nanostructured thin films · field of research, the ten volumes of this single source of...

Nanomaterials for the Life Sciences

Ed ited by Challa Kumar WILEY-YCH

Nanostructured Thin Films and Surfaces

The Series The new book se ries Nanomaterials for tile Life Sc iences successor to

the highly acclaimed series Nanotechnology for the Life Scie nces provides an in-depth overview of all nanomaterial types and their uses in thE life sciences Ea ch volume is dedica ted to a specific material class and covers fu ndamentals synthesis and characterizat ion s trategies structure-property relationships and biomedica l applications The new se ries brings nanomaterials to the life scien tists and life science to the mate rials scie n tis ts so tha t synergies are seen and developed to the full est

Wri tten by inte rnat ional expe rts o f the var ious facets of th is exciting field of research the ten volumes of th is s ingle source of info rm ation comprehen sively cover the com plete range of nanoma te rials for medical biological and cybernetic applications The se ries is aimed at scienti sts of the following disciplines bio logy chemis try m aterials science physics bioengineering and medi cin e toge ther with cell biology biomedi cal engineering pharmaceu tical chemistry and toxicology both in academia and fundamental research as well as in pharmaceutical co m pa nies

Volume 5 Nanostructured Thin Films and Surfaces Volume 5 gives an inSight into thin film s and the ir applica tion to the

life sciences The topics covered range from d ip pen lithogra ph y to

application s of st imuli res ponsive fil m s The m aterials presented ra nge

from polyrneric to ceramic thin film s

For more information on NmLS please visit wwwNmLSwiley-vchde

Challa Kum ar IS w rrenly lhe Director of Nanofabncation amp Nonomalenals at the eMU for

Advanced MIcrostructu res and DeVices (CAM D) Baton Rouge USA He is also the Preslderlt and

CEO of Magnano Technologie s a company established to commerClOlize nanom aterials Jor appli cations in life sciences Hs research in terests are In delJelopmg novel syn the tic m ethods including

those based on m lcrofluidic reactors for multifunctional nanomatenas He has also been Involved

In the de velopment of innovat ive therapeutic amp diagnostic lools based on nanotechnology He has eight years of induSlfial RampD experience workmgfor Imperial Chemicalndustnes ar7d Umled

Breweries He is the founding Editor-m -ChiCf ofth e Journal of Biomedical Nanotechnology pubmiddot

Ished by Ametlcon Scientific publishers and Series editor for the len-volume book series Nanolemiddot

chngies f or he Life Sciences (NI LS) publIshed by Wileymiddot VCH

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VIII I Contents

632 Interactions Lipid Molecuk-Titanlltl Surface 213

6AL] MorphoJogy of CoJlagen Adsorbed Of) an Oxidized Titanium

Surface 22R 64U Adsorption of ColJagen on a Hydroxylattd Titania Surface 22R GAL Morpholugy and Structure of Collagpn Adsorbed on a Calcified Tttania

6)3 Structure and Conformation of Lipid Molecules in the Bilayer on the

Titania Surface 216 6jn Structure of Phosphatjdylcholinc on the Titania Surfdce 217

6A Characteristics of ExiracellllJar Matrix Proteins on the Titania

Surface 226 6A1 Collagen Adsorption on Titania Surfaces 227

Surface 129

6414 Conclusions 231 6415 Structure of Collagen on the Titania Surface Theoretical

Predictions 232 642 Fibronectln Adsorption on the Titania Surface 234

601 Morphology of Fibronectin Adsorbed on the Titania Surfact 235 6422 Fibron(ctin~Titania Interactions 236

6423 Structure of Fihronecdn Ad~orbed onto the Titania Surface 238 6424 Atomic-Scale Picture of Fibronectin Adsorbed on the Titania Surface

Theoretical Predictions 240

6425 Conclusions 241 65 Conclusions 242

AcknoWItcigments 244 References 244

7 Prepatation Characterization and Potential Biomedical Applications of Nanostructured Zirconia Coatings and Films 251 Xuanyong Uu Yjng Xu and Paul K Chu

71 Introduction 2S I 72 Prtparation and Characterization of Nano-ZrO Films 251

721 Cathodic Arc Plasma Deposition 251 722 Plasma Spraying 254 723 SojGel ~ethods 255 724 ElfC troche mical Deposition 257 725 Anodic Oxidation and Micro-Arc Oxidation 260

716 Magnetron Sputttring 262 73 Bioactivity of NanD~ZrO Coatings and FiJms 263 74 CeJj Behavior on Nano-ZrO Coatings and Films 267 75 Applications ofNanomiddotZrO l Fiims to Biosengors 269

Referen((s 273

8 FStanding Nanostructured Thin Films 277 Izumi Ichinose

81 lntroduction 277 82 The Roles of FreemiddotStanding Thin Films 277

bull

7 Preparation Characterization and Potential Biomedical Applications of Nanostructured Zirconia Coatings and Films xuonyoYlg Liu Ying Xu and Paui K Chu

71 Introduction

Zirconia (2r02) has excellent mechanical streng~h thermal stability chemical inertness lack of oxicity and an affinity for grou ps containing oxygen These and

other favorable attributes make ZrOl uramics coatings and films potentially useful as biocoatings femoral heads orthopedic implants and bioscnsors FoJshy

lowing the first report of the biomedical application of zirconia in 1969 its use in the ball head~ of total hip replacements THRs) was introduced in 1988 [1 J In fact the THR femoral head remains one of zirconias main UCS lth more than GOO()()( units having been implanted worldwide mainly in the US and Europe up until 2005 21

Zirconia coatings and films may also be deposited onio other materials in order to improve their surface properties iuch JS wear resistance corrosion resisJance thermal barrier capability and biocompatibility Several techniques including sol-gel processIng plasma spraying anodic oxidation magndron sputtering elelt~ trochemical deposition and plasma deposition have been USEd to prepare ZrO coatings and films In this chapter we revjCw the surface morphology microstrucmiddot hue crystallitl size phase composition and biomedical characterization of nanosshytructured ZrO coatings and films prepared using different techniques

72 Preparation and Characterization of Nano---Zr01 Films

721

Cathodic Arc Plasma Deposition

Among others research groups at the City University of Hong Kong and Shanghai lnstitute of Ceramics Chinese Academy of Sciences (SlCCAS) have fabricated ZrO thin films with nanosiled surfac(s on 5i (JOO wafers using a

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Figure 71 Schematic diagram of the synthesis or ZrO filrrs uSing a filtered cathodic arc system [4]

filtered cathodic arc system [3] (Sll Figurt 7~1) The fxperimental apparatus includes a magnetic duct and cdthodic Jrc plasma source with the zirumiurr discharge being controlled by the main arc current between the cathodk md anode Oxygen gas is bled into the arc region 3Jld the mixed zirconium and oxygen pklSITlJ is guided into the VJcuum chamber by In electromagnetic field applied tv the curved duel TIle duct is bia~(d tv -20 V in order to exert a lateral electric field while the external solenoid coils wrapped around the duct produce the axial magnetic field with a magnitude of lOOG Before deposition the samples that arc typically positioned about 15 em away fronl the pxit of the pJa~m) stream arc sputter~deaned with an argon plasma for i-min Ising a sarnple bias of -500V The bae pressure in the vacuurr tharrber is approximately 1 x 10 Torr and a radiofrequency (RF) power of WOW is applied for J deposition time of 120min TIle as-dcpositeurod ZrOJ thin films are subsequently heat-lreJted a either 800degC or lO()()C lor lh

The Xmiddotray diffraction (XRD) resuhs in Figurf 72 show ~hal the ffsultant thin film is crystallized as irdicatcd by h diffraction pfak- at 2983 ~ alld 3485 0

which (In be attributed respectivfly to the (l01) and (002) planes oftlw tetragonal ZrO ph)e The small peak marked by the arrow in Figure 72 rnay stem from tle (111) planc of the monoclinic phasc The sudau view~ of the asmiddotdepositc-d and therrnaHy treated ZrO thin films observed using scanning electroT micfO-shy

copy (SEM) and atomic force microscopy (AF1) are shown in Figures 73 and 74 The surface of thc as-dcposittd ZrO thin fHm was vcry smooth ~u(h that the surface features could not easily be distinguished using SEM (Figure 73a) However ltmme ve-ry small particlES welC obwrved on the surface of the zrO thin filrr in thE AFM imagE (Figure 73b) Followmg heal treatlllCtt at (ither 800 ~C or 1000 C fOT 2 h nanosized partide could bE observed on the surf~(e of the ZrO thin film (Figure 74) The jizts of the particles on the ZrO) thin

72 Preparation ald CharacterizatIOn oJ NOgt1D-ZOL fAYrJ5125J

20 2~ 3D ~5 40 ~~ ~U ~~ 60 2 Thela Dm bullbulll

Figure 72 -rHn filrrx-ray diffraction patter acqUired from the ZrO thin fil~ depoSted on siICon wafer 151

Figure 73 (a) Scar1r1ng eleclron mcroscopy and (b) atomiC

force rmuoscopy images of tre limiddotdeposJ~ed zrO thin fiin 141

Figure 74 Surface ye s of the ZrO thm films heaHrealed at 800C and 1000C fOf 20 14j

241 7 Preparatiofl CharacteMatiorl ana Poterltial Biomedical ApplicatIOns

film heatmiddottreated at ROOC or l000C were approximately 20nrr and 40nm respectiitely which indicated that th(gt partidt izt could lw reguidtpd byoptimizshying the post-treatment processes

722 Plasma Spraying

Plasma spray-jng ha~ heen used extensively to prepare ceramic coatings since its development by Union Carbide during the mid-19S0s In plasma ~praYlng an electrical arc is used to melt and spray the materials onto he surface ofa substrate (see Fjgure 75) with the paran~eters of ihe density iEmperaurE and VElocity of the plasma Jeam each being important whe-n forming thE coatings Although the temperature In tht cort region of the plagtmJ beam is rdavdy con~tant at approxishymately 12000K it increases dramatically towards tht nozzlf to a point whtrc almost any material can be melted in the plasma jet

Nanostructure-d zirconia coatings have be-e-n prepare-d by the rest~arch group at SlCCAS since 2002 using plasma spraying [7-11J The nanostructured zirconia coating fabricated by Zeng et aL possesses tvmiddoto types of structure (J) a poorly canmiddot soJidated structure composed of nallosiztd particles and til) all ov~rlappjng trucshyture consisting of micrometer-sized particle- [7J The former structure constitutes the main component of the coating Vhilst the zirconia coating has the same phase composition as the starting powder its thickness appears to be inconslstent as shown in the cross-ectional view in Figure 76 Subsequently others have investigated furtber the preparation and prorerties of plasma--prayed nanostrucshytured zirconia coatings with the result that zirconia coatings with nanostnlCtured suriaces and uniform thicknesses have been succt~ssfully fabrlcared by optimizing the spraying parameters (Figure 77)

Spray deposit

Cathode Plasm~ ---shy

~= === Powder andI c311iel gas

Spray distance

Eleclical H Electrical (~l connection connection Substrate and wate out and water in Figure 75 Schemanc djag~arn of pasrna spray lorch [6]

72 Prepo(ofiorl Of( Characterizatof oj Nano-ZrO_ Films 1255

Figure 76 CrO$$-$tctlonal itWS of th~ nanostmctured ICOnl C03W1g fabr carEd by ZEng et 01 [7

Figure 77 (a) (rossmiddotsectlonal and (b) Sl1rFace views of the

nanostructural zirconia coating fabricated by Wang et o( 11

723 Sol-Gel Methods

The sol-gel process has been used extensively to deposit thin nms iltlOum Compared to other conventionaL thin-film processes the ~ol~gel system allows for a beter control of the chfmical composition and microstructure of the film for the preparation of homogeneous films fiJr a re-duction of the dlnsification temperaure and finally the use of simpler equipment and a lower (ost Thi parshyticular acvantagcs of he sol-gel approach include an easy purification of the precursors (hy distillation or crystaUization) and the ability to introduce traces of other elements into the film In addition the precursors can be mixed at the molecubr level ln the solution such that a high degree of homogeneity can be

2561 7 PreparatIOn CharacterizatIOn and Potentwl Biomedical Applications

Figure 78 Morphology of the ZrO film obtained at lS0g Zrel1 1 [121

attained in the films As a consequence the sol-gel process permits a lower temshyperature to be used during the sintering stage The resultant microstructure depends not only on the treatment of the precursors but also on the relative rates of condensation and evaporation during film deposition

In the sol-gel process the thin films are normally produced using spin- or dipshycoating techniques The spin-coating process consists of four stages deposition spin-up spin-off and evaporation I-Iowever for complex-shaped substrates the most frequently used sol-gel technique is dip-coating where the sample is dipped into a solution containing the precursors and then withdrawn at a constant speed usually with the aid of a motor The deposition of a solid film results from gravishytational draining and solvent evaporation accompanied by further condensation reactions

Chang et al [12] have proposed the use of a spin-coating sol-gel method to fabricate highly porous or smooth ultra-thin Zr02 films The morphology and thickness of these thin films can easily Ix controlled by adjusting the concentrashytions of ZrCl j in the sol solutions A porous film with a large specific surface area (180m) g-l) can be obtained Ising 150g Zrel] I without the addition of templates The ZrO film prepared under these conditions is composed of nanofibers with a typical width of approximatcly 100nm The entangled and branched nanofibers that constitute the thin film appear porous (Figure 78) A type II isotherm is clearly found in the Nl adsorption curve indicating the macroporous characterisshytics of the thin film When the concentration of ZrCI I is reduced to 17g1middot 1

the porous surface turns into a smooth thin film A linear relationship between film thickness and the concentration of ZrCl~ ranging from 17 to 3g1 I has been observed for example an ultrathin film with a thickness of 18nm can he fabrishycated when a ZrCl 1 concentration of 3 gl is usedI

The texture of sol-gel-derived thin films is mainly controlled by the rates of hydrolysis condensation and phase separation In theory a smooth morphology

ZrOCloXIIO + (OhoMIO

or I NO-6fIO (Ir 1lt(J611 0

lIh~dJou ((hanoi --- t SrirrlC1 31 ~t)~middot7U C fur 1 h

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t IIIICllld at 600 doped ZrO films

Figure 79 Fow dagra~ demonstrating the preparation of doped zicorja flrrs 14]

should be formed when hydrolyLo and coadensation are comlucted ~cparately at

a slow reaction rate lith decreasing ZrCl concentrations the size of the ZrOt

fibers increases however and the thin films have J selOothc[ morphology due to the slower hydrolytic rate

Lucca et at [13 prepared multilayered ZrG thin films by dipmiddotcoaling and silbshysequent heat treatment at temperatures ranging from 400 to 700 6 C dnd thfn investigated the near-surface mechanical responses of the films to nanoimlentashytion The elastic modulus and hardness afe ~nedsurcd at depths which correspom] to 7-10 of the film thicknes_ The temperature of the heat tflatmnt is found to have a signifiunt effecl on the resultant ncar-surface hardness and elastic mooulus Liu et al 114] have prepared highly oriented CeO YO and MgOdoped 2rO thin films using a sol-gel process by dip-coating in 3n ethanol solution consisting of zirconium oxychloride octahydrate and inorganic dopants as shown in the How diagrail in Figure 79 The doped ZrO t films contained only the zirconia etragonal piuse and exhibited nanoscaJe morphology (Figure 710)

724 Electrochemical Deposition

Electrochemical deposition is used widely to deposit a thin metallic coating onto rht surface of another metaL by the simple electrolysis of an aqlllOUS solution containing the desired metal ion or its complex (Figure 711) Electrochemical deposits posws- a fine structure and vjuablc physical properties such as a high level of hardness and a high reflectivity 115]

In the eJectroc~Hmical deposition process reduction takes place when a cur~ent is ~upplied externally and when the sites for the anodic and Lathodic reactions are separate ThE reduction rnechanism pertaining to the electrochemical oeposition

lSBll Preparation Characterization Qla Potental Biomedcal AppHcatiom

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Figure 710 Atomic force mcroscopy Images of dopec 2rO thin ~Ims (a) lKSZ (~) 8YSZ (c) 8MSZ ~14J

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72 Preparation and Characteozatlofl of NarwmiddotZrO Films 1259

(+) H Anod 1)1ltil Cathode

OHe 16HO

011 0 ( )

H()

(C)

Bulk electrolyte Djffu~iou la~ir HilhnllO]tz laYel IM(HO)o I

Figure 712 Reduction r1echarisrr of solvated rr~tal tormiddotn electroltherica deposition [is

of a 5jrnple soivated metal salt (see Figure 712) em also be extendtd to other ligand-coordinated metal systems The solvated metal inn presput in the electroyte arrives at the cathode under the influence of the imposed ehgtctrlcal field as well a by diffuswn and convectlOn (Figure 712a) and enters the diffusion layer Although the field strength in the diffusion layer is not sufficiently strong to libershyate the frtlt metal ion from thE solvated state the solvated water molecules are aligned by the field (FIgure 7121raquo the metal ion then passe through the diffused part of the double layer As the field strength of the double layer is high (on the order of lOVctn I) the solvated water molecules are removed so as to leave the free metal ion (Figure 7llc) which is then reduced ltlnd deposited at the cathode via an ad-atom mechanisrn [15]

Electrochemical deposition has been used widely io prepare zirconia and comshyposite films For exarnpl( StffanoY it Ill [161 investigated the electrochemical depositIon of zirconia hIm 011 stainless steel here the films were obtained in an electrolyte of anhydrou~ ethyl akohol With the rising cathodic voltage the strueshytun and morphology of the zirconia films exhibited essential changes those films with the most porous structure were formed J 21 V lnJ thmw with the highest density at 23 V The composition in the hulk of the films was close to the stoichioshymetric valuE Shacham et at P71 have reported a novel electrochemical method for the deposition ofZrOj thin fllrns where films with thicknesses ranging from 50 to 600nm were obtained by applying moderate positive or negative potentials from +25 V to middotmiddotmiddot15 V versus SHE) on the conducting surfaces which were immersed in a solution of zirconium tetrHt~propoxide Zr(OPrl1] in iso-propanol in the presence of minute quantities of water (the watermonomer molar ratio ranged from 10 ) to 10 I) The magnitude of the applied po(ntial and its duration were thought to provide a convenient means of controlling the hIm thkkmgtss Thin films of zirconia and an organoceramic tomposite whch consisted of zirconium hydroxide and poly(diaJlyldimethylammonlum chloride (PDDA have been produced Hsing cathodic electrodeposition [181 with films of up 0 lOf-Hn thickness obtained on Ni and porous ~j-yttria-stilbilizoo zirconia YSZ) cermet substrates The amount of materia] depositc-d and its composition can be controlled by varying the current density and the concentrations of the PDDA and zirconimll salt

260 I 7 PrepoTOtio() Chcmtcterizar) ana PDtertw BiOmedJCal AppllcatiG)~

725 Anodic Oxidation and MicromiddotArc Oxidation

Anodic oxidation encompJsses electrode rections in combinaion with electncj

fieldmiddotdriven metal and oxygen ion difTusion leading 10 the formation oLm oxide

birr at the anode surfa(e~ Anodic oxidation is a vleJmiddotestblished method f()~middot the

production of difffrent type5 of protc(ljve oxide films on metals and different

dilute acids (eg HSO Hr04 acetic acid) un he llsed as the electrolyte in th(gt

process The structural and chtrnical properties of the anodic oxides can be varied

over a quite wide range by altering thL process pararnlters such as tht anode potential electrolyte composition temperature and currtnt The anodizing tppamiddot

raus lS shown schematically in Figure 7] MicroHC oxidation (MAO) which is also ffzrrcu to as anodic spark oxidation

or plasma fltttrolytic oxidation is a novel anodic DxidatJon technique that is

w~(d to deposit ceramic coatings on the surfaces of vlvc mEtals such as A] Ti

Mg Ta W Zn and 71 as wen as their alloys In 10 pnKlSsCs the anodt which is composed of the valvt metal is immersed in an aqueous solution and an asyrr~ metric alttrnating voltage applied betwffFl Ihe anode and cJthodc In the anouk half-circle the voltage is usully in themiddot range of150 tu ]000 V while in hc cathodic

half-circle it is in the range of 0 to 100 V MAO processes are typicaHy characterized

by thlt phenomenon ofelectrical discharge on the anode in aqueous solution while

temperatures of up to 10000 K and Jocal preSS1res of several hundred bar in thlt

discharge chaEncls have been reported The quality of he MAO coating is detershy

mined by paramltters such as the (ornposition and tltmperatwe of the electrolyte

tht alloy compoltjtion the voltage current densiry and time highmiddotqual~ty coatings

can be created by employing properly selected deposition parameers Zhao d aL 120] have fabricaed zirconia llanotube arrays -vith a diameter of

approximately BOnm lengths of up to ]90l-lm and aspect ratios of [nore than

1400 by anodizing Lhe zirconium foil in a mixture of ft)rmamidt and glycerol

(volume facio = 1 1) (ontaining 1 wt fH4F and Jwt H0 (Figure 714) The

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I)

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la) Ib)

Figure 74 Sflnning electron microscopy (b) Surface structure after being nmed lnage~ ofr~e as-prepared sarrples after ultrasonlcaliy tel Cross-section (d) Cros)shyanodlzaion of Z~ at 50V for 24 h (a) SJraCigt settlor at lgher magrihcatlon (the fiset S~fJcture (the loset shows a tranSrt1SSICn shows a t~af1smissor electron microscopy electron microscopy inage of the top part) Image of the zi(co~la nanotule) 201

as-prepared nanotube arrays contaln(~d amorpholls zirconia Both mOllocHnic and tetragonal zirconia coexisted when anneled at 400C and 600degC WhtfPJS monoshyclinic zirconia was obtained at 800C th ZrO j nanorubes reaintd their iihape after heating to up to 800C The lower dissolution rate of zirconia in organic electrolytes was considered to be the main reason f()r fabricating zirconia nanotllhe arrays with hgh aspect ratios

Tsuch1ya et at 121] have reportd tht f(mnation of sfforganized porous layltr of ZrOl by the anodization of zirconium in HiSO eifctrolyE~ (onbining low concentrations of NHjF Undtr optimized Ifctrolyte conditions and with polarishyzation 1n the range of several tens ofvoHs an orderly sponge-like porous ZrO was obtained thf layer thickness of which was on the order of several tens of micromshyeters while the pore diJrneter typically varied from 10 to 100mn The pore size was almost independent of thl applied potential whereas the amoun of wellmiddot structured area on the sample surface increasd with higher applied potentials

an d at [22J have r(ported that zirconia Elms can also he prexHeu by the MAO of zirconium in an aque-ou5 solution lORing a pulse power supply The groups

2621 7 Preparation Cnaracteflzation ond Potential Biomedical ApplicatIOns

Figure 715 ScJrface view oftle MAO z rcenla rim (22)

results indicatetl th)t thE ~AO-forrIHtl film~ -wnt nanostructurpd and porous

(Figure 715) ltHId Wfre cmnp)~fd ofzirCQnid partiallytabili7ed with CaO together

with a small amount of rronoclinic ZrO

726

Magnetron Sputtering

Magnetron sputttdng repriSint~ one of th most common methods uspd tor dtposiring thin film its popularity stemming from the simplicity of the phsi

cal processes involved combined with versatility and Aexibilit vtagnctron sput~ tering sources can be dassHi(d as diode devices in which tw magnetic iiEld

arc used HI cOHcnt with the cathode surtau to form eetron traps The charged

partides are umFmed hy a do~ed magntic h(d such that the high-density

plasma is produced In the vicinity of the cathode An elh3r1Ced pbSJt13 ionizamiddot

tion can then be achieved via either additional gas ionizatioll or plasma conflncshy

mcnt Tlli5 sputtering system GUl tlClivltr large ion currents to the ~ubstratts

and rnay be operated owr d wide rangt of )flssurls When using this process

the can be prodwed on subtrates thltIt n1ty be very large and also of

cornplex shape

Huy ct at 231 have deposited zirconia thin films by using Rflt magnftron sputshytering on zirc31oymiddot4 (Zymiddot4) ui)strahs dinxty from the ZrOl target These thin

HImgt 3rc dltposited at differFut su)strate temperatures (from 40 to 800 Q C) and

73 81OoctllJty of Nano-ZrO Coatlrg and Films 1263

over different time (from 10 to 240min) By comparing th- Raman studies on zirconia thin films and on bulk zirconia it em be conduded that

bull ZrO is not completely Jissociated during the deposition process

bull The zirconia films deposited on Jifferent substrates arc polycrystalline

bull The structure and phase composition of the fitrns depend on the substrate temperature and on the depoition time and therefore vary as a function of the di)tance from the film surface

73

Bioactivity of Nano-ZrOl Coatings and Films

Zirconia is gencral1y considered 0 blt a bioinert ceramic because vhcn implanted it shmvs morphological fixation only to the surrounding tissues without producshy

ing any chemicJI or biOlogical bonding However in the past few years many at~empts have been made to prcpare bio1(l1Ve ZrO coatingsfilms or to irnpf)ve their bioactivity by means of post~treatmenL

The ability to luduce apatite formation on a nanocomposlte of cerium-stabilized

tetragonal zirconia polycrystals (CemiddotTZP) and alumina (AIO) polycrystals via chemical treatment in aqlH~ous solutions of H lrO~ HSOj HCi or NaOH has been investigated [241 When this type of nanocornposite is suhjected 0 slich treatshyment at 95C for 4h Zr-OH groups thJt enhame the formation of apatite in simulated body fluids (SBFs) are first formed on the surface The apatite-forming ability of zirconium metal pretrCated in 5 M aqueous NOH solution has also been dfmonstrated in SBF immersion tests [251 Apatite nucleation is helieved to be induced by Zr~middotOH groups in a zirconia hydrogel byer that f(mns on the metal upon exposureo NaOH

Both macro porous and nanonystaHine zirconia films have been prepared by

the MAO of zirconium and the effec~s of chernieal treatments in altJueous H)SOj or NaOH solutions OIl the microstructure and apatit(gtforming dbHity of the films have been investigated )61 Compared to the 1AO film the chemically treated films did not exhibit any apparent changes in their phase component morphology and grain size however there WlH more abundant basic Zr-OH groups The film~ treated kith HS04 dnd NaOH solutions could indllce apatite f()rmJJion on their surfaces in SBFs within 1 day whereas no ltIpatie was detected on the untreated zrO surface even after 30 dJYs ThllS it wa~ considered that the enhanced apatite-forming abHity of the chemically rea~(d ZrO) film was related to the abundant bask Zrmiddot-OH groups on the surface

Plasma-spraytd nanostructuree zirconia coatjng~ stabilized -th 3 mol yttrla (3Y-TZP) also exhibited good bioacivity [11~ After immcr~jon in the SBF solution for 28 days a bone-like apatite vas formed on the surface of the plasma-sprayed nanostwctured zirconia coatings Figure 716) but not on the surface of the polj~hed coating The Zr-OH groups formed in the aging process and the

Figure 716 (a-c~ Surface r1 crogrlp~s of the pJasmamiddotsprayed Zlfconl3 coatl1g Immersed In 5llrrlated body fluId soluton for 28 days (n-agmfications as Hldloted) (d) E1ergyshydIsperSIVe Xmiddotray spectroscopy of tile partdes on tle coaling surface [i 1]

nanostructured surface of Ihe plasTI1ltl-sprayCd 3Y~TZP coating were belicvtd to

be the keys to the bioaclvity of the coating The ZrO j thin fihns prcpartd by cltlthodic arc plasma deposition wert immersed

in SBF to tvaluate their bioactlviy the -urface vlnvs of thegt asdlpo~i tcd and thlr mally treatcd Zr0 thin fihns aftegtr Soaking jn SBF for 28 days are shown in Figure 7]7 Anegtr immersion m SBF for 28 days tll( surface of ttllt a~~degtpositcd lrO thin film was compietegtiy (overegtd by the apdtite layer although relatively few apatite sructures appeared on the surface of thegt Zr01 thin film annealed at ]OOO~C for 2h These resultslndicated tha~ thpound bioactivity ofthe 2rO thin hln might be degraded after thermal treatment

A high-resolution ~ransmission electron microscopy HRTEM) image which was recorded near the apatjtc and Zr0j thin film (Figure 718) showed the apatite layer to bc in direct contact with the ZrO thin film In this imagp the mulY disoropred areas vi~ible around the crystalline apatite indicated that the apatite

layer nn the ZrO) rhIn film had only partially crystallized The (211) planes ofthe apatitegt with a spacing of approximately O28nnl were wen rpsolved in this region The HRTEM image of the ZrO thin film shmled that it consisted of nanosized

73 BlOQcthntr oNano-ZrO Coatings and Films 1265 (a) (b)

Figure 717 Surface yiews of the different Zro thIn films soaked r SImulated body fluid for 28 dayS (a) kmiddotdeposited thIn film (b) Therrraily treated thin film (lOOOC for 2 h) [41

Figure 118 High-resolution t-ansmissor electron 41Croscopy (HRTEM) imltige taken near the apatite 2nd ZrD thin film 51

crystalline ZrOj with the outennost ZrO) crystal smaller than thai in the bulk of the ZrOl thin film as denoed by the arrows in Figure 718) The severalmiddot r~anometer size of the particles in the outermost layer was believed to lw one of the reasons why the Zr01 thin film vas bioactive

The results obtained with the nanoZrO thin films and coatings may indlcate that nanosized surfaces hode weE for bioactivity and biocompaihility when comshypared to (OnVCIltional surfacrs The deposition ofcalcium lons repreS01lts the flrst

2661 7 PrepomtioVl Cnaractenzotion Ot1d PotenJial Blomediwl Applicatlom

and most crucial stfP of carhonate-containing hydroxyapatite nuclfation from an ionic sOlution indeed this procels is believed to mitiate the grov1h of boneMlike apatite on the surface ofhiocompatible implants [27] The formHion of a negatively charged surface gives rit to apatite precipitation because positive calcium ions are attracted from the solution [28J The charge densities of the particles are detershymined by their size in fact Vayssicres ct at [29] have suggested that finer nanoc rystalline particles might have higher surface charge densitie~ than larger particles It has also been demonstrated by using thermodynamic analysis that the surface or interfacial tension diminishes with da-reasing particle size a) a resull of the increased potential energy ofthl bulk atorns in the particlcs 30j Smaller partides with an increased molr free energy are more likely to ddsorb molecules or ions ono the surfaces in order to decrese the total free energy md thus become more stable Therefore the nanosized particles in ~hc outermost laY(gtf ofhc ZrO thin films and coating might represent a key factor for inducing the precipitation of bonp-like apatite on surfaltes during immersion in SBFs

Uchida Lt af 131j have also reportCd that pure zir(mia ge and zirconia gels contajning sodium or calcium induce the fonnalon of apatite in SBFs only wht~n they possess a tetragonal andor a monoclinic structure It has ocen shown previous]y that a pbsmHprayed calcium-stabiHzed zirconia coating is hioactive with the bioactivity depending on the con ten of h( monoclinic phasp in the coating [32J

The bioalt--tivity of zirconia coatings and films is thought to be related to the Clystalline structurf of zirconia as well as to the nanostructural snrface When the coatings and films are immersed in ltI SBF the wattr molecules react with zirconia and (hsso(Jate 10 form surface hydroxyl groups T(middot quantity and nature uf the surface hydroxyl groups depend on the crystalline strUdure of zirconia [53 34]_ Although thp monoclinic phase has the lowest bulk energy among the three zirshyconia polymorphs [lS) its surface energy is higher [36] However upon exposure to water molecules there is a greater tendency for this energy to be lowered by the mOlecular and dissociative adsorption of water which is exothermic in nature The idsorption enthalpy of ha1fmonoiclytr HcO coverage on the monoclinic zirconia surface was shown to IX ~142KJ moll whilst that on the tetragonal surface was ~90 KJ mol-1 [37 38] indicating the higher reactivity of the monoclinic zirconia surface Accordingly Ihe surface concentration of the hydroxyl groups on the monoclinic Zr02 su~face wa higher than that on tetragonal ZrO l341 fn fact thtgt OB concentration of 62 molecul(gts per nm1 for monoclinic zirconia wHh a BET surface area of19mg I was much higher than the vallie of35 molecules per nm for tetragonal zirconia with aBET surfact area of 20 m) g I MorpoVlr in the former case the dOlninant species were tribridged hydroxyi groups that were shown to he more addie and in the latter case a combination of bibridged and termtt1al hydroxyl groups The hightr acidity of the (Zr) OH on the mOTlOciinlc zirconia surface signific-d that it would mort donate proton~ to f()rm negashytiVfly (harged (Zr) 0middot PettCrsson et at [391 htlw reported that the isollectric point of the monoclinic zirconia without dopant was 64 this indicated that the monoclinic zirconia surface should be negatively charged in an SBF solution with

74

a pH value of 74 Tht negatively chargld surfac( Lan attract calcium ions from the SBF solution to its surface

In conclusion nanosized ZrO) coatings and films rompopd of tetragonal or monoclinic phaes can be prepared using a variely of technologies Moreover such coatings and films areuro generally bioactive and can induce the precipitation of apatite onto the surfau when ~hty are soaked in 5BFt- for a certain period of tinH

Cell Behavior on NanomiddotZr02 Coatings and Films

[t has been observed that nano-ZrD had no cylOtoxic properties whln ctlls were cocultured 011 its surface Likewise it has been shovn that nano-Zr02 is una bIt to generate mutations of the cellular genome and no advc-rsc- rpsponsts Ilave bec-t1 reported following the insertion of nano-ZrG into bone or muscle in in vivo

models This bck of cytotoxicity is illustrated in Figure 719 which ~hows bOric marrow mesenchymal stem celis (BMl1SCs seedpd onto ZrD- fIlms JEter diffprmiddot ent culture times At one day the BMMSCs were sttl1 0 grow and proliferate vtry

weI] on the 111m surface (Figure 7_19) which became partiJlly (overed by the cells

figure 719 Bone marrow mesenchytniill stem cells seeded onto the bO fims after different times (a) 1 day (b) 4 days (c) Highe ll2gnIFcaton of 4-clay sample [5J

2681 J Preparaticn Charoctenzaton and Pctentloi Biomedical Appfcotlom

Figure 720 Morphology of the MG63 celis seeded on the surface of the p1asn3sprayed nanoslrucwral 3YTZP coatlf1g for differe1 periods of time a) 1 ddy (0) 3 cays (c) 7 days [11[

and the extracellular matrix Afer a lunger seeding time offinu days the cells had fused to form d cotnplete layer on tle thin film surface (Figure 719b) An examimiddot nation at higher magnification (Figure 719t) showed tht (ells to possess a good morphology wHh abundant dorsal LdTlcs dnd filapodid

The morphology of MGGJ cells sl~(dd onto the SUri~1(e of a plasma sprayed

nanostnlcturcd zirconia coating aHn OTIe thn~ and scv~n days i shown in figure 720 The cells exhibited good adhesion and spreading after one day with

dorsal surface rurnes and filopodia een dearly after three days of culture After

seven days the coating stlfface was completely (overed by MGG3 celk whICh irdicated that this surface fdvored their adheslon and growth Cell attachment adhesion and spreading r~present the first phase of cell-implant inINation and the quality of this ph3~e is known to influ(nce ~he capacity of cells ~ubseque-nty to proliferate and to clifferentiatt When the proliferation ~nd vitaiiy of MC63 cells cULtured on the 3YmiddotTZP coating and the polystyrene (PS) control were monitored using the alamarBlue TIoI assltly the results (Figun 721) confirmed eel proliferation on both surf~ns (albe-it with a longer culture tiInt for PS The fact that no sIgnifishycant difIertnces were idtntifieJ between the 3YmiddotTZP coating and PS control indimiddot cated thJt the cytocompatibihty of bOlh rnaerials was similar

fsectampS~Polystyrene

5

4

3

2

Culture TIme (days)

~~3Y-TZPcoating

u ~ ~ ~

0 f

bull

Figure 721 Pefcenage aanarBhJe r reccfon for MG63 cells seeded on the DiasmHprayed nanostrcJcural WmiddotTZP coatings and the polystyrene control over different periods [11 J

Vincenzo et (II [40~ attEmpted to address the gen(tic effects of zirconia coatings on osteoblast-like cells by using a DNA microarray technique The study results showed dearly that ZrOj could upregulatEjdownregulaC certain functional activi~ ties of the osteoblast-like (ells such ltIS cell cyde regulation signal transduction immunity and the cytoskpoundJetol1 components The surface morphology of the ample VaS shown to havE a major influence on the gene expression of proteins for cellular binding with cell adhesionanchoring being improved hy the presence of surface canyons (-1 ~m deep) placed between the large cry-tals that were di tributed homogeneously over tht surface

75 Applications of Nano-ZrO~ Films to Biosensors

Nanostructural materials have been u~ed extensively filf bmh the efficient trammiddot port of electrons and optical excitation based on their high 3urrKe-to-volurne ratio and tunable electron-transport properties-two fdetors which are crucial to the function and integration of nanoscale dfvices Since the lizes of biological macshyromolecules such as proteins enzymes and nudeic acids are comparable to those of nanoscale bUilding blocks any interacion betwtrt these biomolecules should induce significant changes in the eiectrical properties of the nanos~ructured bioshyinterfaces A range of nanostructured materials such as nanopartjdes nanotubes and nanowires-all of which have been produced from metals semi(onductors carbon or polymeric specie~- haVt~ been investigated intensely for their ability to

270 I 7 Preparatiof Charactenzation and Potential Biomedical AppiJcatlorl$

fabricate the functional biointerfaces and to enhulce the response of biosensors Nmoscale biointerraces on electrode surfaces (an be obtained in a variety of way including modification of the electrode surfaces using biological receptor molecule such as enzymes antibodies or oligonucleotides or modification with nanosiructured materials As a result nanosructurtd biointcrfaccs have been recognized as having impressive functional properties that poim naturally towards bioeJectrochemicai applications

Methods for preparing nanostructurfd biointerfaces on electrodes include physshyical or chemical adsorption self-asstmbly sol-gel processes electrochemical deposition and electrochemical polymerizatlOn Nanoscalt inorganic matrices such as nano Au Ag Zr01 Si02gt TiO ZnO ~nOh aluminum silkalt magneshysium silicate phylosiiicate sol-gel matrices and rnagnetlc iron oxide nanoparti des have good mechanical properties and therrral stabillty and are also resistant to microbial attack and organic solvents Thererof(~ nost of these arc used as carshyriers and suppots (tspecially the nanostructured biocompositCs) and provide a well-defined r(cognition interface For these reasons they have hecome tht ideal matCflals for the immobilization of biomolecu1cs

Nanostructural zirconia partidts and films have recently been considered as a pot~~ntlal solid support for the immobilization ofbioJctive molecules in biosensor applications due to their large specific surface area high tllPrmaljmcchanicalJ chemical resistance_ eXCellent hlocompatibility and their affinity towards groups containing oxygen During the past f~w ye1rs both fUrlctionalized and unfuncmiddot tionalized zirconla nanopartides have been dewloped as solid supports for enzyme immobilization and bioc3talysis For example nanosized zirconia gel has been used to form a reproducible and reversible adsorption~desorption interface for DKA to immobUize hemoglobin Cor a novel hydrogen peroxide biosensor 10

immobilize DNA for investigating the dTects oClanthanide on is electron transfer behavior for the dctlction of DNA hybridization and to be grafted with pbosphoric and benzenephosphonic acids for the immobilization of myoglobin Zirconia films art abo able 0 bond to nonbiomoiecuies such as rDDA by coc1cctrodepositjon

Tong ct al have reported a novel and simplE immobilization method for the fabrication of hydrogen peroxide (HiOl biosensor) using hOlseradish peroxidase (HRP)~ZrO composite films [41] Such compoltite films are synhesized on a gold electrode surface based on the electrodepositlon of zirconia doped wih HRP by cyclic voltammetric scanning in a KCIsolution corHaimng ZrO and HRP Vithin the HRP-ZrO film the HRP retain its bioactivity and exhibits an excellent decshytrocatalytical response to the reduction of fJ)h The nsults have indicated that ZrO) is a good biomaterial capabJc of retainIng the bioactivity of biomoltcules while the HRP doped in biological HRP-ZrO l fi]ms exhibit a good electrocataJyti~ cal response to the reduction of H-O

A highly reproducible and reversible adsorption~~desorpion interface of DNA based on tlw nanosized zirconia film in solutions of differfnt pH values has been successfully fabricated by liu d al [42] ThCir results showed that DNA could adRorb onto the nanosized zirconia film from its solution yft desorb from thtgt

m1nopartides in D1 M KOH solution The ZrO film serves ltIS a bridge for the immobiHzation of DNA on the surface of the glassy (urbon (GC electrodt This reversible adtgtorptionmiddot~desorptjon performanngt of the nanosized zirconia film gives rise to pot(ntial applications in the preparation of removable and reprodudblt biochips ltInd infofl1ation stor3ge dtvins

Thegt direct eectrochcmistry and thermal stability of hemoglobin (Hb) Whtgtfl immobilized on a nanometerIzed zirconium dioxldc (ZrO)dimethyl sulfoxide (DMSO) middotmodifieurod pyrolytic graphite (PG) electrode have been studied by Uu et aiI43 Herc- Hb showed a high affinity to HOh and both nanosized ZrO) and DMSO (ould accelerate electron trmsfer between Hb and the electrode The Zr01 nanoparticles were more important in facilitating the electron exchange than was DMSO as they provided a three-dimensional stage while some of the restricttd orientations also favortu a direct electron transfer betwevn the protein molecules and the conductor surface The particles were able to stabHiztmiddot the oxidized form ofHb to decreltIse the polarization impedaflce and to enhance the thermal stabHity of the biosensor These finding mlty lead 10 a new approach for the construction of mediator-free sensors hy immobilizing proteins or enzymes on the ZrO) nanoshyparticles enabling hc determinatlon of different substrates such as gluLost by using glucose oxidase

The detection of DNA hybridization is of paramount importance for the djagshynosi~ afld treatment of gendic diseltses the detection of infectious agents and for reliable forensic analyses A novel electrochemical DNA biosensor based on methyiegtnc blue (MB) and zirconia (Zr01) f-ilmmiddotmodified gold electrode for DNA hybrjdizatlon deteclion was described by Zhu et at 44] in which the ZrO firm was eleLlmuepoited onto a bare Au electrode surface This was considered to be a simpleuro yet practical means of creating inorgani( material microstructurps notably because it overcomes the inherent drawbatk of sol~gel materials namely brittleness The DNA probe with a phosphate group at its 5 end can he attached onto the ZrOl film surface which has a high affinity towardgt phosphate groups As the eurolectroactive 1 B is able to bind specifically to th( guaninr bases on the DNA mojpcules it can bc used ltIS an indicator in the eltdrocheuromkal DNA hybridshyization assay The steps involved in the fabrication of the probe DNA-modified electrode and the detection of a target spquence are illustrated schematicaliy in FIgure 722

Liu et al [45] haVE also developed) new method of immobilizing DNA based on the solmiddotmiddotmiddotgei technique In this experilllent d Zr01 gel-derived DNA-modified electrode was used as the working electrode with studies being (ondudpd of the electron tr3t1sfer of Dtl in LOmM potassium ferricyanide system in different cOrlcCntrations of lanthanum(HI) europium(III) and (jjkium(H) The ft~ults

showed that lanthanide ions could greatly expedite the elec~ron transfer rate of DNA in the Fe(CN)+ solution thp orde~ of effect being Eu i

gt La raquoCa l this

indicated that the lanhanide ions had a sronger interaction with tIw immobilized DNA than did the calcium ions with the order being consistent with the chargeionk radius ratio Th~ suggested reasons for tht effpct that lanthanidt ions had on current enhancemen included an e1petrostatk effect and ltl weak

2721 7 Preparation CharacteflzclOn and Potential Biomedical Appiiwtions

EN vs AgfAgCl

Figure 722 S~eps pvolved It the fabHalon of Ihe probe D~Al1odified electroce and the ce~ecton of a target seqlltence

coordination of thE La l ions to DNA Th negative charg on thE phosphate backshybones of DNA was seen to be- neutralized by the metals with posiiv charge~

which in turn decrtased the repulsion of the DNA-modified electrode surface to FCCN)r+ and led to an increase in the current

Four different types of layer-by-layer (LBL) film have been assembled on solid surfaces_ These have been designated as PDDA(ZrOj (PDDAZrOljrr PDDANPZrOn and [PDDAjPSSn where ZrO represents the zirconia sol~ gEl formed by a vapor~stHftcE sol-gel deposition 146J Among the four him typfS PDDAZrOlln demonstrated a bEttpr porosity and permeability and was capable of loading greater quantities of myoglobin (1b) from solution Because of the better porosity of this film the small counterions in the buffer solution could (nter and exit it mon easily and this resulted in the fUm having a better cyclic voltammiddot metry response according to the m(Chanism of clectron hopping The fact that the PDDAIfZrO)Jn~Mb films showed a larger surEce concentration of dectroac~ ttve Mb (r) than did the PDDAZrO)n-Mb films was probably becallse the of polyelectrolyte PDDA in the PDDAlZrOn films blocked some porcs or channels in the ZrOl byers Compared to the ZrOMbJn films which were directly assembled LBL by Mb and ZrO sol-gcl he advantage of the PDDAI Zr01n-Mb films is that any possible denaura~ion of Mb could be prevcnhd as its loading into the films was completely spontaneous Moreover any pussible djrect contacl of Mh with the organic solvent used in the vapor~SHrface sol~el deposition ofZrO) could bE avoiJed In this way Mb was able to retain its original stnKture and bioactivity

Today the interfaces between protein molecnles and inorganic materials arc among the ~hotest research topicS in biomedicine biochemistry biophysics and even in industrial applications If there is a need to modify a substrate surface with

References 1213

protein molecules the first step is to altquir( a complete understanding of the mechanism that underlies any sp~cific binding between the targtt~pc(lfic prottin and the target in a direct way Tomohiro Hayashi et al [47] have analyzed the adhesion force using AFM and revealed for the fir~t time the mechanism that underlies the specific binding between a titanium surface and ferritin that posshysesses the sequence of a Ti-binding peptide in lt~ t-middotterminal domain Based on such experimental data it can be concluded that the electrostatic interaClion between charged groups the hydrophobicity or hydrophHkiry of thcgt surface and

the ~urfactant addition each play imponarH roles in the sptcific hinding between the Ti-binding peptide (minTBP-l) and Ti Although the adhesion force decreases dramaticaJ1y in solution with the surfactant the nonspecific interactions are supshypressed and the specificity and selectivity of the minTlmiddotlF an enhanced dut to

accretion of the surfactant In conclusion nano-ZrOl films have been utilized tlS a solid support for the

immobilization ofbioactive molecules in biosensor applications due to their high thermalmechanicalchemical resistancp Excellent biocompatibility and their affinity to cerlain functional groups It is possibJe that the phase (whethpr tetra gomiddot Ita1 or monoclinic) morphology surface microstructure and crystallite size of ZrOJ thin fllms (ould vary with under different synthesis processes and this would result in ditlerences between the electrochemical properties and the biocompatishybilily of the ZrO~ films Although nanoZIO j exhibits many excel1cn characterismiddot tics the electrochemical properties and Diocom patibHily ofnanD- ZI01 in hiosensors remain inadequate 1t lS important therefore to explore new methods that can be used to improve the electrochemical properties and hiocompatibility of thp nanoshyZrO) surfaces

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16 StcLmov P Stoychev D Stochet3 M_ lkonomov J and Marlilova T (2000)

XPS and SEM charactertZdtion of zirconia thin films prepared by ele(tfOchem1(ol depoition 511ifaa umi [nurian Anuiysh 30 ()2H-ll

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24 Uchidd M Kim HM Kukubo L NdWL M Asano T TJf1aa K loa ~akamllr] T 20021 palitlforming ability of zinoniafalumina nano ~omtsite illdllUd hy (h(HlI(JI tr(atHlPoL

jOlml)-l or Bwmtdiml Muotui) ywcm fI 60 277~S2

2S UchidJ M Kiw PM Knkubo T

MlyaF r dlld ~akmllla T 20(2) Apalilt fonnation 011 zirtonlJm metal treated with aqaeou NaOH Bomalcnah 23 313~17

26 an l Hall Y and Lu C (200R) The e~kct of thcf1lKal treatment on 3pattemiddot f()rrrng ltlbihty or tht rnanoporous

zrmnil filrr rOrlwd by microart DxiJlt-ltion Appid Surj(J(t S(icnn 254 41B3-9_

21 SvctilL M Ciacchi LC Sbaiz(ro 0 Mcrimi S ami De Vita gt (2001) Dq)o-Ition of calntHn i()n~ on flJt1(

(110) J firt pnnciples ilVCslig)tioc A ta MultTluiu 49 2169~77

28 LL P OhtsllkJ c Kokuho T Nakmigtill K Sop N and GrooL K illY4) The role ofl~ydralnj ilie] tihUli1 and alHrtlinu If illdtUlg ltIfltlte nil implmis ourml of BiomGliwl M(ltrioIh Rtseur(fI 28 )-15

29 Vavssiamprrs L ChanC3c C TronE E ano

J01i(L JP (1998) Size Tailoring of nagrwtil( rlartlCles (ormed by Jqt(ous

precipitation In cxa01rkmiddot of therrnodynamt( stability of ndtlomdrlc oxide rartjc1e~ journal CO(lid amJ lntrrfuo Srtnn 20S 205-12

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31 L(nida M Kim U1 Kokuho T TunaKa K and Nakamura T (2002) Structural dppPJldeH(( of iipiiJitl

formation on zirconiJ g 1 0 slfnulalecl

lxxly l1uid Journal oj hr Cerami Socidy 0napao 110 710~1

32 Warf( G q LIl X and Ding C 200H) PbsI (Omp0ltHm and iHitro bioactivity or pla~fr1 spr3ypd (doltl tltlbili7~middotd

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41 Tum L Yuan K ChJi y Xif Y und Chen S (2007) A now am sin~pe

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43 Liu S Dai Z Ctwn H In] Ju H (2004) Immobilization of Jeuoglnbi1 on

zirCOnium d1uxidc ndnOplrtidcs for

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44 Zhu i_ Zhrlg A Wal1g Q He P anti Ful Y (2(J(4) Elcctmr1clt1kal dtlectloTl

of DNA h)bndiation u~il1A mcthylrnf blw- and (kttro-Jeposlted zirtonia thin films on gold (lrctrodcs Altaiytica Chimiw Acla 510 163~K

45 LiLl S XII J and Cfwn H (2002J ZrO gcl-clericd DNAmiddotmodifled (lrcmde )nd

the effed of lanthamdc or its ccctron transfer )(~lavI0L Bi(leitrochotmlry 57

149--54

46 War~- G Iw Yi 3nd Hu N (2007)

Comp~alvc (gti(crodltlHltal study 01

11yolobin lodtci in dintf(nt type of Jat -h)- ayer asstmbly fihm Elca(Otnimicu Atta 53 207J~t)

4-7 Hayashi T Sa no K Shiba K Kumashiro Y IwahorL K Yal1dfl3 1

and l-Iar1 M (2006j Mc(haciMn

undcrlying specificity of protVTlgt

lltlrgeling illoff~anic mattriak Na)w Lftr~li S15-19

The Series The new book se ries Nanomaterials for tile Life Sc iences successor to

the highly acclaimed series Nanotechnology for the Life Scie nces provides an in-depth overview of all nanomaterial types and their uses in thE life sciences Ea ch volume is dedica ted to a specific material class and covers fu ndamentals synthesis and characterizat ion s trategies structure-property relationships and biomedica l applications The new se ries brings nanomaterials to the life scien tists and life science to the mate rials scie n tis ts so tha t synergies are seen and developed to the full est

Wri tten by inte rnat ional expe rts o f the var ious facets of th is exciting field of research the ten volumes of th is s ingle source of info rm ation comprehen sively cover the com plete range of nanoma te rials for medical biological and cybernetic applications The se ries is aimed at scienti sts of the following disciplines bio logy chemis try m aterials science physics bioengineering and medi cin e toge ther with cell biology biomedi cal engineering pharmaceu tical chemistry and toxicology both in academia and fundamental research as well as in pharmaceutical co m pa nies

Volume 5 Nanostructured Thin Films and Surfaces Volume 5 gives an inSight into thin film s and the ir applica tion to the

life sciences The topics covered range from d ip pen lithogra ph y to

application s of st imuli res ponsive fil m s The m aterials presented ra nge

from polyrneric to ceramic thin film s

For more information on NmLS please visit wwwNmLSwiley-vchde

Challa Kum ar IS w rrenly lhe Director of Nanofabncation amp Nonomalenals at the eMU for

Advanced MIcrostructu res and DeVices (CAM D) Baton Rouge USA He is also the Preslderlt and

CEO of Magnano Technologie s a company established to commerClOlize nanom aterials Jor appli cations in life sciences Hs research in terests are In delJelopmg novel syn the tic m ethods including

those based on m lcrofluidic reactors for multifunctional nanomatenas He has also been Involved

In the de velopment of innovat ive therapeutic amp diagnostic lools based on nanotechnology He has eight years of induSlfial RampD experience workmgfor Imperial Chemicalndustnes ar7d Umled

Breweries He is the founding Editor-m -ChiCf ofth e Journal of Biomedical Nanotechnology pubmiddot

Ished by Ametlcon Scientific publishers and Series editor for the len-volume book series Nanolemiddot

chngies f or he Life Sciences (NI LS) publIshed by Wileymiddot VCH

[58N978-3- 527-32155 -1

I I wwwwil ey-vchde 9 7 83527

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