ebook img

UV-Curable Aliphatic Silicone Acrylate Organic–Inorganic Hybrid Coatings with Antibacterial Activity PDF

13 Pages·2017·15.11 MB·English
by  
Save to my drive
Quick download
Download
Most books are stored in the elastic cloud where traffic is expensive. For this reason, we have a limit on daily download.

Preview UV-Curable Aliphatic Silicone Acrylate Organic–Inorganic Hybrid Coatings with Antibacterial Activity

molecules Article UV-Curable Aliphatic Silicone Acrylate Organic–Inorganic Hybrid Coatings with Antibacterial Activity VirginijaJankauskaite˙ 1,*,AlgirdasLazauskas2,EgidijusGriškonis3,Aiste˙ Lisauskaite˙ 1 andKristinaŽukiene˙ 1 1 FacultyofMechanicalEngineeringandDesign,KaunasUniversityofTechnology,Studentu˛St.56, LT-51424Kaunas,Lithuania;[email protected](A.L.);[email protected](K.Ž.) 2 InstituteofMaterialsScience,KaunasUniversityofTechnology,BaršauskoSt.59,LT-51423Kaunas, Lithuania;[email protected] 3 FacultyofChemicalTechnology,KaunasUniversityofTechnology,Radvile˙nu˛St.19,LT-50254Kaunas, Lithuania;[email protected] * Correspondence:[email protected];Tel.:+370-610-05-190 Received:31March2017;Accepted:7June2017;Published:9June2017 Abstract: The most effective means to protect against bacterial invasion and to reduce the risk of healthcare-associated infections are antibacterial components synthesis. In this study, a novel process for the synthesis of organic–inorganic hybrid coatings containing silver nanoparticles is presented. Silver nanoparticles and polymer formation proceeds simultaneously through the in situ photoreduction of silver salt to silver nanoparticles and UV-crosslinking of bifunctional aliphatic silicone acrylate. The nanocomposite films with 0.5–1.43 wt % of silver nanoparticles concentration were obtained and investigated. The formation of silver nanoparticles in polymer matrixwasconfirmedviaUV-visiblespectroscopy,X-raydiffraction(XRD),Fouriertransforminfrared spectroscopy,scanningelectronspectroscopy,andenergydispersivespectroscopy. Ourinvestigations clearlyshowtheformationofsilvernanoparticlesinsiliconeacrylatenetwork. Directphotoreduction ofsilversaltbyUV-radiationintheorganicmediaproducedsilvernanoparticlesexhibitingcubic crystalstructure. Thesizeofnanoparticleswasdeterminedtobenear20±5nm. Theantibacterial activitiesofcoatingsweredeterminedusingthediscdiffusionanddirectcontactmethods.UV-curable siliconeacrylatehybridcoatingsexhibitedantibacterialactivityagainstharmfulbacteriastrains. Keywords: siliconeacrylate;silvernanoparticles;UV-curable;antibacterial 1. Introduction Hybridmaterialscontainingorganic–inorganicconstituentshavegainedincreasedinterestdue to their exceptional multifunctional properties. Different combinations allow the achievement of exceptional electrical, catalytic, antibacterial, radiation-resistant, optical, thermal, and mechanical properties. The potential applications of these materials can cover multiple fields, ranging from engineeringtomedical[1–3]. Hybridorganic–inorganicmaterialscanbedefinedasnanocomposites obtainedbyintimatemixingoforganicandinorganiccomponents.Thecommonrouteforthesynthesis of these nanocomposites corresponds to the use of bridged and polyfunctional precursors, very convenientsol–gelchemistry,andhydrothermalsynthesis[4]. Moresophisticatedtechniquesinclude theuseofself-assembly,integrativesynthesisroutes,ortemplatedgrowthbyorganicsurfactants[5]. Organic–inorganicpolymerhybridsarebasedonthecombinationsofpolymermatrixeswith metals,ceramics,orboth,andcanbepreparedbyavarietyofmethodsfordifferentapplications[6,7]. The most widely used organic matrices for the incorporation of inorganic nanoparticles include Molecules2017,22,964;doi:10.3390/molecules22060964 www.mdpi.com/journal/molecules Molecules2017,22,964 2of13 poly(methyl methacrylate), poly(vinyl chloride), polycarbonate, poly(ethylene terephthalate), and polystyrene[8–12]. Silicone-modified acrylates form a new class of hybrid surface-modifying materials. These substances are not merely blends of silicone and acrylates. Instead, they are hybrids obtained by thechemicalincorporationofsiliconechainsintobasicacrylatestructure[13]. Silicone-acrylatesare obtainedviatheradicalpolymerizationofacrylatesormethacrylateswithsiliconemacromers(i.e.,long chains of polydimethylsiloxane) [14]. A single terminal reactive group (e.g., acrylic, methacrylic, orvinylfunctionalgroups)isattheendofthechain. Hereby,insuchacomposition,siliconesoflow surfacetensionarecombinedwithpolyacrylateshavingrelativelyhighsurfacetension. Thestrong surface orientation of the silicone chains creates a very strong repulsion effect against water and contaminants,suchasoilanddirt,andbacterialadhesion. Biofilm-producingpathogensarefrequentlyassociatedwithhealthcare-associatedinfectionsthat oftenneedsurgicalinterventionandthewidespreaduseofbroad-spectrumantibiotics[15]. Therisk of such infections can be reduced by the modification of medical device materials with additives possessingantimicrobialactivitywiththeabilitytodecreasebacterialadhesion. Antibacterialcomponentssynthesisisthemosteffectivemeansofprotectingagainstcolonization by bacterial pathogens and dangerous infections. Silver nanoparticles are a well-known potent antimicrobial agent. A number of different synthesis methods of silver nanoparticles have been developed,includingchemical,photochemical,andthermal[16–19]. Specifically,thephoto-induced synthesisstrategyisveryattractive,asitisaversatileandconvenientprocesswithdistinguishing advantages, such as space-selective fabrication [20]. Direct photoreduction is a very important techniquefornanoparticlesynthesis,wherethedirectexcitationofametalsourceisemployedfor theformationofmetalnanoparticles. Additionally,thereisnoneedforreducingagents. Moreover, itcanbeemployedinvariousmedia,includingpolymercoatingsandthinfilms. Silvernanoparticles withtheirattractivephysicochemicalproperties,size,andshapevarietypushtheintensiveresearch with great scientific interest into a wide range of applications, including biological, chemical, and physicalsectors[21].Theyareknowntoexerttoxicitythroughmechanismsdifferentfromconventional antibiotics[22,23];theseincludedisruptionofcellmorphology,inactivationofvitalcellularenzymes and proteins, DNA condensation [24], inhibition of ribosome interaction, accumulation at lethal concentrationincells[25],proteindenaturation[26],modulationofcellularsignaling,generationof reactiveoxygenspecies, oxidativestress[27], lossofDNAreplication, anddepletionofadenosine triphosphate[28]. Thiscanbeespeciallyusefultoensureasterileenvironmentinmedicalapplications (e.g.,surgicalsettings)bypreventingbacteriafromgrowingonoradheringtothesurface[29,30]. In the present study, a simple and fast hybrid organic–inorganic polymer synthesis method is investigated. UV-cured aliphatic silicone acrylate coatings containing silver nanoparticles were formedviaphoto-polymerizationtechnique. Thesecoatingswerecharacterizedemployingmultiple analyticaltechniques. 2. ResultsandDiscussion 2.1. StructureAnalysis In order to confirm the presence of silver nanoparticles in the fabricated UV-cured silicone acrylatecompositestructure,UV-visiblespectroscopywasusedinthefirstinstance. Figure1shows the UV-visible light spectrum of silicone acrylate-silver nanocomposite, presented as a Gaussian functionwhichhasacharacteristicabsorptionpeakataround416nmduetothesurface-plasmon resonancebandofthesilvernanoparticles[31,32]. Inmostcases,theabsorptionpeakisobservedin therangeof410–460nmduetosurfaceplasmonresonanceinsilvernanoparticles. Itisknownthat theabsorptionbandwidthoftheplasmonbanddependsheavilyonthesizeandinteractionwiththe surroundingmedium[33]. Thebandcenteredat416nmintheUV-visiblelightabsorbancespectrum Molecules 2017, 22, 964 3 of 12 Molecules2017,22,964 3of13 surrounding medium [33]. The band centered at 416 nm in the UV-visible light absorbance spectrum (3(33377––884400 nnmm) )ininddiciacatetes sththee ppreresesennccee oof fsislivlveer rnnaannooppaartritcilceles sinin ththee ppoolylymmeer rmmaatrtirxix, ,yyieieldldiningg aa uunniqiquuee spspeectcrtaral lfifinnggeerprprirnint tfofor rpplalassmmoonnicic nnaannooppaarrtitcicleless wwitihth aa ssizizee ccoorrrreessppoonnddiningg ttoo 2200 ±± 5 5nmnm [3[43]4. ]. 441166 )) .. uu .. aa (( ee cc nn aa bb rr oo ss bb AA 335500 440000 445500 550000 555500 660000 665500 770000 775500 880000 WWaavveelleennggtthh ((nnmm)) FFigiguurer e11. .UUVV-v-visiisbilbel elilgighht tababsosorbrabnancec espspecetcrtar aoof fsislivlvere rnnaannoopparatritcilcelse scoconntatianininign gUUVV-c-ucurerded sisliilcioconne e acarcyrylaltaet ecocommppoosistiet ecocoaatitningg. . The structural peculiarities of synthesized silver nanoparticles were determined using X-ray The structural peculiarities of synthesized silver nanoparticles were determined using X-ray diffraction (XRD). Figure 2 shows an XRD pattern of a UV-cured aliphatic silicone acrylate diffraction (XRD). Figure 2 shows an XRD pattern of a UV-cured aliphatic silicone acrylate nanocomposite coating which contains silver nanoparticles. After the reduction process, silver nanocomposite coating which contains silver nanoparticles. After the reduction process, silver nanoparticles crystallized into cubic crystal structure (as per JCPDS file no. 04-016-5006) with space nanoparticlescrystallizedintocubiccrystalstructure(asperJCPDSfileno. 04-016-5006)withspace group Fm-3m (group number = 225), and the (2 0 0), (2 2 0), (3 1 1), (4 0 0), and (4 2 0) crystallographic groupFm-3m(groupnumber=225),andthe(200),(220),(311),(400),and(420)crystallographic plane orientations were observable. The diffraction pattern also reveals two broad components in the planeorientationswereobservable. Thediffractionpatternalsorevealstwobroadcomponentsinthe range of 2θ = 8.0–28.0°, which are attributed to the amorphous structure of aliphatic silicone acrylate. rangeof2θ=8.0–28.0◦,whichareattributedtotheamorphousstructureofaliphaticsiliconeacrylate. The chemical structure of UV-cured silicone acrylate nanocomposite was identified via FTIR The chemical structure of UV-cured silicone acrylate nanocomposite was identified via FTIR spectroscopy (Figure 3). The sharp peak at 1720 cm−1 is attributed to the stretching vibration of C=O spectroscopy(Figure3). Thesharppeakat1720cm−1isattributedtothestretchingvibrationofC=O groups, and a peak at 1258 cm−1 is related to C–O stretching vibration of the acrylic moiety [35]. groups, and a peak at 1258 cm−1 is related to C–O stretching vibration of the acrylic moiety [35]. An absorption peak at 2960 cm−1 corresponds to C–H symmetric and asymmetric stretching of Anabsorptionpeakat2960cm−1correspondstoC–Hsymmetricandasymmetricstretchingofmethyl methyl and methylene groups. The presence of this group is also confirmed by peaks at 1450 cm−1 and methylene groups. The presence of this group is also confirmed by peaks at 1450 cm−1 and and 1387 cm−1, which are associated with a bending vibration of C–H groups. 1387cm−1,whichareassociatedwithabendingvibrationofC–Hgroups. The silicone part could be characterized by Si–CH3 symmetric deformation and stretching The silicone part could be characterized by Si–CH symmetric deformation and stretching 3 vibration at 1260 and 788 cm−1, respectively. The bands in the 1070–1015 cm−1 region are attributed to vibrationat1260and788cm−1,respectively. Thebandsinthe1070–1015cm−1regionareattributed Si–O–Si stretching vibration [36–39]. There are no noticeable shifts in the peak positions when the toSi–O–Sistretchingvibration[36–39]. Therearenonoticeableshiftsinthepeakpositionswhenthe silicone acrylate polymer without nanoparticles and polymer with embedded silver nanoparticles siliconeacrylatepolymerwithoutnanoparticlesandpolymerwithembeddedsilvernanoparticles are compared, except for a broader and stronger O–H absorption band at 3350 cm−1. It can be are compared, except for a broader and stronger O–H absorption band at 3350 cm−1. It can be assumed that the OH group is engaged in the formation of hydrogen bonds or complexation with assumedthattheOHgroupisengagedintheformationofhydrogenbondsorcomplexationwith metal nanoparticles. metalnanoparticles. Molecules2017,22,964 4of13 Molecules 2017, 22, 964 4 of 12 Molecules 2017, 22, 964 4 of 12 )) .. uu)) .. ..uu aa ((a.a. yy(( tty y ii sstt nnsisi eenn ttee nn tt IInn II 1100 2200 3300 4400 5500 6600 7700 8800 9900 110000 111100 112200 113300 1100 2200 3300 4400 5500 6600 7700 8800 9900 110000 111100 112200 113300 22TThheettaa ((CCoouupplleedd TTwwooTThheettaa//TThheettaa)) WWLL==11..5544006600 22TThheettaa ((CCoouupplleedd TTwwooTThheettaa//TThheettaa)) WWLL==11..5544006600 FFiigguurree 22.. XXRRDD ppaatttteerrnn ooff ssiillvveerr nnaannooppaarrttiicclleess ccoonnttaaiinniinngg UUVV--ccuurreedd ssiilliiccoonnee aaccrryyllaattee ccoommppoossiittee ccooaattiinngg wFiigtuhrcer y2s. tXalRloDg rpaapttheircnp olaf nseilvoerrie nnatantoiopnarstiocflessi lvcoenrtpahinaisnegi nUdVic-cauterded. silicone acrylate composite coating with crystallographic plane orientations of silver phase indicated. with crystallographic plane orientations of silver phase indicated. 100 100 a a 80 80 % b e, % b ancce, 6600 nsmittmittan 40 rans 40 Ta r T 20 20 0 0 3650 3150 2650 2150 1650 1150 650 3650 3150 2650 2150 1650 1150 650 Wavenumber, cm-1 Wavenumber, cm-1 Figure 3. Fourier transform infrared (FTIR) spectra of UV-curable aliphatic silicone acrylate coating (FFaii)gg wuurrieeth 33o..u FFtoo auunrrdiiee r(rb tt)rr aawnnisstfhfoo r1rmm.0 iwinnftfr r%aarr eoedfd (s F(ilFTvTIeRIrR )n)s apsnpeoceptcrtaarraot ifoclUfe UsV. -Vcu-cruarbalbelael iaplhipahtiactisci lisciolincoenaec rayclraytelactoe actoinagtin(ag) w(ai)t whoituhtoauntd a(nbd) (wbi)t hw1it.h0 1w.0t %wto %fs oilfv seirlvnearn noapnaortpicalretsic.les. The surface morphologies of the silicone acrylate–silver nanocomposites were investigated by The surface morphologies of the silicone acrylate–silver nanocomposites were investigated by scannTihneg seulercfatrcoenm moircprhosocloogpiye s(SoEfMth) easnidli coenneergaycr ydliastpee–rssiilvvee rXn–arnayo csopmecptorosistceospwy e(rEeDiSn)v easntiaglyasteisd. scanning electron microscopy (SEM) and energy dispersive X–ray spectroscopy (EDS) analysis. Tbhyes cparnenseinngtedel eScEtMro nmmicircorgorsacpohpsy ((FSiEguMr)e a4n) dcleeanrelryg syhdowisp tehres ifvoermXa–triaoyn sopf escitlvroesrc noapnyo(pEaDrtSic)leasn ainly tshies. The presented SEM micrographs (Figure 4) clearly show the formation of silver nanoparticles in the aTlhipehparteics esniltiecdonSeE Macrmyliactreo gnreatpwhosr(kF. igSiulvreer4 )ncalneaorplayrstihcolews athree fworemll adtiisopneorsfesdil viner tnhaen pooplayrmtieclre msiantrtihxe. aliphatic silicone acrylate network. Silver nanoparticles are well dispersed in the polymer matrix. Haloipwheavteicr, stihliec oinncereaacsrey loaft esinlveetrw noarnko.pSairlvtieclrens acnoonpceanrttricalteiosna rceauwseesl ltdheis pacecrusemduilnatitohne opfo nlyamnoepramrtaictlreisx,. However, the increase of silver nanoparticles concentration causes the accumulation of nanoparticles, wHhoiwchev fearc,itlihteieisn tchreea fsoermofastiilovne ronf acnluosptaerrtsi c(lFeisgucorne c4ebn)t.r Tathioe nEcDaSu ssepsetchtreuamcc oufm thuela stiiolincoonfen aacnroyplaatret iaclneds, which facilities the formation of clusters (Figure 4b). The EDS spectrum of the silicone acrylate and swilhviecrh nfaanciolictoiemspthoesitfeo rimn aFtiigounreo f5 calulssot ecrosn(fFirimguerde t4hbe) .foTrhmeaEtDioSn sopf escitlvruemr noafntohpeasritliiccloesn eina tchrye lsaitleicaonnde silver nanocomposite in Figure 5 also confirmed the formation of silver nanoparticles in the silicone asiclrvyelratnea mnoactorimx.p ositeinFigure5alsoconfirmedtheformationofsilvernanoparticlesinthesilicone acrylate matrix. acrylCatheamngaetrsi xo.f surface free energy due to the incorporation of silver nanoparticles into the aliphatic Changes of surface free energy due to the incorporation of silver nanoparticles into the aliphatic silicone acrylate coating were determined using contact angle (CA) measurements. The 5 μL water silicone acrylate coating were determined using contact angle (CA) measurements. The 5 μL water droplet measurements were employed (Figure 6). The UV-cured aliphatic silicone acrylate was droplet measurements were employed (Figure 6). The UV-cured aliphatic silicone acrylate was found to be hydrophobic (CA = 94° ± 1°). The formation of silver nanoparticles in aliphatic silicone found to be hydrophobic (CA = 94° ± 1°). The formation of silver nanoparticles in aliphatic silicone Molecules 2017, 22, 964 5 of 12 Molecules 2017, 22, 964 5 of 12 acrylate during the UV-curing process reduces the contact angle, because metallic silver particles acrylate during the UV-curing process reduces the contact angle, because metallic silver particles have a large surface energy. Importantly, CA values do not depend on the nanoparticles have a large surface energy. Importantly, CA values do not depend on the nanoparticles concentration—an increase of the content of silver nanoparticles from 0.5 to 1.43 wt % resulted in a concentration—an increase of the content of silver nanoparticles from 0.5 to 1.43 wt % resulted in a CA value of 84 ± 2°. It is possible that with the increase of metallic silver concentration the CA value of 84 ± 2°. It is possible that with the increase of metallic silver concentration the nanoparticles tend to accumulate, thereby creating clusters. The smaller the silver particles, the nanoparticles tend to accumulate, thereby creating clusters. The smaller the silver particles, the higher are their surface energy and surface activity. According to [40], polymer composites exhibit higher are their surface energy and surface activity. According to [40], polymer composites exhibit hMioglehceulre sc2o0n1t7a,2c2t ,a9n64gle when the concentration of silver nanoparticles is increased due to the forma5toifo1n3 higher contact angle when the concentration of silver nanoparticles is increased due to the formation of silver clusters of large dimensions. of silver clusters of large dimensions. (a) (b) (a) (b) Figure 4. SEM micrographs of silver-containing UV-cured aliphatic silicone acrylate coating: (a) Figure4.SEMmicrographsofsilver-containingUV-curedaliphaticsiliconeacrylatecoating:(a)0.5wt% Figure 4. SEM micrographs of silver-containing UV-cured aliphatic silicone acrylate coating: (a) 0.5 wt % silver nanoparticles; (b) 1.43 wt % silver nanoparticles. silvernanoparticles;(b)1.43wt%silvernanoparticles. 0.5 wt % silver nanoparticles; (b) 1.43 wt % silver nanoparticles. Element wt % at % Errorin% Element wt % at % Errorin% Carbon K 41.53 61.16 6.79 CEarlebmone Kn t 41w.5t3 % 61a.1t6% Er6r.o7r9 in% Oxygen K 10.81 11.95 3.47 Oxygen K 10.81 11.95 3.47 CSailrvbeor nL K 64.817.5 3 16.11.31 6 06.1.79 9 Silver L 6.87 1.13 0.19 OSixliycgonen KK 318.04.88 1 2141.2.49 5 13.6.43 7 Silicon K 38.48 24.24 1.63 SilverL 6.87 1.13 0.19 Figure 5. EDS spectrum of silver containing (1 wt %) UV-cured aliphatic silicone acrylate coating. SiliconK 38.48 24.24 1.63 Figure 5. EDS spectrum of silver containing (1 wt %) UV-cured aliphatic silicone acrylate coating. Figure5.EDSspectrumofsilvercontaining(1wt%)UV-curedaliphaticsiliconeacrylatecoating. Changesofsurfacefreeenergyduetotheincorporationofsilvernanoparticlesintothealiphatic siliconeacrylatecoatingweredeterminedusingcontactangle(CA)measurements. The5µLwater dropletmeasurementswereemployed(Figure6). TheUV-curedaliphaticsiliconeacrylatewasfound tobehydrophobic(CA=94◦ ±1◦). Theformationofsilvernanoparticlesinaliphaticsiliconeacrylate duringtheUV-curingprocessreducesthecontactangle,becausemetallicsilverparticleshavealarge surfaceenergy. Importantly,CAvaluesdonotdependonthenanoparticlesconcentration—anincrease Molecules2017,22,964 6of13 ofthecontentofsilvernanoparticlesfrom0.5to1.43wt%resultedinaCAvalueof84 ± 2◦. Itis possiblethatwiththeincreaseofmetallicsilverconcentrationthenanoparticlestendtoaccumulate, therebycreatingclusters.Thesmallerthesilverparticles,thehigheraretheirsurfaceenergyandsurface activity. Accordingto[40],polymercompositesexhibithighercontactanglewhentheconcentrationof silvernanoparticlesisincreasedduetotheformationofsilverclustersoflargedimensions. Molecules 2017, 22, 964 6 of 12 (a) (b) (c) Figure 6. Five microliter water droplet on UV-cured aliphatic silicone acrylate coating (a) without Figure6. FivemicroliterwaterdropletonUV-curedaliphaticsiliconeacrylatecoating(a)without nanoparticles and containing (b) 0.5 wt % and (c) 1.43 wt % of silver nanoparticles. nanoparticlesandcontaining(b)0.5wt%and(c)1.43wt%ofsilvernanoparticles. 2.2. Antibacterial Activity 2.2. AntibacterialActivity The antibacterial activity of the hybrid silver nanoparticles containing UV-cured aliphatic silicone TheantibacterialactivityofthehybridsilvernanoparticlescontainingUV-curedaliphaticsilicone acrylate coatings obtained via in situ formation method was investigated by different methods. At first, acrylate coatings obtained via in situ formation method was investigated by different methods. qualitative assessment of the antibacterial activity was used by measuring the diameter of the At first, qualitative assessment of the antibacterial activity was used by measuring the diameter growth inhibition zone. Disks of hybrid silicone acrylate films were placed on the agar plates ofthegrowthinhibitionzone. Disksofhybridsiliconeacrylatefilmswereplacedontheagarplates inoculated with the Gram-negative bacteria Escherichia coli ATCC 25922 and the Gram-positive inoculatedwiththeGram-negativebacteriaEscherichiacoliATCC25922andtheGram-positivebacteria bacteria Staphylococcus aureus ATCC 25923. Figure 7 illustrates the antibacterial activity of the silicone StaphylococcusaureusATCC25923. Figure7illustratestheantibacterialactivityofthesiliconeacrylate acrylate organic–inorganic hybrid coatings containing different amounts of silver nanoparticles (from organic–inorganichybridcoatingscontainingdifferentamountsofsilvernanoparticles(from0.5to 0.5 to 1.43 wt %). The antibacterial effect increased gradually as the silver nanoparticles concentration 1.43 wt %). The antibacterial effect increased gradually as the silver nanoparticles concentration increases. The zone of inhibition for E. coli increased by 20–30%, while for S. aureus this increase was increases. ThezoneofinhibitionforE.coliincreasedby20–30%,whileforS.aureusthisincreasewas noticeably higher, at 60–90% (Table 1). Importantly, silver nanoparticles synthesized during silicone noticeablyhigher,at60–90%(Table1). Importantly,silvernanoparticlessynthesizedduringsilicone acrylate polymerization process acted as an effective antibacterial agent. acrylatepolymerizationprocessactedasaneffectiveantibacterialagent. Table1. MeaninhibitionzoneofsilvernanoparticlescontainingUV-curedsiliconeacrylatecoating againstdifferentpathogenspresentedasanintervalrange. InhibitionZone* SilverNanoparticles Concentration(wt%) E.coli S.aureus 0 0 0 0.5 1.14–1.27 1.61–1.66 1.0 1.15–1.34 1.82–1.94 1.43 E. col1i .26–1.34 1.83–2.01 Notes:*Threereplicateswerecarriedoutforeachtesting. S. aureus Figure 7. Antibacterial activity against E. coli and S. aureus of UV-cured silicone acrylate composite samples with different concentration of silver nanoparticles: (a,d) 0.5 wt %; (b,e) 1 wt %; (c,f) 1.43 wt %. Molecules 2017, 22, 964 6 of 12 (a) (b) (c) Figure 6. Five microliter water droplet on UV-cured aliphatic silicone acrylate coating (a) without nanoparticles and containing (b) 0.5 wt % and (c) 1.43 wt % of silver nanoparticles. 2.2. Antibacterial Activity The antibacterial activity of the hybrid silver nanoparticles containing UV-cured aliphatic silicone acrylate coatings obtained via in situ formation method was investigated by different methods. At first, qualitative assessment of the antibacterial activity was used by measuring the diameter of the growth inhibition zone. Disks of hybrid silicone acrylate films were placed on the agar plates inoculated with the Gram-negative bacteria Escherichia coli ATCC 25922 and the Gram-positive bacteria Staphylococcus aureus ATCC 25923. Figure 7 illustrates the antibacterial activity of the silicone acrylate organic–inorganic hybrid coatings containing different amounts of silver nanoparticles (from 0.5 to 1.43 wt %). The antibacterial effect increased gradually as the silver nanoparticles concentration increases. The zone of inhibition for E. coli increased by 20–30%, while for S. aureus this increase was nMootleiccuelaesb2ly01 7h,i2g2h,9e6r4, at 60–90% (Table 1). Importantly, silver nanoparticles synthesized during sili7coofn1e3 acrylate polymerization process acted as an effective antibacterial agent. E. coli Molecules 2017, 22, 964 7 of 12 Table 1. Mean inhibition zone of silver nanoparticles containing UV-cured silicone acrylate coating against different pathogens presented as an interval range. InhibitionZone * Silver Nanoparticles Concentration (wt %) E. coli S. aureus 0 0 0 0.5 1.14–1.27 1.61–1.66 S. aureus 1.0 1.15–1.34 1.82–1.94 FFiigguurree 77.. AAnnttiibbaacctteerriiaall aaccttiivviittyy aaggaa1iinn.4ss3tt EE.. ccoollii aanndd SS.. aauurreeuuss ooff UU1VV.2--cc6uu–rr1ee.dd3 4ssi illiicc1oo.nn8ee3 –aa2ccrr.0yy1llaa ttee ccoommppoossiittee ssaammpplleess wwitihthd ifdfeifrfeenretncot nccoenntcreantitorantioofns ilovfe rsnilavneorp anratincolepsa:r(tai,cdle)s0:. 5(wa,td%) ;0(.b5, ew)1t w%t;% ;(b(c,e,f)) 11.4 3wwt t%%;. Notes: * Three replicates were carried out for each testing. (c,f) 1.43 wt %. TThhee ggrroowwtthh iinnhhiibbiittiioonna arroouunnddt htheeh yhbyrbidridco caotiantigndgi sdkisskcsre carteeadtendo tnloart glearigneh iibnihtiiobnitzioonn ezso.nTehsi.s Tmhaisy mbeayd ubee tdouteh teoi nthceo minpcolemtepplehtye spichaylsciocanlt acoctnbtaecttw beeetnwteheens tihlvee srilnvaenr onpaanrotipcalersticinletsh ien hthyeb rhidybcroidat cinogatainngd athned stuhrer osuunrdroinugndcuinltgu rceumltuerdei umme.dTihuemre. fTorhee,rienfothree, sienc otnhde rsoeuconndd,a rdoiurencdt, cao ndtaircetctte sctowntaascpt etrefsot rmwaeds pfoerrfqourmanetdifi cfaotri oqnuoafntthifeicbaaticotenr iocifd tahlee fbfeacctt.eAriccioduanl teofffetchte. cAo locnouienstr eovfe tahleed ctohlaotntihees UreVv-ecaulreedd athliapth tahtiec UsiVlic-counreedac arylilpahteatoicr gsailnicico–nien oarcgryanlaitcec oormgapnoisci–teincooragtainngic sciogmnipfiocasnittel ycoinathiinbgit seidgnthifeicgarnotwlyt hinohfibSi.teadur tehues , garsoswhothw nofi nSF. iaguurreeu8s,. Tash eshbaocwtenr iaind eFcirgeuarsee d8.t oTzheer obiancttherrieae oduetcroefafsoeudr rteop zeteirtoio nins atfhtererein ocuubt aotifo fnofuorr r2e4phet.itions after incubation for 24 h. FFiigguurree 88.. BBacatcetreirciicdiadla lefeffefcetc toof fUUVV-c-cuureredd ssiliilcicoonnee aaccrryylalatete ccooaatitningg ccoonnttaainininingg 11.4.433%% ooff ssiillvveerr nnaannooppaarrttiicclleess oonn SS.. aauurreeuuss aafftteerr ddiiffffeerreenntt ccoonnttaacctt ttiimmee.. The antibacterial effect could be the result of the dissociation of silver nanoparticles into Ag+ ions and their accumulation on the coating surface. Silver ions accumulate on the bacterial cell surface, which interacts with the microbial membrane to cause structural change, permeability, and finally bacterial cell death [31]. The influence on bacteria viability depends extremely on the size, shape, and concentration of nanoparticles [32,33]. In [34], it is reported that silver nanoparticles accumulation on the E. coli cell membrane makes gaps in the entirety of the bilayer, which predisposes it to the increased penetrability and finally bacterial cell death [31]. The model of the silicone acrylate formation with simultaneous conversion of silver perchlorate to silver nanoparticles and possible bacterial inactivation mechanism is presented in Figure 9. Molecules2017,22,964 8of13 TheantibacterialeffectcouldbetheresultofthedissociationofsilvernanoparticlesintoAg+ions andtheiraccumulationonthecoatingsurface. Silverionsaccumulateonthebacterialcellsurface, whichinteractswiththemicrobialmembranetocausestructuralchange,permeability,andfinally bacterialcelldeath[31]. Theinfluenceonbacteriaviabilitydependsextremelyonthesize,shape,and concentrationofnanoparticles[32,33]. In[34],itisreportedthatsilvernanoparticlesaccumulationon theE.colicellmembranemakesgapsintheentiretyofthebilayer,whichpredisposesittotheincreased penetrabilityandfinallybacterialcelldeath[31]. Themodelofthesiliconeacrylateformationwithsimultaneousconversionofsilverperchlorate tMoosleicluvleesr 2n01a7n, o22p, a96r4ti clesandpossiblebacterialinactivationmechanismispresentedinFigure9. 8 of 12 FFiigguurree 99.. SScchheemmee ooff tthhee ffoorrmmaattiioonn ooff ssiillvveerr nnaannooppaarrttiicclleess ccoonnttaaiinniinngg UUVV--ccuurreedd aalliipphhaattiicc ssiilliiccoonnee aaccrryyllaattee ccooaattiinngg aanndd ppoossssiibbllee bbaacctteerriiaall iinnaacctitvivaatitoionn mmeecchhaannisimsm vviai ainintetrearcatciotino nwwithit hanatnibtiabcatectreiarli aclocaotiantgin sgusrufarcfea.c e. According to the studies of other researchers, silver nanoparticles possess a strong antibacterial Accordingtothestudiesofotherresearchers,silvernanoparticlespossessastrongantibacterial and antiviral activity. Acting with microorganisms, they impact the growth of bacterial biofilms. andantiviralactivity. Actingwithmicroorganisms,theyimpactthegrowthofbacterialbiofilms. Silver Silver nanoparticles interact with bacterial surfaces, as well as with their particular structure [22–29]. nanoparticlesinteractwithbacterialsurfaces,aswellaswiththeirparticularstructure[22–29]. When When the size of silver nanoparticles is larger than 10 nm, the predominant bacteria inactivation thesizeofsilvernanoparticlesislargerthan10nm,thepredominantbacteriainactivationmechanism mechanism is through silver ions [30]. Although nanoparticles’ antibacterial effects have been isthroughsilverions[30]. Althoughnanoparticles’antibacterialeffectshavebeendescribedindetail, described in detail, their mechanism of action still requires further elucidation both from chemical theirmechanismofactionstillrequiresfurtherelucidationbothfromchemicalandbiologicalpoints and biological points of view. ofview. 3. Materials and Methods 3. MaterialsandMethods 33..11.. MMaatteerriiaallss BBiiffuunnccttiioonnaall aalliipphhaattiicc ssiilliiccoonnee aaccrryyllaattee oolliiggoommeerr wwiitthh vviissccoossiittyy ooff 5500––7700 PPaass,, ssuuiittaabbllee ffoorr uussee iinn UUVV aanndd eelleeccttrroonn bbeeaamm ccuurriinngg ccoommppoossiitteess ((CCNN99880000)),, wwaass ppuurrcchhaasseedd ffrroomm SSaarrttoommeerr ((AArrkkeemmaa GGrroouupp,, CCoolloommbbeess CCeeddeexx,, FFrraannccee)).. IIttss ppoollyymmeerriizzaattiioonn wwaass ccaarrrriieedd oouutt uussiinngg mmiixxttuurree bbiiss((22,,66--ddiimmeetthhooxxyybbeennzzooyyll))-- 22,,44,,44--ttrriimmeetthhyyll ppeennttyylplphhoosspphhinineeooxxidideea nandd2 -2h-yhdyrdorxoyx-y2--2m-methetyhl-y1l--p1-hpehneynl-yplr-poproapna-1n--o1n-oenine ainr aat iroatoifo1 o:3f (1I:r3g a(Icrugraec1u7r0e0 1)7a0s0p) haost opihnoittioatinorit,isautoprp, liseudpbpylieBdA bSFy (BSAouStFh fi(Seoldu,tMhfiIe,lUdS, AM).I,S UilvSeAr)p. eSriclhvleorr apteercAhgloCrlaOte 4 (AAggC>lO540 (.A5%g )>a 5n0d.5a%cr)y alnicda accidrywlice raecpidu wrcehraes epdurfrcohmaseSdig fmroamA Sldigrmicha (ASltd. Lriochu i(sS,tM. LOo,uUisS, AM)O. , USA). 3.2. Nanocomposite Preparation Silver perchlorate salt (0.05–0.15 g) was first dissolved in 1.00 mL of acrylic acid, and then 0.1–0.3 g of photoinitiator Irgacure 17,000 was added (in ratio AgClO4:photoinitiator = 1:2). The mixture was continuously stirred at ambient temperature until a homogeneous solution was obtained. Silver nanoparticles precursor, solvent, and photoinitiator mixture were mixed with 4.00 g of bifunctional aliphatic silicone acrylate oligomer CN9800 for 10 min at ambient temperature until a homogeneous suspension was formed and then kept under vacuum for 10 min at ambient temperature to remove air bubbles. After that, the obtained mixture was poured onto a glass plate. The polymerization and silver salt photoreduction to silver nanoparticles initiated by Irgacure 1700 was carried out with a medium pressure mercury lamp (1 kW, Hibridas Photosensitive Paste UV Exposure Unit MA-4). After irradiation of the composition for 120 s, silicone acrylate coatings having a thickness of 1 mm without or with silver nanoparticles of 0.5–1.43 wt % concentration were formed. Higher silver Molecules2017,22,964 9of13 3.2. NanocompositePreparation Silverperchloratesalt(0.05–0.15g)wasfirstdissolvedin1.00mLofacrylicacid,andthen0.1–0.3g ofphotoinitiatorIrgacure17,000wasadded(inratioAgClO :photoinitiator=1:2). Themixturewas 4 continuously stirred at ambient temperature until a homogeneous solution was obtained. Silver nanoparticlesprecursor,solvent,andphotoinitiatormixtureweremixedwith4.00gofbifunctional aliphaticsiliconeacrylateoligomerCN9800for10minatambienttemperatureuntilahomogeneous suspensionwasformedandthenkeptundervacuumfor10minatambienttemperaturetoremove airbubbles. Afterthat,theobtainedmixturewaspouredontoaglassplate. Thepolymerizationand silversaltphotoreductiontosilvernanoparticlesinitiatedbyIrgacure1700wascarriedoutwitha mediumpressuremercurylamp(1kW,HibridasPhotosensitivePasteUVExposureUnitMA-4). After irradiationofthecompositionfor120s,siliconeacrylatecoatingshavingathicknessof1mmwithout Molecules 2017, 22, 964 9 of 12 orwithsilvernanoparticlesof0.5–1.43wt%concentrationwereformed. Highersilvernanoparticles concentrationinpolymermatrixviainsituphoto-reductionmethodbecomesproblematic. Visual nanoparticles concentration in polymer matrix via in situ photo-reduction method becomes problematic. obsVeirsvuaatl ioobnseorfvtahteiorne souf ltthaen rtemsualttaenrita mlsastheroiwalss sthhoawttsh tehayte tlhloew yieslhlowfilimshs fwilmitsh owuitthsoiluvte srilnvaern onpanaortpiaclretisclheas ve aghoaovde oap gtiocoadl troapntiscpala rteranncsyp;amreenacny;w mhielaen,wthhoislee, wthiothsee wmibthe dedmebdedsidlveder snilavnero pnaarntoicplaerstifculersn ifsuhrnaisbhr oaw n colborroawtinon co(Floirgautiroen1 (0F)i.gure 10). (a) (b) FigFuigreur1e0 1.0. AAlliipphhaattiicc ssiililcicoonnee acarcyrlyaltae tceoacotiantgi nfgilmfisl:m (as): w(ait)howuitt hsiolvuetr snilavneorpanratincolepsa; r(tbi)c lwesi;th( bsi)lvweri th silvnearnnopanarotpicalertsi.c les. 3.3. Nanocomposite Characterization 3.3. NanocompositeCharacterization An optical spectrometer Avantes that is composed of a deuterium halogen light source AnopticalspectrometerAvantesthatiscomposedofadeuteriumhalogenlightsource(AvaLight (AvaLight DHc, Avantes, Apeldoorn, The Netherlands) and spectrometer (Avaspec-2048, Avantes, DHc,Avantes,Apeldoorn,TheNetherlands)andspectrometer(Avaspec-2048,Avantes,Apeldoorn, Apeldoorn, The Netherlands) was used to record UV-visible light absorbance spectra. The analysis TheNetherlands)wasusedtorecordUV-visiblelightabsorbancespectra. Theanalysiswasperformed was performed in the wavelength range of 337–840 nm. inthewavelengthrangeof337–840nm. The structural peculiarities of the synthesized silver nanoparticles was determined using X-ray ThestructuralpeculiaritiesofthesynthesizedsilvernanoparticleswasdeterminedusingX-ray diffractometer D8 Discover (Bruker AXS GmbH, Billerica, MA, USA) with parallel beam focusing diffractometer D8 Discover (Bruker AXS GmbH, Billerica, MA, USA) with parallel beam focusing geometry of Cu Kα1 (λ = 0.154 nm) radiation. Processing of the resultant diffractograms was geometryofCuKα (λ=0.154nm)radiation.Processingoftheresultantdiffractogramswasperformed performed with D1IFFRAC.EVA software (version 3.0, Billerica, MA, USA). Phase identification and withDIFFRAC.EVAsoftware(version3.0,Billerica,MA,USA).Phaseidentificationandinterpretation interpretation involved matching the diffraction pattern of free-standing silver nanoparticles invcoolnvteadinimnga tcshiliicnognteh eacdryiflfartaec tciooantipnagt tetor npoafttferrenes- sotaf nsdininggles-pilhvaesre nraenfoerpeanrcteic lmesatceorniatlasi. nRinegfesreilniccoe ne acrpyaltatteerncso aftrionmg ttohep aJtotienrtn sCoofmsminitgtleee- pohna sPeorwefdeerre nDceiffmraacttieornia lSst.anRdeaferdresn–Icneteprantatteironnsalf rComenttrhee fJoori nt CoDmimffriattcetieoonn DPaotaw (dJCerPDDSif–fIrCacDtiDo)n dSattaanbdaaserd ws–eIrne tuesrenda.t ionalCentreforDiffractionData(JCPDS–ICDD) databasTehwe eFroeuursieerd .transform infrared (FTIR) spectra were obtained by using Spectrum GX FTIR speTchtreomFoeuterri e(rPetrraknins-fEolrmmeri,n Wfraarlethdam(F,T MIRA), spUeScAtr)a ewqueirpepeodb tawinitehd ab hyouriszionngtaSl paetctetnruumateGd XtoFtaTl IR spercetfrleocmtieotne r((HPeArTkiRn)- Ealmcceers,sWorayl.t hTahme, MHAA,TURS AF)TeIRqu ispppeecdtraw iothf ashamorpizleosn tawleartete nruecaoterddetdo taaltr erfloeocmtio n (HtAeTmRp)eraactcuerses oinr yt.heT wheavHenAuTmRbFeTr IrRansgpee ocft r4a00o0f–s6a5m0 pcmle−s1 wwietrhe ar erecsoorlduetdiona torfo 1o cmmt−1e. mEapcehr astpuercetriunmt he wawveans uamvebreargerdan fgroemof 1460 0sc0a–n6s5 0atc ma s−c1anw irtahtea orfe s0o.2l uctmio∙ns−1o. fC1ocllmec−te1d. Esapcehctsrap ewcterruem prwocaesssaevde rwagitehd tfhreo m 16Sspcaecntsruamt a® vs5c.a0n.1r saotfetwoafr0e. 2frcomm ·Ps−er1k.inC-oElllmecetre (dWsapltehcatrma, wMeAre, UpSrAoc)e. ssed with the Spectrum® v5.0.1 The CA measurements were performed at room temperature (23 °C) using sessile drop method. softwarefromPerkin-Elmer(Waltham,MA,USA). One droplet of deionized water (~5 μL) was deposited on the sample surface. Optical images of the droplet were obtained, and contact angle was measured using a method based on B-spline snakes (active contours). SEM analysis of coatings structure was performed with a microscope Quanta 200 FEG (FEI, Eindhoven, The Netherlands) operating in a low vacuum at 20.0 kV using an LDF detector. The chemical analysis of nanocomposites was performed by EDS technique with a Bruker XFlash 4030 detector (Berlin, Germany) (accelerating voltage 10 kV, distance between the bottom of the objective lens and the object 10 mm). 3.4. Antibacterial Studies The antibacterial activities of the silver nanoparticles containing UV-cured aliphatic silicone acrylate organic–inorganic composite coatings were tested using standard strains of E. coli and Molecules2017,22,964 10of13 TheCAmeasurementswereperformedatroomtemperature(23◦C)usingsessiledropmethod. Onedropletofdeionizedwater(~5µL)wasdepositedonthesamplesurface. Opticalimagesofthe dropletwereobtained,andcontactanglewasmeasuredusingamethodbasedonB-splinesnakes (activecontours). SEM analysis of coatings structure was performed with a microscope Quanta 200 FEG (FEI, Eindhoven, The Netherlands) operating in a low vacuum at 20.0 kV using an LDF detector. ThechemicalanalysisofnanocompositeswasperformedbyEDStechniquewithaBrukerXFlash4030 detector(Berlin,Germany)(acceleratingvoltage10kV,distancebetweenthebottomoftheobjective lensandtheobject10mm). 3.4. AntibacterialStudies The antibacterial activities of the silver nanoparticles containing UV-cured aliphatic silicone acrylateorganic–inorganiccompositecoatingsweretestedusingstandardstrainsofE.coliandS.aureus. Twomethods—theagardiskdiffusiontestandthedirectcontacttest—werechosenforevaluationof antibacterialactivity. Forthediskdiffusionprocedure,E.coliandS.aureuswereculturedinTryptoneSoyaBroth(TSB) solution.Followingthat,about1mLofthebacteriawaspipettedfromtheovernightphaseintoanother flaskwith30mLoffreshly-preparedTSB.Bacteriaweregrownat37◦Cintheincubatorshakerfor another5htoobtainbacteriawithhigheractivityandmoreviabilitythaninothergrowthphases. Commercially-availableMueller-Hintonagarplateswereusedinantibacterialtesting. Thestationary phasebacteriumwasdilutedintoaconcentrationofabout103CFU/mLwithNaClsolution(0.85%). Dilutedsuspensions(0.1mL)ofthepreviouslymentionedmicroorganismsweretransferredandspread ontothesolidsurfaceoftheplate. Intheinhibitionexperiment,thesilvernanoparticlescontaining siliconeacrylatediscswereplacedonMueller-HintonagarplatesinoculatedwithE.coliandS.aureus andincubatedat37◦Cfor24h. Later,thezoneofinhibitionwasnotedandtabulated. Threereplicates werecarriedoutforeachtesting. Toquantifytheantimicrobialactivityofthehybridcomposite,amodifieddirectcontacttestwas used [41]. Overnight cultures were diluted into a concentration at 105 CFU/mL with 0.85% NaCl suspension. Thebacterialsuspension(0.1mL)wasdepositedonglassslidesandcoveredwiththin film(thicknessca. 0.4mm; dimension25mm × 25mm)ofUV-curedsiliconeacrylatetofacilitate directcontactofthebacteriawiththesilvernanoparticlesontheacrylatesiliconecompositesurface. Two-layer assembly with the liquid film containing bacteria were placed in petri plate containing 1mLofphosphate-bufferedsaline(PBS)tomaintainadampenvironmentandincubatedatroom temperaturefor3,6,and24h. Afterthat,9mLofPBSwasaddedintoeachpetriplatetodetachthe assemblyofglassslideandpolymerfilmbysoftshaking. Lastly,thebacterialsuspensionsweregrown innutrientagarmediumtocountcoloniesandcalculateCFU/mL.Lowerthan500bacterialcounts intheculturemediumwereattributedtotheantibacterialactivityoftheinvestigatedhybridcoating. Fourrepetitionswerecarriedoutforeachtesting. 4. Conclusions Thealiphaticsiliconeacrylatecompositescontainingsilvernanoparticlescanbeeasilysynthesized viain-situphotopolymerizationtechnique. Theformationofapolymericmatrixandtheconversion of silver salt into silver nanoparticles proceeds simultaneously. Silicone acrylate composites with 0.5–1.43wt%ofsilvernanoparticleswereobtained. SiliconeacrylatepolymerOHgroupisengagedin theformationofhydrogenbondsorcomplexationwithsilvernanoparticles. Thesynthesizedsilver nanoparticleshavingasizeof20±5nmarehomogeneouslydispersedinsiliconeacrylatehybrid coating. DirectphotoreductionofsilversaltbyUV-radiationintheorganicmediaproducedsilver nanoparticlesexhibitingcubiccrystalstructurewithspacegroupFm-3m.Silvernanoparticlesincreased thesurfaceenergyofthesiliconeacrylatehybridcoating. Aliphaticsiliconeacrylatehybridcoatings exhibitedantibacterialactivity,andcanbeusedtoprotectagainstbacterialinvasion. Thepredominant

Description:
of these nanocomposites corresponds to the use of bridged and polyfunctional precursors, very convenient sol–gel chemistry, and hydrothermal synthesis [4]. More sophisticated techniques include the use of self-assembly, integrative synthesis routes, or templated growth by organic surfactants [5].
See more

The list of books you might like

Most books are stored in the elastic cloud where traffic is expensive. For this reason, we have a limit on daily download.