Abstract
Electrospinning was employed to obtain chitosan nanofibers from blends of chitosans (CS) and poly(ethylene oxide) (PEO). Blends of chitosan (MW (weight-average molecular weight) = 102 kg/mol) and PEO (M (molecular weight) = 1000 kg/mol) were selected to optimize the electrospinning process parameters. The PEO powder was solubilized into chitosan solution at different weight ratios in 0.5 M acetic acid. The physicochemical changes of the nanofibers were determined by scanning electron microscopy (SEM), swelling capacity, and nuclear magnetic resonance (NMR) spectroscopy. For stabilization, the produced nanofibers were neutralized with K2CO3 in water or 70% ethanol/30% water as solvent. Subsequently, repeated washings with pure water were performed to extract PEO, potassium acetate and carbonate salts formed in the course of chitosan nanofiber purification. The increase of PEO content in the blend from 20 to 40 w% exhibited bead-free fibers with average diameters 85 ± 19 and 147 ± 28 nm, respectively. Their NMR analysis proved that PEO and the salts were nearly completely removed from the nanostructure of chitosan, demonstrating that the adopted strategy is successful for producing pure chitosan nanofibers. In addition, the nanofibers obtained after neutralization in ethanol-aqueous solution has better structural stability, at least for six months in aqueous solutions (phosphate buffer (PBS) or water).
Highlights
Researchers have been working on the processing of chitosan to produce new biomaterials, especially developed for biomedical applications [1,2,3,4,5,6,7,8,9,10]
The results have demonstrated that CS/poly(ethylene oxide) (PEO) solutions containing 20 wt % and more than 20 wt % of powdered PEO solubilized into the chitosan 5% (w/w) solution improved spinnability, producing bead-free nanofibers
Image analyses on the nanofiber matrix from blends of CS/PEO (60/40) and (80/20) demonstrate that, after neutralization in 70% of ethanol aqueous solution, chitosan fiber morphology is stable in the aqueous solution at pH > 6.5
Summary
Researchers have been working on the processing of chitosan to produce new biomaterials, especially developed for biomedical applications [1,2,3,4,5,6,7,8,9,10]. A neutralization step is important to obtain the insoluble chitosan For this purpose, it was proposed that the nanofiber membrane be immersed in 5 M NaOH or 5 M Na2CO3 aqueous solutions for 3 h at ambient conditions [27] or in 1 M K2CO3 for 3 h at 25 ◦C [14]. ETheensteirdeartaancgoenfoirfmfrethqeuceonocpyewraatisvetested interaction between chitosan and PEO especially when the experimental data from Figure 2, curve c but thisecsoomluptairoendstobetchoemadednitoivni-tyNceawlctuolnatieadn.inTFhiegsuered2a,tacucrovnefibr.mAltlhtehecsoeospoelurtaitoinvsewinetreerealcetcitoronspbuetnween chitowsainthaonutdaPnyEOdifefiscpueltcyi,aellxycewpthpeunrethcehietoxspaenraimndenchtaitlosdaantablfernodmedFwigituhre102%, cPuErOv.e c is compared to the additivity calculated, curve b All these solutions were electrospun without any difficulty, except pure chitosan and chitosan blended with 10% PEO. FoctcFafoiaigltglcaucouuultrtcCFlraeolapaieSaltgtlo2a-ctep2u1eu.lld.yor0dlVpeV2amlfoyao/t2aPeflrmer.yodrEirVemiareOaatacfretioceroioarichroanasnoccntcveaoinhoeoaanofcncfnlucfevuhtetnontrhaenhcfatvslettruettriaohaioavelovfutentsiiinis“eoovsocsanocniifos”noftocisihsnaonfit“ietdshttya“itywdhteha”yeae”aeemtdaitmagmta0di0ihdix0.n.xd5it.5tdxt5tufeouestrssdrud−ra−p−ee1c1r1ussteiiooi..nnorsoff(et(.tfnaaoaao(ca)d)doahdpdPfp)dPiuedEtPPueEdorOeEdEreOsdPOeaOsPEcnoPs hEcOlosECihu.OotlO(otiuSlMitsuo-(ota1Mi(ntsonM=0iaoni21nn=Cn0=i1S00niCa0.-10n51nS00k00Md0.-g251.05/k(0mM ackg2M)cog/ebmla at/)alincecmecoednxelaato)pdtcini(clriesccd)edx)casaep hscbxc(eriiilcp;dtdeed)o(rsnbise sndba)sesl;npsade(ede(cnCbbdirdhnd)cS)iieitsta-pnaoni1dvdset0cpiadrto2dhnyceif/iiterttiPconivveEstiinatOtoyntyf aCsSa-1fu02n/cPtiEoOn oasf tahfeuwncetiigohntofrfatchteiowneoifghPtEfOract.ion of PEO .○
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