Cells adhesion and growth on gold nanoparticle grafted glass

Applied Surface Science 307 (2014) 217–223

Contents lists available at ScienceDirect

Applied Surface Science journal homepage: www.elsevier.com/locate/apsusc

Cells adhesion and growth on gold nanoparticle grafted glass Zdenka Novotna a,∗ , Alena Reznickova a , Ondrej Kvitek a , Nikola Slepickova Kasalkova a , Zdenka Kolska b , Vaclav Svorcik a a b

Department of Solid State Engineering, Institute of Chemical Technology Prague, 166 28 Prague, Czech Republic Faculty of Science, J. E. Purkynˇe University, Ústí nad Labem, Czech Republic

a r t i c l e

i n f o

Article history: Received 25 November 2013 Received in revised form 27 March 2014 Accepted 2 April 2014 Available online 13 April 2014 Keywords: Glass Gold sputtering Gold nanoparticle grafting Surface properties Cell adhesion and proliferation

a b s t r a c t The surface of glass substrate was plasma treated, coated by gold nano-structures and subsequently grafted with nanoparticles. The samples were plasma treated, sputtered with Au nanostructures which was followed by grafting with biphenyl-4,4 -dithiol (BPD) and then gold nanoparticles. The wettability, optical and chemical properties and surface morphology were studied. The adhesion and proliferation of vascular smooth muscle cells (VSMCs) on the samples were investigated in-vitro as well. Grafting of gold nanoparticles with the dithiol increases the UV–vis absorbance, the surface becomes more hydrophobic, rougher and more rugged compared to pristine, sputtered and only dithiol treated surface. Gold nanoparticles bound over dithiol and Au nanostructures cause better cell proliferation than purely BPD treated or pristine glass. © 2014 Elsevier B.V. All rights reserved.

1. Introduction Noble metal nanoparticles have unique electronic, optical, and catalytic properties. The integration of metal nanoparticles into thin films is particularly important for various applications, for example in tissue engineering, biological sensing and in the preparation of electronic nano-devices [1–4]. Gold nanoparticles (AuNPs) are very used metal nanoparticles. AuNPs have several distinctive physical and chemical attributes; their optical [5] and electrochemical properties [6] and catalytic activity are different from bulk gold. Other versatile features of AuNPs include chemical inertness, simple preparation, modification, and control of particle size. AuNPs colloidal gold particles of size ranging from ca 1 to ca 100 nm in size [7,8]. AuNPs are approximately four orders of magnitude smaller than human cells and as such they are of appropriate dimensions for applications in tissue engineering [9]. Particularly, nanoparticles may interact with biomolecules (e.g. enzymes, receptors, antibodies, DNA) and cells, but they are also very attractive candidates for use as carriers in medical diagnosis and treatment [10,11]. Moreover, AuNPs are known to possess very low or no cytotoxicity effect on cells making them useful for nano-medicine applications [12]. The use of AuNPs in biological environment requires the improvement their stability using ligands [13,14]. Noble metal

nanoparticles were chiefly modified by thiols [13–15], disulfides [16], amines [5], phosphines [17], carboxylic acids and mercaptoalkanoic acid derivatives [14]. Sulfur possesses a huge affinity to metal surfaces and organosulfur compounds will therefore adsorb spontaneously [18]. The metal/sulfur interaction is strong enough to immobilize the thiol-groups on the surface of metal nanoparticles. Thiol stabilized AuNPs can exhibit desired reactivities due to the variety of functionalizations and the strong Au S bond between the softly acidic Au and the soft thiolate base [19,20]. The formation of self-assembled mono- and multi-layer films of smallligand-stabilized metal nanoparticles enables applications such as separative layers and chemical sensors [20–22]. In this work, we have treated the glass with argon plasma and Au was subsequently sputtered on the samples under different conditions. The AuNPs were then grafted on the biphenyl-4,4 -dithiol (BPD) activated glass/gold surface. Surface changes were studied with several analytical techniques (UV–vis and XPS spectroscopy, AFM microscopy, contact angles and electrokinetic analysis). The influence of the plasma treatment, Au deposition, grafting with BPD and then with AuNPs on adhesion and proliferation of living cells was evaluated in vitro method.

2. Materials and methods ∗ Corresponding author. Tel.: +420 732301981. E-mail address: [email protected] (Z. Novotna). http://dx.doi.org/10.1016/j.apsusc.2014.04.017 0169-4332/© 2014 Elsevier B.V. All rights reserved.

The gold layers were sputtered on 1.8 × 1.8 cm2 borosilicate microscopic glass (supplied by Glassbel Ltd., CR).

218

Z. Novotna et al. / Applied Surface Science 307 (2014) 217–223

The samples were treated in direct current (DC, glow, diode) Ar+ plasma on Balzers SCD 050 device under the following conditions: gas purity 99.997%, flow rate 0.3 l s−1 , pressure 10 Pa, electrode distance 50 mm and its area 48 cm2 , chamber volume approx. 1000 cm3 , and plasma volume 240 cm3 . Exposure time was 240 s, discharge power 8.3 W, and the treatment was accomplished at room temperature. The samples were cleaned by nitrogen flow. The gold sputtering was accomplished on Balzers SCD 050 device from gold target (supplied by Goodfellow Ltd., England). The deposition conditions were DC Ar+ plasma, gas purity of 99.995%, sputtering time was 20 and 150 s at deposition current of 20 and 40 mA (discharge power 6.6 and 15.2 W), Ar+ pressure about 5 Pa, and electrode distance of 50 mm. Power density of Ar+ plasma in was 0.13 W cm−2 , the average deposition rate was 0.15 nm s−1 . The glass substrate was cleaned with pure methanol and dried in a stream of N2 . Immediately after sputtering, the samples were immersed in a methanol solution (4 × 10−3 mol l−1 ) of biphenyl-4,4 -dithiol (BPD) for 24 h [23]. Samples with grafted BPD (see Fig. 1) were cleaned with pure methanol and then immersed for 24 h into freshly prepared colloidal citrate stabilized solution of AuNPs (concentration ca 2.75 × 10−9 mol l−1 [24,25]). The average diameter of the spherically shaped nanoparticles was ca 15 nm (as determined by TEM). Finally, the samples were again rinsed with methanol and dried in a stream of N2 . UV–vis absorption spectra were measured using PerkinElmer’s Lambda 25 UV–vis-NIR Spectrometer in the spectral range 300–900 nm at scanning rate of 240 nm min−1 and data collection interval of 1 nm. A pristine glass slide was used for background measurement. The typical data uncertainty obtained under this arrangement is below ±5%. Static contact angles (CA) of distilled water (pH = 6.0), characterizing structural and compositional changes caused by the gold deposition and by grafting process, were measured at room temperature on two samples and in seven positions using a Surface Energy Evolution System (SEES, Masaryk University, Czech Republic). Drops of 8.0 ± 0.2 ␮l volume were deposited using automatic pipette (Transferpette Electronic Brand, Germany) and their images were taken after a 5 s delay. Contact angles were then evaluated using SEES code.

Fig. 1. Schema of sample preparation: (A)—plasma modification, (B)—sputtering of Au, (C)—BPD treatment, (D)—grafting with AuNPs and (E)—cells adhesion and proliferation.

The chemical composition of prepared structures was determined from X-ray photoelectron spectra (ARXPS), measured by Omicron Nanotechnology ESCAProbeP spectrometer. X-ray source was monochromated at 1486.7 eV and area of 2 × 3 mm2 was exposed and analyzed. Spectra were measured stepwise with a binding energy step of 0.05 eV, the take off angles were 0◦ and 81◦ according to surface normal. The spectra evaluation was carried out

Fig. 2. Photographs of samples with sputtered Au (time 20 and 150 s, current 20 mA) and subsequently grafted with BPD and AuNPs: (i) deposition/BPD, (ii) plasma/deposition/BPD, (iii) deposition/BPD/AuNPs, and (iv) plasma/deposition/BPD/AuNPs.

Z. Novotna et al. / Applied Surface Science 307 (2014) 217–223

by CasaXPS software. Before the measurement the samples were stored under standard laboratory conditions. The surface morphology of glass and prepared structures was examined by Atomic force microscopy (AFM) using VEECO CP II system, surface roughness (Ra ) was measured in tapping mode with silicon P-doped probes RTESPA-CP with the spring constant of 0.9 N m−1 . By the repeated measurements of the same region (1 × 1 ␮m2 in area) we proved that the surface morphology did not change after three consecutive scans. Electrokinetic analysis of all samples was accomplished on SurPASS Instrument (Anton Paar GmbH, Austria) by a streaming current method and zeta potential was calculated by the Helmholtz–Smoluchowski equation (HS) [26]. Samples were studied inside the adjustable gap cell with a KCl electrolyte of 0.001 mol dm−3 concentration. All samples were measured 8 times at room temperature and at constant pH = 6.0 value with the relative error of 10%. The pH value is the same as at goniometry for better correlation of these two surface properties. For in vitro experiments, 4 samples from each modification and for selected time (20 and 150 s) of gold deposition were used. Glass samples with deposited Au were sterilized for 1 h in ethanol (70%), air-dried and inserted into polystyrene 12-well plates (TPP, Switzerland; well diameter 20 mm). 50 000 cells were seeded on each sample (i.e. about 16 000 cells cm−2 ) into 3 ml of Dulbecco’s modified Eagle’s Minimum Essential Medium (DMEM; Sigma, USA, Cat. No. D5648), containing 10% fetal bovine serum (FBS; Sebak GmbH, Aidenbach, Germany). Cells were cultivated at 37 ◦ C in a humidified air atmosphere containing 5% of CO2 . The number and the morphology of initially adhered cells and their viability was evaluated 24 h after seeding. The cell proliferation activity and their viability were estimated from the increase in the cell numbers

219

Fig. 3. UV–vis spectra: (i) dashed—glass/gold samples (sputtering time 20 and 150 s, current 20 mA), (ii) grafted with BPD (. . ./BPD) and (iii) grafted with AuNPs (. . ./BPD/AuNP).

Fig. 4. AFM images of plasma treated samples, Au sputtered (time 20 s, current 40 mA): (i) pristine glass (SiO2 ), (ii) plasma/20 s,40 mA, (iii) plasma/20 s,40 mA/BPD, (iv) plasma/20 s,40 mA/BPD/AuNPs.

220

Z. Novotna et al. / Applied Surface Science 307 (2014) 217–223

achieved on the 3rd and 6th day after seeding. The number and the morphology of the adhered and proliferated cells on the sample surface were then evaluated on microphotographs taken using an Olympus IX 51 microscope (obj. 20×; visualized area of 0.136 mm2 ), equipped with an Olympus DP 70 digital camera. The number of the cells was determined using the image analysis software NIS Elements. For each sample type, 20 independent measurements were performed. For viability analysis the cells were detached from the materials by a trypsin-EDTA solution (SigmaeAldrich, Cat. N T4174) and the viability were determined using by trypan blue dye exclusion method on Vi-CELL Series Cell Viability Analyzers.

Table 1 The dependence of the contact angle (in◦ ) on the conditions of gold sputtering (time 20 and 150 s, discharge current 20 mA) for gold-coated glass (SiO2 /plasma/Au), glass treated with BPD (SiO2 /plasma/Au/BPD), and glass subsequently grafted with AuNP (SiO2 /plasma/Au/BPD/AuNPs). The value of the contact angle for pristine glass (SiO2 ) was 59◦ .

3. Results and discussion

value of absorbance does not increase a lot, but the character of spectra changes considerably. The plasmon resonance peak diminishes which is caused by interconnection of the surface material. The outstanding grains of nanostructured Au can be washed away during the BPD treatment leading to formation of a smoother surface. The resulting spectra are much more similar to that of a bulk Au. After the grafting of AuNPs mean value of absorbance increases greatly as more Au is introduced to the surface and the thickness of the layer increases. The influence of surface modification on the morphology is further discussed in the section of AFM results. It is well known that cytocompatibility of substrates is strongly influenced by wettability of their surface. The changes in the contact angle of samples were determined by goniometry (see Table 1). All modified samples show increased values of contact angle. Contact angle of samples after BPD treatment and AuNPs grafting increases with higher time of Au sputtering. Grafting of AuNPs leads to increase of the hydrophobicity of the surface in comparison to samples with the sputtered layer only. Results of surface element concentration (XPS analyses) of plasma treated samples with sputtered gold nanostructures subsequently grafted with BPD and AuNPs are presented in Table 2. According to expectations increasing deposition current and time of deposition the amount of detected Si decreases as thicker layer of Au is created. Presence of S is proven on the samples treated with BPD so we can assume BPD was successfully bound to the Au nanostructures on the sample surface. Samples with grafted

Physico-chemical properties and cytocompatibility of glass/gold nanostructures then grafted with biphenyl-4,4 -dithiol and AuNPs were studied. Samples of glass were treated by plasma before gold sputtering to enhance adhesion of gold nanostructures. This is necessary, because of 6 days of exposure of the samples to aqueous medium during interaction with VSMCs. The improvement of gold adhesion was observed on substrates [27]. In Fig. 2 samples before (left) and after (right) plasma treatment are shown. It is obvious that plasma treatment leads to improvement of Au nanostructure adhesion to the glass surface. UV–vis spectra of samples glass/Au grafted with BPD and then with AuNP are shown in Fig. 3. It can be seen that with increasing time of deposition increase of absorbance takes place which is caused by increasing thickness (from 2.3 to 20.4 nm [28]) of sputtered Au layer. As sputtered samples show weak and broad plasmon resonance peak which suggests presence of nanosized Au grains of wide size distribution on the surface. After BPD introduction mean

Fig. 5. Zeta potential of plasma treated samples, Au sputtered (time 20 and 150 s, current 20 and 40 mA) and subsequently grafted with BPD and AuNPs: (i) pristine glass (SiO2 ), (ii) plasma/deposition, (iii) plasma/deposition/BPD, (iv) plasma/deposition/BPD/AuNPs.

Ausputtering time (s)

Sample

SiO2 /plasma/Au SiO2 /plasma/Au/BPD SiO2 /plasma/Au/BPD/AuNPs

20

150

67 78 84

77 79 87

Fig. 6. The number of VSMCs after different cultivation times (1st, 3rd and 6th day) on: (i) pristine glass (SiO2 ), (ii) plasma modified and gold-coated glass (20/150 s, 20/40 mA), (iii) plasma modified, gold-coated (20/150 s, 20/40 mA) and BPD treated glass, (iv) plasma modified, gold-coated (20/150 s, 20/40 mA), BPD treated and AuNPs grafted glass.

Z. Novotna et al. / Applied Surface Science 307 (2014) 217–223

221

Fig. 7. The photographs of VSMCs adhered (1st day after seeding) and proliferated (6th day after seeding) on plasma treated samples, gold-coated (time 20 s, current 20 mA) and subsequently grafted with BPD and AuNPs: (i) pristine glass (SiO2 ), (ii) plasma/20 s, 20 mA, (iii) plasma/20 s, 20 mA/BPD, (iv) plasma/20 s, 20 mA/BPD/AuNPs. Table 2 Element concentration of Si, C, O, S and Au determined by ARXPS method from different angles (0 and 81◦ ) of pristine (SiO2 ), plasma treated (pl) and Au sputtered (time 20 and 150 s, current 20 and 40 mA) glass and glass treated with BPD and subsequently grafted with AuNPs. Element concentration (at.%)

Sample Si (2s)

C (1s)

O (1s)

S (2p)

Au (4f)

◦

Angle ( )

SiO2 20 mA/pl/20 s 20 mA/pl/20 s/BPD 20 mA/pl/20 s/BPD/AuNPs 20 mA/pl/150 s 20 mA/pl/150 s/BPD 20 mA/pl/150 s/BPD/AuNPs 40 mA/pl/20 s 40 mA/pl/20 s/BPD 40 mA/pl/20 s/BPD/AuNPs 40 mA/pl/150 s 40 mA/pl/150 s/BPD 40 mA/pl/150 s/BPD/AuNPs

0

81

0

81

0

81

0

17.7 11.6 3.4 5.6 2.9 2.7 3.3 – – – – – –

10.8 1.9 2.4 9.6 10.8 6.3 – – – – – – –

23.4 33.2 64.0 61.0 38.7 57.6 60.7 53.5 63.4 69.3 48.9 62.5 72.8

68.7 58.2 76.0 68.3 64.2 69.2 81.8 68.8 79.5 86.9 65.5 73.4 85.7

49.5 30.6 10.2 12.9 5.8 4.4 5.2 11.8 4.8 6.6 8.3 4.4 11.3

18.2 3.6 6.7 12.8 7.1 5.5 4.0 10.4 9.7 7.6 6.3 6.2 7.8

– – 3.9 5.3 – 7.0 6.8 – 5.1 6.0 – 3.4 5.3

81 – – 8.4 5.7 – 10.7 8.2 – 6.1 3.4 – 7.4 3.4

0

81

– 21.8 18.5 15.2 51.3 28.3 24.0 34.7 26.7 18.1 42.8 25.8 10.6

– 36.3 6.5 3.6 17.9 8.3 6.0 20.8 4.7 2.1 28.2 12.9 3.1

222

Z. Novotna et al. / Applied Surface Science 307 (2014) 217–223

AuNPs showed lower amount of Au on the surface than samples just treated in BPD surprisingly. Further steps of sample preparation lead to decrease of detected Au concentration. The decrease is noticeable when comparing analyses carried out under different incident angles as well. In this case surface layer of 6–8 vs 1–2 atomic layers is studied. Table 2 shows dramatic increase of detected amount of C and O, which cannot originate just in the glass substrate, because after deposition at 20 mA only relatively low concentration was detected and in the case of 40 mA no Si was detected. Decrease of detected amount of Au after AuNPs grafting could be caused by increased concentration of carbon compounds bound to their surface during AuNPs preparation (stabilization agents). The presence of carbon can be attributed to contamination with hydrocarbons and other carbon-rich compounds from ambient atmosphere as well [29]. AFM method was used to study the influence of Au sputtering, BPD treatment and AuNPs grafting on surface morphology. The changes in morphology and roughness (Ra ) of samples are shown in Fig. 4. After Au sputtering surface roughness increases significantly and inhomogeneously distributed gold nanoclusters are formed on the glass. BPD treatment does not have significant effect on the value of Ra of the samples. Morphology of the surface is however altered as the surface becomes less rugged and rough. Sample with grafted AuNPs shows homogeneously distributed clusters. The value of Ra reaches its maximum in this case. The number of AuNPs bound to the sample surface determined from the AFM scans is 194 ␮m−2 with 15% relative error of measurement. Results of electrokinetic analysis are shown in Fig. 5. Deposition conditions have significant influence on the value of the surface zeta potential as with increasing deposition time and current zeta potential decreases due to formation of continuous Au film on the substrate. Grafting of BPD and AuNPs does not result in a decrease of zeta potential as could be expected due to presence of SH group and Au on surface. The reason is that the grafted amount of both agents is relatively low (confirmed by XPS measurement). BPD is bound to the surface only in a monolayer which is similar on all the surfaces. Therefore the value of zeta potential is alike after the BPD treatment for all the samples. The same is applied for subsequent AuNPs grafting. Influence of the presence of Au nanostructures, BPD treatment and grafted AuNPs on the cell adhesion (1st day) and proliferation (3rd and 6th day) of VSMCs is shown in Fig. 6. The largest amount of cells (ca 9500 cells cm−2 ) adhered to the surface after 24 h from seeding of cells in the case of samples with Au sputtered for 150 s at 20 mA and 20 s at 40 mA. Third day after seeding increased number of cells was observed on all samples. After 6th day of cultivation the largest number of cells was found on the samples with Au sputtered for 20 s at 20 mA and 20 s at 40 mA and on the sample with grafted AuNPs with Au layer sputtered for 20 s at 20 mA. Under these conditions discontinuous layer is created, which is more favorable for cell growth than a continuous Au layer [28]. The lowest amount of cells was found on pristine glass and on substrates after BPD treatment. Fig. 6 documents decreasing amount of cells with increasing time and current of Au sputtering. Grafting of AuNPs increases the number of cells compared to the deposited Au surface, depending on the conditions of deposition. In the case of deposition current of 20 mA the number of cells on the AuNPs is higher than on the deposited Au surface. The growth of the cells is improved after AuNPs grafting in comparison with samples just treated with BPD. Deviations of the number of cells are negligible for biological measurements [30]. Photographs of VSMCs after 1st day (adhesion) and 6th day (proliferation) of cultivation on pristine glass, plasma treated and gold-coated glass subsequently grafted with BPD and then with AuNPs are shown in Fig. 7. Cells on pristine glass after 6th day of cultivation have varying sizes and inhomogeneous distribution over the surface. Portion of the cells is not spread enough, portion of the

cells does not have physiological shape, tendency to form clusters is apparent. After AuNPs grafting, however, cells take their natural shape, size and spread homogeneously over the entire surface. Clusters of cells are not formed and they grow in contact with the substrate not forming multiple layers preferentially. Another factor to consider when considering usability of substrate is viability of the cultivated cells. The viability of the adhered (1st day after seeding) and proliferated (3rd and 6th day from cultivation) of cells is demonstrated in Fig. 8. The viability of cells on most samples is low (less than 80%) after 1 day of cultivation. The cells are still adapting to the new environment and many of them die. The changes in cell’s viability were detected after 3 days of cultivation. The viability of the proliferated cells was significantly increased on most samples (80–100%). The exceptions were the samples sputtered for 20 s at 20 mA and subsequently grafted with BPD and samples sputtered at 40 mA for 150 s and grafted with BPD. Viability of the cells cultivated on these sam-

Fig. 8. The values of viability of VSMCs cultivated 1st, 3rd and 6th day on: (i) pristine glass (SiO2 ), (ii) plasma modified and gold-coated glass (20/150 s, 20/40 mA), (iii) plasma modified, gold-coated (20/150 s, 20/40 mA) and BPD treated glass, (iv) plasma modified, gold-coated (20/150 s, 20/40 mA), BPD treated and AuNPs grafted glass.

Z. Novotna et al. / Applied Surface Science 307 (2014) 217–223

ples was lower (50–70%). The highest values of the viability of the proliferated cells were determined 6 days after seeding. Significantly lower values were detected on the samples modified by the plasma discharge and subsequently grafted with BPD. After 6th day of cultivation the viability of the cells range between 93 and 97% in the case of samples with sputtered Au. Cells on samples treated with BPD have viability of 67–80% after AuNPs grafting the viability raises to 77–96%. Short-time sputtering of Au increases the substrate attractivity for VSMCs dramatically, after BPD treatment the cytocompatibility drops considerably, after grafting of AuNPs it significantly raises again. It is evident that viability of cells is on average higher with increasing time of cultivation. These results could be very important for considerations in tissue engineering. 4. Conclusions Physico-chemical properties of the plasma treated, Au sputtered, BPD and AuNPs grafted glass samples were determined. The cytocompatibility of these samples with VSMCs was studied using in vitro method. Grafting of AuNPs through BPD increases the UV–vis absorbance, the surface is more hydrophobic and more rugged compared to surface with just sputtered Au. XPS measurements confirmed successful binding of BPD to Au sputtered surface. Subsequent AuNPs grafting leads to increase of detected C, which could originate from chemicals used during AuNPs synthesis. These results were confirmed by electrokinetic measurements as well. AFM documented grafted AuNPs form homogeneously distributed clusters, average roughness of the surface increases. Grafting of AuNPs to substrates treated in BPD leads to increase of cell proliferation. The highest amount of cells was observed for samples with Au layers sputtered for shorter times at lower currents. Sputtered Au nanostructures considerably increase proliferation of VSMCs on the glass substrate. Acknowledgment This work was supported by the GACR under project No. 108/12/G108. References [1] C.M. Niemeyer, Nanoparticles, proteins, and nucleic acids: biotechnology meets materials science, Angew. Chem. Int. Ed. 40 (2001) 4128–4158. [2] P.V. Kamat, Photophysical, photochemical and photocatalytic aspects of metal nanoparticles, J. Phys. Chem. B 106 (2002) 7729–7744. [3] A.N. Shipway, E. Katz, I. Willner, Nanoparticle arrays on surfaces for electronic, optical, and sensor applications, ChemPhysChem 1 (2000) 18–52. [4] A. Yu, Z.J. Liang, J. Cho, F. Caruso, Nanostructured electrochemical sensor based on dense gold nanoparticle films, Nano Lett. 3 (2003) 1203–1207. [5] K.L. Kelly, E. Coronado, L.L. Zhao, G.C. Schatz, The optical properties of metal nanoparticles: the influence of size, shape, and dielectric environment, J. Phys. Chem. B 107 (2003) 668–677. [6] J.M. Pingarron, P. Yanez-Sedeno, A. Gonzalez-Cortes, Gold nanoparticle-based electrochemical biosensors, Electrochim. Acta 53 (2008) 5848–5866.

223

[7] M.C. Daniel, D. Astruc, Gold nanoparticles: assembly, supramolecular chemistry, quantum-size-related properties, and applicatons toward biology, catalysis, and nanotechnology, Chem. Rev. 104 (2004) 293–346. [8] E. Boisselier, D. Astruc, Gold nanoparticles in nanomedicine: preparations, imaging, diagnostics, therapies and toxicity, Chem. Soc. Rev. 38 (2009) 1759–1782. [9] G.M. Whitesides, The ‘right’ size in nanobiotechnology, Nat. Biotechnol. 21 (2003) 1161–1165. [10] X. Huang, S. Neretina, M.A. El-Sayed, Gold nanorods: from synthesis and properties to biological and biomedical applications, Adv. Mater. 21 (2009) 4880–4910. [11] X. Huang, P.K. Jain, I.H. El-Sayed, M.A. El-Sayed, Plasmonic photothermal therapy (PPTT) using gold nanoparticles, Lasers Med. Sci. 23 (2008) 217–228. [12] K. Rahme, L. Chen, R.G. Hobbs, M.A. Morris, C. O’Driscoll, J.D. Holmes, PEGylated gold nanoparticles: polymer quantification as a function of PEG lengths and nanoparticle dimensions, RSC Adv. 3 (2013) 6085–6094. [13] M. Schulz-Dobrick, K.V. Sarathy, M. Jansen, Surfactant-free synthesis and functionalization of gold nanoparticles, J. Am. Chem. Soc. 127 (2005) 12816–12817. [14] S. Roux, B. Garcia, J.L. Bridot, M. Salome, C. Marquette, L. Lemelle, P. Gillet, L. Blum, P. Perriat, O. Tillement, Synthesis, characterization of dihydrolipoic acid capped gold nanoparticles, and functionalization by the electroluminescent luminol, Langmuir 21 (2005) 2526–2536. [15] M. Brust, M. Walker, D. Bethell, D.J. Schiffrin, R. Whyman, Synthesis of thiolderivatised gold nanoparticles in a 2-phase liquid–liquid system, J. Chem. Soc., Chem. Commun. 0 (1994) 801–802. [16] A. Ulman, Formation and structure of self-assembled monolayers, Chem. Rev. 96 (1996) 1533–1554. [17] G.H. Woehrle, L.O. Brown, J.E. Hutchison, Thiol-functionalized, 1.5-nm gold nanoparticles through ligand exchange reactions: scope and mechanism of ligand exchange, J. Am. Chem. Soc. 127 (2005) 2172–2183. [18] J.J. Gooding, F. Mearns, W.R. Yang, J.Q. Liu, Self-assembled monolayers into the 21st century: recent advances and applications, Electroanalysis 15 (2003) 81–96. [19] M. Giersig, P. Mulvaney, Preparation of ordered colloid monolayers by electrophoretic deposition, Langmuir 9 (1993) 3408–3413. [20] P. Slepicka, N. Slepickova-Kasalkova, L. Bacakova, Z. Kolska, V. Svorcik, Enhancement of polymer cytocompatibility by nanostructuring of polymer surface, J. Nanomater. (2012) 1–17. [21] G.A. DeVries, M. Brunnbauer, Y. Hu, A.M. Jackson, B. Long, B.T. Neltner, O. Uzun, B.H. Wunsch, F. Stellacci, Divalent metal nanoparticles, Science 315 (2007) 358–361. [22] R.A. Sperling, P. Rivera Gil, F. Zhang, M. Zanella, W.J. Parak, Biological applications of gold nanoparticles, Chem. Soc. Rev. 37 (2008) 1896–1908. [23] V. Svorcik, Z. Kolska, O. Kvitek, J. Siegel, A. Reznickova, P. Rezanka, K. Zaruba, Soft and rigid dithiols and Au nanoparticles grafting on plasma-treated polyethyleneterephthalate, Nanoscale Res. Lett. 6 (2011) 607–613. [24] P. Rezanka, H. Rezankova, P. Matejka, V. Kral, The chemometric analysis of UV–visible spectra as a new approach to the study of the NaCl influence on aggregation of cysteine-capped gold nanoparticles, Colloids Surf., A: Physicochem. Eng. Aspects 364 (2010) 94–98. [25] P. Rezanka, K. Zaruba, V. Kral, A change in nucleotide selectivity pattern of porphyrin derivatives after immobilization on gold nanoparticles, Tetrahedron Lett. 49 (2008) 6448–6453. [26] Z. Kolska, A. Reznickova, V. Svorcik, Surface characterization of polymer foils, e-Polymers 83 (2012) 1–13. [27] V. Svorcik, A. Chaloupka, K. Zaruba, V. Kral, O. Blahova, A. Mackova, Deposition of gold nano-particles and nano-layers on polyethylene modified by plasma discharge and chemical treatment, Nucl. Instrum. Methods Phys. Res., Sect. B: Beam Interact. Mater. Atoms 267 (2009) 2484–2488. [28] A. Reznickova, Z. Novotna, N. Slepickova-Kasalkova, V. Svorcik, Gold nanoparticles deposited on glass: physicochemical characterization and cytocompatibility, Nanoscale Res. Lett. 28 (2013) 252–259. [29] J. Siegel, M. Polivkova, N. Slepickova-Kasalkova, Z. Kolska, V. Svorcik, Properties of silver nanostructure-coated PTFE and its biocompatibility, Nanoscale Res. Lett. 8 (2013) 388–397. [30] Z. Ma, Z. Mao, C. Gao, Surface modification and property analysis of biomedical polymers used for tissue engineering, Colloids Surf., B: Biointerfaces 60 (2007) 137–157.