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Colloids and Surfaces A: Physicochem. Eng. Aspects 433 (2013) 212 218

Contents lists available at SciVerse ScienceDirect

Colloids and Surfaces A: Physicochemical andEngineering Aspects

jo ur nal ho me p ag e: www.elsev ier .com/ locate /co lsur fa

reparation of poly(ethylene imine) particles for versatile applications

urettin Sahinera,b,

Faculty of Science & Arts, Chemistry Department, Canakkale Onsekiz Mart University, Terzioglu Campus, 17100 Canakkale, TurkeyNanoscience and Technology Research and Application Center (NANORAC), Canakkale Onsekiz Mart University, Terzioglu Campus, 17100 Canakkale,urkey

i g h l i g h t s

Single step PEI microgel preparation.PEI microgels for biomedical applica-tion.PEI microgels for in situ metalnanoparticle preparation.PEI microgels for environmental,energy and catalysis applications.

g r a p h i c a l a b s t r a c t

a r t i c l e i n f o

rticle history:eceived 31 March 2013eceived in revised form 4 May 2013ccepted 8 May 2013vailable online 16 May 2013

a b s t r a c t

Polyethylene imine (PEI) particles were readily prepared via a simple microemulsion polymerizationmethod using AOT as surfactant in commercially available gasoline with moderately high yield (75%)depending on the MW of PEI. The aqueous solution of branched PEI crosslinked with divinyl sulfone(DVS), called c-PEI particles were in the size range of tens of nanometers to tens of micrometers andupon filtration the desired size range was readily obtained. The prepared c-PEI particles were highlyeywords:ydrogelrosslinked PEI microgelanogel compositeunable particle

positively charged depending on the used amounts of crosslinker and the extent of modifying agentssuch as alkyl halide for different purposes e.g., CH3I that can conveniently be used for the quaternizationreaction. The prepared c-PEI particles were demonstrated to be very useful as antimicrobial materials,drug delivery materials, as a template for metal nanoparticle preparation, as a catalysis medium forthe reduction of 4-nitrophenol (4-NP) to 4-amino phenol (4-AP), and for hydrogen generation from thehydrolysis of NaBH4.. Introduction

Polymeric particles from various sources have been preparedor different purposes such as tissue engineering, drug deliv-ry, environmental and advanced material design. More recently,

aterials with tunable charges and sizes are in demand for ver-

atile applications. Especially cationic polymers have attractedreat attention for different purposes [14]. Moreover, for gene

Correspondence address: Faculty of Science & Arts, Chemistry Department,anakkale Onsekiz Mart University, Terzioglu Campus, 17100 Canakkale, Turkey.el.: +90 286 2180018x2041; fax: +90 286 2181948.

E-mail address: sahiner71@gmail.com

927-7757/$ see front matter 2013 Elsevier B.V. All rights reserved.ttp://dx.doi.org/10.1016/j.colsurfa.2013.05.029 2013 Elsevier B.V. All rights reserved.

delivery systems, cationic polymers gain special attention, andamongst these cationic polymers PEI, with various formulations,is the frontrunner for highly efficient and effective delivery sys-tems [5,6]. Polyethylene imines (PEI) offer unique opportunitiesfor advanced material design due to their highly positively chargednature and high transfection efficiency for gene therapy [79]. Theyhave been used mostly as DNA compacting materials [10]. PEI iswidely used in condensing structures such as DNA and PLA and usedin drug delivery [11,12]. Due to this condensing ability and the effi-ciency of PEI for DNA and siRNA, and some other anionic structures,

PEI-based material has been extensively investigated for deliverypurposes both in vitro and in vivo [13,8,7,14]. Although PEI-basedmaterials are very effective agents for cell transfection, they suf-fer from extreme cell death due to cyctotoxicity [8,7,1519]. To

dx.doi.org/10.1016/j.colsurfa.2013.05.029http://www.sciencedirect.com/science/journal/09277757http://www.elsevier.com/locate/colsurfahttp://crossmark.dyndns.org/dialog/?doi=10.1016/j.colsurfa.2013.05.029&domain=pdfmailto:sahiner71@gmail.comdx.doi.org/10.1016/j.colsurfa.2013.05.029

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ircumvent these problems PEI polymers have been modified withther peptides, polymers (PEG) and structures to increase theiresponsiveness [12,2022]. In addition, cationic polymers are theubjects of intense research as non-viral gene delivery systemsue to their flexible properties, facile synthesis, robustness, androven gene delivery efficiency [7,5,23,24,16]. Nevertheless, lowransfection efficiency and undesirable cytotoxicity remain theost challenging aspects of these cationic polymers. To over-ome these disadvantages, various modifications have been madeo improve their gene delivery efficacy. Among them, hydropho-ic modifications of the cationic polymers are receiving more andore attention [5,21]. As a cationic polymer, PEI can be employed

or advanced materials design for versatile applications e.g., onef the intriguing uses of PEI-based materials is CO2 capture. Itas reported that PEI supported on pore-expanded MCM-41 canccommodate PEI loadings of up to 83 wt% with an adsorptionapacity of as high as 250 mg/g in the presence of pure CO2 at 75 C25].

The resourcefulness of PEI material is so diverse that here,hown for the first time, is a facile PEI particle preparation viaicroemulsion template crosslinking using a single step by link-

ng amine groups with DVS. It was further demonstrated that-PEI particles can be applied in biomedical fields as drug deliveryevices, antimicrobial materials, as template for metal nanoparti-le preparation and in catalysis for reduction of nitro compoundsnd hydrogen generation.

. Materials and methods

.1. Materials

Polyethlene imine (PEI) with MWs (SigmaAldrich, 50 wt%,n: 1200, 60 000, and 600 000), divinyl sulfone (DVS, 98%, Fluka)s a chemical crosslinker, sodium bis(2-ethylhexyl) sulfosucci-ate (AOT, 96%, SigmaAldrich) as a surfactant, and gasolines a solvent were used as received. Nickel(II) chloride hexahy-rate (NiCl26H2O, 97%, Riedel-de Han), and cobalt(II) chlorideexahydrate (CoCl26H2O, 99% SigmaAldrich) were used aseceived in the preparation of metal nanoparticles. NaBH4 (99.9%,igmaAldrich) was used as reduction agent and reagent for-nitrophenol reduction and in the hydrolysis reaction for H2 gen-ration. All the solvents, acetone and ethanol were of the highesturity available. All the reagents and solvents (acetone and ethanol,cetonitrile) were of analytical grade or highest purity available,nd used without further purification. Ultra pure distilled water8.2 M cm (Millipore-Direct Q UV3) was used throughout thetudies.

.2. Synthesis of polyethylene imine particles

PEI microgels as c-PEI were synthesized by using microemulsionolymerization. To obtain c-PEI microgel, 1 mL of PEI regardless ofW was dispersed in 30 mL of 0.1 M AOT solution in gasoline. Theixture was vortexed until a clear suspension was obtained. Then,

he crosslinker, DVS, in varying amounts (50100 mol% relative tohe PEI repeating unit) for Mn 1200 and, 30 L for 1 mL PEI solutionith Mn: 60 000 and 600 000 was subsequently added to the mix-

ure and thoroughly mixed to disperse the DVS. The reaction wasllowed to proceed for 1 h at ambient temperature with vigoroustirring at 1200 rpm. Then, the obtained particles were precipitatedn excess acetone and purified by centrifugation at 10 000 rpm for

0 min at 20 C several times and dried with a heat gun. The driedEI particles were stored in a closed container. The yield depend-ng on MW of PEI varied from 30 to 70%; for higher MW PEI e.g.,00 000 higher yield of about 75% was obtained.em. Eng. Aspects 433 (2013) 212 218 213

2.3. Characterization of c-PEI particles

Thermal behavior of c-PEI-based particles was investigated witha thermogravimetric analyzer (TGA, Seiko, SII TG/DTA 6300). TGAmeasurements were carried out by heating samples from 50 to600 C under nitrogen flow of 100 mL/min with 10 C/min heatingrate. Approximately 4 mg samples were used and their weight lossagainst temperature was recorded. The functional group charac-terizations of the particles were done using an FT-IR (Perkin-ElmerSpectrum 100) instrument with ATR apparatus with resolutionbetween 4000 cm1 and 650 cm1. The SEM (SEM, Jeol, JSM-5600) images were obtained by placing the particles onto carbontape-attached aluminum SEM stubs at ambient temperature aftercoating with gold to a few nanometer thickness under vacuum, withan operating voltage of 20 kV.

The sizes of c-PEI particles were determined with dynamic lightscattering (DLS) measurements after filtration. The particle sizeanalyzer (DLS, 90 plus Brookhaven Instrument Crop.) measure-ments were carried out at 90 C angle using 35 mW solid statelaser detector operating at 658 nm by suspending certain amountsof particles in 103 M KCl aqueous solution with 20 s integrationtime. The zeta potential measurements were conducted by using aZetaPals Zeta Potential Analyzer BIC (Brookhaven Instrument Cor-poration) with a diluted aqueous solution of c-PEI-based particles.

2.4. Antimicrobial properties of c-PEI particles

Particles derived from PEI were tested against two commonbacteria for their antimicrobial properties. Certain amounts of c-PEIparticles (100, 50, 25, 5, 1 g/mL) and modified c-PEI particles werecontacted with various bacteria such as Escherichia coli ATCC8739and Staphylococcus aureus ATCC 8739 for 1824 h, and their MIC(Minimum Inhibitory Concentration) and MBC (minimum bacteri-cidal concentration) were determined using bacterial suspensionin nutrient broth. The particles were sterilized under UV irradi-ation for 2 min for sterilization, and were added to sterile 10 mLglass tubes. The appropriate volume of a solution containing of9 108 CFU/mL of each bacterial suspension in nutrient broth wasadded. Tubes only containing inoculated broth were used as neg-ative control. Tubes were vortexed and 1/10, 1/100, 1/1000 and1/1 000 000 diluted samples prepared. From these, 10 l sampleswere taken and plated on 1% agar and incubated for 1824 h at35 C. Colonies were counted and MIC and MBC values of the c-PEIparticles were determined.

To confirm c-PEI can be used as drug delivery device, naproxen(NP) was chosen as a model drug. For loading, 200 mg dried c-PEIwas placed in 300 ppm 50 mL NP solution in ethanol for 12 h underconstant shaking at ambient temperature. For the release studies,50 mg NP-loaded c-PEI particles were placed in PBS buffer at pH7.4 at room temperature and the released amounts of NP per gramc-PEI with time were measured using UVvis spectroscopy. NP hasan absorption maximum at 330 nm in both ethanol and PBS solu-tions and the loading and released amounts were determined fromthe previously constructed calibration curve of the solvent. Therelease experiments were repeated three times and the averagevalues with standard deviation are given.

2.5. Metal nanoparticle preparation within c-PEI and catalysisstudies

To prepare metal nanoparticles within c-PEI particles, about200 mg c-PEI particles were placed in 50 mL 1000 ppm Co(II) or

Ni(II) solution under constant stirring (400 rpm) for 16 h. Thenthese metal ion-loaded c-PEI microgels were separated by centrifu-gation at 10 000 rpm and washed with excess DI and were reducedwith 50 mL 0.1 M NaBH4 for 4 h at room temperature at 400 rpm

214 N. Sahiner / Colloids and Surfaces A: Physicochem. Eng. Aspects 433 (2013) 212 218

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ig. 1. (a) The schematic PEI particle preparation from branched PEI, and (b) and (n 1200 and 60 000, respectively.

ixing rate. Again, c-PEI-M (Ni and Co) composite systems weree-centrifuged at 10 000 rpm and washed with DI water and usedor the reduction of 4-NP to 4-AP, and for NaBH4 hydrolysis.

The reduction of 4-NP was carried out by preparing in 50 mL.01 M 4-NP solution containing 0.4 M NaBH4 using 0.070 g c-PEI-Momposite system. As soon as the catalyst was placed in the reac-ion mixture under constant mixing rate 400 rpm, at certain timentervals (2, 3, 5, 7, 9, 11, 13 and 15 min) 100 L solution was with-rawn and diluted to 10 mL with DI water and their UVvis spectraere recorded. The reduction of 4-NP at 400 nm was monitorednd measured via a previously constructed calibration curve.For the hydrolysis reactions, 200 mg c-PEI-M composite system

as used in 50 mL DI water containing 0.0965 g NaBH4. The amountf produced hydrogen was determined from an inverted cylinderlled with water. The produced hydrogen was passed through con-entrated H2SO4 to capture water vapor for accurate determinationf the generated hydrogen from the hydrolysis reaction.

. Results and discussion

Particles of hydrogel, due to their tissue-like resemblance, flex-ble porous morphology and ample functional groups to renderesired tasks, stands as frontrunner for biomedical, environmentalnd catalyst applications e.g., vehicles for drug delivery and geneherapy, removing toxic species from contaminated environmentsnd/or converting them to more environmentally benign forms,nd templates for material synthesis. Therefore, here PEI particlesere prepared with a simple crosslinking technique using DVSs crosslinker in AOT emulsion in gasoline for the first time. It is

ery well known that vinyl sulfones are excellent Michael accep-ors due to the electron-poor nature of their double bond and alsohe sulfones electron withdrawing ability makes them good elec-rophiles. Therefore, DVS has been used as a good crosslinker forcorresponding optical microscopy images of swollen c-PEI particles obtained with

reactions with nucleophilic groups such as hydroxyl and amineshetero atomic nucleophiles [26,27].

The branched PEI chain linked by using DVS as crosslinker toobtain non-soluble PEI microgels is illustrated in Fig. 1(a). As shown,the nucleophile amine groups can easily react with vinyl groups ofDVS to generate 3D microgels up to several tens of m from a fewof tens of nanometers. The wide size distribution of PEI microgelshas great advantages as the smaller sizes can be readily separatedby simple filtration, even with a simple filter apparatus. The opticalmicroscopy images shown in Fig. 1(b) and (c) are the c-PEI particlesobtained with DVS crosslinking of Mn: 1200 and 60 000 g/mol PEI,respectively. It is important to note that even very small PEI parti-cles can be separated with centrifugal separation at different ratesof rpm for particle mixtures of different sizes as they may have dif-ferent potential uses. To confirm that PEI chains are crosslinked viaDVS, FT-IR analysis of PEI and c-PEI were carried out and are givenin Fig. 2(a). As the amine groups are linked with DVS, the mostobvious peak at 1120 cm1 for c-PEI, belonging to S O stretching,is clearly seen.

Other common peaks such as N H wagging at 813 cm1, N Hbending about 1658 cm1, N H stretching 3287 cm1, C H bend-ings about 1299, 1458, and 1570 cm1 and C H stretching at about2817 and 2937 cm1 are clearly seen for both PEI and c-PEI micro-gels.

To determine whether the crosslinking of PEI induced any ther-mal stability into branched PEI, thermogravimetric analysis of PEIand c-PEI were carried out and the results are given in Fig. 2(b).As can be seen the PEI starts to degrade about 213 C with 97.6%weight loss and at 323 C with 74.2% weight loss and continues to

degrade up to 400 C with almost 99% weight loss. The onset of thedegradation of c-PEI is about 300 C and it continuously degradesup to about 400 C with 82.6 wt% weight loss. It is obvious that thedifference between weight loss of c-PEI and PEI is about 17.44%,

N. Sahiner / Colloids and Surfaces A: Physicochem. Eng. Aspects 433 (2013) 212 218 215

ab

4000 3500 3000 2500 2000 1500 1000 650Wavelength (cm-1)

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30

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Fig. 2. (a) FT-IR spectra and (b) thermogram of (1) PEI and (2) c-PEI particles.

hich can be attributed to the croslinking of PEI chains generatingore thermal stability.Turning branched PEI into crosslinked microgel form provides

dvantages in terms of their handling in applications such as envi-onmental and medical fields, as templates for metal nanoparticlereparation, and as antimicrobial agents e.g., it is possible to designew materials for wound dressing materials with antimicrobialroperties that can be made by embedding c-PEI into hydrogel filmsontaining different functional groups. To further corroborate thathe prepared c-PEI particles can be separated by simple filtrationith filter paper or syringe, PEI particles were filtered with filteraper (>2 m) and then syringe filtered with >0.8 m. As illustrated

n Fig. 3(a), the particles with sizes about 550 and 1200 nm can beeadily obtained by these simple filtration methods or centrifuga-ion. The other validation for the versatility of PEI microgel is their

0

20

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0 50 0 100 0 150 0

Inte

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Diameter (n m)

FilteredPEI microgel

Not filteredPEI microgel

(a)

ig. 3. (a) The sizes of PEI with and without filtration at 558 and 1175 nm respectively, anespectively.Fig. 4. Naproxene (NP) release profile from c-PEI particles in PBS.

modifiability with a simple quaternization agent such as CH3I. Asillustrated in Fig. 3(b), the c-PEI microgel zeta potential increased toalmost +26 mV from +18.6 mV by chemical modification with CH3Iat room temperature. The zeta potential measurements of c-PEIwere carried out in 0.01 M KNO3 as illustrated in Fig. 3(b).

To illustrate that c-PEI can even be employed as a drug deliv-ery material, Naproxene, NP a non-steroidal and anti-inflammatorydrug was chosen as a model active agent, and used for loading intoc-PEI from ethanol, and released into PBS at ambient temperatures.The loading efficiency of NP into c-PEI particles was 83.5% from300 ppm 50 mL ethanol in NP solution for 200 mg c-PEI particlesfor 12 h at room temperature. The release experiment was carriedout with NP-loaded 50 mg c-PEI particles from a dialysis membrane(MW cut off >12 000) into 25 mL PBS at 400 rpm mixing rate atambient temperature. The chemical structure and the release pro-file of NP from c-PEI are shown in Fig. 4. As can be seen NP has anacid group, it was assessed that this group can readily interact with

the quaternized amine groups of c-PEI via electrostatic interaction,and this interaction can readily be surmounted in PBS providingefficient release of the loaded NP from c-PEI particles. It is obvious

0

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216 N. Sahiner / Colloids and Surfaces A: Physicochem. Eng. Aspects 433 (2013) 212 218

Table 1MBC and MIC values for PEI-based polymers.

Polymer MIC values(mg/mL)

MBC values(mg/mL)

E. coli ATCC8739

S. aureusATCC 8739

E. coli ATCC8739

S. aureusATCC 8739

PEI 0.025 0.005 >0.1 0.1

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Fig. 5. The reduction of 4-nitro phenol (4-NP) to 4-amino phenol (4-AP) in the pres-ence of c-PEI-Ni catalyst system, and the loss of absorption maximum of 4-NP withtime. Reaction conditions: 50 mL 0.01 M 4-NP solution containing 0.4 M NaBH4 using0.070 g c-PEI-M composite system.

0

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0 50 10 0 15 0 20 0 25 0

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l)

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c-PEI -Co

Time (min)

Volu

me

of p

rodu

ced

H 2(m

l)

Time (min)

c-PEI -Ni

c-PEI -Co

(a)

(b)

Fig. 6. (a) The hydrolysis reaction of NaBH4 by c-PEI-M (M: Ni and Co) without thec-PEI-NaOH 0.1 0.05 >0.1 0.1c-PEI-CH3I 0.05 0.05 >0.05 0.1

rom Fig. 4 that about 61.6 mg NP, that is about 98.4% of the loadedrug, was released in about 8 h.From the graph, in the first hour, the release is very fast with an

lmost linear release profile similar to most micro and nanoparticlerug release behavior, and between 1 and 6 h the release slowedown as almost over 90% of loaded NP released. Overall, it can beoncluded that c-PEI can even be used for active agent absorptionnd delivery devices where fast absorption/release is required forertain applications such as removal of toxins or stimulants, etc.

Due to the highly charged nature of c-PEI, it was expected that c-EI particles can also be used as antimicrobial materials. Therefore,-PEI particles antimicrobial behavior against two common bacte-ia, E. coli and S. aureus, were tested. It was found that there was anbservable antibacterial effect for c-PEI and modified c-PEI parti-les at the used concentrations (1100 g/mL) against all bacteriaested. Table 1 lists the MIC and MBC values of c-PEI particles. TheIC value is the lowest concentration of the particles where noisible bacterial growth or turbidity could be seen; in other words,

lower MIC value means a higher antibacterial effect. It is obvi-us from Table 1 that all the particles gave low MIC concentrationsbove 0.05 mg/mL for two bacteria. The MBC values determine theinimum amount of particle concentration that kills the bacte-

ia, and it is obvious that c-PEI-based particles have MBC valuesbout 0.1 mg/mL for both bacteria. Therefore, it can be concludedhat PEI polymer and its modified particles can retain their antimi-robial property and can be used as bactericidal agents for variousiomedical applications.Complimentary to the versatility of c-PEI nanoparticles, metal

anoparticles, such Ni and Co, can be readily prepared within the-PEI network and used as catalyst systems for reduction of 4-nitrohenol and hydrogen production from the hydrolysis of NaBH4. Its very well known that 4-NP is an environmental concern as a toxicrganic pollutant and a carcinogenic material that is discharged tohe environment from various industrial sites such as oil refiner-es, chemical, agriculture and paint industries, as well as variousthers. Therefore, the conversion of 4-NP to the more useful andess harmful 4-AP form is desirable [2830]. To demonstrate that-PEI-M composite system can be used as a catalyst system, theeduction of 4-NP to 4-AP in aqueous media with these catalyst sys-ems was completed. As revealed in Fig. 5, the complete reductionf 4-NP with c-PEI-Ni microgel composite catalyst system is veryast and almost all 4-NP was completely converted to 4-AP in about5 min from 0.01 M aqueous solution of 4-NP. This demonstrateshat c-PEI-Ni particles are very effective in some environmentalpplications such as the reduction of some organic pollutants.Another potential catalyst application of these prepared c-PEI-

composite systems is their usefulness in clean and renewablenergy production, such as hydrogen from NaBH4 hydrolysis.ecently, various polymer composites have been paid great andncreasing attention for H2 generation from metal hydride hydrol-sis [31,32]. Among these materials, the use of microgels is a very

ovel and original concept. Here, the prepared c-PEI particles wereoaded with Ni(II) and Co(II) ions and reduced to their correspond-ng metal nanoparticles and were used successfully in hydrogenroduction from the hydrolysis of NaBH4 as illustrated in Fig. 6.

use of a base at 30 C using 0.200 g PEI template (loading capacity of 5.56 mg Co and70.33 mg Ni per gram of PEI). (b) The same NaBH4 hydrolysis reaction per one of Mcatalyst. Reaction condition: 0.0965 g M NaBH4 in 50 mL DI.

N. Sahiner / Colloids and Surfaces A: Physicoch

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ig. 7. Digital camera images of (a) PEI microgels, (b) magnetic ferrite-containingEI microgel, and (c) and their behavior under an externally applied magnetic field.

ig. 6(a) reveals that the Ni amount (70.33 mg) is much more thano (5.56 mg) per gram of c-PEI composite catalyst system. Theirse in NaBH4 hydrolysis showed that Ni-containing particles of-PEI produced the same amount of H2 (252 mL) faster than theo-containing c-PEI composite system. This is due to the higher Niontent of c-PEI particles. If the same graphic as shown in Fig. 6(b), isedrawn for per mole metal catalyst that requires a greater amountf PEI Co template, the H2 production rate for Co is much faster thani nanoparticles. This is in accordance with the literature [3336].ne of the most important findings of the c-PEI-M system reportedere is that these composite catalyst systems do not require theasic medium that almost all the NaBH4 catalysis reactions in theresence of metal nanoparticles, including noble metals such as Au,t, Ru and Rh, need [35,31,37]. The presence of the amine group in-PEI could be accommodating for the lack of basic medium as theeaction is taking place about the periphery of metal nanoparticleshat are sited within c-PEI matrices. All these are extraordinary andppealing; in fact; this phenomena is currently under investigationy our group.The use of c-PEI microgel as template for metal nanoparticles is

aptivating as even magnetic ferrite particles can also be preparedn situ within the macro, micro and even nanogels [38]. Therefore,s a proof of concept, here it is also shown that magnetic ferritearticles can be prepared in situ by loading Fe(II) and Fe(III) into-PEI from the corresponding aqueous solution of the metal ions,nd precipitating by NaOH. As the digital camera images show inig. 7, the magnetic-PEI microgels can be readily separated from anquatic environment by a simple externally applied magnetic field39].

This type of multipurpose material, such as magnetic field-esponsive c-PEI microgel, has great potential in various applica-ions e.g., removal or enrichment of certain species of DNA, gener toxic species from various media or control of different reac-ions such reduction and hydrolysis of various organic reagents asemonstrated earlier [40,41].

. Conclusion

With this investigation, a facile method for PEI microgel prepa-ation was reported in a single step using an AOT microemulsionystem. The obtained PEI particle size distribution spanned fromens of nanometers to tens of micrometers. The prepared PEI par-icles were demonstrated to be versatile as antimicrobial agents,rug delivery devices and templates for metal nanoparticle prepa-ation. It was proven that PEI particles are resourceful as they can

e further modified to increase positive charges for potential appli-ations in microbiology as antimicrobial materials. The wide sizeistribution of PEI particles is another advantage as the smallerizes of PEI particles (>1 m) can be used in biomedical fields such

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em. Eng. Aspects 433 (2013) 212 218 217

as DNA condensing, as antimicrobial agents, and for gene therapypurposes. The bigger sizes (

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[gels for the interaction with nucleic acids, Colloid Chem. II 227 (2003)18 N. Sahiner / Colloids and Surfaces A: Phy

for plasmid DNA: tumor immunotoxicity in B16F10 melanoma, Biomaterials32 (2011) 98399847.

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23] W. Shao, A. Paul, S. Abbasi, P.S. Chahal, J.A. Mena, J. Montes, A. Kamen, S. Prakash,A novel polyethyleneimine-coated adeno-associated virus-like particle formu-lation for efficient siRNA delivery in breast cancer therapy: preparation andin vitro analysis, Int. J. Nanomed. 7 (2012) 15751586.

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Preparation of poly(ethylene imine) particles for versatile applications1 Introduction2 Materials and methods2.1 Materials2.2 Synthesis of polyethylene imine particles2.3 Characterization of c-PEI particles2.4 Antimicrobial properties of c-PEI particles2.5 Metal nanoparticle preparation within c-PEI and catalysis studies

3 Results and discussion4 ConclusionAcknowledgementsReferences