Polymer-free electrospun nanofibers from sulfobutyl ether7-beta-cyclodextrin (SBE7-β-CD) inclusion complex with sulfisoxazole: fast-dissolving and enhanced water-solubility of sulfisoxazole

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Polymer-free

electrospun

nano

ﬁbers

from

sulfobutyl

ether

7 -beta-cyclodextrin

(SBE

7 -

b

-CD)

inclusion

complex

with

sul

ﬁsoxazole:

Fast-dissolving

and

enhanced

water-solubility

of

sul

ﬁsoxazole

Zehra

Irem

Yildiz,

Asli

Celebioglu,

Tamer

Uyar

*

InstituteofMaterialsScience&Nanotechnology,UNAM-NationalNanotechnologyResearchCenter,BilkentUniversity,Ankara06800,Turkey

ARTICLE INFO

Articlehistory:

Received27February2017

Receivedinrevisedform13April2017 Accepted20April2017

Availableonline23April2017 Keywords:

Electrospinning Electrospunnanoﬁbers

Sulfobutylether7-beta-cyclodextrin

(Captisol1) Sulﬁsoxazole Inclusioncomplex Water-Solubility

ABSTRACT

In this study, our aim was to develop solid drug-cyclodextrin inclusion complex system having nanoﬁbrousmorphologyinordertohave fast-dissolvingpropertyandenhancedwater-solubilityof poorly water-solubledrug.Here,we preparedahighly concentratedaqueoussolutionof inclusion complexbetweensulﬁsoxazoleandsulfobutylether7-beta-cyclodextrin(SBE7-b-CD,Captisol1),and

then,withoutusinganypolymericmatrix,theelectrospinningofsulﬁsoxazole/SBE7-b-CD-ICnanoﬁbers

was performedinordertoobtainfree-standing andhandynanofibrousweb.As acontrolsample, nanofibersfrompureSBE7-b-CDwasalsoelectrospunandfree-standingnanofibrouswebwasobtained.

TheSEMimagingrevealedthatthebead-freeanduniformnanofibermorphologywiththeaveragefiber diameter(AFD)of650290nmforsulfisoxazole/SBE7-b-CD-ICNFand890415nmforpureSBE7-b-CD

NF was obtained. The inclusion complex formation between sulﬁsoxazole and SBE7-b-CD in

sulﬁsoxazole/SBE7-b-CD-ICNFsamplewasconﬁrmedby1HNMR,TGA,DSC,XRDandFTIRanalyses.

Due tothe combined advantageof cyclodextrininclusion complexation and high surface area of electrospun nanofibers, fast-dissolving property with enhanced water-solubility was successfully achievedforsulfisoxazole/SBE7-b-CD-ICNF.Ourfindingssuggestthatelectrospunnanofibers/nanowebs

fromCD-ICofpoorlywater-solubledrugsmayofferapplicableapproachesforhighwater-solubilityand fast-dissolvingtabletformulationsfordrugdeliverysystems.

1.Introduction

Cyclodextrins(CDs)arecyclicoligosaccharideshavingeither6, 7,or8glucopyranoseunitslinkedby

a

-1,4linkagesinthecycleand arenamedas

a

-CD,

b

-CDand

g

-CD,respectively(Szejtli,1998).

CDshavetruncatedcone-shapedmolecularstructurewhichcan

formsupramolecular structures by forming non-covalent

host-guestinclusioncomplexeswithvarietyofmolecules(Szejtli, 1998). TheinnersideoftheCDisrelativelyhydrophobicandtheouter sideishydrophilicwhichmakesCDstoforminclusioncomplexes

with various hydrophobic molecules including drug molecules

(Ogawaetal.,2015).Oneofthemainproblemsinpharmaceutical

industry is low water-solubility of the drugs which result in

decreasein bioavailability; nevertheless, theinclusion complex formationofdrugswithcyclodextrinsovercomesthisproblemand

enhancesthebioavailabilityofthedrugsbyincreasingtheir water-solubility.But,nativecyclodextrins(

a

-CD,

b

-CDand

g

-CD)have lower water-solubility which sometimes restrictedtheir usein pharmaceuticalformulation. Yet,chemicallymodiﬁedCD deriv-ativessuchashydroxypropyl-CD,methylated-CD,sulfobutyl

ether-CD have much higher water solubility. Sulfobutyl

ether-beta-cyclodextrin (SBE7-

b

-CD, Captisol1) is sulfobutyl derivative of

b

-CD with a 6.6 average degree of substitution (Fig.1a). This

substitution decreases nephrotoxicity of cyclodextrin while

increases its aqueous solubility to a great extent (Beig et al., 2015).OneofthedistinctivefeaturesofSBE7-

b

-CDisextensionof

thecavityduetorepulsionofendgroups'negativechargeswhich providesstrongerbindingtothedrugmolecules(Beigetal.,2015). TheotherfeatureisthepresenceofnegativechargesinSBE7-

b

-CD

atphysiologicalpHwhichmakesbindingwithapositivelycharged drugmoleculepossible.Therefore,theinclusioncomplex forma-tionwithSBE7-

b

-CDhasadvantagesfordrugdeliverysystems.

TheapplicationofinclusioncomplexesofCDswithdrugmaybe

widen by the incorporation of such molecular complexation

*Correspondingauthor.

E-mailaddresses:tamer@unam.bilkent.edu.tr,tameruyar@gmail.com(T.Uyar).

http://dx.doi.org/10.1016/j.ijpharm.2017.04.047

InternationalJournalofPharmaceutics531(2017)550–558

ContentslistsavailableatScienceDirect

International

Journal

of

Pharmaceutics

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systemsinto highlyporous nanoﬁbrous carriermatrix.

Electro-spinning, being one of the versatile methods for nanoﬁber

production, enables us to produce nanoﬁbers and nanoﬁbrous

webshavinghighsurfaceareatovolumeratio,nano-scaleporosity anddesignﬂexibilityforchemical/physicalfunctionalization,etc.

Due to their exceptional properties, it has been shown that

electrospun nanoﬁbers and their nanomats/nanowebs have

potential use in various application areas in biotechnology,

membranes/ﬁlters, food, agriculture, sensor, energy etc, (Aytac etal.,2015,2017;Noruzi,2016;Sahayetal.,2012;UyarandKny, 2017).Electrospunnanoﬁberscouldalsobeusedfordrugdelivery systemsfortargeteddeliveryand/orforinhibitionofdrugadverse side effects withcontrolledrelease (Aytacet al., 2015;Mendes etal.,2016;Wangetal.,2016).

Electrospun polymeric nanoﬁbers incorporating drug-cyclo-dextrininclusioncomplexes(CD-ICs)haveshowntobepromising matrixfordrugreleasesystems(Aytacetal.,2015;AytacandUyar, 2017;Tonglairoumetal.,2013).Forinstance,Siafakaetal.(2016)

hasperformeda studyonthecomparisonofelectrospun

nano-ﬁbersand cyclodextrinasdrug deliverysystem suggestingthat

both systems weregood for drug delivery and showed similar

efﬁciency. In our approach, we combine the efﬁciency of

cyclodextrin inclusion complexation and high surface area of

electrospunnanoﬁbersfor effectivedrugdelivery system.Since

electrospinning of nanoﬁbers from small molecules is quite a

challenge,mostlypolymericmatrixisneededtoobtainnanofibers (UyarandKny,2017;Wendorffetal.,2012).Nevertheless,inour recentstudiesweachievedtheelectrospinningofnanofibersfrom purecyclodextrintypes(nativeCDsandmodifiedCDs)(Celebioglu and Uyar, 2012, 2013; Celebioglu et al., 2014b) and CD-ICs (CelebiogluandUyar,2011;Celebiogluetal.,2014a,2016;Aytac etal.,2016a,b)withoutusingpolymericcarriermatrix.

Sulfonamidesaresyntheticdrugsknownbytheirantimicrobial effectsondifferentpathogenicmicroorganisms(Ta9cicetal.,2014). However,theuseofthesetypesofdrugsissometimeslimiteddue totheirpoorwater-solubility.Theoxazolesubtitutedsulfonamide iscalledassulfisoxazole(Fig.1a).Sulfisoxazoleisaweakacidand slightly soluble inwater. Inthis study, ouraimwas todevelop nanofibroussulfisoxazole-cyclodextrininclusioncomplexsystem (Fig.1a)inordertohavefast-dissolvingcharacterandenhancethe

water-solubility of sulﬁsoxazole. Here, we prepared a highly

concentrated aqueous solution of inclusion complex between

sulﬁsoxazole and SBE7-

b

-CD, and then, without using any

polymeric matrix, sulﬁsoxazole/SBE7-

b

-CD-IC was electrospun

into nanoﬁbrous structure toobtaina free-standingand handy solidform(Fig.1b).Weobservedthatsulﬁsoxazole/SBE7-

b

-CD-IC

nano_ﬁbrous web was readily soluble in water and the

water-solubilityofsulfisoxazolewasenhancedsignificantly.Ourfindings

Fig.1.(a)ThechemicalstructureofsulﬁsoxazoleandSBE7-b-CDwithaschematicrepresentationofsulﬁsoxazole,SBE7-b-CDandtheirIC,(b)Schematicrepresentationof

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suggestedthatsulﬁsoxazole/SBE7-

b

-CD-ICin theformof

nano-ﬁbrous webs can be quite useful in fast-dissolving tablet

formulationsfordrugdelivery.

2.Materialsandmethods

Sulﬁsoxazole(99%)wasobtainedfromSigma-Aldrich commer-cially.SBE7-

b

-CD(Captisol1,averagedegreeofsubstitution=6.6)

waskindlydonatedbyCydexPharmaceuticalsInc.(Kansas,USA). Potassiumbromide(KBr,99%,FTIRgrade,Sigma-Aldrich), deuter-ateddimethylsulfoxide(d6-DMSO,deuterationdegreemin.99.8% forNMRspectroscopy,Merck)wereusedinthisstudy.Thewater

used wasfroma MilliporeMilli-Qultrapurewater system. The

materialswereusedas-receivedwithoutanyfurtherpuriﬁcation process.

2.1.Preparationofsolutions

TheinclusioncomplexsolutionofsulﬁsoxazolewithSBE7-

b

-CD

was initiallyprepared by1:1 molarratioof sulﬁsoxazole:SBE7

-b

-CD.However,themolarratiowaschangedto1:2(sulﬁsoxazole: SBE7-

b

-CD)sinceelectrospinningofuniformnanoﬁbercannotbe

obtainedfrom1:1complexsolution.Firstly,sulﬁsoxazolepowder wasdispersedinwaterthenSBE7-

b

-CD(200%(w/v))wasaddedto

thedispersion.Afterthat,thesolutionwasstirred24huntilclear

and homogenous solution was obtained. Besides, to make

comparison,highlyconcentratedSBE7-

b

-CD(200%(w/v))solution

withoutsulﬁsoxazolewasalsopreparedinwaterforthe electro-spinningofpureSBE7-

b

-CDnanoﬁbers.Sulﬁsoxazole/SBE7-

b

-CD-ICwasalsoobtainedinthepowderforminordertocomparewith sulﬁsoxazole/SBE7-

b

-CD-ICNFintermsofthedissolvingrateand

watersolubility.Sulﬁsoxazolepowderwasdispersedinwaterand

then SBE7-

b

-CD was added with the molar ratio of 1:2

(sulﬁsoxazole:SBE7-

b

-CD). After 24h stirring, this inclusion

complex solutionwas frozenat 80_C _for _two _days _and _then

lyophilizedinafreeze-dryerfor24htoobtainsulﬁsoxazole/SBE7

-b

-CD-ICpowder.

2.2.Electrospinningofnanoﬁbers

Sulﬁsoxazole/SBE7-

b

-CD-IC solutionwas loadedto the 1mL

syringeﬁttedwitha0.4mminnerdiameterhavingneedle. The

syringe was placed horizontally on the syringe pump (KD

Scientiﬁc,KDS101) and thesolutionwas pumpedwithrate of

Fig.2. Phase solubilitydiagram of sulﬁsoxazole/SBE7-b-CD systemsin water

(n=3).

Fig.3.Photographsofelectrospun(a)SBE7-b-CDNF,(b)sulﬁsoxazole/SBE7-b-CD-ICNF,andSEMimagesof(c)SBE7-b-CDNF,(d)sulﬁsoxazole/SBE7-b-CD-ICNF.

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0.5–1mL/h.Agroundedmetalcollectorcoveredbyaluminumfoil wasplacedat10_–15cmfromthetipoftheneedleandtheapplied voltagewas10–15kV.TheelectrospinningofpristineSBE7-

b

-CD

NF was performed with the same conditions/parameters. The

electrospinning system was enclosed by Plexiglass box and

electrospinningwasperformedat25Cand30%relativehumidity.

2.3.Measurementsandcharacterizations

Phase solubilitymeasurement was carried out according to

Higuchi andConnors (1965). Anexcessamountofsulﬁsoxazole

was added to 5mL of aqueoussolutions containing increasing

concentration of SBE7-

b

-CD ranging from 0 to 7.4mM. The

Fig.4.1

HNMRspectraof(a)sulfisoxazolepowder,(b)SBE7-b-CDNFandSBE7-b-CDpowder,(c)sulfisoxazole/SBE7-b-CD-ICNF,(d)sulfisoxazole/SBE7-b-CD-ICpowder.

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suspensionswereshakenfor48hatroomtemperaturetoreach

equilibrium. Then, all suspensions were ﬁltered by a 0.45

m

membraneﬁltertoremoveundissolvedpartsandallsuspensions weredilutedwithwater.Sulﬁsoxazoleconcentrationwithrespect toincreasingSBE7-

b

-CDconcentrationwasdeterminedbyUV–vis

spectroscopy(Varian,Cary 100)at 260nm. The resultof phase

solubility was given as a plot of the molar concentration of

sulﬁsoxazole versus molar concentration of SBE7-

b

-CD. The

apparent stability constant (Ks) of sulﬁsoxazole/SBE7-

b

-CD-IC

werecalculatedfromthephasesolubilitydiagramaccordingtothe followingequation:

Ks=slope/S0(1-slope) (1)

whereS0istheintrinsicsolubilityofsulﬁsoxazole.

The samples of electrospun nanoﬁbers (SBE7-

b

-CD NF and

sulﬁsoxazole/SBE7-

b

-CD-ICNF)wereinvestigated

morphological-lybyscanningelectronmicroscopy(SEM,FEI-Quanta200FEG).

Nanoﬁbers weresputtered with 5nm Au/Pd layer to minimize

charging by PECS-682. Average ﬁber diameter (AFD) for both

nanoﬁbrouswebwascalculatedfromSEMimagesof100ﬁbers. Theprotonnuclearmagneticresonance(1_H_NMR,_Bruker_D

PX-400) system was used to determine molar ratio between

sulﬁsoxazole and SBE7-

b

-CD. In addition, SBE7-

b

-CD powder

wasalsoanalyzedby1HNMRtoseeifthereisanychangedueto degradation in chemical structure of SBE7-

b

-CD after

electro-spinning process. 30gL1 concentration of pure sulﬁsoxazole, SBE7-

b

-CDpowder,SBE7-

b

-CDNF,sulﬁsoxazole/SBE7-

b

-CD-ICNF

and sulﬁsoxazole/SBE7-

b

-CD-IC powder was dissolved in

d6-DMSO separately for the preparation of solution for 1_H _NMR

measurements.

Thermogravimetricanalysis(TGA,TAQ500,USA)wascarried outtodeterminethethermal properties ofsulﬁsoxazole, SBE7

-b

-CDNFandsulﬁsoxazole/SBE7-

b

-CD-ICNF.Thesestudiesofthe

sampleswereperformedfrom25to600_C_with_a_heating_rate_of

20C/minundernitrogengasﬂow.

Differential scanning calorimetry(DSC, TAQ2000, USA) was

usedtoanalyzeinclusioncomplex formationbetweensul

ﬁsox-azole and SBE7-

b

-CD. DSC measurement was performed for

sulﬁsoxazole,SBE7-

b

-CD-ICNF and

b

-CD-IC powder under N2. Samples were

equilibratedat50Candheatedto220Cwitharateof10C/min.

X-raydiffraction(XRD)(PANalyticalX’Pertpowder diffractom-eter)measurementsofpuresulﬁsoxazole,SBE7-

b

-CDNF,sul

ﬁsox-azole/SBE7-

b

-CD-IC NF and sulﬁsoxazole/SBE7-

b

-CD-IC powder

wererecordedbyapplyingCuK

a

radiationinarangeof2

u

=5–30

todeterminethecrystallinestructureofthesamples.

Fourier transform infrared spectrometry (FTIR, Bruker-VER-TEX70)wasusedtoobtaintheinfraredspectraofthesamples.The samplesweremixedwithpotassiumbromide(KBr)andpressedas pellets.64scanswererecordedbetween4000and400cm1ata resolutionof4cm1.

Thewater solubilityofsul_fisoxazoleis quite limited(Gladys etal.,2003).Here,excessamountofsulfisoxazole(1.3mgmL1), andsulfisoxazole/SBE7-

b

-CD-ICNFandsulﬁsoxazole/SBE7-

b

-CD-ICpowderhavingthesameamountofsulﬁsoxazolewereaddedto thewaterandstirredovernight.Tomakecomparison,thesolution ofsulﬁsoxazolewithconcentrationofitswatersolubility(about 0.2mgmL1)wasalsopreparedandstirredovernight.Afterthat,

allsampleswereﬁlteredthrougha0.45

m

mmembrane ﬁlterto

Fig.6. DSCthermogramofsulﬁsoxazole,SBE7-b-CDNF,sulﬁsoxazole/SBE7-b

-CD-ICNFandsulﬁsoxazole/SBE7-b-CD-ICpowder.

Fig.7. XRDpatternsofsulﬁsoxazole,SBE7-b-CDNFsulﬁsoxazole/SBE7-b-CD-ICNF

andsulﬁsoxazole/SBE7-b-CD-ICpowder.

Fig.8. FTIRspectraofsulﬁsoxazole,SBE7-b-CDNFandsulﬁsoxazole/SBE7-b-CD-IC

NF.

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remove undissolved sulﬁsoxazole. Then, absorbance versus

wavelength plots of four samples was obtained from UV–vis

spectroscopy(Varian, Cary 100). In addition, toshow the fast-dissolvingcharacterandwater-solubilityenhancementofthedrug visually, the water is directlyadded to solid sulﬁsoxazole, and sulﬁsoxazole/SBE7-

b

-CD-IC

powder samples. The videos and pictures have been taken in

which,sulﬁsoxazolepowderandthesulﬁsoxazole/SBE7-

b

-CD-IC

NFwereplacedintopetridishesseparatelyandthen,5mLofwater wasaddedtopetridishes.Then,tomakecomparisonsulﬁsoxazole/ SBE7-

b

-CD-ICpowderwerealsoplacedintoapetridishandthen,

5mLofwaterwasadded.

3.Resultsanddiscussion 3.1.Phasesolubilitystudies

Phasesolubilitydiagramplottedbysulﬁsoxazoleconcentration

versus SBE7-

b

-CD concentration was given in Fig. 2 which

corresponds that with increase in SBE7-

b

-CD concentration,

sulﬁsoxazoleconcentrationalsoincreases.Thecomplexshowed

linear trend (AL-type) demonstrating 1:1 complex formation

tendencyofsulﬁsoxazoleandSBE7-

b

-CDmolecules.Thestability

constant (Ks) was calculated as 880M1 from the diagram

according to Eqn. (1) and this value indicates better stability whencomparedtothepreviouslydonestudyonHP

b

CDbyGladys etal.(2003).

3.2.ElectrospinningofSBE7-

b

-CDNFandSulﬁsoxazole/SBE7-

b

-CD-IC

NF

Sincethephasesolubilitystudiesindicated1:1(sulﬁsoxazole: SBE7-

b

-CD)complexformation tendency betweensulﬁsoxazole

and SBE7-

b

-CD, ﬁrst, we prepared 1:1 molar ratio inclusion

complexbetween sulﬁsoxazole and SBE7-

b

-CDby usinghighly

concentrated SBE7-

b

-CD (200% (w/v))aqueoussolution for the

complexation.However,theelectrospinningofuniformnanoﬁbers

from1:1molarratioofsulﬁsoxazole/SBE7-

b

-CD-ICsystemwasnot

successful underthe appliedelectrospinning conditions/param-eters.Hence,weoptimizedtheCD-ICsolutionsandfoundoutthat sulﬁsoxazole/SBE7-

b

-CD-IC solution having 1:2 (sulﬁsoxazole:

SBE7-

b

-CD)molarratiowasmorefavorablefortheelectrospinning

ofuniformnanoﬁbers.Asacontrolsample,pristineSBE7-

b

-CDNF

was also electrospun and we obtained bead-free and uniform

nanoﬁbermorphology forthefree-standingnanoﬁbrousweb of

SBE7-

b

-CD.Theoptimizedparametersfortheelectrospinningof

thebead-free nanoﬁbers frompristine SBE7-

b

-CDand sul

ﬁsox-azole/SBE7-

b

-CD-ICsystemsweregivenindetailinexperimental

section. The photos of free-standing and _ﬂexible electrospun

nanoﬁbroussamples weregivenin Fig. 3a–b forpristine SBE7

-b

-CDNF andsulﬁsoxazole/SBE7-

b

-CD-ICNF.Therepresentative

SEMimagesoftheseSBE7-

b

-CD-ICNFsamplesweregiveninFig.3c–d,respectively.FromtheSEM images,theaverageﬁberdiameter(AFD)forsulﬁsoxazole/SBE7

-b

-CD-IC NF and pristine SBE7-

b

-CD NF was calculated as

650290nmand890415nm,respectively.

3.3.StructuralcharacterizationofSBE7-

b

-CDNFandSulﬁsoxazole/

SBE7-

b

-CD-ICNF

ThestructuralcharacterizationofSBE7-

b

-CDNF,sulﬁsoxazole/

SBE7-

b

-CD-ICpowdersamples

wasdonebyusingthedifferentmethods.1_H_NMR_spectroscopy

wasusedtoobtainmolarratioofsulﬁsoxazoletoSBE7-

b

-CDinthe

b

-CD-IC NF matrix and sulﬁsoxazole/SBE7

-b

-CD-IC powder. The 1_H _NMR _spectra _of _sul_ﬁsoxazole, _SBE

7

-b

-CDpowder,SBE7-

b

-CD-ICNFand

b

-CD-IC powder wereevaluated (Fig. 4a–d).

ProtonsofSBE7-

b

-CDNFandas-receivedpowderSBE7-

b

-CDwere

appearedintherangeof

_d

1.5–5.8ppmwhichiscorrelatedwith previousliterature(Devasarietal.,2015;KulkarniandBelgamwar, 2017).Asshown in Fig.4b, the1_H _NMR _spectra _of _SBE

7-

b

-CD

powderandSBE7-

b

-CDNFpresentthesamecharacteristicshifts

whichindicatedthattheelectrospinningprocessdidnotcauseany chemical degradationtothestructure ofSBE7-

b

-CD. Themolar

ratiowascalculatedfromintegrationofpeakratiobetweenpeakof sulﬁsoxazoleataround7.35(H-a)andSBE7-

b

-CDpeakataround

5.00ppm(H-1)as0.28:1.00forbothsulﬁsoxazole/SBE7-

b

-CD-IC

NF and sulﬁsoxazole/SBE7-

b

-CD-IC powder (Fig. 4c–d). This

suggeststhatmorethan50%(w/w)ofinitialsulﬁsoxazoleamount

waspreservedforbothnanoﬁbrouswebandpowderform.

Thethermaldecompositionofsulﬁsoxazole,SBE7-

b

-CDNFand

b

-CD-IC NF were investigated by thermal

gravimetric analysis (TGA) (Fig. 5). The weight losses below 100Cbelongtothewaterlossforallsamples.Puresulﬁsoxazole decompositionoccuredbetween190-400CwhileSBE7-

b

-CDNF

exhibitedmaindegredationbetween250and500C.Alongwith this, thermal decomposition of sul_{ﬁsoxazole/SBE}7-

b

-CD-IC NF

started at 220C and continued up to 500C. There are two

differencesbetweenSBE7-

b

-CD-IC NFdegradation.First oneis thesmall stepstartingat 220_C

whichpossiblybelongtothesulfisoxazole.Theshiftingofthermal decompositiononsetofsulfisoxazolefrom190Cto220Cshowed theICformationbetweensulfisoxazoleandSBE7-

b

-CD.Thesecond

differenceistheintensityofpeakat300Cwhichalsoprovesthe formationofinclusioncomplexes.

DSC is one of the widely used techniques to evaluate IC

formationbetweenCDandguestmoleculeinsuchawaythatthe meltingpointofguestmoleculesisnotobservedifguestmolecules fullycomplexedwithintheCDcavities(Uyaretal.,2006).TheDSC scans of pure sulﬁsoxazole, SBE7-

b

-CD NF, sulﬁsoxazole/SBE7

-b

b

-CD-ICpowderweregivenin Fig.6.ThepuresulﬁsoxazoleDSCscanexhibitedameltingpointat

Fig.9. Watersolubilitydiagramof*_{sulﬁsoxazole}_with_{concentration}_of_its_water

solubility (green),**_excess _amount _of _{sulfisoxazole} _(pink), _{sulfisoxazole/SBE} 7 -b-CD-ICNFhavingthesameexcessamountofsulfisoxazole(blue),sulfisoxazole/ SBE7-b-CD-ICpowderhavingthesameexcessamountofsulfisoxazole(purple).

(Forinterpretationofthereferencestocolourinthisﬁgurelegend,thereaderis referredtothewebversionofthisarticle.)

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197_C,_whereas_no_melting_point_was_observed_for_sul_ﬁsoxazole

for thesamples of sulﬁsoxazole/SBE7-

b

-CD-IC NF and sul

ﬁsox-azole/SBE7-

b

-CD-ICpowder.TheDSCresultsfurtherconﬁrmthat

thesulﬁsoxazolemoleculesarefullycomplexedwithSBE7-

b

-CDin

thesamplesofsulﬁsoxazole/SBE7-

b

-CD-ICNFandsulﬁsoxazole/

SBE7-

b

-CD-ICpowder.

Thecrystallinestructuresofpuresulﬁsoxazole,SBE7-

b

-CDNF,

b

-CD-IC

powder wereinvestigated by XRD to show theevidence of IC

formationbetweensulﬁsoxazoleandSBE7-

b

-CD.Sulﬁsoxazoleisa

crystallinematerialhavingasharpdiffractionpeaksatdifferent2

u

values;however,theXRDpatternofSBE7-

b

-CDNF,sulﬁsoxazole/

SBE7-

b

-CD-ICpowderarevery

similarwhichhaveamorphousstructures.Thesul_{ﬁsoxazole/SBE}7

-b

b

-CD-ICpowderdonotshow

anydiffractionpeaksofsulﬁsoxazole(Fig.7).Inotherwords,XRD resultsrevealedtheICformationbetweensulﬁsoxazoleandSBE7

-b

-CD in the samples of sulﬁsoxazole/SBE7-

b

-CD-IC NF and

b

-CD-ICpowder.TheXRDresultsuggeststhat

sulﬁsoxazolemoleculesareisolatedfromeachotherbyentering intoSBE7-

b

-CDcavitiesand cannot formany crystalline

aggre-gates. Since drugs in crystalline forms are more stable, their solubility decreases (Babu and Nangia, 2011); however, CD-IC

formationpreventcrystallizationofdrugs.Therefore,thesolubility of sulﬁsoxazole increasesby SBE7-

b

-CD-IC formation since the

crystallizationofsulﬁsoxazolewaspreventedasconﬁrmedbythe XRDpattern.

Thepresenceofguestmoleculeinstructureandtheformation

ofinclusioncomplexesbetweenhostandguestmoleculecanbe

provedbyFTIR analysis.The FTIRspectraofpuresulﬁsoxazole, SBE7-

b

-CD-ICNFarerepresented

inFig.8.TheFTIRspectrumofsulﬁsoxazoledisplayedsalientpeaks at 876–688cm1 range (CH bending), at 1347cm1, (SO2

stretching); at 1326cm1 (aromatic ring stretching); at

1597cm1 (C¼C stretching); at 1632 cm1 (NH2 deformation

vibrations).TheFTIRspectrumofSBE7-

b

-CDshowedabroadpeak

at between3015and 3760cm1(O_H stretchingvibration); a

peak at 2931cm1 (CH stretching vibrations); peaks at

1159cm1and1043cm1(CHandCOstretchingvibrations). SulfisoxazolepeakswereoverlappedbyCDpeakswhichmakesthe identificationof eachcompounds complicatedat thespectraof inclusioncomplexnanofibers.However,thesharpestabsorption peakofsulfisoxazoleatabout1597cm1correspondingtoCH stretchingvibrationcausesincreaseinintensityatthatwavelength

of inclusion complex nanoﬁber. This result suggested that

sulﬁsoxazoleispresentininclusioncomplexnanoﬁbers.

Fig.10.Presentationofthesolubilitybehaviourofsulfisoxazole(representedby“SFO”),sulfisoxazole/SBE7-b-CD-ICNFandsulfisoxazole/SBE7-b-CD-ICpowderforafew

secondsofwaterexposure.ThepictureswerecapturedfromthevideoswhichweregivenasSupportinginformation. 556 Z.I.Yildizetal./InternationalJournalofPharmaceutics531(2017)550–558

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3.4.Water-solubilityofSulﬁsoxazole/SBE7-

b

-CD-ICNF

As mentioned Section 2.3, excess amount of sulﬁsoxazole

(1.3mgmL1) and sulﬁsoxazole/SBE7-

b

-CD-IC NF and sul

ﬁsox-azole/SBE7-

b

-CD-ICpowderhavingthesameamountofsul

ﬁsox-azole were added to water. In order to make comparison, the

solutionofsulﬁsoxazolewithconcentrationofitswatersolubility (about 0.2mgmL1) was also prepared to see water-solubility

enhancement. The plot (Fig. 9) shows that the solutions of

sulﬁsoxazolewith0.2mgmL1concentrationandofsulﬁsoxazole

with1.3mgmL1demonstratedpeakatalmostthesame

absor-bance.Ontheotherhand,sul_{ﬁsoxazole/SBE}7-

b

-CD-ICNFsample

solution having 1.3mgmL1 of sulﬁsoxazole concentration

showed peak at 10 times higher absorbance. This shows that

the solubility of sulﬁsoxazole was increasedby 10 times with sulﬁsoxazole/SBE7-

b

-CD-IC NF formation. As seen from Fig. 9,

b

-CD-ICpowderalsoenhanceswatersolubility

ofsulﬁsoxazoleduetoformationofCD-IC,howeversulﬁsoxazole/ SBE7-

b

-CD-IC NF shows higher absorbance than sulﬁsoxazole/

SBE7-

b

-CD-ICpowder.Thehighsurfaceareatovolumeratio,high

porosityofnanoﬁbersstructurecontributetotheenhancementof watersolubilityofthedrug(Sebeetal.,2015);therefore,thewater solubilityenhancementinsulﬁsoxazole/SBE7-

b

-CD-ICNFbecome

highercomparedtosulﬁsoxazole/SBE7-

b

-CD-ICpowder.The

fast-dissolving property and water-solubility enhancement of the

sulﬁsoxazoleinsulﬁsoxazole/SBE7-

b

-CD-ICNFandsulﬁsoxazole/

SBE7-

b

-CD-ICpowderwerealsovisuallyproven(VideoS1,Video

S2andFig.10).Afteradditionof5mLwatertothepetridishes, whilesulﬁsoxazole/SBE7-

b

-CD-ICNFwasdissolvedimmediately,

thedissolutionofsulﬁsoxazole/SBE7-

b

-CD-ICpowdertookplacea

littlebitslower thansulﬁsoxazole/SBE7-

b

-CD-ICNF sampleand

thepuresulﬁsoxazoleremainundissolved.Thisclearlyshowedthe fast-dissolvingproperty of sulﬁsoxazole/SBE7-

b

-CD-IC NF along

withhighly-increased water-solubilityof sulﬁsoxazole by sul ﬁ-soxazole/SBE7-

b

-CD-ICNFformation.

4.Conclusions

Inthisstudy,free-standingandeasilyhandlednanoﬁbrousweb ofsulﬁsoxazole/SBE7-

b

-CD-ICwassuccessfullyproducedbyusing

electrospinning technique. The electrospun sulﬁsoxazole/SBE7

-b

-CD-ICnanoﬁbrouswebhasshownthefast-dissolvingproperty aswellastheprovidingenhancedwater-solubilitytosulﬁsoxazole. Based onourresults, it is concluded that SBE7-

b

-CDis a good

candidate toform ICs withsulfisoxazole to increase its water-solubilitytoa great extent. Moreover,electrospinning of nano-fibersfromsulfisoxazole/SBE7-

b

-CD-ICsystemhavinghighsurface

area to volume ratio and nano-scale porosity provides

fast-dissolvingproperty.Inbrief,electrospinningofnano ﬁbers/nano-websfromdrug/CD-ICssystemsmayprovidenovelapproachesfor enhancedwater-solubilityandfast-dissolvingtabletformulations fordrugdeliverysystems.

Acknowledgements

T. Uyar acknowledges The Turkish Academy of Sciences

Outstanding Young Scientists Award Program

(TUBA-GEBIP)-Turkey for partial support of theresearch. Z. I. Yildiz thank to TUBITAK-BIDEBforthePh.D.scholarship.

AppendixA.Supplementarydata

Supplementarydataassociatedwiththisarticlecanbefound,in

the online version, at http://dx.doi.org/10.1016/j.

ijpharm.2017.04.047.

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