controlled protein oxide)

International Journal of Pharmaceutics 338 (2007) 276283

Pharmaceutical Nanotechno

Controlled protein release from electrospuandb, T

e andersity

ary 22007

Abstract

A blend m ) wasa protein dr polypoly(d,l-lac lysoz(DMSO). T es. Agood morph contreduced init of lymodulated. , indby controlle the e 2007 Elsevier B.V. All rights reserved.

Keywords: Electro-spinning; Biodegradable; Nanofibers; Protein release; Lysozyme

1. Introdu

Electrosthe past seing tissue edrug deliveprepared binterest formanner, su

plasmid Dal., 2005;trospinningdirectly enby dissolvielectrospindimensionaarea, proviIt has been

CorresponE-mail ad

0378-5173/$doi:10.1016/jction

pun ultrafine nanofibers have been explored duringveral years as potential biomedical device includ-ngineering scaffolds, wound dressing materials, andry carriers. Recently, nanofibrous polymeric meshesy an electrospinning technique have gained muchdelivering various bioactive agents in a sustained

ch as antibiotics, anti-tumor agents, proteins, andNA (Luu et al., 2003; Kim et al., 2004; Casper etChew et al., 2005; Zeng et al., 2005a). The elec-

process enables a diverse range of drugs to becapsulated within the bulk phase of nanoscale fibersng or dispersing them in the organic solvent used forning. The resultant fibrous mesh possesses a three-l open porous structure with a high specific surface

ding an ideal condition for controlled drug delivery.shown that drug release patterns from nanofibrous

ding author. Tel.: +82 42 869 2621; fax: +82 42 869 2610.dress: [email protected] (T.G. Park).

meshes can be tailored by various formulation conditions suchas polymer type, polymer concentration, blending of differ-ent polymers, surface coating, and the state of drug moleculesin an electrospinning medium (e.g. emulsion or suspension,direct dissolution, and coaxial electrospinning) (Zeng et al.,2003; Jiang et al., 2005; Xu et al., 2005; Zeng et al., 2005a).In addition, drug solubility and compatibility with the poly-mer solution have decisively influenced drug release profiles byaltering the drug distribution inside the electrospun nanofibers(Zeng et al., 2005b; Jiang et al., 2006). More recently, elec-trospun core/shell nanofibrous polymer meshes prepared bycoaxial electrospinning were also utilized for delivering proteindrugs in a sustained manner. The core-shell structured fibersshowed a wide range of protein release profiles by varyingthe electrospinning parameters. However, most biodegradablenanofibers directly entrapping water soluble drugs exhibitedhigh burst effects with poor controlled release patterns, prob-ably due to incompatibility of drug/polymer/solvent system andslow degradation of biodegradable polymer (Zeng et al., 2003,2005b).

Biodegradable nanofibrous polymer scaffolds with an openpore structure have been extensively investigated for tissue

see front matter 2007 Elsevier B.V. All rights reserved..ijpharm.2007.01.040composed of poly(-caprolactone)Taek Gyoung Kim a, Doo Sung Lee

a Department of Biological Sciences, Korea Advanced Institute of Sciencb Department of Polymer Science and Engineering, Sungkyunkwan Univ

Received 25 October 2006; received in revised form 2 JanuAvailable online 2 February

ixture of poly(-caprolactone) (PCL) and poly(ethylene oxide) (PEOug in a controlled manner. Various biodegradable polymers, such astic-co-glycolic acid) (PLGA) were dissolved, along with PEO andhe mixture was electrospun to produce lysozyme loaded fibrous meshological stability upon incubation in the buffer solution, resulting inial bursts. With varying the PCL/PEO blending ratio, the release rateThe lysozyme release was facilitated by increasing the amount of PEOd dissolution of PEO from the blend meshes. Lysozyme released fromlogy

n biodegradable fiber meshpoly(ethylene oxide)

ae Gwan Park a,Technology, Daejeon 305-701, South Korea

, Suwon, Kyoungki-do 440-746, South Korea007; accepted 28 January 2007

electrospun to produce fibrous meshes that could release(l-lactic acid) (PLLA), poly(-caprolactone) (PCL), andyme, in a mixture of chloroform and dimethylsulfoxidemong the polymers, the PCL/PEO blend meshes showedrolled release of lysozyme over an extended period withsozyme from the corresponding meshes could be readilyicating that entrapped lysozyme was mainly released outlectrospun fibers retained sufficient catalytic activity.

T.G. Kim et al. / International Journal of Pharmaceutics 338 (2007) 276283 277

engineering applications, since they have a nanofibrous skele-tal structure similar to that of the extracellular matrix (ECM)present inthe surfaceTyr (GRGDmesh (Kimwere produPLGA-b-Pconjugationtionalized mand prolifebrous mesfor tissueTo furtherreleasing ndesirable, btions suchreleasing gdressing mfactors atused for wpotent mito2001).

In this sa proteindirectly disolvent meous biodegwere blendlysozyme ispun to proPEO wasbiodegradaby formingbuffer medvarying theblend ratioanalyzed.

2. Materia

2.1. Mater

PEO (Pfrom Unioglycolic acwas purchGermany).poly(l-lactby Aldrichington, PAwhite, 50,tide N-aceand fluoreUSA). MicPierce (Rograde.

2.2. Electrospinning

lendrati/v)

ere d% (w

l. Lto reHCl,ssolvme sn, fosed

us stn waG) a

l 210sitivT, Ca Dlymor plses w

hara

mor

outNe

he San imte ofme iine isitefluong cny).

vitr

circwer

mer, 0.0nmenasee ofed soit.

olym

nd Psol

m wthe living tissue. We previously reported a study onimmobilization of a cell adhesive Gly-Arg-Gly-Asp-Y) peptide on the electrospun PLGA nanofibrousand Park, 2006). Amine functionalized nanofibers

ced by electrospinning a blend mixture of PLGA andEG-NH2 di-block copolymer, followed by covalent

with the peptide. The cell adhesive peptide func-eshes exhibited enhanced cell adhesion, spreading,

ration. The ECM mimicking electrospun nanofi-hes can be used as attractive scaffold materialsregeneration (Mo et al., 2004; Khil et al., 2005).mimic the function of the ECM, growth factoranofibrous and biodegradable meshes are highlyecause they could modulate diverse cellular func-

as differentiation. In particular, nanofibrous meshesrowth factors can be potentially used as woundaterial that provides sustained release of growththe wound site. Many growth factors have beenound healing and tissue regeneration due to theirgenic effects (Pandit et al., 2000; Breitbart et al.,

tudy, biodegradable fibrous meshes that can releasedrug in a sustained manner were produced byssolving protein molecules in an electrospinningdium. Lysozyme was used as a model protein. Vari-radable polymers such as PLLA, PCL, and PLGAed with PEO in varying ratios, co-dissolved with

n a mixed solvent of chloroform/DMSO, and electro-duce lysozyme loaded fibrous meshes. Hydrophilicincorporated into the hydrophobic bulk phase ofble fibers in order to facilitate lysozyme release

extractable pore channels upon incubation in theium. Lysozyme release patterns were examined byformulation parameters such as polymer type and

. Enzyme activity of the released fractions was

ls and methods

ials

olyox WSRN-80, Mw: 200,000) was obtainedn Carbide Corp. (Danbury, CT). Poly(d,l-lactic-co-id) (PLGA RG756 LA/GA = 75/25, Mw: 100,000)ased from Boehringer Ingelheim (Ingelheim,Poly(-caprolactone) (PCL, Mw: 65,000) and

ic acid) (PLLA, Mw: 50,000) were supplied(Milwaukee, WI) and Polysciences Inc. (War-

), respectively. Lysozyme (from chicken egg000 units/mg protein) (E.C. 3.2.1.17, mucopep-tylmuramylhydrolase), Micrococcus lysodeikticus,scamine were obtained from Sigma (St. Louis,ro-bicinchoninic acid (BCA) assay kit was from

ckford, IL). All other chemicals were of analytical

A bweight15% (w5/5) w1015was 3 mwater1.0 Mwas dilysozysolutioratus upreviosolutiodle (22(modeThe poK03VItip andfied pocollectproces

2.3. C

Thecarried535M,From tusingInstitulysozyrescam

compotion ofscanniGerma

2.4. In

The20 mg)and impH 7.4enviroof relevolumcollectassay k

2.5. P

Bleof PBSmediumixture of PEO and PLLA, PCL, or PLGA (7/3o) was dissolved in chloroform at a concentration of. PEO/PCL blends with varying ratios (9/1, 7/3, andissolved in chloroform at a concentration range of/v). The final volume of each polymer blend solutionysozyme was first dialyzed against distilled deionizedmove residual salts. After adjusting pH to 3.0 withthe solution was lyophilized. Salt-free dry lysozymeed in DMSO at a concentration of 30 mg/ml. Theolution (0.2 ml) was mixed with the polymer blendllowed by gentle stirring. The electrospinning appa-in the present study was constructed based on ourudy (Kim and Park, 2006). Each polymer/lysozymes added into a 5 ml syringe with a metal blunt nee-nd then mounted in a programmable syringe pump, KD Scientific Inc., USA) operated at 20l/min.e lead from high voltage power generator (CPS-40hungpa EMT Co., Korea) was connected to the needleC voltage of 15 kV was applied. Stretched and solidi-eric fibers were deposited on a rotating mandrel-typeaced 12 cm away from the needle. All electrospinningere carried out under ambient conditions.

cterization of electrospun ber meshes

phological observation of each electrospun fiber waswith a scanning electron microscope (SEM, Philips

therlands) after sputter coating with Au particles.EM images, each fiber diameter was determined byage analyzer (Image J, developed by the National

Health, USA). For visual observation of encapsulatedn the fiber, lysozyme was pre-conjugated with fluo-n DMSO, and then the fluorescent lysozyme/polymersolution was electrospun onto a slide glass. Distribu-rescent lysozyme in the fiber was examined by a laseronfocal microscope (LSCM, Carl Zeiss LSM5100,

o lysozyme release

ular pieces of lysozyme loaded fibrous mesh (ca.e placed, in triplicate, in a 12 well tissue culture platesed in 2 ml of 33 mM phosphate buffer saline (PBS,2% NaN3) solution at 37 C in a humidified 5% CO2tal incubator. At pre-determined time intervals, 1 ml

medium was collected and replaced with an equalfresh buffer medium. The amount of lysozyme in thelution was measured by using a micro-BCA protein

er erosion

EO/PCL electrospun meshes were incubated in 5 mlution at 37 C under static condition. The incubationas changed daily. The samples were retrieved after

278 T.G. Kim et al. / International Journal of Pharmaceutics 338 (2007) 276283

fixed time intervals, washed three times with deionized water,and freeze-dried. The remaining weight was calculated by com-paring initi(Wt) as foll

Remaining

In ordeing PEO/Pcalorimetryused to tracsample wasgas with a

2.6. Measu

Residuapoint werestrate. Thepoint was apension in6.24), folloabsorbancetrophotomedetermininof lysozymhighest val

3. Results

Three dPLGA) wtion of lyPEO (Mwpore formilysozymeare semi-cpolymer. Thave lowermarily uselysozyme bmer. Howbe used fowater-absoronment. Bwith PEOseparatedthe fiber smoleculesPEO domapores thatPEO phaseMeanwhilemer domamaintaininrelease.

3.1. PEO/PLLA, PCL, and PLGA electrospun bers forlysozyme release

iousropeng vn ththe

nekc po

as

, an

ers iechat al.ationn belymas d

wt%orateolecdryi998e posolu

artialt 15otiog cohowin F

EO/Ptivelnon

ral dn bebute toed ther crt canPEO

CL ficrysspinee bof bdur

LGAss coitial

tribufibe

alsoby

mi-cal mass (W0) with mass obtained at each time pointows.

weight (%) = W0 WtW0

100

r to characterize morphological changes of erod-CL blend electrospun meshes, differential scanning

(DSC) (DSC 6100, Seiko Instruments, Japan) wase thermal melting behaviors of PEO and PCL. Eachscanned from 10 to 100 C under a flow of nitrogen

heating rate of 10 C/min.

rement of lysozyme activity

l activities of released lysozyme fractions at each timemeasured by using M. lysodeikticus cells as a sub-collected sample (0.1 mL) retrieved at a given timedded to 2.5 ml of 0.015% (w/v) M. lysodeikticus sus-a 66 mM potassium phosphate buffer solution (pHwed by shaking the mixture for 5 min. Decrease invalue at 450 nm was measured using a UV spec-

ter. The specific activity was then calculated byg M. lysodeikticus lysis activity divided by amounte. The activity of each sample was normalized to theue.

and discussion

ifferent biodegradable polymers (PLLA, PCL, andere used as skeletal base materials for produc-sozyme loaded fibrous mesh, whereas high Mw

200,000) was blended, as an extractable self-ng polymer additive, to control the release rate offrom the blend fibrous meshes. PLLA and PCLrystalline polymers, while PLGA is an amorphoushe three biodegradable polymers employed heremolecular weight than that of PEO. PEO is pri-

d to improve compatibility with the encapsulatedecause it is a hydrophilic and biocompatible poly-

ever, PEO electrospun fiber mesh alone cannotr controlled release of lysozyme due to its highrbing capacity and rapid dissolution in aqueous envi-y blending hydrophobic biodegradable polymerswith higher Mw, the two polymers were phase

to form hydrophilic and hydrophobic domains intructure. It was expected that entrapped lysozymewere preferentially located within more hydrophilicins and diffused out through the self-generatedwere gradually created by slow dissolution of thedomains upon incubation in the aqueous medium.

, phase separated hydrophobic biodegradable poly-ins constituted a porous skeletal structure whileg structural integrity of the fibrous mesh during

Vartion pspinnibetweeminingand ReElectrisidereddensitypolymand m(Park edegraducts caand poblend w1015incorpwas m

freezeet al., 1with thmixedwas pfixed aping mrotatinmesh sshownand Prespecters ofstructucles cafibers,bly duexpellpolymcess. Ion thePEO/Pferentelectrothe thrextentpatternPEO/Pwith lehigh inwas aton themeshcausedthan seelectrospinning parameters including polymer solu-rty (surface tension, conductivity, and viscosity),oltage, flow rate, motion of collector, and distancee needle tip and collector were responsible for deter-

morphology of electrospun fiber meshes (Doshier, 1995; Fridrikh et al., 2003; Theron et al., 2004).tential and polymer concentration are generally con-the key factors governing fiber diameter, apparentd porosity (Zong et al., 2002). Blending differents a straightforward way to create a unique physicalnical property that each polymer does not possess, 1992; Nijenhuis et al., 1996). Overall morphology,

rate, and matrix characteristics of the final prod-tailored by controlling electrospinning parameters

er blend composition. In this study, each polymerissolved in chloroform at different concentrations ofto produce a stable and regular fibrous structure. Tolysozyme in the bulk phase of the fiber, lysozyme

ularly dissolved in DMSO after the desalting andng process, as reported in our previous study (Park). The lysozyme/DMSO solution was then combinedlymer/chloroform solution for electrospinning. Thetion was slightly cloudy, indicating that lysozymely aggregated. The electric voltage used here waskV. When a higher voltage was applied, a large whip-n was detected, resulting in uneven deposition on thellector. After electrospinning, the dried electrospuned mechanical stability good enough to handle. Asig. 1, average diameters of PEO/PLLA, PEO/PCL,LGA blend fibers were 1.43, 1.02, and 0.99m,

y. They all exhibited typical morphological charac--woven electrospun fiber mesh without showing anyefects. It is of interest to note that lysozyme parti-seen on the surface of PEO/PLLA and PEO/PCL

not for PEO/PLGA blend fibers. This was proba-the semi-crystalline nature of PLLA and PCL thate lysozyme aggregates onto the fiber surface duringystallization under the electrified jet thinning pro-be visualized that the number of lysozyme particles/PLLA fiber surface was greater than that on theber surface. This was most likely caused by the dif-

tallization behavior between PLLA and PCL duringning. Fig. 2 shows lysozyme release profiles fromlend fibers. The PEO/PCL mesh shows the smallesturst release (ca. 26%) with a more sustained releaseing a one week period, whereas the PEO/PLLA and

meshes show much higher extents of initial burstntrolled release profiles during the same period. Theburst (ca. 45%) observed for the PEO/PLLA mesh

ted to the presence of unentrapped lysozyme particlesr surface as shown in Fig. 1. Similarly, PEO/PLGAexhibited high burst release, which was probablythe fact that amorphous PLGA is more hydrophilicrystalline PLLA, thus absorbing water more quickly


Fig. 1. SEM images of PEO/PLLA (A and B), PEO/PCL (C and D), and PEO/PLGA (E and

Fig. 2. Lysozyme release profiles from electrospun PEO/PLLA, PEO/PCL, andPEO/PLGA fibers with a 70/30 blend weight composition.

than the othresult, mosbe releasedelectrospunmeability,aqueous mmore thansirable forThe PEO/Ping the relmesh wasdistributionfluorescentfluorescentFig. 3 showtributed aloaggregatesbe moleculfibers.F) electrospun fibers at a 70/30 blend weight composition.

er semi-crystalline polymers upon incubation. As at of the entrapped lysozyme molecules were likely to

out in an initial burst. Although the PEO/PLGAmesh showed good lysozyme loading and per-

it exhibited a very large dimensional change inedium, resulting from hydration. The mesh shrunk60% from its original area, which was very unde-use as drug delivery devices (Zong et al., 2003).CL mesh maintained its original dimension dur-

ease period. Therefore, the PEO/PCL electrospunchosen for further studies. In order to visualize the

of lysozymes in the PEO/PCL electrospun fibers,dye labeled lysozyme was incorporated, and theimage was observed under a confocal microscope.s that lysozyme molecules were homogeneously dis-ng the fiber with the presence of a few lysozymenear the surface. This indicates that lysozyme couldarly incorporated into the bulk phase of PEO/PCL


Fig. 3. LCSM image of (A) electrospun PEO/PCL (70/30) blend fibers encapsulated with fluoresc

3.2. Erosion study of PEO/PCL blend meshes

Based ogood to uswere perforing blend raw/w). Fig.meshes witamount ofmass erosiosharp masshydrophilicend of the ifor 90/10, 7respectivelPCL in thepart was mothe hydropblend fibrotheir structu

Fig. 4. Rema70/30, and 50

dissolutioncasting film

phye (l

CL ban thight

se sethatfibroed bd pot evan PE

n theHenape

sked ouEOor t

ologe strun the observation that the PEO/PCL blend mesh wase for delivering lysozyme, subsequent experimentsmed to optimize lysozyme release profiles with vary-tios between PEO and PCL (90/10, 70/30, and 50/50,4 shows mass erosion behaviors of PEO/PCL blendh different blend ratios. As expected, increasing thePEO in the blend fiber resulted in a more rapidn. In the case of 90/10 PEO/PCL blend mesh, veryerosion occurred within a day, indicting that thePEO part was dissolved out immediately. At the

ncubation period, the remaining weight percentages0/30, and 50/50 blend meshes were 14, 35, and 55%,

y, which were close to the initial weight percents ofblend mixture. This reveals that the hydrophilic PEOstly dissolved out into the incubation medium, while

hobic PCL part remained in the mesh. The PEO/PCLus meshes produced by electrospinning maintainedral integrities in the form of a fiber, although massive

severe

tion timPEO/Ption thThis mof phalikelyin theprepara blensolvenbetweethose iration.and shfibrousleache70/30 Ptime. Fmorphsurfacining weight of various electrospun PEO/PCL blend fibers (90/10,/50).

diameter chthe high wadomains emin a swollecant changea higher PCto some exoccurring ition, differeshown in Ffibers wereblended, mthat of PCLPEO, suggIn semi-crypolymer blently labeled lysozyme and (B) higher magnification image.

of PEO occurred. This is in contrast to the polymerhaving an identical blend composition, but exhibited

sical disintegration within a short period of incuba-ess than 24 h) (data not shown). It is not clear why thelend fiber was more resistant to physical disintegra-

e PEO/PCL blend film having the same composition.be due to the effect of electrospinning on the degreeparation between the PEO and PCL domains. It wasthe sizes of phase separated PEO and PCL domainsus structure were much smaller than those in the filmy solvent evaporation. Electrified rapid ejection oflymer solution through a narrow nozzle with quickporation might kinetically arrest phase separationO and PCL, leading to smaller domain sizes than

film that were formed by much slower solvent evapo-ce, the blend fiber mesh could maintain its dimensionbecause the remaining PCL domains constituted aletal structure even after the PEO domains were

t massively. Fig. 5 shows SEM pictures for 90/10 and/PCL blend fibrous meshes as a function of incubationhe 90/10 blend mesh, it can be seen that the fibrousy was still maintained with a swollen and ruggedcture even after 12 day incubation. The average fiber

anged from 1.16 to 1.55m. This was clearly due toter absorbing capacity and rapid dissolution of PEObedded in the fiber, making the individual fiber to be

n state (Miller-Chou and Koenig, 2003). No signifi-, however, occurred in the 70/30 blend mesh, becauseL percent prevented the blend fibers from swellingtent. In order to examine morphological changesn the 70/30 PEO/PCL blend mesh during incuba-ntial scanning calorimetric study was performed. As

ig. 6, melting temperatures for PEO and PCL as-spunobserved at 68.6 and 61.6 C, respectively. When

elting temperature of PEO appears at 66.1 C, whilewas imbedded in the broad melting endotherm of

esting that PEO and PCL are slightly phase-mixed.stalline polymer blends, it is known that miscible

ends show a shift in each melting temperature to be


Fig. 5. SEM itime.

close togettive of partthe amorphPEO domaPCL doma12, the melstrating thabehind thein good agFig. 4.

3.3. Lysozy

Fig. 7 shmeshes witis releasedin the blendrelease permages for morphological changes of 90/10 (A, C, and E) and 70/30 (B, D, and E) PEO

her (Na et al., 2002). The DSC result was indica-ial miscibility between PEO and PCL, especially inous region. The melting endotherm of crystallineins gradually disappeared, while that of crystallineins gradually appeared with incubation time. At dayting endotherm of PCL was only observed, demon-t PEO domains were almost dissolved out, leavingPCL skeletal fiber structure. The DSC results are

reement with the mass erosion results presented in

me release from PEO/PCL blend meshes

ows lysozyme release profiles from PEO/PCL blendh different blend ratios. It can be seen that lysozymeout more rapidly when the amount of PEO increases. For the 90/10 blend mesh, the cumulative lysozymecent reached to about 87% after 12 day incubation.

For the 50out duringwas muchThe resultsin the fibeSince lysozphous phaslysozyme sfilled porougradual disincompletecaused byrestrictingthe fiber. Isuch as agcontributeddevices to2004; Dai/PCL electrospun blend fibrous mesh as a function of incubation

/50 blend mesh, however, about 32% was releasedthe same period. The extent of initial burst releasehigher for the fiber mesh containing higher PEO.suggest that the dissolution rate of PEO domains

r structure controlled the release rate of lysozyme.yme molecules were likely partitioned into the amor-e of PEO domains in the blend mixture, entrappedpecies were released out through the aqueous fluids and interconnected channels that were created fromsolution of phase separated PEO domains. Thus therelease observed in the 70/30 blend mesh was also

poor inter-connectivity between the PEO domains,the diffusion of lysozyme entrapped deep insidet should be noted that protein stability problemsgregation and non-specific adsorption additionally

to protein release behaviors from biodegradablevarying extents (Perez et al., 2002; Kim and Park,et al., 2005). In this sense, the observed lysozyme


Fig. 6. Differ(70/30) blend

release patmechanismshows biolPEO/PCLthat the reretained abof native ling the elecmixed orgastreamlineconditions.

Fig. 7. Lysozvarying blend

Fig. 8. Relatifibrous meshwas normaliz

nclu

his seshe1 w

, PCr bleinedere

hydr. Thesolufiberential scanning calorimetric thermograms of electrospun PEO/PCLfibrous mesh as a function of incubation time.

terns can not be solely explained from the combinedof polymer erosion and lysozyme diffusion. Fig. 8

ogical activities of lysozyme released from the 90/10blend mesh at early incubation stage. It can be seenleased lysozyme fraction after 12 h incubation stillout 90% of its catalytic activity compared to that

4. Co

In tspun mover a

(PLLAmer fomaintathey wof thebationthe disin theysozyme. This reveals that lysozyme survived dur-trospinning process involving direct dissolution in anic solvent of DMSO and chloroform and rapid jet-ejection through a nozzle under high electric voltage

yme release profiles from electrospun PEO/PCL fibrous mesh withweight compositions (90/10, 70/30, and 50/50).

produced bimportantfibrous PEOegy basedbe potentiaengineeringgrowth fac

Acknowled

This stutory grant fgrant (KRFdation andUniversity,

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sions

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Controlled protein release from electrospun biodegradable fiber mesh composed of poly(epsiv-caprolactone) and poly(ethylene oxide)IntroductionMaterials and methodsMaterialsElectrospinningCharacterization of electrospun fiber meshesIn vitro lysozyme releasePolymer erosionMeasurement of lysozyme activity

Results and discussionPEO/PLLA, PCL, and PLGA electrospun fibers for lysozyme releaseErosion study of PEO/PCL blend meshesLysozyme release from PEO/PCL blend meshes

ConclusionsAcknowledgementsReferences

controlled protein oxide)

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