Surface Antimicrobial Effects of Zr61al7.5Ni10cu17.5Si4 Thin Film
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Fooyin J Health Sci 2010;2(1):12−20 ORIGINAL ARTICLE Surface Antimicrobial Effects of Zr61Al7.5Ni10Cu17.5Si4 Thin Film Metallic Glasses on Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, Acinetobacter baumannii and Candida albicans Pai-Tsung Chiang1,2*, Guo-Ju Chen1, Sheng-Rui Jian1, Yung-Hui Shih1, Jason Shian-Ching Jang3, Chung-Hsu Lai4 1Department of Materials Science and Engineering, I-Shou University, Kaohsiung, Taiwan 2Department of Plastic Surgery, Fooyin University Hospital, Pingtung, Taiwan 3Department of Mechanical Engineering, Institute of Materials Science and Engineering, National Central University, Chung-Li, Taiwan 4Department of Infectious Disease, I-Shou University, Kaohsiung, Taiwan Received: November 11, 2009 Revised: January 21, 2010 Accepted: February 8, 2010 Zr61Al7.5Ni10Cu17.5Si4 (ZrAlNiCuSi) thin film metallic glasses (TFMGs) can modify the surface of 304 stainless steel, and they are widely used in health care systems. We investigated modified surfaces with ZrAlNiCuSi TFMGs and their anti- microbial effects on those five microbes which are the most common nosocomial infection pathogens. The transfor- mation of ZrAlNiCuSi bulk metallic glass into TFMG was achieved by sputtering onto stainless steel. Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, Acinetobacter baumannii and Candida albicans were then isolated. The microbes were sampled on ZrAlNiCuSi TFMGs, and this was compared with stainless steel plates. After microbe− material interaction under humidity at room temperature for 3 hours, the specimens were attached to a Mueller- Hinton agar plate (Gibco, Middleton, WI, USA) and incubated at 37.0ºC for 24, 48 and 96 hours. The areas of microbe growth were recorded by serial subtraction photography and then assessed using Image-Pro Plus software (Media Cybernetics, Bethesda, MD, USA). ZrAlNiCuSi TFMGs presented an amorphous rough surface and exhibited hydropho- bic properties. ZrAlNiCuSi TFMGs suppressed E. coli growth on Mueller-Hinton plates for 96 hours, and there was no E. coli growth on blood agar plate enriched media and eosin-methylene blue agar selective media after 96 hours of incu- bation. The five microbes tested on ZrAlNiCuSi TFMGs showed a decreased growth curve after 24 hours. After 24 hours, P. aeruginosa showed a slow growth curve and A. baumannii had a sharp growth curve with TFMG interaction. ZrAlNiCuSi TFMGs prolonged the lag phase of the microbes’ growth curve in S. aureus and C. albicans for 48 hours. ZrAlNiCuSi TFMGs were able to modify the surface of stainless steel, which was very hard and was found to have scratch adhesion abilities and smooth surface effects against five different microbes for at least 24 hours. This is the first description of microbe interactions with zirconium-based TFMGs. Further studies to investigate the mechanism of antimicrobial effects on ZrAlNiCuSi TFMGs are now required. Key Words: antimicrobial effects; surface; thin film metallic glass *Corresponding author. Department of Plastic Surgery, Fooyin University Hospital, No. 5, Zhongshan Road, Donggang Town, Pingtung County 928, Taiwan. E-mail: [email protected] ©2010 Fooyin University Hospital Antimicrobial effects of Zr-based TFMG 13 Introduction biofilms and the increasing resistance of microbes to antibiotics. Fortunately, nosocomial infection control In health care, the most common pathogens caus- can be improved by inhibiting the growth of fungi, ing outbreaks of infection are Escherichia coli, bacteria and viruses in the environment of health Staphylococcus aureus, Pseudomonas aeruginosa, care systems.11,14,15 Microbial growth and biofilm Acinetobacter baumannii, and Candida albicans.1−3 formation are characterized by their colonized en- E. coli is the primary organism isolated from vari- vironmental conditions. Environmental factors in- ous clinical specimens. It adapts to environmental clude nutrient sources and local conditions such as challenges with exceptional alacrity.4 The preva- pH, osmolarity, temperature, oxygen, hydrodynamic lence of nasal S. aureus carriage is approximately conditions, and surface properties. The surface of 20−25% but varies among different populations, and an object could affect planktonic organisms, and is influenced by age, underlying illness, race, certain therefore, surface properties might be involved in behaviors, and the environment in which the person antimicrobial mechanisms.3,16,17 lives or works.5 The wearing of a clean gown and Stainless steel can be found in health care in gloves for any physical contact with a patient or their door handles, push plates and devices such as sur- environment is necessary to prevent an outbreak of gical instruments.18−20 Sputtering hard smooth thin infection; nonetheless, new cases of methicillin- films onto stainless steel can change surface con- resistant Staphylococcus aureus continue to arise.6 ditions. Good adhesion between microbes and the The outbreak of infection caused by Pseudo- host’s or material’s surface is the initial step in inoc- monas respiratory colonization in immunocompro- ulation to induce nosocomial infection, and bacterial mised patients is a nosocomial acquisition, and adhesion to solid surfaces depends on the interac- probably occurs by transmission through contami- tion between the adhesion quantity of bacteria and nated nebulizer devices.7 The best approach to surface quality of the material.20−24 Surface modi- control P. aeruginosa ventilator-associated pneumo- fication using thin films onto 304 stainless steel nia is to prevent the endogenous and exogenous door contactors might be an effective way to control transmission of P. aeruginosa in colonization of the infection.18−20,23,25,26 lungs in mechanically ventilated patients.8 Thin film metallic glasses (TFMGs) can modify Although no definitive virulence factors are the surface of stainless steel. Metallic glass is a new known, A. baumannii is relatively common in both category within metallic materials. There has been hospitalized patients and the hospital environment.9 extensive research in metallic glasses over the past Candida species are the fourth most common cause 20 years. After a breakthrough in the early 1990s, of nosocomial bloodstream infection and are involved many systems such as lanthanum-, magnesium- in 8% of disseminated microbial infections.10 Thus, and zirconium (Zr)-based bulk metallic glasses new modifications are required to reduce the number (BMGs) were developed. In addition to the metal- of microbes on surfaces in health care institutions lic glasses in bulk form, metallic glasses have re- and minimize the acquisition of infections. cently been extended to the thin or thick film area; Antibiotics are usually used to control infections; this is an attempt to find applications in micro- this occurs because of their bactericidal, bacterio- electromechanical systems. For such applications, static or mycostatic effects. However, many pan-drug the amorphous alloys sometimes need to be fabri- resistant microbes have been observed.11−13 Noso- cated via sputtering or other thin film processes. comial infections in intensive care units have steadily The as-deposited TFMGs usually exhibit a uniform increased over the past several decades. Health care composition without microsegregation, thus avoid- is a challenge when endogenous flora are combined ing possible local crystallization during the fabri- 27 with reactivation of latent infectious agents and ex- cation process. Zr61Al7.5Ni10Cu17.5Si4 (ZrAlNiCuSi) ogenous environmental microbes in outbreaks noso- TFMGs can modify the surface of stainless steel.28 comial infections. Nosocomial infections are also Zr-based BMGs are recognized as one of the frequently caused by transmission of pathogens in most promising structural materials because of their the health care environment from instruments or high tensile strength, high elastic modulus, and high equipment, and by direct hand-to-hand contact of corrosion resistance. In addition, Zr-based BMGs health care providers with patients. In intensive care possess a high glass-forming ability, relatively good units, mechanical ventilation is applied after placing thermal stability, an extremely wide supercooled a cuffed polymer endotracheal tube. This tube is liquid region (exceeding 100 K), homogeneous dis- a continuous source of microbial colonization of tribution of multiple elements, and ease of fabri- the lower respiratory tract, ultimately resulting in cation.24,29−31 Zr-based TFMGs exhibit inherent ventilator-related pneumonia. Treatment of infec- optimum properties and can be applied to modify tions associated with medical devices is often frus- the surface condition of stainless steel.28 The direct trated by the inability of antibiotics to penetrate current (DC) sputtering method is a simple method 14 P.T. Chiang et al of changing the surface condition of stainless steel, Technologies Inc., Tainan, Taiwan) for the substrate and is used to transform ZrAlNiCuSi BMGs into and ZrAlNiCuSi TFMGs. ZrAlNiCuSi TFMGs, which are coated onto the stain- less steel substrate. Previous reports have tended Mechanical testing to focus on Zr-based BMGs or TFMGs for manufactur- ing or processing methods, or have examined the The adhesion capability between the films and the microstructure properties or mechanical properties 304 stainless steel substrate was evaluated using a of materials.4,27−33 However, there are few reports on Teer ST 2330 scratch tester (Teer Coatings Ltd., biologic use with regard to