TESTING METHODS FOR ANTIMICROBIAL ACTIVITY OF TiO2 ... · TESTING METHODS FOR ANTIMICROBIAL ACTIVITY OF TiO2 PHOTOCATALYST Siniša L. Markov, Ana M. Vidaković* University of Novi

APTEFF, 45, 1-283 (2014) UDC: 615.281:546.82+542.92’73 DOI: 10.2298/APT1445141M BIBLID: 1450-7188 (2014) 45, 141-152

Original scientific paper

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TESTING METHODS FOR ANTIMICROBIAL ACTIVITY OF TiO2 PHOTOCATALYST

Siniša L. Markov, Ana M. Vidaković*

University of Novi Sad, Faculty of Technology Novi Sad, Bulevar cara Lazara 1, 21000 Novi Sad, Serbia

In recent years, a lot of commercial TiO2 photocatalyst products have been develo-ped and extensively studied for prospective and safe antimicrobial application in daily life, medicine, laboratories, food and pharmaceutical industry, waste water treatments and in development of new self-cleaning and antimicrobial materials, surfaces and paints. This paper reviews the studies published worldwide on killing microorganisms, methods for testing the antimicrobial activity, light sources and intensities, as well as calculation methods usually used when evaluating the antimicrobial properties of the TiO2-based products. Additionally, some strengths and weaknesses of the available methods for testing the antimicrobial activity of TiO2 photocatalyst products have been pointed out.

KEY WORDS: antimicrobial activity, titanium dioxide, light sources, calculations,

testing methods

INTRODUCTION

Titanium(IV) oxide, TiO2, commonly known as titania or titanium dioxide, is natu-rally occurring oxide of titanium, which exists in three forms: rutile, anatase and brookite. All these forms are usually linked to minerals such as quartz, tourmaline, barite, hematite, silicates, feldspar, chalcopyrite, and sphene (1). Scientific studies have approved that ana-tase appears to be the most photoactive and stable for widespread applications, whereas rutile is photocatalytically less active, although it expresses photoactive selectivity in so-me cases (2). TiO2 powders have been used as a white pigment from ancient times. Also, it is widely used to provide whiteness in lacquers, plastic and paper. In addition, nanopar-ticles of titania are also used as an opacifier in textiles, leather, glass and porcelain ena-mels. Moreover, TiO2 is a permitted dye in the food industry as E171, and it is commonly found in pharmaceuticals, cosmetics, and skin care products (3). Since the magnificent discovery of photocatalytic cleavage of water on TiO2 electro-des in 1972 by Fujishima and Honda (4), this research field has received greater aware-ness in the recent years. The breakthrough work of Matsunaga et al. in 1985, reporting

* Corresponding author: Ana M. Vidaković, University of Novi Sad, Faculty of Technology Novi Sad, Bulevar

cara Lazara 1, 21000 Novi Sad, Serbia, e-mail: [email protected]



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the application of TiO2 photocatalysis for the destruction of Lactobacillus acidophilus, Saccharomyces cerevisiae and Escherichia coli using Pt-loaded TiO2, established for the first time antimicrobial properties of TiO2 (5). Since then, research efforts have been ma-de in order to improve the efficiency of the TiO2 photocatalysis by doping it with various metals (6,7) and nonmetals (8). There are many confirmed advantages of using photocatalytic methods. Firstly, all reactions are carried out under ambient temperature and pressure. Additionally, minerali-zation of organic compounds is completed in an environmentally friendly way without creating any secondary pollutants, as final reaction product. Also, TiO2 catalyst is charac-terized by non-toxicity, high stability and low cost (9). Because of the numerous benefits, TiO2 as a photocatalyst has been extensively studied, and its applications in medicine, water treatment, food and pharmacy have been reported (10). Although there are plenty of TiO2 coated products on the market with antimicrobial activity, there has been no standard method, except Japanese standard JIS Z2801:2000 (11), with good experimental basis suggested for testing antimicrobial activity. For this reason, researchers use different experimental setups, light sources, and calculations of the antimicrobial activity. The current review will focus on four important segments of studying and testing the antimicrobial activity of TiO2 photocatalyst: (i) photokilling mechanisms, (ii) experimen-tal setup, (iii) light sources and intensity, and (iv) calculation methods.

Photokilling mechanisms

The irradiation of TiO2 with ultraviolet light, whose wavelength is less than 385 nm, leads to generation of an electron-hole pair on the TiO2 surface. The electrons and holes react on the surface and convert water and oxygen into reactive oxygen species (ROS) such as hydroxyl radicals (•OH), superoxide ion (O2

•-) and hydrogen peroxide (H2O2) (12). The primary oxidizing agents are short-living hydroxyl radicals that can bind to the surface. Those hydroxyl radicals have significantly short life span (10-9), which prevents them from diffusing to a long distance. Consequently, only microbial cells that adhere to the surface of the TiO2 catalyst may react with the hydroxyl radical that usually causes the loss of membrane integrity (13). In turn, superoxide ions are long-lived, although due to the negative charge, they cannot penetrate into the cell membrane. The penetration is possible by hydrogen peroxide (14). In 1988, three years after publishing the first results of killing microbial cells by contact with the TiO2-Pt catalyst upon illumination with near UV light, the same group of scientists successfully constructed a practical photochemical device in which TiO2 pow-der was immobilized on an acetylcellulose membrane (15). An E. coli cell suspension following through the device was completely killed; therefore, Matsunaga and coworkers (5,15) proposed the first killing mechanism. They believed that direct photochemical oxidation of intracellular coenzyme A to its dimeric form was the reason of the decreases in the respiratory activities that led to cell death. In the next years, Saito et al. (16) pro-posed that TiO2 photochemical reaction leads to the disruption of the cell membrane and cell wall of Streptococcus sobrinus, caused by leakage of intracellular K+ ions. On the other hand, Sunada et al. (17) recommend that the primary cause of the cell death during



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the TiO2 photochemical reaction may be the destruction of the E. coli endotoxin, an integral component of the outer membrane. If the TiO2particles are sufficiently small, they can penetrate into the microbial cell, where the photocatalytic process takes place. Also, free TiO2 particles can attack intracellular components directly if it is enhanced with UV irradiation. This may lead to physical and chemical damages of DNA and RNA, causing the conversion of the pyrimidine and purine bases to carbon dioxide, ammonia and nitrate ions (18,19). Although there are at least three hypotheses of the antimicrobial effect of TiO2 photocatalytic reaction, that mechanism is still to be proved.

EXPERIMENTAL

Heterogeneous photocatalysis, an Advanced Oxidation Technology that uses light sources, commonly UV, and TiO2, has emerged in the last decade as an innovative method of disinfection. The antimicrobial activity of TiO2 has been assayed in several bacteria and yeasts including Escherichia coli (5,20-24), Lactobacillus acidophilus (5), Bacillus subtilis, Pseudomonas putida, Staphylococcus aureus, Listeria innocua (refe-rences in (23)), Enterobacter cloacae (25), Candida albicans (24), and Saccharomyces cerevisiae (5). On the other hand, only a few studies have explored the ability of TiO2 photocatalysis to inactivate resistant microbial forms such as fungal spores, protozoan cysts and oocysts or bacterial spores. The main reasons for this are the thickness and structure complexity of their wall. However, Maneerat and Hayata (26) have reported the antifungal effect of TiO2 against Penicillium expansum in fruit root and proposed the potential treatment for post-harvest disease control. Other researchers reported about the resistance of fungi spores including Fusarium sp. and Aspergillus niger (27,28,29). Zhao and coworkers (30) reported photocatalytic inactivation of Bacillus cereus spores. Also, it has been confirmed that TiO2 photocatalyst has antiviral activity, which is very important for the application of the photocatalysts in hospitals (20). Although the antimicrobial properties of the TiO2 photocatalyst have been established, it is difficult to compare results among authors due to different experimental setups. Different experimental setups are a consequence of the absence of a universal standard method with good practical settings. Generally, in the available literature there are at least three methods for testing the antimicrobial efficiency of TiO2 photocatalyst (17,20,24,31). The most used methods are thin-film method and adhesion-test method with film, while the inhibition-zone method has been recently used. During studying the antimicrobial effect of the TiO2 photocatalyst, Sunada et al. (17,32) have mainly used the thin film method. TiO2 thin films were prepared by conventional dip-coating technique on silica-coated soda-lime glass plate. The coated glass was placed on a Petri dish and 150 μl of the E. coli cell suspension was applicated onto it. The system was put in a chamber and irradiated upon Pyrex window. In order to maintain the humidity, 10 ml of water was poured below the Petri dish (Figure 1a). This group of scientists has obtained the complete sterilization within one hour of the irradia-tion. In the absence of TiO2, the UV irradiation caused only 50 % sterilization in 4 hours. The same experimental setting has been extensively used in the next years (20,23).



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The same group of workers modified the previous system in order to improve it (17, 32). Namely, they separated 2 ml of the E. coli cell suspension from the TiO2 surface by a porous 50 µm thick PTFE membrane (Figure 1b). Also, the complete system was irradiated from below. According to the obtained results, a similar antimicrobial efficien-cy was observed as in the system without the membrane. It is necessary to emphasize that the •OH reactive species are probably deactivated before traversing the 50 µm thickness, due to their short life (13). Therefore, other active oxygen species (O2

•- and H2O2) are responsible for the sterilization in the membrane system (12).

(a) (b) Figure 1. Schematic illustration of the irradiation system for antimicrobial testing of the

photocatalyst: thin film method (a) Petri dish system and (b) PTFE membrane-separated system

The adhesion test with film is a newly developed method by Kim and coworkers (31). They placed the photocatalytic product (TiO2) coated glass, paper and plastic on a Petri dish. Afterwards, 0.5 ml of the E. coli cell suspension was placed onto them. The adhe-sion film was placed on the suspension in order to facilitate the attachment of the micro-organism to the TiO2 surface. Everything was covered with the Petri dish lid in order to maintain the humidity at more than 90 %. In the work, three types of the adhesion film were used: polyethylene (PE), polypropylene (PP) and acrylic. The Black Light Blue (BLB) lamps were used for light irradiation and positioned above the Petri dish (Figure 2). The antimicrobial efficacy of TiO2 coated glass, paper and plastic was determined by adhesion film method after 3 hours of irradiation, and it was 99.5 %, 99.8 % and 60 %, respectively. Also, the PP film was determined to be optimal adhesion film for this method. The adhesion film method is relatively new, although its application has been reported (31,33). Two groups of researchers (29,34) employed the inhibition zone method in order to test the antimicrobial activity of the TiO2-coated products upon UV irradiation. The inhibition zone method, also called Kirby-Bauer Test, is usually used clinically to measure antibiotic resistance, as well as industrially in order to test the ability of solids and textiles to inhibit microbial growth. In this method, sterilized culture media is poured in Petri dishes and, after solidification of the media the suspension of test microorganism is spread on the plate using an L-rod. The TiO2 coated products are placed into the Petri



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dishes with the coated zone on the culture media and incubated. After the incubation period, diameter of the inhibition zone (the zone without microbial growth) is measured (Figure 3) (29,34).

Figure 2. Schematic illustration of the photocatalytic TiO2 adhesion test method

Figure 3. Inhibition zone method for antimicrobial testing of

photocatalytic activity of TiO2

Light sources and intensity

In 1877, Downes and Blunt (35) discovered by chance that sunlight could kill bac-teria. They noticed that sugar water placed on the window remained cloudy in the night, while in the sun the water became clear. By microscopy, they determined that the number of bacteria was significantly higher during the night than during the day. In 1892, Mar-



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shall Ward demonstrated that the bactericidal actions were from the ultraviolet part of the light spectrum. Since then, the application of UV light is widespread in many areas such as: medicine, laboratory sterilization, food and pharmacy industry, etc. (10,36). Photocatalysis, especially with TiO2, is a modern method for inactivating microbes on surfaces. In order to manifest its photocatalytic and antimicrobial effect, TiO2 requires light as an excitation source. If the photocatalysis is used indoor, it is necessary to take all the protective steps. According to The American Conference of Govermental Industrial Hygiensts (ACGIH) for safety indoor application, UVA (ultraviolet radiation at 320-400 nm) exposure must be less than 10 W/m2 for periods lasting more than 1000 s (30). Because of the ACGIH requirements, the light irradiance effect on photocatalysis is very important. Rincon and Pulgarin reported about an effect of UVA and UVA/TiO2 inactivation (37). Namely, the study showed linear trends for the UVA inactivation alone and nonlinear trends for combined inactivation with UVA and photocatalyst. Based on the obtained results, they first suggested the presence of an optimum between the light intensity and duration of irradiation (37). Another explanation was proposed by Zhao et al. (30), who considered the generation of ROS by the photocatalyst upon UV irradiation. When UVA irradiation is low, the generation rate of ROS by UVA is low as well. The increase in the UVA irradiance increases the energy input and the rate of ROS genera-tion. On the other hand, the radical generation by photocatalysis requires very low energy input, and is therefore predominant at low UVA irradiation. When the UVA irradiation is high, the effectiveness of the photocatalysis is usually reduced (30). Therefore, Kim et al. (31) determined the optimal light intensity and irradiation time for testing the antimicro-bial activity of TiO2 photocatalysis to be 1.0 mW/cm2 and 3 hours, respectively. Rajsgo-pal et al. (37) also reported that the light intensity affects not only the photoinactivation rate, but also the behavior of bacteria after stopping irradiation. Namely, after the irradia-tion of TiO2 coated samples, the number of bacteria keeps decreasing in the dark. Never-theless, the recovery of bacteria is observed on the samples without TiO2. Also, inactiva-tion of the bacterial cells on the samples without catalyst addition was more affected by the increase in the intensity as compared to the photocatalytic system (37). However, one of the biggest problems in this area is the presence of non-comparable results of antimicrobial effect among authors. Different authors use different microorga-nisms, photocatalysts, light sources, irradiation intensities and time, as well as distances between the samples and light sources during testing. A choice of experimental condi-tions of some researchers is presented in Table 1. Testing the antimicrobial activity of TiO2 photocatalysts is performed using at least five different light sources (Table 1). Additionally, the irradiation intensity is in the range from 0.1 to 30 W/m2, while the irradiation time varies from 0 to 1440 minutes. Also, big oversight of the experiments is the distance between the tested samples and the light source, which is reported only in a few papers (Table 1). Moreover, the number of light sources is different from paper to paper, and it varies from one to sixteen (23-25, 30-31). In the future, all these parameters have to be optimized and even standardized in order to allow the work to be repeated by others.



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Table 1. Chosen experimental light settings for testing the antimicrobial efficiency of TiO2-based photocatalysts

* Total flux (kW)

Calculation methods

Generally, both qualitative and quantitative assessments of the antimicrobial efficacy of the TiO2-based photocatalysts have been performed. A qualitative estimation of the antimicrobial efficacy of the TiO2-based photocatalyts is obtained by comparison of the Petri dishes inoculated with the irradiated and non-irradiated suspension of the test micro-organism taken from the coated surface of the photocatalyst (37). Also, Chung et al. (41) suggested comparison of the inoculated Petri dishes after testing samples with and without TiO2. The same group of researchers employed JIS Z2801:2000 as a standard to test the antimicrobial efficacy (40,41). According to the Japanese standard, the results of a quan-titative evaluation of the antimicrobial efficacy should be calculated as follows (11):

NA=CA×DA×VA [1] R = [log(NB/NA) – log(NC/NA)] = [log(NB/NC)] [2]

where: NA – the number of viable bacteria after inoculation, CA - the number of bacteria colonies, DA - the fold of dilution, VA - the volume (ml) of the dilute buffer, R - antimic-robial activity, NB - the number of viable bacteria of the uncoated sample after irradia-tion, NC - the number of viable bacteria of the coated sample after irradiation. This kind of qualitative evaluation of the antimicrobial activity is performed by many researchers with or without small modifications (24,39,41). An obvious oversight of the proposed calculation is not taking into account the number of viable bacteria after inocu-

Test microorganism Photocatalyst Light Irradiation

intensity (W/m2)

Irradiation time (min)

Distance (cm)

Ref.

Bacterial biofilm TiO2 Polychromatic 250* 2-10 15 (37) E. coli (ATCC 8739) Degussa P25 UVA 0.1 0-360 / (31)

E. coli (ATCC25922), S. aureus, P. putida, L. innoua

Degussa P25 UVA 9 30-300 10 (23)

B. cereus (ATCC 2) Degussa P25 Solar 30 150-330 / (30) E. coli K-12 Degussa P25 UVA 8 30 / (22) P. expansum TiO2 UVA 0.1 72 / (26)

E. coli Ag2O/TiON Metal-halogen 0.16 30 / (38) E. cloacae Degussa P25 UVA 0.55 40 / (25)

P. aeruginosa TiO2 UVA 0.08 330-1440 33 (39) E. coli, P. aeruginosa, S. aureus, S. cerevisiae, C.

albicans, A. niger TiO2 Sodium 0.04* 240 10 (28)

S. aureus, S. flexneri, A. baumannii

C/TiO2 Incandescent 9 40 5 (40)

E. coli, P. aeruginosa, S. aureus, E. faecium, C.

albicans Degussa P25 UVA 2 x 0.015* 60 / (24)



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lation, NA (Eq. (2)). This parameter is very important to get an objective picture of the bacterial number reduction in all steps of the experiment. Pal et al. (42) proposed the bacterial inactivation efficiency followed first order ki-netics with respect to bacterial colony count (Nt), which is shown by Eq. (3):

ln(Nt/N0)= -kt [3] where: Nt - the number of CFUs (Colony-forming units) after irradiation for t min, N0 - the number of CFUs at 0 min, k - the inactivation rate constant, Nt/N0 - the survival ratio. The survival ratio was calculated by normalizing the resultant CFUs on any plate to that on the plate without exposure to light. On the other hand, Kim et al. (31) suggested that the inactivation percentage is a sufficient indicator of the antimicrobial activity of TiO2-based photocatalyst and the inactivation ratio should be calculated as:

Ir (%) = ((Ma-Mb)/Ma) ×100 [4] where: Ir - inactivation ratio, Ma - the initial concentration of microorganism, Mb - the concentration of the microorganism on the TiO2 coated sample. The results of the antimicrobial activity of TiO2-based products in the inhibition zone method are accessible as millimeters of the zone around the test sample without the mic-robial growth (the inhibition zone) (34). An improvement in measuring the inhibition zone is recently published by Vučetić et al. (29). The group of researchers imported the images of the Petri dishes after the incubation period into the software Matlab R2012a, where the images were converted to binary images. The percentage of the surface covera-ge is calculated by a specifically designed program code, which determines the ratio of the black and white pixels. The black pixels correspond to the surface covered with mic-robial growth (29). This kind of calculation of the antimicrobial efficacy of the TiO2-ba-sed products is significantly simplier and easier. Moreover, subjective error is remarkably reduced by using the designed program code.

CONCLUSIONS

This study reviews the killing mechanisms, experimental setups for testing the anti-microbial efficiency of TiO2 coated, light sources and intensity, as well as the pertaining calculation methods. On analyzing the investigations that have been done worldwide, it clearly comes out that great effort should be put in the optimization and improvement of all segments of the available antimicrobial testing methods of TiO2 photocatalysts. In the future, a new testing method with good settings basis that can be used in many research fields should be developed. In that way, the problem of the comparison of the obtained results among researches could be solved.



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Acknowledgement

The financial support of the Ministry of Education, Science and Technological Deve-lopment of the republic of Serbia (Contract No. III45008) and of the Provincial Secreta-riat for Science and Technological Development of Vojvodina Region (Contract No 114-451-3426/2013-02) are gratefully acknowledged.

REFERENCES

1. Dubrovinsky, L.S., Dubrovinskaia, N.A., Swamy, V., Muscat, J., Harrison, N.M.,

Ahuja, R., Holm, B. and Johansson B.: Materials Science: The Hardest Known Oxide. Nature 410 (2001) 653-654.

2. Hoffman, M.R., Martin, S.T., Choi W. and Babnemann, D.W.: Environmental Applications of Semiconductor Photocatalysis. Chem. Rev. 95 (1995) 69-96.

3. Frazer, L.: Titanium Dioxide: Environmental White Knight. Helath Perspect. 109, 4 (2001) 174-177.

4. Fujishima, A., Honda, K.: Electrochemical photolysis of water at a semiconductor electrode. Nature 238 (1972) 37-38.

5. Matsunaga, T.R., Tomoda, Y., Nakajima, T. and Wake, H.: Photochemical Steriliza-tion of Microbial Cells by Semiconductor Powders. FEMS Microbiol. Lett. 29 (1985) 211-214.

6. Karvinen, S.M.: The Effects of Trace Element Doping on the Optical Properties and Photocatalytic Activity of Nanostructured Titanium Dioxide. I&ЕC Research 42, 5 (2003) 1035-1043.

7. Skorb, E.V., Antonouskaya, L.I., Belyasova, N.A., Shchukin, D.G., Möhwald, H. and Sviridov, D.V.: Antibacterial Activity of Thin Film Photocatalysts Based on Metal-Modified TiO2 and TiO2:In2O3 Nanocomposite. Appl. Catal. B- Environ. 84, 1-2 (2008) 94-99.

8. Yu, J.C., Ho, W., Yu, J., Yip, H., Po, K.W. and Zhao, J.: Efficient Visible-Light-Induced Photocatalytic Disinfection on Sulfur-Doped Nanocrystalline Titania. Envi-ron. Sci. Technol. 39, 4 (2005) 1175-1179.

9. Markowska-Szczupak, A., Ulfig, K., Morawski, A.W.: The Application of Titanium Dioxide for Deactivation of Bioparticulates: An overview. Catal. Today 169, (2011) 249-257.

10. Gamage, J. and Zhang, Z.: Applications of Photocatalytic Disinfection. Inter. Jour. of Photoen. 2010 (2010) 1-11.

11. JIS Z2801: 2000, Japanese Industrial Standard (2001). 12. Srinivasan, C. and Somasundaram, N.: Bactericidal and Detoxification Effects of Irra-

diated Semiconductor Catalyst, TiO2. Current Sci. 85, 10 (2003) 1431-1438. 13. Gogniat, G., Thyssen, M., Denis M., Pulgarin, C. and Dukan, S.: The bactericidal

effect of TiO2 photocatalysis involves absorption onto catalyst and the loss of mem-brane integrity. FEMS Microbiol. Lett. 258 (2006) 18-24.

14. Banerjee, S., Gopal, J., Muraleedharan, P., Tyagi, A.K. and Raj, B.: Physis and che-mistry of photocatalytic titanium dioxide: Visualization of bacterial activity using ato-mic force microscopy. Curr. Sci. 90 (2006) 1378-1383.



150

15. Matsunaga, T.R., Tomoda, Y., Nakajima, T., Nakamura, N., and Komine, T.: Conti-nuous-Sterilization System That Uses Photosemiconductor Powders. Appl. Environ. Microbiol. 54 (1988) 1330-1333.

16. Saito, T., Iwase, T. and Morioka, T.: Mode of photocatalytic bactericidal action of powdered semiconductor TiO2 on mutans streptococci. J. Photochem. Photobiol. B-Biol. 14 (1992) 369-379.

17. Sunada, K., Kikuchi, Y., Hashimoto, K. and Fujishima, A.: Bactericidal and Detoxifi-cation effects of TiO2 thin film photocatalysts. Environ. Sci. Technol. 32 (1998) 726-728.

18. Gogniat, G. and Dukan, S.: TiO2 photocatalysis causes DNA damage via Fenton Reaction-Generated Hidroxyl Radical during the recovery period. Appl. Environ. Microbiol. 73 (2007) 7740-7743.

19. Hirakawa, K., Mori, M., Yoshida, M., Oikawa, S. and Kawanishi, S.: Photo-irradiated titanium dioxide catalyzes site specific DNA damage via generation ofhidrogen pero-xide. Free. Radic. Res. 38 (2004) 349-355.

20. Ditta, I.B., Stelle, A., Liptrot, C., Tobin, J., Tyler, H., Yates, M.H., Sheel, D.W. and Foster, H.A.: Photocatalytic antimicrobial activity of thin surface films of TiO2, CuO and TiO2/CuO dual layers on Escherichia coli and bacteriophage T4. Appl. Mic-rob.Cell Physiol. 79 (2008) 127-133.

21. Coleman, H.M., Marquis, C.P., Scott, J.A., Chen, S.S. and Amal, R.: Bactericidal effects of titanium dioxide-based photocatalysts. Chem. Engineer. J. 113 (2005) 55-63.

22. Maness, P.C., Smolinski, S., Blake, D.M., Huang, Z., Wolfrum E.J. and Jacoby, W.A.: Bactericidal activity of photocatalytic TiO2 reaction: toward an understanding of its killing mechanism. Appl. Environ. Microbiol. 65, 9 (1999) 4094-4098.

23. Bonetta, S., Bonetta, S., Motta, F., Strini, A. and Carraro, E.: Photocatalytic bacterial inactivation by TiO2 coated surfaces. AMB Express 3, 59 (2013) 1-8.

24. Kuhn, K.P., Chaberny, I.F., Massholder, K., Stickler, M., Benz, V.W., Sonntag, H.G. and Erdinger, L.: Disinfection of surface by photocatalytic oxidation with titanium dioxide and UVA light. Chemosphere 53 (2003) 71-77.

25. Ibanez, J.A., Litter, M.I. and Pizarro, R.A.: Photocatalytic bactericidal effect of TiO2 ON Enterobacter cloacae Comparative study with other Gram (-) bacteria. J. Photo-chem. Photobiol. A-Chem. 157 (2003) 81-85.

26. Maneerat, C. and Hayata, Y.: Antifungal activity of TiO2 photocatalysis against Peni-cillium expansum in vitro and in fruit tests. Inter. Jour. Food Microbiol. 107 (2006) 99-103.

27. Polo-Lopez, M.I., Fernandez-Ibanez, P., Garcia-Fernandez, I., Oller, I., Salgado-Tran-sito, I. and Sichel, C.: Resistance of Fusarium sp spores to solar TiO2 photocatalysis: influence of spore type and water (scaling-up results). J. Chem. Technol. Biotechnol. 85 (2010) 1038-1048.

28. Seven, O., Dindar, B., Aydemir, S., Metin, D., Ozinel, M.A. and Icli, S.: Solar photocatalytic disinfection of a group of bacteria and fungi aqueous suspensions with TiO2, ZnO and Sahara desert dust. J. Photochem. Photobiol. A-Chem. 165 (2004) 103-107



151

29. Vučetić, S.B., Rudić, O.L., Markov, S.L., Bera, O.J., Vidaković, A.M., Skapin, A.S. and Ranogajec, J.G.: Antifungal assesment of the TiO2 coating on facade paints. Environ. Sci. Pollut. Res. Int. (2014), DOI 10.1007/s11356-014-3066-6.

30. Zhao, J., Krishna, V., Hua, B., Moudgil, B. and Koopman, B.: Effect of UVA irradi-ance on photocatalytic and UVA inactivation of Bacillus cereus spores. J. Photochem. Photobiol. B-Biol. 94 (2009) 96-100.

31. Kim, J.Y., Park, C. and Yoon, J.: Developing a test method for antimicrobial efficacy on TiO2 photocatalytic products. Enciron. Eng. Res. 13 (2008) 136-140.

32. Sunada, K., Kikuchi, Y., Iyoda, T., Hashimoto, K. and Fujishima, A.: Photocatalytic bacterial effect of TiO2 thin films dynamic view of the active oxygen species respon-sible for the effect. J. Photochem. Photobiol. A-Chem. 106 (1997) 51-56.

33. Kim, D.S. and Kwak, S.Y.: Photocatalytic inactivation of E. coli with mesoporous TiO2 coated film using the film adhesion method. Environ. Sci. Technol. 43 (2009) 148-151.

34. Sarachandra , N., Pavithra, M. and Sivakumar, A.: Antimicrobial applications of TiO2 coated modified polyethylene (HDPE) films. Arch. Appl. Sci. Res. 5 (2013) 189-194.

35. Downes, A. and Blunt, T.P.: Researches on the effect of light upon bacteria and other organisms. Proceedings of the Royal Society of London 26 (1877) 488-500.

36. Trapani, S.R.: Room sterilization method and system. Patent Application Publication, Pub. No.: US2012/0282135 A1 (2012).

37. Rajsgopal, G., Maruthamuthu, S., Mohanan, S. and Palaniswamy, N.: Biocidal effects of photocatalytic semiconductor TiO2. Colloids Surfaces B. 51 (2006) 107-111.

38. Wu, P., Xie, R., Imlay, K. and Shang, J.K.: Visible-light induced Bactericidal Activity of Titanium Dioxide Co-doped with Nitrogen and Silver. Environ. Sci. Technol. 44 (2010) 6992-6997.

39. Radeka, M., Markov, S., Lončar, E., Rudić, O., Vučetić, S., Ranogajec, J.: Photocata-lytic effects of TiO2 mesoporous coating immobilized on clay roofing tiles. J. Eur. Ceram. Soc. 34 (2014) 127-136.

40. Cheng, C., Sun, D.S., Chu, W.C., Tseng, Y.H., Ho, H.C., Wang, J.B., Chung, P.H., Chen, J.H., Tsai, P.J., Lin, N.T., Yu, M.S. and Chang, H.H.: The effects of the bacterial interaction with visible-light responsive titania photocatalyst on the bacteri-cidal performance. J. Biomed. Sci. 16 (2009) doi:10.1186/1423-0127-16-7.

41. Chung, C.J., Lin, H.I. and He, J.L.: Antimicrobial efficacy of photocatalytic TiO2 coa-tings prepared by arc ion plating. Surf. Coat. Tech. 202 (2007) 1302-1307.

42. Pal, A., Pehkonen, S.O., Yu, L.E. and Ray, M.B.: Photocatalytic inactivation of Gram-positive and Gram- negative bacteria using fluorescent light. J. Photochem. Photobiol. A-Chem. 186 (2007) 335-341.



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МЕТОДЕ ЗА ИСПИТИВАЊЕ АНТИМИКРОБНЕ АКТИВНОСТИ TiO2 ФОТОКАТАЛИЗАТОРА

Синиша Л. Марков, Ана М. Видаковић

Универзитет у Новом Саду, Технолошки факултет Нови Сад, Булевар цара Лазара 1, 21000 Нови Сад, Србија

Током последњих година развијају се бројни комерцијални производи на бази фотокаталитичког TiO2 чије се антимикробне активности интензивно испитују у циљу њиховог потенцијалног и безбедног коришћења у свакодневном животу, медицини, лабораторијама, индустрији хране и лекова, третману отпадних вода као и у развоју материјала, површина и боја са функцијом самочишћења и антимик-робним својствима. У овом раду направљен је преглед публикација које су објав-љене широм света о механизму умирања ћелија микроорганизама, методама за ис-питивање антимикробне активности, изворима и интензитету зрачења, као и мето-дама изражавања резултата које се најчешће користе приликом испитивања анти-микробног деловања продуката на бази TiO2. Осим тога, указане су предности и мане тренутно коришћених метода за испитивање антимикробне активности про-дуката на бази TiO2.

Кључне речи: антимикробна активност, титанијум диоксид, извори зрачења, про-

рачуни, методе испитивања

Received: 17 September 2014. Accepted: 21 October 2014.

TESTING METHODS FOR ANTIMICROBIAL ACTIVITY OF TiO2 ... · TESTING METHODS FOR ANTIMICROBIAL ACTIVITY OF TiO2 PHOTOCATALYST Siniša L. Markov, Ana M. Vidaković* University of Novi

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