Recent Developments in Accelerated Antibacterial Inactivation on 2D Cu-Titania Surfaces under ...

29 Pages·2017·2.17 MB·English

coatings
Review
Recent Developments in Accelerated Antibacterial
Inactivation on 2D Cu-Titania Surfaces under Indoor
Visible Light
SamiRtimi*,CesarPulgarinandJohnKiwi*
EcolePolytechniqueFédéraledeLausanne,EPFL-SB-ISIC-GPAO,Station6,CH-1015Lausanne,Switzerland;
cesar.pulgarin@epfl.ch
* Correspondence:sami.rtimi@epfl.ch(S.R.);john.kiwi@epfl.ch(J.K.);Tel.:[phone](S.R.&J.K.)
AcademicEditor:NabaDutta
Received:15September2016;Accepted:23January2017;Published:6February2017
Abstract: This review focuses on Cu/TiO sequentially sputtered and Cu-TiO co-sputtered
2 2
catalytic/photocatalyticsurfacesthatleadtobacterialinactivation,discussingtheirstability,synthesis,
adhesion,andantibacterialkinetics. TheinterventionofTiO ,Cu,andthesynergiceffectofCuand
2
TiO onfilmspreparedbyacolloidalsol-gelmethodleadingtobacterialinactivationisreviewed.
2
Processesinaerobicandanaerobicmedialeadingtobacteriallossofviabilityinmultidrugresistant
(MDR)pathogens,Gram-negative,andGram-positivebacteriaaredescribed. Insightisprovidedfor
theinterfacialchargetransfermechanismundersolarirradiationoccurringbetweenTiO andCu.
2
Surfacepropertiesof2DTiO /CuandTiO -Cufilmsarecorrelatedwiththebacterialinactivation
2 2
kineticsindarkandunderlightconditions. Theinterventionoftheseantibacterialsputteredsurfaces
in health-care facilities, leading to Methicillin-resistant Staphylococcus Aureus (MRSA)-isolates
inactivation,isdescribedindarkandunderactiniclightconditions. Thesynergicinterventionofthe
CuandTiO filmsleadingtobacterialinactivationpreparedbydirectcurrentmagnetronsputtering
2
(DCMS),pulseddirectcurrentmagnetronsputtering(DCMSP),andhighpowerimpulsemagnetron
sputtering(HIPIMS)isreportedinadetailedmanner.
Keywords: magnetronsputtering;highpowerimpulsemagnetronsputtering(HIPIMS);bacterial
inactivationkinetics;Cu-TiO synergiceffects;interfacialchargetransfer(IFCT)
2
1. Introduction
Thefocusofinnovativeantibacterialmaterialsistofindcompositesincolloidformordeposited
on surfaces that are able to inactivate bacteria/pathogens within very short times and that have
longoperationallifetimes(highstability)[1–5]. Biofilmsthatspreadbacteriainhospitals, schools,
andpublicplacesarethemostcommonanddangerousformsofinfectionbypathogens:bacteria,fungi,
andviruses. Pathogensarecapableoflivinginanyenvironmentwheretheminimalconditionsoflife
areencountered,sincetheyhavetheabilitytoformbiofilms,adheringtoeachotherandtosurfaces.
Thesepathogenicbacteriaarecontinuouslyspreadinclosedenvironments,mostcommonlyinhealth
facilities[6–14]. Healthcareassociatedinfections(HCAIs)arebecomingaworldwideproblemsince
bacteriacansurviveonabioticsurfacesforalongtime. Inthisway,theydisseminateawiderangeof
infections. TheCenterforDiseaseControlandPrevention(CDC)estimatesthatapproximatelytwo
millionpatients/yearareaffectedbyHCAIsintheUSA[15,16]. InEurope,HCAIsaffect~3.2million
patients/year,andleadtomortalityoranincreaseofthedurationofahospitalstayandassociated
costs[17]. Nosocomialinfectionoccursbysimplytouchingthehandsofhealthcareworkersorby
hospitalclothing,equipment,airconditioners,andhospitalwaterdistributionnetworks[18]. Theuse
Coatings2017,7,20;doi:10.3390/coatings7020020 www.mdpi.com/journal/coatings
Coatings2017,7,20 2of29
ofgloves,gowns,andmasks,aswellaspatientisolation,havelimitedthespreadofinfections,butby
themselvesarenotabletopreventthetransmissionofHCAIs[19,20].
ThelevelsofcontaminationinUKhospitalshavebeenreportedtobe~105CFU/cm2indiabetic
wound dressing rooms, and in hospital residence rooms a density of 102 CFU/cm2 was found.
ThisreviewwilladdressseveralstudiesonsurfacescoatedwithTiO ,Cu,andCu/TiO thathave
2 2
thepotentialtodecreasetheenvironmentalbacterialdensityinhospitalfacilities. Theaddedbenefit
ofthesecoatingsisthattheyavoid,toacertaindegree,biofilmformation[21–26]. WhenHCAIsare
causedbymultidrug-resistant(MDR)pathogensthisproblembecomescritical,sinceantibioticsarenot
availableorareineffectiveduetotheirprolongedapplicationtimes,makingthepathogensresistantto
theirinitiallydesignedabatementeffect.
At the present time, more work is required to improve antibacterial coatings that induce fast
bacterialreduction,andhavehighadhesion,robustlayeredstructures,andstabilityprecludingHCAIs.
Theapplicationofnanotechnologytoproduceinnovative2Dbiomaterialsurfacesthatareusefulin
medicinepossessesasignificantpotentialforthepreventionandtreatmentofinfections. Nevertheless,
concernsexistabouttheuseofthesenewnanoparticulatematerialsduetotheincompleteknowledge
oftheirtoxicology[27,28].
The present write-up reviews the recent work on TiO , Cu, and the recent films made by Cu
2
andTiO thatleadtofastbacterialinactivationkineticsprecludingpartialortotalbiofilmformation.
2
The spread of pathogenic infections will be decreased depending on the type of pathogen or its
local concentration. Biofilm formation is the origin of 80% of all microbial infections in the body,
makingbiofilmsaprimaryhealthconcern[6–14]. Biofilmpathogensadheretoahostsurface,organize
theircommunitystructure,andremaintherebyproducinganextra-cellularpolysaccharides(EPS)
polymer matrix to cement the biofilm to the support in a permanent way. In the present review,
theco-sputteredfilmsofCuandTiwillbedesignatedasCu-TiO andthesequentiallysputteredfilms
2
(TiO sputteredfirst,followedbyCusputtering)willbedesignatedasCu/TiO . WereportCu-TiO
2 2 2
inactivationofE.coliandMethicillin-resistantStaphylococcusAureus(MRSA),abacteriastrainresistant
totheeffectofantibioticsandtoalesserdegree,totheabatementofotherbacteria. Whatmakesthe
problemevenmorecomplicatedisthatbacteriaembeddedinabiofilmcansurviveconcentrationsof
antiseptic/antibioticsthatareseveraltimeshigherthantheconcentrationabletokillplanktoniccells
ofthesamespecies[29].
2. BacterialInactivationPerformanceonTiO /CuandSurfaceProperties
2
2.1. ShortDescriptionoftheMainIssuesofConcernAffectingtheTiO PhotocatalysisApplicationin
2
MicrobialAbatement
After the seminal report by Matsunaga et al. [30], a large number of papers appear devoted
to the issue of microbial abatement in suspension or on supported TiO surfaces. Lately, some
2
reviews/monographs/reportshaveappearedonTiO photocatalysisinvolvingalarge-scaleeffort
2
addressedto: (a)thereportingofthereferencesonTiO photocatalysis;(b)theclassificationofthe
2
availabledata;and(c)proofofvalidityofthereporteddatabytherecentreviews.
Fosteretal. havereportedontheTiO mediateddisinfectionofalargevarietyofpathogens[31].
2
The main barriers to the application of TiO photocatalysis in suspension have been recently
2
reported by Guillard et al. [32], Morawski et al. [33], Robertson et al. [34], Dalrymple et al. [35],
andGamageetal.[36].ReviewsontheantimicrobialmechanismmediatedbyTiO compositefilmsand
2
suspensionshavesbeenreportedbyseveralgroupssuchasKubackaetal.[37]andDalrympleetal.[38].
TiO , upon band–gap light irradiation, photogenerates charges that react with adsorbed O and
2 2
H O (at the solid-air interface), leading to reactive oxygen species (ROS) that present a high
2 vapor
oxidationpotentialtodegradeorganiccompoundsandbacteria[39,40]. These(ROS)radicalsareHO•,
O •−,andHO •,andhavebeendocumentedandcharacterizedformostoftheirpropertiessuchas
2 2
concentration,lifetimes,spectra,andredoxpotentialsbynumerousresearchers. Linsebigleretal.[41],
Nakanoetal.[42],Fujishimaetal.[43],Douadetal.[44],Griesseretal.[45],andHuetal.[46]reported
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thephotocatalyticactivityofTiO thinfilms. However,moreworkusingfastkineticsbyfemto-and
2
picosecondspectroscopyinthevisibleregionisstillnecessarytoidentifythenatureandlifetimeof
theseROSspeciesinterveningintheindividualpathogeninactivation. Recentworksinvolvingthe
fastkineticsofsurfacesproducingROSundervisiblelightthatleadtosubsequentE.coliinactivation
havebeenreportedrecentlybyKiwietal.[47]andRtimietal.[48].
PhotocatalyticdegradationofpollutantsandbacteriamediatedbyTiO isapromisingapproach
2
tofacetheincreasingenvironmentalcontamination. However,becauseofitswidebandgap(3.2eV)
TiO canabsorbmostlyUV-light(λ<387nm)andonlyabout4%–5%ofthevisibleradiationofthe
2
solarspectrum. SensitizationofTiO modificationbySorNanions,ormetal/oxidessuchasCu/CuO
2 x
has been used to extend the TiO response into the visible region. In this way, accelerated TiO
2 2
reactionkineticsundervisiblelight,leadingtobacterialinactivationondopedTiO ,binaryoxides,
2
TiO composites,ordecorated2D-surfaces,havebeenrecentlyreportedbyDionysiouetal.[49,50],
2
Pillaietal.[51–53],Rtimietal.[48],Kavithaetal.[54],Fotiouetal.[55],andBahnemanetal.[56].
WettabilityplaysanimportantroleontheTiO surfaceunderband-gapirradiation. Thesurface
2
wettabilityisevaluatedbythewatercontactangle(CA).TheCA(θ)isdefinedastheanglebetween
thesolidsurfaceandthetangentlineoftheaqueoussolutionattheliquid-solidinterface. Hashimoto,
Fujishima,etal.[57,58]reportedtheimportanceofthehydrophilicitychangesinTiO underband-gap
2
irradiationontheTiO surfaceduringpollutant/bacteriadegradation. AhydrophobicTiO surfaceat
2 2
timezerowasreportedtobecomehighlyhydrophilicorsuperhydrophilic(θ<5◦)underband-gap
excitation. Thissurfacewillgraduallyreverttotheoriginalsurfaceafterrelativelylongperiodsin
thedark. Thisconsiderationisimportantinbacterialinactivationprocesses,sincehighlyhydrophilic
conversionsleadtocleansurfacesduetothedestructionofbacteriaadsorbedontheTiO surface
2
duringthesampleirradiation. Thephoto-generatedholeshavebeenshowntoberesponsibleforthe
TiO surfaceconversiontoahighlyhydrophilicsurface. Theseholes(a)diffusetotheTiO surface
2 2
andtotheoxygenlatticesitesreactingwithbacteriaor(b)produceHO•-radicalsreactingwiththe
embeddedHO• ontheTiO surface. However,apartofthephoto-generatedholesbreakthe–Ti–O–
2
lattice bonds by coordinating H O at the Ti-lattice sites. The coordinated water releases a proton
2
(chargecompensation)andanewHO• isformed,increasingthenumberofsurfaceHO• radicals[59].
Transparent, non-scattering PE (PE = polyethylene), sputtered by direct current magnetron
sputtering (DCMS) for 8 min with TiO thin film, inactivated E. coli within one hour under low
2
intensitysolarsimulatedirradiation(52mW/cm2). Theschemeofthesputteringunitisshownin
Figure1. ThePEwaspretreatedfor15minbyRF-plasmatograftalargeramountofpolarnegative
groupsabletobondthepositiveTiO onthePE-surface[60–62]. ThePE-TiO samplespretreatedfor
2 2
15minandsputteredfor8minpresentedthehighestamountofTiO sitesinexposedpositions,leading
2
tothefavorablebacterialinactivationkinetics.Adecreasefromtheinitialcontactangle(CA)ofPE-TiO
2
attimezeroand~121◦Ctoθ<5◦ within60minofirradiation,inducingPE-TiO super-hydrophilicity,
2
wasobservedtobeconcomitantwiththetimeofbacterialinactivation. Thisseemstobeanecessary
conditiontoattaintheoptimalE.coliinactivationkinetics. Samplessputteredfortimes>8minledto
athickercoating,inducingchargebulkinwarddiffusionthatdecreasedthechargetransferbetween
thePE-TiO andbacteria[63]. Therateofthehydrophobictohydrophilictransformationwasfoundto
2
be0.28min−1. Thereversereactionrateinthedarkwasfoundtobe8.7×10−3 min−1. Thereverse
reactiontimenecessarytoreachtheinitialhydrophobicCA~121◦ wascompletedwithinabout24h.
TheserateswerecalculatedbyintegratingcosθintheYoung’sequation[58,59].
TiO sputteringfor8minledtoaTiO loadingwiththemostsuitablethicknessforthecharge
2 2
diffusiongeneratedintheTiO toreachthebacteria. Nobacterialre-growthwasobserved,meaning
2
that there were no bacteria adhered to the surface after the inactivation cycle. After each cycle,
thesampleswerewashedwithdistilledwateranddried. Then,thesampleswerekeptinanovenat
60◦Ctoavoidbacterialcontamination. Afterwashing,thePE-TiO sampleswereleftstandingfor24h
2
toregaintheinitialhydrophobicity.
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Coatings 2017, 7, 20  4 of 28 

Figure 1. Sputtering unit used during the sputtering of antibacterial layers on diverse substrates. 
Figure1.Sputteringunitusedduringthesputteringofantibacteriallayersondiversesubstrates.
According to Young’s theory, the cosθ of a liquid droplet on a solid is a function of the interfacial 
Acceonerdrgiyn gbettowYeeonu nthge’ ssothlideo arnyd, tthhee clioqsuθido. fTaheli qwueitdtabdirliotyp lies tcoonmmaosonllyid eivsalauafutendc tinio tneromfst hoef tihnet erfacial
energybceotnwtaecet nantghlee (sCoAli)d, wanhidcht hise gliivqeuni dby. TYohuenwg’es tetqaubailtiitoyn i[s58c]o: mmonlyevaluatedintermsofthecontact
angle(CA),whichisgivenbyYoung’sequaγtSi o=n γS[5L8 +] :γL·cosθ  (1) 
In Equation (1), γS and γL are the surface free energies per unit area of the solid and the liquid, 
γS=γSL+γL·cosθ (1)
respectively, and γSL is the interfacial free energy per unit area. In addition, γSL can be approximated 
using the Girifalco‐Good Equation (2), with γS and γL, as: 
InEquation(1),γSandγLarethesurfacefreeenergiesperunitareaofthesolidandtheliquid,
γSL = γS + γL − Φ(γS/γL)1/2  (2) 
respectively,andγSListheinterfacialfreeenergyperunitarea. Inaddition,γSLcanbeapproximated
usingtheGiHriefrael,c Φo -iGs ao ocodnsEtaqnuta ptaioranm(e2t)e,r wraintghinγgS fraonmd 0γ.6L t,oa 1s.:1, depending on the solid. In addition, γL 
is the water surface free energy, which has a constant value of 74 mJ/m2. Therefore, by combining 
Equations (1) and (2), the CA canγ bSeL s=imγpSly +exγpLre−sseΦd (aγs:S /γL)1/2 (2)
cosθ = cγS1/2 − 1 (c: constant)  (3) 
Here, ΦThies haigcholyn shtyadnrotpphailriac mstaettee grernaenragteind gbyf rUoVm lig0h.6t gtroad1u.1a,llyd ereptuenrnds itnog thoen intithiael shoydlirdo.phInobaicd dition,
γListhestwatea tienr tshuer fdaacrek.f rTeheee inneitrigaly ,cwonhtaiccth ahnagslea ocno nRsFt‐apnrettvreaaltuede oDfC7M4Sm sJp/umtte2r.eTdh PeEre‐TfoiOre2 ,sbamypcloems bining
Equatiodnesc(r1ea)saend dto( 2an), atnhgeleC <A 5°c wanithbien s6i0m mpinly oef xirprardesiasteiodn.a Ts:he hydrophobic or hydrophilic nature of a 
surface is important for the adhesion of bacteria to a TiO2 layered surface and for regulating the 
subsequent light or dark inducedc oksinθe=ticc bγaSc1te/r2ia−l in1a(ccti:vcaotinonst. ant) (3)
E. coli and Staphylococcus aureus present a preferential adhesion to hydrophilic surfaces [32,64–67]. 
Efficient antimicrobial activity on Cu‐surfaces has been recently reported against methicillin‐resistant 
ThehighlyhydrophilicstategeneratedbyUVlightgraduallyreturnstotheinitialhydrophobic
Staphylococcus aureus (MRSA) and the bacterial reduction was evaluated by four methods. A 
state in the dark. The initial contact angle on RF-pretreated DCMS sputtered PE-TiO samples
reduction of 4log10 in the initial MRSA concentration of 106 CFU was found for ten clinical MR2SA 
decreaseisdolatotesa nwiathnign l1e h<, 5su◦gwgeistthining t6h0e msuiintaboiflitiyrr oafd tihaet iCoun‐.suTrhfaecehs yind rporpevheonbtiincg othreh tyradnrsompihssiiloicn nofa tureof
asurfacteheissei gmrapmo‐rptoasnittivfeo rbatchteeriaad [6h4e]s. iTohne loofssb oafc vteiarbiailittyo taesTtiniOg 2wlaasy peerrefodrmsuedrf bayc ecoamnbdinfionrg rtheeg udalatat ingthe
subsequoebntatilniegdh btyo rdidreacrtk trianndsfuecr eodn kaginare tpilcatbeas catnedr isatlerienoamctiicvroastcioopny.. Two different methods were used 
to evaluate the bactericidal activity of the Cu‐sputtered samples. 
E.coliandStaphylococcusaureuspresentapreferentialadhesiontohydrophilicsurfaces[32,64–67].
Bacteria with hydrophobic surface properties such as S. epidermis adhere preferentially to 
EfficientantimicrobialactivityonCu-surfaceshasbeenrecentlyreportedagainstmethicillin-resistant
hydrophobic surfaces [66]. Hydrophobic bacteria such as E. coli, with an initial contact angle of 121° 
Staphylococcusaureus(MRSA)andthebacterialreductionwasevaluatedbyfourmethods. Areduction
reduced to less than 5° (full hydrophilicity) have been reported within 5–10 min. E. coli was shown to 
of4log10adinhetrhe etoi nCiuti aalnMd TRiSOA2‐Ccuo nsucrefnactersa t[i4o0n,46o,6f01,6016,6C7]F. UThwe naesgfaotiuven dchfaorgret eonn cthlien iccaatallyMstR/pShAotoiscaotlaalytests within
1h,suggspeustttienrgedt hseursfuacitea obnil iTtyiOo2,f TthiOe2C‐Cuu-, saunrdfa TceiOs2i‐nZrpOr2e‐pvoelnyteisntegr t(hPeEStr) asnusrfmaciesss iios nouotflitnheeds ebeglroawm i-np ositive
bacteriaE[q6u4a]t.ioTnhs e(5l)–o(s9s): ofviabilitytestingwasperformedbycombiningthedataobtainedbydirect
transfer on agarBapcltaetreias +a [nPdES‐sTteiOre2]o +m liigchrto sc [oPpEyS.‐TiTOw2*o] Bdaicftfeerirae nt Bmacetethrioa+d +s PwESe‐r(TeiOu2s)cebde‐t o ev(a4l)u  ate the
bactericidalactivityoftheCu-sputteredsamples.
PES‐(TiO2) cbe‐ + O2 + H+  HO2•      E0 ‐0.05 NHE [43,56]  (5) 
Bacteria with hydrophobic surface properties such as S. epidermis adhere preferentially to
hydroph obicsurfaces[66]. HydrophobicbacteriasuchasE.coli,withaninitialcontactangleof121◦
reducedtolessthan5◦ (fullhydrophilicity)havebeenreportedwithin5–10min. E.coliwasshownto
adheretoCuandTiO -Cusurfaces[40,46,60,61,67]. Thenegativechargeonthecatalyst/photocatalyst
2
sputtered surface on TiO , TiO -Cu, and TiO -ZrO -polyester (PES) surfaces is outlined below in
2 2 2 2
Equations(5)–(9):
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Bacteria+[PES-TiO ]+light→[PES-TiO *]Bacteria→Bacteria++PES-(TiO )cbe- (4)
2 2 2
PES-(TiO )cbe-+O +H+→HO • E -0.05NHE[43,56] (5)
2 2 2 0
PES-(TiO )cbe-+O →O •− E -0.16NHE[43,56] (6)
2 2ads 2 ads 0
PES-(TiO )vbh++OH− →HO◦ E -1.90NHE[49] (7)
2 ads 0
PES-(TiO )vbh++H O →HO• +H+ (8)
2 2 ads ads
O •−+H+⇔HO • pKa4.8 (9)
2 2
Inreaction(2),theHO •radicalisstableatpH<4.8,andabovethispH,morethan50%ispresent
2
intheformofO •−,asnotedinEquation(9).
2
Mostofthebacteriaacquireanegativeelectricchargeinaqueoussuspensionorinthepresence
ofairhumidity,andthisaspecthasbeenrevealedtobeimportantinbacterialadhesiontocharged
surfaces[68]. Ithasbeenknownforalongtimethatsurfaceswithhighsurfaceenergies,suchasthe
ones encountered in hydrophilic surfaces, are to a great extent negative and develop resistance to
bio-adhesion[69,70]. Thesetwolastconsiderationshavetobeconsideredfromcase-to-casewhen
inactivatingaspecificpathogenonawell-definedantibacterialsurface[6–13].
Inthelast30years,theTiO mediatedphotocatalyticinactivationofpathogenshasbeenthefocus
2
of bacterial disinfection studies. Inactivation by TiO suspensions, supported photocatalysts, and
2
nano-rodsunderdiverselightsourceshasbeenreportedwithinminutes/hours[71]. Indarkcontrol
experiments,TiO hasbeenreportedtoexertnomicrobialinactivationorverylowantibacterialactivity.
2
Recently,researchhasprovidedevidencethatselectedexperimentalconditions(pH,TiO amount
2
andparticlesize,bacterialconcentration)belowtheTiO isoelectricpointledto104CFU/mLE.coli
2
inactivationinthedarkwithin120min. Thiswasabout50%oftheE.coliinactivationinducedunder
thesameexperimentalconditionswhenapplyingaUV-lightcenteredat366nm. Nophoto-generated
electrons/holesorROSwerepresentintheabsenceofband-gapirradiation[71]. Thisworkshowed
thattheelectrostaticandorCoulombinteractionatpHsbetween4and4.5suppressesthedivisionof
bacterialeadingtoE.colilossofcultivability.
A subsequent study presenting evidence for the lack of cultivability in the dark due to the
interactionbetweenTiO surfacesintheminuterangehasbeenrecentlyreported[72]. Thebacterial
2
cellsinteractionwithTiO aggregateswasfollowedbyelectronmicroscopy. TheinteractionoftheTiO
2 2
inthedarkwithE.coliledtocellwalldamage/inactivationduetoelectrostaticforcescompetingwith
VanderWaalsforcesoccurringatphysiologicalpH-valuesandinducingdamage/deformationinthe
cell-wallpackingstructure,withanincreaseofthemembranepermeability. TiO -polyestersamples
2
demonstratedrepetitivebacterialinactivation(lossofcultivability)inthedark. Bacterialinactivation
in the dark occurred within 120 min compared to the E. coli mediated TiO photocatalysis that
2
occurredwithin60minunderanactiniclightLumilux18W/827source(OSRAMGmbH,Winterthur,
Switzerland),radiatingwithin350and740nm,withanintensityof4.1mW/cm2. Thisstudyreports
onanimportantissueinthefieldofdisinfectiontechnology. TheTiO -polyesterledtodisinfection
2
processesbeingcarriedoutinarepetitiveway. Thisisamoreconvenientapproachwhencomparedto
TiO suspensionswheretheTiO nanoparticleshavetoberemovedfromthesolutionaftereachcycle,
2 2
notallowingforacontinuousdisinfectiontreatment. Therefore,TiO -supportedpolyestersurfaces
2
showapracticalpotentialtoprecludepathogenicbiofilmformationinthedark. AlterationoftheE.coli
cellpermeabilityincontactwithTiO inthedarkhasalsobeenreportedrecentlyandthemorphological
2
changesofthebacteriawerefurtherdocumentedbyGuillardetal.[32]. Thedamagetothebilayercell
envelopewasascribedtothelipo-saccharide(LPS)packingstructuredamage. Incontrast,SiO under
2
thesameconditionsdidnotinducedetrimentaleffectsonthebacteria,inhibitingitsreproductiondue
tothevarianceoftheelectrostaticcharges/interactionatthereactionpH.TiO nanoparticlespresent
2
apotentialriskoftheseparticlestopenetrateintissuesandbiologicalmembranes. Ecotoxicologyof
TiO hasrecentlybeenaddressedinseveralstudies/reviews,whichindicatethehighstabilityofTiO
2 2
nanoparticleswithlimitedcytotoxiceffects[27,73–76].
ThewaylightisappliedtoTiO suspensionstoinactivatebacteriahasbeenreportedrecently
2
in detail by Pulgarin et al. [77] to have significant effects on the inactivation kinetics. The way
Coatings2017,7,20 6of29
light is applied during bacterial disinfection may or may not lead to complete bacterial removal:
continuousirradiationleadstoarapidremovalofbacteriacomparedtothesamelightdoseapplied
intermittently. No bacterial re-growth was observed after illumination of a contaminated TiO
2
suspension. In contrast, without catalyst, illuminated bacteria in solution recovered their initial
concentrationafter3hinthedark. Inasubsequentstudy,TiO suspensionswereshowntobeeffective
2
inreducingE.coliwhenirradiatedinthepresenceofabacterialconsortium. Theinactivationratewas
dependentonbiologicalparameterssuchasphysiologicalstate,pH,initialconcentrationofbacteria,
andtheorganic/inorganicimpurities/residuespresentinthesolution. Afterilluminationperiods
withdifferentlengths,a“residualdisinfectingeffect”inthedarkwasobservedafterthelightwas
turnedoff,asafunctionoftheappliedintensity(40–100mW/cm2). Enterococcussp.,aGram-positive
bacteriumwithcell-wallthicknessesbetween30and80nmappeartobelesssensitivecomparedto
coliformsandotherGram-negativebacteriawithcell-wallthicknesses10–20nmtotheeffectofTiO
2
underlight[78].
Generally, the bacterial inactivation kinetics is determined by the hydrophobic-hydrophilic
properties of the surface mediating the bacterial disinfection. For different processes involving
TiO surfaces,thehydrophobic-hydrophilicconversioninairundersolarlightirradiationproceeds
2
with shorter times compared to the time required for E. coli inactivation. References [79,80] by
Rtimietal. showthatinitialhydrophobicPE-TiO surfacesundersolarsimulatedirradiationbecame
2
super-hydrophilicsurfacewithintimes<1h.Theconversionoftheinitialhydrophobicsurfaces(contact
angle>150◦)tosuper-hydrophilicsurfaces(contactangle<5◦)isacceptedasanecessaryconditionbut
nottheonlynecessaryconditionforbacterialinactivationonPE-TiO surfaces. ThePE-filmpresents
2
asmoothsurfacethatallowsthemeasurementofsputteredTiO byapplyingdifferentpowersand
2
convenientlyfollowsthechangeinthedynamiccontactanglemeasurementswithtime[81].
In TiO dispersions/suspensions made up of colloids or pre-formed powder nanoparticles,
2
thephotocatalysisledtomanystudiesfocusingonbacterialabatement[12,30–63,71,72]andshowing
the inactivation of spores [82–85], viruses [86], algae [87], and fungi [88]. The TiO suspensions,
2
althoughsuccessfulinabatingavarietyofpathogensunderlightirradiation,requiretimesthatseemto
betoolongtotreatlargewatervolumes. Thesecondinconvenienceistheseparationofthesuspension
fromthebacterialresiduesafterthedisinfectionprocess. Thisisexpensiveintermsoftime,labor,and
reagents. Therefore,somelaboratorieshavebeguntousesupportedTiO materialsindisinfection
2
processes mediated by TiO . To avoid the separation step at the end of the bacterial abatement,
2
Kuhnetal.[89]reportedin2003thatpreformedTiO nanoparticlesgraftedonplexiglasssurfaces
2
inactivateE.coliunderUV-light,butonlytoasmallextent. Nevertheless,thesesurfacesshowedavery
heterogeneous(non-uniform)TiO coating. Generally,coatingwithcolloidalTiO onthermalresistant
2 2
substratessuchasglass,ironplates,andceramicsprovidelayersthatarenotreproducibleandcanbe
wipedoffbyrubbingusingnakedhands[90].
The synthesis of uniform 2D-coatings on supports by applying direct current magnetron
sputtering(DCMS),pulseddirectcurrentmagnetronsputtering(DCSMP),andhighlyionizedpulsed
plasma magnetron sputtering (HIPIMS) have been reported to uniformly cover surfaces resistant
tothermalstress. However,sputteringmethodshavebeenusedtocoattextilessuchascottonand
polyester (PES) and low cost inert thin polymer films such as polyethylene (PE) that present low
thermalstability≤100–130◦Ccomprise80%ofthecommercialmarket.
2.2. TiO /CuSynthesisLeadingtoUniform,Adhesive,andAntibacterialFilms
2
Physicalvapordeposition(PVD)iscarriedoutinavacuumbycondensationofametal/non-metal
vaporontothesupportsurfacethatisgenerallyinthereactionchamberatarelativelylowtemperature.
This method involves high temperature vacuum evaporation of the material to be coated on the
support. Anataselayershavebeendepositedinthisway,showingasuper-hydrophilicbehaviorunder
band-gapirradiationasreportedbyseveralresearchersinthefield[91]. Whenusingchemicalvapor
deposition(CVD),thesubstrateisexposedtovolatilecompoundsthatdecomposeonthesubstrate,
Coatings2017,7,20 7of29
leadingtothedesiredcoatings[92–94]. Auniform,thin,adhesive,robustTiO filmhasbeendeposited
2
onglass[95]fromTi-chloride/ethyl-acetateatabout500◦C.CVDisabletodepositcontinuousfilms
withouttheneedofapost-annealingprocesstocrystallizetheTiO nanoparticulates.
2
Diversepulsemagnetronsputtering(PMS)systemshavebeenusedtodepositTiO filmswith
2
thicknessesofupto300nmandlayerscomprisingmainlyanataseattemperatures≤130◦C.Using
thisapproach,textilespresentinglowthermalresistance,thinpolymerfilms,andpolycarbonates(PC)
havebeencoatedwithTiO ,TiO -metal,andTiO metal-oxides[61,96–98]. Thebasicinstallationof
2 2 2
aDCMSunitisshowninFigure1.
OneofthefirstreportsonDCMSsputteredphotocatalyticTiO onSi-wafersandceramictargets
2
was reported by Miron et al. [99]. The utility of TiO sputtered surfaces was already recognized
2
manyyearsago. Duringthephotocatalyticdisinfection,theelectronacceptor,O ,incontactwiththe
2
sputteredTiO ,isreadilyavailablefromtheairanditsconcentrationisnormallyreplenishedbythe
2
catalystsurfaceduringdisinfection. Theefficiencyoftheantibacterialcatalyticsurfaceisinfluenced
bythesurfaceporosity,theintensityofthelight,thesampleroughnessanduniformity,thetypeof
bacteria (eitherGram-negative orGram-positive), thedistance ofthe light source tothe sputtered
sample,thesurfacepH,andthehydrophilic-hydrophobicbalanceofthesputteredsample.
2.3. Cu-LoadedSputteredSurfacesActiveintheDarkandunderLight,LeadingtoMicrobialAbatement
Antimicrobialnanoparticulatefilmspreparationisatopicofincreasingattentionsinceitsobjective
is to reduce or eliminate the formation of infectious bacteria biofilms leading to hospital acquired
infections(HAI)[100]. However,moreeffectivebacterialinactivationfilmsonflatorcomplex2D/3D
surfacesareneededduetotheincreasingresistanceofpathogenicbacteriatosyntheticantibiotics
administeredforlongperiodsoftime. Additionally,nosocomialinfectionsduetoantibioticresistant
bacteriaarebecomingmorefrequent[25]. SurfacessputteredbyDCMS/DCMSPcontainingmetals,
oxides,orsemiconductors(eitherheatresistantornot)havebeenreportedrecently,leadingtoeffective,
stable,anduniformbactericidefilms[101–103]. Therecentlydevelopedhighlyionizedpulsedplasma
magnetronsputtering(HIPIMS)leadstofilmsbyapplyinghighelectricalpulsesof1–10Aandup
to100V,whichleadstolayersthatpresentsuperiorresistanceandcompactnessagainstcorrosion
andoxidation. TheHIPIMSsputteringon3D-complexobjectsaddressestheproblemsencountered
whendepositingthinfilmsonsubstratesbyDCMS/DCMSP[102]sincetheadhesionofthesputtered
films(byDCMS/DCMSP)isnotverystrong. Thisisduetotherelativelylowbiasvoltageapplied
onthesubstrateduringthesputteringtime[103]. HIPIMSsputteringinducesastronginteraction
with2D/3DsubstratesduetothehigherfractionoftheCu+/Cu2+-ions;upto70%comparedwith
DCMS/DCMSP[104]. TheCu-ionsgeneratedbyDCMSwerereportedbyCastroetal.[105]andby
usingX-rayPhoto-electronSpectroscopy(XPS),evidencewasshownfortheCu+/Cu2+ andCu3+ ions.
Subsequently,alargeramountofCu-ionswasreportedonasupportbyOsorioetal. afterapplying
DCMSP[106]. Morerecently,astudyusingHIPIMSreportedbyRtimietal.[107]ledtoasignificantly
higheramountofCu-ionsontheCu-PESsurfaces, acceleratingbacterialinactivationcomparedto
DCMSandDCMSP.TherelativelylowersputteringenergiesemployedduringDCMSandDCMSP
sputteringwouldatfirstsightbeareasontoexpectahigheramountofCu-ionsbeingabletoleavethe
Cu-PESsurfaceandinteract/sticktotheoutercellwallofE.coli,andthendiffusethroughtheporins
andtranslocatetothecytoplasm,inducingbacterialinactivation/death. However,theoppositeeffect
wasobserved. HIPIMSsputteringionized70%oftheCu• toCu-ionsintheHIPIMSchamber,leading
tohighlychargedCu-ionsurfaces. ThehigheramountofCu-ionslatertranslocatedthroughtheE.coli
porins,inducinganacceleratedbacterialinactivation[108].
The strong adherence of the sputtered atoms/ions on complex shape biased objects is due to
thehigherion-arrivalenergyonthesurfacecomparedtothemoretraditionalDC/DCPsputtering
methods [104]. Cu-ions in ppb-amounts, besides electrostatically interacting with the bacterial
envelope, lead to the partial unpacking/damage of the LPS of the outer E. coli bacterial cell
wall, later penetrating the bacterial cell-porins with diameters of 1.1–1.3 nm [109]. Cu-ions will
Coatings2017,7,20 8of29
also diffuse through skin pores of ~100 nm [6,12,27–31]. To preclude the viral and diverse
types of nosocomial infections caused by antibiotic resistant bacteria, Borkow and Gabbay have
reported studies on Cu-loaded textiles [110–113]. These studies report in a detailed, systematic,
andcomprehensivewaythepreparationandevaluationofthepathogenabatementontheseinnovative
surfaces. Furthermore,colloidalCu-coatedtextilesshowingantibacterialpropertieswerereportedby
Gedanken’sgroup[114,115],focusingonZnOandCuOcolloidsdepositedontextilesbysonication.
Cu-colloidswereimpregnatedonpolyester(PES)toinactivatebacteriaunderlowintensitysunlight.
The PES was previously pre-treated by RF-plasma to increase the amount of negative carboxylic
sitesabletobondtoCu-ions[116]. Thenon-uniformdispersionoftheCu/CuO onthePESsurface
x
motivatedustoworkonthepreparationofCu-antibacterialfilmsbysputteringinordertoobtain
adhesive,uniform,andreproducibleCu/CuO coatings. Inthisway,weovercametheshortcomings
x
ofcolloidallyloadedPESandthisworkwillbedescribedintheparagraphbelow.
DCMSpreparedsampleswerecarriedoutwithCu-targets(99.9%)fromLeskerAG,Hastings,
East Sussex, UK, and the textiles/thin polymer films were sputtered in a magnetron chamber at
apressureof0.1–1Pa.ThedistancebetweentheCu-targetandthesubstratewas~10cm,thedeposition
currentwas30–250mA,andthevoltagewasvariedbetween100and500V.TheCu-filmthickness
wasdeterminedwithaprofilometer(Alphastep500,Tencor,Rocklin,CA,USA).Cu-DCMSsputtered
for40sformeda3nmthickfilm(or15atomiclayers)andledtothefastestE.coliinactivation[105].
The most favorable structure-reactivity Cu-cluster agglomerates sputtered on cotton is defined as
the Cu-nanoparticulate on cotton, and led to the most favorable bacterial inactivation kinetics.
During several studies on Cu, CuO, and Cu/TiO sputtered nanoparticulates, it was shown that
2
the Cu-sputtering time or the amount of Cu sputtered on the substrate did not directly relate to
thebacterialinactivationtime[105–107,117–119].FromthisitwasconcludedthattheCu-ionsplay
animportantroleinmediatingbacterialdisinfectionandtheseCu-ionsweredeterminedbyX-ray
photoelectronspectroscopy(XPS).
ThemagneticsputteringchambercontainsArthatuponimpactoftheappliedcurrentionizes
toAr+
Ar→Ar++e− orAr*+e− (10)
Ar++Cu• →Cu++Ar• (11)
e− +Cu• →Cu++2e− (12)
InEquation(12),thedirectelectronimpactofhighlyenergetic/highspeedelectronskicksoff
an e− of the Cu-target. The intensity of the e− collision with the Cu•-target is proportional to the
energy/currentappliedinthesputteringchamber. TheArmayalsoattainonlyexcitedstatesand
ionize the Cu•, as shown in Equation (13), because the Ar has a higher energetic content than the
ionizationenergynecessarytoionizeCuObyaprocesscalledpenningionization:
Ar*+Cu• →Cu++Ar+e− (13)
The Cu ions produced in the Ar-plasma are accommodated on the substrate, leading to
Cu-films by epitaxial growth through nucleation, followed by growth that leads to atomic
clusters/agglomeration/crystals that present metal/oxide character depending on their size and
thegrowthsymmetry[21,117,120]. ThecondensationofCuandCu-ionsnecessarytoformCu-films
on the substrate involve the preference of Cu-atoms for binding to other Cu-atoms/ions rather
thantothesubstrate,leadingtoagglomerates[121,122]. DependingontheCu-sputteringtimeand
energy,Cu-clustersareformedthatarenotnecessarilycrystallographic,whichdependontheaffinity
betweentheCu-atomsandthesubstrate. DuringtheCu-atom/ionscondensation/coalescenceduring
the formation of the film, sometimes the Cu-nuclei merge on the substrate without forming grain
boundaries[123,124].
Coatings2017,7,20 9of29
Once the Cu clusters/atoms are on the surface of a substrate, they interact with O which
2
leadstoCuOorCu O[105–107,117,119–122,125–131]. TheoxidativestateofthenanoparticulateCu
2
determinesthebacterialmechanism/kinetics. ThesemiconductorcharacterofCuOallowsforthe
generationofphoto-inducedcharges. Theamountofthesespeciesisafunctionoftheappliedlight
dose. TheCuOandCu Omechanisticstepsinducingchargeseparationunderband-gapirradiation,
2
leadingsubsequentlytobacterialinactivation,couldbesuggestedas:
CuO+hν(sunlight)→CuO(cbe−),CuO(vbh+) (14)
whereCuO(cbe−)referstotheconductionbandelectronsgeneratedandtheCuO-semiconductorunder
band-gapirradiation,andCuO(vbh+)aretheholesgeneratedconcomitantlyintheCuO-valenceband.
UnderphotonenergiesexceedingtheCuOband-gap,thecbe− electroncouldeitherreactdirectlywith
theO ,formingO −,orreducetheCu2+toCu+assuggestedbelow:
2 2
CuO(cbe−)+O →CuO+O − (15)
2 2
CuO(cbe−)→CuO(Cu+) (16)
CuO(Cu+)+O →CuO(Cu2+)+O − (17)
2 2
The cbe− in Equation (17) is produced by a CuO (p-type) with a band-gap energy of 1.7 eV,
aflat-bandpotentialof−0.3VSCE(pH7),andavalencebandat+1.4VSCE[56].
CuO(Cu+)→CuOvacancy+Cu+ (18)
CuO(vbh+)+bacteria→CO ,H O,inorganicN,S (19)
2 2
The photocatalytic reactions for the Cu O mediated bacterial inactivation are suggested in
2
Equations (20)–(23). The highly mobile electrons first transfer from Cu O(cbe−) to the TiO cb as
2 2
suggestedinEquation(21).
Cu O+hν→Cu O(cbe−),Cu O(vbh+) (20)
2 2 2
Cu O(cbe−)+TiO →TiO − or(Ti3+) (21)
2 2 2
TiO − +O →TiO +O − (22)
2 2 2 2
Cu O(vbh+)+bacteria→CO ,H O,inorganicN,S (23)
2 2 2
Taking 0.3 nm as the distance between the Cu-atoms on the film surface and the thickness of
anatomiclayer~0.2nm,aCu-coating20nmthick(about100layers)wasdepositedbyDCMSfor20s
withacontentof1×1017Cuatoms/cm2atarateof5×1015atoms/cm2·s.
DCMSPofCuwithenergypulsesbetween5and15eVledtofasterbacterialinactivationkinetics
comparedtoDCMS[106]. Morerecently,higherenergiesperpulsecomparedtoDCMSPinvolving
HIPIMSsputteringwasreportedbyPetrovetal.[104]. HIPIMSsputteringonCu-PESledtoE.coli
bacterialinactivationwithin90minwhenCuwassputteredbyHIPIMSpulsesthatwere60slongat
60A[117]. Effectivebacterialinactivationwasalsoobservedinthedark. Theenergyanddurationof
theHIPIMSpulsewasalsolimitedbytheheatresistanceoftheCu-target. TheamountofCu-sputtered
by HIPIMS inactivated E. coli with a Cu-loading three times lower that that compared to DCMS,
leadingtoE.colibacterialinactivationwithinsimilartimes. ThisdemonstratessubstantialCu-metal
savingswhenusingCutoprepareCu-HIPIMSantibacterialfilms. AhigheramountofCu-ionswas
detectedbyX-rayphotoelectronspectroscopy(XPS)onthetextilesurfaceforHIPIMSsputteredfilms
comparedtofilmssputteredbyDCMSandDCMSP[64,105,106,117].
Coatings2017,7,20 10of29
2.4. BehaviorofCu-SputteredSurfacesintheDarkandunderHospitalSettings(IndoorActinicLight),
LeadingtoMRSA-IsolateInactivation
Coatings 2017, 7, 20  10 of 28 
StudiesshowingthereductionofthebacterialloadonvariousCu-surfacesareofgrowinginterest
regarfdilimngs.i Cndu‐oPoErSe snavmirpolnesm sepnuttst.erFeidg uforre 126s0h so wwesrea osibmseprvliefide dtos icnhdeumcee af o6rlobga1c0 tCeFriUa lloinsas cotfi vvaiatiboilnitym feodr iated
MRSA and A. baumanni within 30 min. The loss of bacterial viability on the Cu‐PES surface for other 
byCu/CuOunderlightirradiation. Cu-particlesarecoveredbyCuOwhenexposedtoairandpresent
MDR bacteria proceeded with similar times in dark/light conditions, suggesting that Cu/Cu‐ions and 
semiconductorbehavior,leadingtotheseparationofchargesthatinducesbacterialinactivationunder
not CuOx led to the observed bacterial loss of viability. The use of gloves, gowns, and masks, as well 
light. This mechanism has been accepted during the last three decades addressing the bacterial
as patient isolation, have limited the spread of infections, but on their own are not able to avoid the 
inactivationbyCuOasshowninFigure2.
transmission of HCAIs [134,135]. 

FigureF2ig.uCreo n2.v Ceonntvioennatilonbaalc btearcitaerliianl aincatcivtiavtaitoionnm mooddeell oonn PPEE‐C-CuuOOx fxilmfilsm usnduenrd soelrasr olilgahrt liirgrhadtiiartrioand.i ation.
Copper is required by eukaryotic and prokaryotic cells at low concentrations as cofactors in 
Tmheetail‐nparcottievinast iaonnd oefnzVyamnecso, mbuytc aint hriegshi sctoannctenetnratetirooncso, cCcui‐((VII)R hEa)s aan todxiMc eRffSeAct. iCsoul aintetesrviseniems pboy rtant
due stuhbesirtitusttirnogn gessiennfteiaclt iioounss aenffde cbtlsocakinndg tthhee fufanccttiotnhaal tgrtohuepys coaf nprsouterivnsiv, einafcotrivamtiongn tehnszyimnehs,e alth
facilitwiehsic[6h– p1r4o,2d3u–c2e6s ]h.Tighhelyi noaxcitdiavtaivtieo nfreoef mraudlitciadlsr usgu-crhe saiss taHnOt•(,M HDOR2•), paantdh oOg2e−•n swshuicchh adsamGraagmes- pthoes itive,
membrane integrity [30–40]. A number of studies have demonstrated the efficient killing of 
Gram-negative,orfungionCu-polyester(Cu-PES)hasbeenreported[132,133]. TheDCMSofCuwas
bacteria/fungi on Cu‐surfaces and Cu‐alloys, both in vitro and in a clinical setting; Espirito Santo et al. 
carriedoutonpolyester(PES)fordifferenttimesandledtouniformadhesiveCunanoparticulate
[136,137], Grass et al. [138], and Casey et al. [139]. These studies show that Cu‐surfaces rapidly and 
films. Cu-PESsamplessputteredfor160swereobservedtoinducea6log CFUlossofviabilityfor
efficiently kill bacteria, in some cases accumulating Cu‐ions on the cell wal1l 0membranes. This step 
MRSAandA.baumanniwithin30min. ThelossofbacterialviabilityontheCu-PESsurfaceforother
seems to be followed by Cu‐uptake, leading to loss of integrity of the cell wall and Cu‐translocation. 
MDRbacteriaproceededwithsimilartimesindark/lightconditions,suggestingthatCu/Cu-ionsand
These studies also report that Cu/Cu‐ions are effective against a wide variety of microbes, but the 
notCmuOodxel oefd intotetrhveenotbiosne rovf ethdeb Cauct/Ceruia‐ilolnoss asnodf tvhiea binialicttyi.vaTthioenu mseecohfagnliosmve sst,ilgl orewmnasi,nas ncodnmtroavsekrss,iaals. well
aspaEtixepnetriimsoelnattaiol env,ihdaenvceel fiomr irteeadcttihvee osxpirdeaatidveo sftirnesfes c(tRiOonSs) ,obnu ttheo ncytthopeilrasomw onf aCrue‐sntroetssaebdl eyetoasat vhoasid  the
transmbeiesns ipornesoefntHedC. ANIesw[ 1b3io4m,13at5e]r.ials consider additives that interfere with biofilm formation, adhesive 
Cprooppperetrieiss, arnedq uinivreodlveb ay meiuckroasrtyruocttiucrae nddrivpinrogk thaer yaonttiibcaccetelrlsiala atcltoiown [c1o3n]. cTeensttirnagt itohne sanatsibcaoctfearcitaol rs in
metala-cptiroont eoifn msaannyd meentzaylsm ones T,ibOu2 tfialmths,i gthhe cmoentcael‐niotrna ttoioxincsit,yC ouf -C(IuI‐)iohnass waatso fxoiucnedff teoc tb.eC muuicnht ehrigvheenre sby
compared to Ag‐, Zn‐, Co‐, Al‐, and Hg‐ions. The in vitro growth inhibition revealed the higher 
substitutingessentialionsandblockingthefunctionalgroupsofproteins,inactivatingenzymes,which
activity of Cu‐ions as an antibacterial and bio‐tolerant additive in ppb amounts [140]. Due to the fact 
produceshighlyoxidativefreeradicalssuchasHO•,HO •,andO −• whichdamagesthemembrane
that many bacteria grow easily on polyethylene that is 2widely us2ed to wrap all kinds of objects: 
integrity [30–40]. A number of studies have demonstrated the efficient killing of bacteria/fungi
pharmaceuticals, perishables, and surgical materials by Cu‐polyethylene (Cu‐PE) thin polymeric 
on Cu-surfaces and Cu-alloys, both invitro and in a clinical setting; Espirito Santo et al. [136,137],
films, our laboratory decided to sputter Cu on PE by DCMS and test its bacterial inactivation 
Grasspeertfoarlm.[a1n3c8e] ,[1a4n1d]. CCua‐sceoyateintgasl o.f[ 12359 n]m. T thhiecskenesstsu wdieerse ssphuotwtertehda att C60u W-su arnfda cdeesporasipteidd l0y.1a6%nd weefifighcite ntly
kill bCauct/wereiiag,hitn PEs,o lmeaedincags teos baacctceurimal uinlaacttiinvgatiConu -uinodnesr olonwt ihnetecneslitlyw siamllulmateemd sburnalnigehst. (2T0h%i sthset esoplasre ems
to beirfroadllioawtioend rbeaychCinug- uthpet aekqeu,atloera daitn ngootno ploresssenotfinign t1e0g0r imtyWo/cfmth2)e. Tcheelslew fialmllsa wndereC aul-stor aanbslelo tcoa tion.
Theseinsdtuucdei ecosmalpsloetree bpaocrtetrtihala itnCacuti/vCatuio-nio inns thaer edearffke wctiitvheina 9g0a imnisnt aanwd iadt ea vfaasrtieert yraotef wmiitchrion b1e5s m,binu tthe
under low intensity sunlight. Repetitive photo‐induced bacterial inactivation was observed on the 
modeofinterventionoftheCu/Cu-ionsandtheinactivationmechanismstillremainscontroversial.
ExpeCriumOexn‐PtEal. eTvhied eCnuc erefloearsereda cinti vtheeo pxpidba‐rtaivneges tdruesrisng(R tOheS )caotnalythste rceycytoclpinlags mwaos fdCetue-rsmtrinesesde dbyy east
inductively coupled plasma mass‐spectrometry (ICP‐MS). An increase in the applied light intensity 
has been presented. New biomaterials consider additives that interfere with biofilm formation,
accelerated the bacterial inactivation kinetics, providing evidence for the semiconductor behavior of 
adhesiveproperties,andinvolveamicrostructuredrivingtheantibacterialaction[13]. Testingthe
the CuOx film. Using X‐ray photoelectron spectroscopy (XPS), the binding energy (BE) of the Cu‐
antibsapcetecireisa wlaacst oiobnseorvfemd taon syhimft eatftaelrs thoen bTaciOter2iafil limnasc,titvhaetiomn ecytaclle-i, opnrotvoidxiincgit eyvoidfeCncue- fioorn resdwoxa psrfoocuesnsdes tobe
muchduhriignhg ebracctoemriapl ianraecdtivtaotiAong. -,Zn-,Co-,Al-,andHg-ions. Theinvitrogrowthinhibitionrevealed