The impact of ultraviolet light on bacterial adhesion ... - Semantic Scholar
Colloids and Surfaces B: Biointerfaces 41 (2005) 153–161
The impact of ultraviolet light on bacterial adhesion to glass and metal oxide-coated surface Baikun Lia , Bruce E. Loganb,∗ b
a Environmental Engineering Program, The Pennsylvania State University at Harrisburg, Middletown, PA 17057, USA Department of Civil and Environmental Engineering, The Pennsylvania State University, University Park, PA 16802, USA
Received 16 July 2004; received in revised form 9 December 2004; accepted 10 December 2004
Abstract Biofouling of glass and quartz surfaces can be reduced when the surface is coated with photocatalytically active metal oxides, such as TiO2 (anatase form) or SnO2 . We measured the attachment of eight strains of bacteria to these two metal oxides (TiO2 and SnO2 ), and to an uncoated glass (control; designated Si-m) before and after exposure to UV light at wavelengths of 254 nm (UVC) or 340 nm UV (UVA). TiO2 -coated surfaces were photocatalytically active at both 254 and 340 nm as evidenced by a decrease in the water contact angle of the surface from 59◦ ± 2 to 5◦ . One drop of a liquid (3 L) was deposited onto a dry glass surface. The contact angle formed by the liquid drop on the glass surface was measured using
an image analysis program (Scion Beta 4.02 for Windows, Scioncorp, Frederick, MD). 2.6. Bacterial viability The viability of bacteria before and after UV exposure was examined using fluorescent stains (LIVE/DEAD Baclight kit, Molecular Probe). Bacterial adhered to the glass and metal oxide surfaces were stained with Baclight dye solution for 2–4 min, followed by observation using a fluorescence microscope (Olympus BH2). Living cells stained green while dead cells were red. 3. Results 3.1. The effect of UV light on surface hydrophobicity UV exposure substantially decreased the hydrophobicity of TiO2 surfaces. Exposure to UV light at either wavelength
Fig. 1. Bacterial attachment to glass and metal oxide surfaces: solid bar, adhesion without UV treatment; striped bar, post-UV treatment for 1 h (340 nm, 2300 W/cm2 ).
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B. Li, B.E. Logan / Colloids and Surfaces B: Biointerfaces 41 (2005) 153–161
Fig. 2. Results of bacterial adhesion tests using TiO2 , SnO2 and Si-m (control) surfaces exposed to UVA light (340 nm, 2300 W/cm2 ). (A) Fraction of cells removed due to change in surface hydrophobicity (pre-UV treatment); (B) fraction of cells removed due to reduction in hydrophobicity and photocatalysis (post-UV treatment); (C) fraction of cells removed attributed to photocatalysis (difference between pre- and post-UV treatment tests).
(254 nm or 340 nm) or intensity (2800 or 4600 W/cm2 ) for 1 h changed the TiO2 surface from hydrophobic (59 ± 2◦ ) to hydrophilic (contact angle
The impact of ultraviolet light on bacterial adhesion to glass and metal oxide-coated surface Baikun Lia , Bruce E. Loganb,∗ b
a Environmental Engineering Program, The Pennsylvania State University at Harrisburg, Middletown, PA 17057, USA Department of Civil and Environmental Engineering, The Pennsylvania State University, University Park, PA 16802, USA
Received 16 July 2004; received in revised form 9 December 2004; accepted 10 December 2004
Abstract Biofouling of glass and quartz surfaces can be reduced when the surface is coated with photocatalytically active metal oxides, such as TiO2 (anatase form) or SnO2 . We measured the attachment of eight strains of bacteria to these two metal oxides (TiO2 and SnO2 ), and to an uncoated glass (control; designated Si-m) before and after exposure to UV light at wavelengths of 254 nm (UVC) or 340 nm UV (UVA). TiO2 -coated surfaces were photocatalytically active at both 254 and 340 nm as evidenced by a decrease in the water contact angle of the surface from 59◦ ± 2 to 5◦ . One drop of a liquid (3 L) was deposited onto a dry glass surface. The contact angle formed by the liquid drop on the glass surface was measured using
an image analysis program (Scion Beta 4.02 for Windows, Scioncorp, Frederick, MD). 2.6. Bacterial viability The viability of bacteria before and after UV exposure was examined using fluorescent stains (LIVE/DEAD Baclight kit, Molecular Probe). Bacterial adhered to the glass and metal oxide surfaces were stained with Baclight dye solution for 2–4 min, followed by observation using a fluorescence microscope (Olympus BH2). Living cells stained green while dead cells were red. 3. Results 3.1. The effect of UV light on surface hydrophobicity UV exposure substantially decreased the hydrophobicity of TiO2 surfaces. Exposure to UV light at either wavelength
Fig. 1. Bacterial attachment to glass and metal oxide surfaces: solid bar, adhesion without UV treatment; striped bar, post-UV treatment for 1 h (340 nm, 2300 W/cm2 ).
156
B. Li, B.E. Logan / Colloids and Surfaces B: Biointerfaces 41 (2005) 153–161
Fig. 2. Results of bacterial adhesion tests using TiO2 , SnO2 and Si-m (control) surfaces exposed to UVA light (340 nm, 2300 W/cm2 ). (A) Fraction of cells removed due to change in surface hydrophobicity (pre-UV treatment); (B) fraction of cells removed due to reduction in hydrophobicity and photocatalysis (post-UV treatment); (C) fraction of cells removed attributed to photocatalysis (difference between pre- and post-UV treatment tests).
(254 nm or 340 nm) or intensity (2800 or 4600 W/cm2 ) for 1 h changed the TiO2 surface from hydrophobic (59 ± 2◦ ) to hydrophilic (contact angle
