenused widely because of the simple and low-cost manufacturing process [6, 7].

Natural tapioca starch (NTS) is of

particular interest among commercialstarches due to a lower amylase content thanmost starches, low levels of residual materialsand high molecular weights of amylose andamylopectin which enable this starch to bedirectly used as a native starch substitutein industrial applications as well as astarting material for physical and chemicalmodification [8]. The use of tapioca starch isalso of much interest in Thailand sinceThailand is one of the world leaders in tapiocaproduct exports.

The electrospinning technique iscomposed of two distinct process,electrospray and spinning (electro+spinning),which can produce fibers on the microscaleto the nanoscale from a wide range of naturaland synthetic polymers [9]. For the basicelectrospinning set up, a high electric field isapplied to droplets of a polymer solution(or melt), coming out from the tip of a die,which acts as one of the electrodes. Thetheory is based on the assumption thatwhen a high voltage, usually in a range of 1 to30 kV, is applied to the polymer melt orsolution, it will experience two major typesof electrostatic and coulombic forces. Thefirst electrostatic force originates from therepulsion between the surface charges whilethe second is generated by an external electricfield [9-10]. These electrostatic interactionscause the droplet to accelerate, undergo jetbending instability and split into micro ornanofibers as a non-woven mat on thegrounded collector [9-12]. It has been foundthat microfibrous and nanofibrous structuresfrom the electrospinning technique possesslarge surface area to volume ratios [13].

The initially generated mats then need tobe separated and structured using anelectrospinning technique to generateprocessed fibers which have modifiedproperties including different diameters,composition, structure, morphology and

Chiang Mai J. Sci. 2014; 41(1) 215

orientation depending on the fiber spinningmethod [14]. Modification of the setup forelectrospinning can be done in by modifyingthe collector and spinneret. Reneker et al.produced a fluffy columnar network of fiberscalled a “garland”, which slowly moved inlarge loops and long curves and providedrelatively uniform mats [14-16]. Ultra-thinfibers with high productivity were successfullyfabricated using an array of multiple hollowneedles as the spinneret as reported by Chuet al. [14, 17]. Many researchers have usedspinnerets consisting of two coaxial capillaries,resulting in electrospun composite nanofiberswith core/sheath or hollow structures [14, 18-20]. With these approaches the structure andmorphology of the electrospun fibers can becarefully controlled.

In addition, the morphology andproperties of the electrospun fibers arehighly tunable by modifying any number offabrication parameters, including theconcentration of polymer solution, thevoltage between the nozzle and collector,humidity in the chamber, temperature, andsolvents [12, 21]. The choice of solvent isalso critical as to whether fibers are capableof forming and can also influence fiberporosity. To allow for sufficient solventevaporation to occur in the time between thecapillary tip and the collector, a volatile solventmust be used. Phase separation may alsooccur during the fiber jet trajectory throughthe atmosphere toward the collector beforethe solid polymer fibers are deposited.This process is greatly influenced by thevolatility of the solvent.

The traditional electrospinning techniquerequires starch fibers to dehydrate in the shorttraveling time between the nozzle andcollector. This is particularly difficult forstarches such as pure Tapioca starch fiberssince they can become quite swollen and bedifficult to dehydrate. Thus, an innovative

method capable of fabricating electrospuntapioca starch is required. The researchdescribed here examines the fabrication ofhighly pure Tapioca starch fibers, using amodified electrospinning setup with theaddition of an ethanol collector bath cooledat -20°C in order to increase the dehydrationspeed of the swollen electrospun tapiocafibers. The processing parameters includesuch intrinsic properties of the polymersolution as concentration and viscosity andoperation conditions such as the strength ofthe applied electric field, the distance betweenthe nozzle and collector, and the flow rate.The prepared NTS fiber properties such assize, structure, morphology, water swellingratio and disintegration properties [22-23]were then investigated.

2. MATERIALS AND METHODS2.1 Preparation of Natural Tapioca StarchSolutions

NTS was purchased from E.T.C.International Trading Co., Ltd. (Thailand)and deionized water was supplied byElectroceramics Research, Physics andMaterial Science, Chiang Mai University,Thailand. They were mixed in concentrationsof NTS of 3, 3.5, 4, 4.5 and 5 wt% and themixtures were then stirred for 20 min at75°C in order to fully dissolve the starch.After that, the prepared solutions were cooledto room temperature to be ready to beelectrospun.

2.2 Electrospinning of Tapioca StarchSolution

Electrospinning is a process adaptedfrom electrospraying where droplets of solidpolymer are formed instead of fibers.In electrospinning, a number of processingparameters are, carefully controlled in orderto generate the polymer fibers with thedesired formation and structure as opposed

216 Chiang Mai J. Sci. 2014; 41(1)

to just droplets. Three important parameters;the applied voltage, polymer flow rate andcapillary-collector distance, are normallyoptimized. In this work, to form the requiredNTS fiber structure, these three parameterswere first varied and then kept at optimumvalues of 20 kV for the applied voltage,10 ml/h for the polymer flow rate, 0.9 mmdiameter of the tip and 15 cm for the capillary-collector distance.

Figure 1 shows the experimental setupfor the modified electrospinning technique.The ethanol bath at -20°C (Ethanol of 99.9%

purity from Merck), was added to a typicalsyringe pump electrospinning system inorder to enhance the rate of dehydration ofthe electrospun tapioca starch fibers. A metalgrid was used as a target immersed within theethanol bath. Tapioca starch pastes of variousconcentrations were forced through theneedle using a syringe pump and then wereelectrospun directly to the metal target in the-20°C cooled ethanol bath. After that, waterand ethanol stored within the electrospuntapioca starch fibers were removed using avacuum pump.

2.3 Structure CharacterizationFT-IR analysis was used to qualitatively

characterize the functional groups of thetapioca starch powder and the electrospunfibers. The FTIR spectra were collected ata resolution of 2 cm-1 on a Nicolet 6700FT-IR, from Thermo Electron ScientificInstrument,LLC (USA). The X-ray diffraction(XRD) patterns of the tapioca starch powderand fibers were investigated using anX-ray diffractometer (X’ Pert Pro MTD,PANalytical) with Nickel-filtered Cu Kαradiation at 40 kV and 50 mA in the 2θ rangeof 5°- 60°.

2.4 Morphology ObservationsThe morphology of the tapioca starch

fibers was examined using a scanningelectron microscope (SEM; SNE-3000M,Nanoeye) to determine the pore and diametercharacteristics. The samples were arrangedon a metal stub using carbon adhesive tapeand coated with gold under vacuum beforeobservation.

2.5 Water Swelling RatioNTS fibers were left in a hot air oven;

redLINE (BINDER, Germany) at 30±0.5°Cfor 2 days. The water swelling ratio (WSR)

Figure 1. The modified electrospinning setup with -20°C ethanol bath.

Chiang Mai J. Sci. 2014; 41(1) 217

W1 - W0

W0

× 100%

of the electrospun tapioca starch fiberswas calculated using the following equation:

WSR =

where W0 is the weight of the tapioca starchfiber which was dried at 60°C until aconstant weight was achieved and W1 is theweight of the fully swollen fiber after beingcentrifuged at 4000 rev/min for 10 min.All the experiments were performed intriplicate [24- 26].

2.6 Disintegration PropertiesIn this test, the electrospun NTS fibers

at 4.5 wt% of NTS solution were comparedwith NTS powders. NTS fibers of 4.5 wt%were was used as a disintegrating excipientin tablet form with concentrations of 1,2.5, 5, 7.5 and 10 wt% in dibasic calciumphosphate dihydrate, compared with thesame amount of tapioca starch, and theeffects of both excipients on disintegrationwere studied. A direct compression dibasiccalcium phosphate dihydrate (Sudeep PharmaLtd., India) was tumble-mixed for 5 minutesin a plastic bag with the starch. Subsequentlythe homogeneous powder was thoroughlycombined with magnesium stearate aslubricant, in the amount of 0.5 percent byweight, for one minute. The mixed powderwas then compressed on a single stroketablet-making machine (Hanseaten Exacta E1,Germany) using a compression force of1800 kg. The tablets so obtained have around shape and a flat surface, with a diameterof 10 mm, and a weight of 500 mg pertablet. The tablets were checked for hardnessby hardness tester (Erweka, TBA-100,Germany). The tablet is placed between twojaws that crush the tablet. The machinemeasures the force applied to the tablet anddetects when it fractures. And disintegrationtime was measured by disintegration apparatus

(Pharmatest, PTZ-AUTO, Germany) indistilled water at 37°C, following USP 32/NF 27.

3. RESULT AND DISCUSSION3.1 Structure and MorphologyCharacterization3.1.1 FT-IR analysis

Figure 2 shows the FT-IR spectra of thenative tapioca starch powders and electrospuntapioca starch fibers. It can be seen that theFTIR spectra of the native tapioca starchpowders have three main peaks withmaximum absorbance at 1149 cm-1, 1077cm-1 and 995 cm-1. The bands at 1149cm-1and 1077 cm-1 are associated with theordered structures of starch, whereas, theband at 995 cm-1 is indicative of amorphousstructured starch [27]. Other characteristicbands at 1210 cm-1 and 1720 cm-1 can beattributed to the bending and stretchingvibration of the C-O bond while the broad3423 cm-1 band corresponds to the stretchingvibration of the O-H bond [28].

Figure 2. The FT-IR spectra of NTS powdersand NTS fibers.

218 Chiang Mai J. Sci. 2014; 41(1)

It can be seen that the intensity of the995 cm-1 band of the electrospun NTS fibersincreased between the NTS fibers withconcentrations of 3.0 wt% and 3.5 wt%.These results suggest that the orderedstructure of the native starch was disruptedwhich may occur during the preparation ofthe tapioca starch solution at 75°C to dissolvethe starch in deionized water. The heatrequired during this process may disrupt thestructure of the starch, resulting in a moreamorphous structure of the electrospunfibers. For the NTS fibers prepared by NTSsolution concentrations up to 4.0 wt% and4.5 wt%, the 995 cm-1 band were decreasing.This is indicative of the increase in crystallinityof the fibers containing higher concentrationsof tapioca starch due to the retrogradationof starch [27].

It is also interesting to note that the nativestarch has a prominent band at 927 cm-1.This is a water sensitive band characteristicof hydrophilicity in starches [29]. Consideringthe FT-IR spectra of all electrospun fibers,the intensity of this band slightlyincreased compared to that of native tapioca

starch powder, suggesting an increase inhydrophilicity. This may be related to theenhancement of the amorphous nature in theelectrospun starch samples with a concomitantdecrease in their ordered structure [24].

3.1.2 X-ray diffraction studiesThe X-ray diffraction patterns of the

NTS powder and electrospun NTS fibersare shown in Figure3. From the XRDpatterns of the NTS powders there arediffraction peaks at 2θ of 15.2, 17.2, 19.9,23.3 and 26.5 degrees, which are characteristicof an A-type starch [30]. All of the XRDpatterns of the NTS fibers illustrate anamorphous type pattern showing a verybroad pattern. For the electrospun fiberswith 4.5 wt% of NTS concentration there isa noticeable diffraction peak at around2θ=13°. This may be attributed to increase incrystallinity of this 4.5wt% electrospun fiber.This result agrees well with FT-IR spectra asan increase in the crytallinity of the electrospunNTS was observed in these high concentrationsamples.

Figure 3. XRD patterns of NTS powder and the electrospun NTS fibers with starchconcentrations of 3.0 wt%, 3.5 wt%, 4.0 wt%, and 4.5 wt%.

Chiang Mai J. Sci. 2014; 41(1) 219

3.1.3 Morphology observationsThe morphology of the NTS fibers

was observed using a Scanning ElectronMicroscope and is shown in Figure 4. Theelectrospun NTS fibers have diameters of1.3-14.5 μm. All formed well defined matsexcept for that of the 3 wt% sample, whichshowed a large connected area. This may bedue to the incomplete dehydration process

of the 3 wt% electrospun fibers where theremaining water may later dissolve somefibers resulting in a large connected area.It can be also noticed that the increase inNTS concentration gave rise to smoothnessin the electrospun fibers with an optimumvalue of 4.5 wt%. The 5 wt% solution causedthe block up of the spinneret tip as a resultof its high viscosity.

Figure 4. The morphology of the electrospun NTS fibers with starch concentrations of(a) 3 wt%, (b) 3.5 wt%, (c) 4 wt% and (d) 4.5 wt%.

3.2 Water Swelling RatioThe tablet disintegration process is the

beginning of the drug release process. If thetablet has rapid disintegration time thisresults in fast release. Swelling is the mainmechanisms of the disintegration process.Normally, swelling agents absorb amountsof water and generate driving forces todisintegrate the tablet into small piecesbefore the dissolution process [31]. For drug-release application purposes, the waterswelling ratios (WSR) of each of theelectrospun NTS fiber mats were measured.Figure 5 shows the relationship between the

WSR of the electrospun NTS fibers and theirconcentrations. It can be clearly seen thatthe WSR of the NTS fibers increased as theconcentration of the NTS solution increased.Considering the morphology of theNTS fibers (Figure 4), the increase in NTSconcentration not only affected thesmoothness of the fibers but also increasedthe surface area of the fiber mats, leading toan increase in their WSR. This result isconsistent with the FT-IR result as an increasein hydrophilicity of the electrospun NTSfibers was also observed with increasingstarch concentration.

220 Chiang Mai J. Sci. 2014; 41(1)

3.3 Disintegrating PropertiesThe average disintegration times of

tablets which contain 4.5 wt% NTS fiber(table 1) in percentages of 1, 2.5 and 5 wt%were 284, 241 and 223 seconds respectively.In comparison with NTS powder of thesame amount, it was found that thedisintegration times of tablets using NTSpowder as disintegrate were more than10 minutes longer than that of NTS fiber.For higher content, i.e. 7.5 and 10 wt%, theNTS powder showed lower values of 55and 80 seconds disintegration time, whileNTS fiber took 234 and 462 seconds. Withhigher content of NTS fiber, it was possibleto prevent water uptake by the tablet surfacethus also delaying disintegration because ofits high swelling property, leading to blocking

Figure 5. The relationship between the starch concentration and water swelling ratio.

the water. From the results obtained, it can beconcluded that NTS fiber can be used inmuch smaller amounts than NTS powder topromote tablet disintegration. This researchcontrols the hardness in the range of 5-7 kgffor comparable disintegration times ofNTS powders and NTS fibers. When 2.5 or5.0 wt% each of NTS fiber and NTS powderwere used in combination in tablet, it wasevident that there were synergistic effectsleading to a shorter tablet disintegrationtime, i.e. 95 and 84 seconds, compared withusing a single component with the sameamounts. To find other possible applicationsin pharmaceutical formulations of thisnew NTS fiber, further studies will beconducted.

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Table 1. The disintegration times of tablets which contain NTS fibers and NTS powder.

No.

1

2

3

4

5

6

x

SD

Disintegrations times (sec.)

Emcompress

> 900

> 900

> 900

> 900

> 900

> 900

-

-

1

276

248

274

258

330

318

284.0

32.9

2.5

251

251

241

267

225

213

241.3

19.6

5

217

243

202

260

204

215

223.5

23.1

7.5

213

229

232

228

253

249

234.0

14.8

10

490

400

508

486

539

354

462.8

70.6

NTS fibers (wt%) NTS powders (wt%)

1

> 900

> 900

> 900

> 900

> 900

> 900

-

-

2.5

> 900

> 900

> 900

> 900

> 900

> 900

-

-

5

> 900

> 900

> 900

> 900

527

698

-

-

7.5

67

55

46

39

63

59

54.8

10.6

10

80

69

111

90

76

51

79.5

20.2

4. CONCLUSIONAn electrospinning technique with the

addition of a cooled collecting bath ofethanol at -20°C was employed successfullyfor the fabrication of highly pure electrospunNTS fibers. Starch concentration of 4.5 wt%in deionized water gave rise to electrospunfiber mats with a smooth and homogeneousfiber surface. The largest surface area wasalso obtained for the 4.5 wt% sample whichresulted in the highest value of the waterswelling ratio. The structural studies in bothFT-IR and XRD revealed an increase in theamorphous nature of all electrospun NTSfibers compared to that of NTS powder.This electrospun high purity NTS fiber matmay be of particular interest in drug-releaseapplications. The use of NTS fiber andNTS powder in combination with a loweramount as disintegrant for each tablet,rendered good disintegrating times of aboutone and a half minutes. NTS fiber itself,however, cannot be compared with asuperdisintegrant. To ensure the safe use ofthis product, further experiment inbiocompatibility should be conducted.

ACKNOWLEDGEMENTSThe authors would like to express their

sincere gratitude to the Thailand Research

Fund (TRF), the Royal Golden JubileePh.D. Program, Office of the HigherEducation Commission (OHEC) and theGraduate School and Faculty of Science,Chiang Mai University, Thailand for theirfinancial support. We also wish to thankthe National Research University Projectunder Thailand’s Office of the HigherEducation Commission for financialsupport. The authors would to thank Dr.Denis Russell Sweatman for checking themanuscript.

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