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11 December 2012 Efficient photodynamic therapy against Staphylococcus aureus using [Ru(bpy)2(dppn)]2+: a novel cationic photosensitizer
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[Ru(bpy)2(dppn)]2+, one of Ru(II) polypyridyl complexes, present inner dicationic charge and high 1O2 quantum yield. In this study, the synthetic compound was used as photosensitizer (PS) to photoinactivate a reference strain of Staphylococcus aureus ATCC 25923. Bacterial suspensions consisting of 108 colony-forming units (CFU) per milliliter were incubated with PS of different concentrations (0.025μM ~ 25μM). After a 30 minutes period, the suspensions were exposed to 457nm laser light, determined by the absorption spectra of the PS in phosphate buffered saline (PBS), with a power density of 40 mW/cm2 for 10 minutes (energy density of 24 J/cm2). PS group, light group and the blank control were also concerned. Viability of bacteria was determined by pour plates. The Log10 reductions were calculated and killing effects in photodynamic inactivation (PDI) group were analysed contrast to the blank control. We observed that neither the laser light nor the PS per se had any inhibitory effect on the viability of the bacteria. PS at low dose (0.025μM) followed by illumination yielded no significant decrease in the viable number. PS at 0.25μM and 2.5μM with irradiation induced reductions of 1.69 Log10 and 5.97 Log10, respectively. PS at 10μM and 25μM combined with light brought viable bacterial cells down to undetectable levels (reductions < 7 Log10). We concluded that with the PS of appropriate doses, [Ru(bpy)2(dppn)]2+ mediated PDI inactivated S.aureus efficiently. At the concentration of 2.5μM, bactericidal activity was reached where the viability of bacteria fell more than 3 Log10 based on previous researches.
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Yucheng Wang, Ying Wang, and Ying Gu "Efficient photodynamic therapy against Staphylococcus aureus using [Ru(bpy)2(dppn)]2+: a novel cationic photosensitizer", Proc. SPIE 8553, Optics in Health Care and Biomedical Optics V, 85530H (11 December 2012);

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