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A stain-based screening method was developed to screen different catalyst coatings for their germicidal activity.A Baclight dead/livebacteria viability kit(invitrogen,molecular probes)was used for staining the cell.The screening was carried out following a standardprocedure.This included loading cell suspension to solid surface and maintaining contact for 30 min,then staining with a mixturecontaining dyes.The stained cells were observed using an epifluorescent microscope and photographed with a CCD camera under UV.Metal-doped TiO2 coatings on Al plates were prepared and tested for non-UV germicidal activity without using UV.It was tested usingmodel microorganisms such as Bakers Yeast(Saccharomyces cerevisiae),Bacillus subtilis,Pseudomonas putida,and Escherichia coli.On the basis of the germicidal activity of catalyst and the degree of damage caused to the cells,the stained cells may appear green(viable),green with red or yellow nuclei and yellow(compromised)or red(nonviable).According to their stained color,cells werecounted to calculate the percentage of dead,live,and compromised cells.Compromised cells are cells that grow very slowly afterreculturing indicating a degree of reversible cell damage.Screening the germicidal activity using this staining method is accurate andeffcient,and requires less time than the culture-based method.A modification to the procedure for measuring germicidal activity ofrough surfaces or fibrous coatings was developed.Both TiO2 and metal-doped TiO2(Ag,Pt,Au,Cu)possess non-UV based germicidalactivity.The germicidal activity of TiO2 was found to be related with its wetting property and can be improved by UV irradiation beforetesting.It is not greatly affected by contact time,indicating a fast acting germicidal activity.
A stain-based screening method was developed to screen different catalyst coatings for their germicidal activity. A Baclight dead / livebacteria viability kit (invitrogen, molecular probes) was used for staining the cell. The screening was carried out following a standardprocedure.This included loading cell suspension to solid surface and maintaining contact for 30 min, then staining with a mixture of staining dyes. stained cells were observed using an epifluorescent microscope and photographed with a CCD camera under UV.Metal-doped TiO2 coatings on Al plates were prepared and tested for non-UV germicidal activity without using UV. It was tested using model microorganisms such as Bakers Yeast (Saccharomyces cerevisiae), Bacillus subtilis, Pseudomonas putida, and Escherichia coli. On the basis of the germicidal activity of catalyst and the degree of damage caused to the cells, the stained cells may appear green (viable), green with red or yellow nuclei and yellow (compromised) or red (nonviable) .According to their stained color, cells were counted to calculate the percentage of dead, live, and compromised cells. Compromised cells are cells that grow very slowly afterreculturing indicating a degree of reversible cell damage. Screening the germicidal activity using this staining method is accurate andeffcient, and requires less time than the culture-based method. A modification to the procedure for measuring germicidal activity ofrough surfaces or fibrous coatings was developed. Both TiO2 and metal-doped TiO2 (Ag, Pt, Au, Cu) possess non-UV based germicidalactivity. The germicidal activity of TiO2 was found to be related with its wetting property and can be improved by UV irradiation before testing. It is not greatly affected by contact time, indicating a fast acting germicidal activity.