The implementation of photodynamic therapy (PDT) usually uses red light as the excitation source to obtain a deeper penetration depth. However, for some superficial infectious diseases, using red-light PDT may damage the normal tissues underneath. If we choose a shorter wavelength light, then the effect of PDT can be limited to the superficial region. This study assessed the effect of blue-light PDT against Staphylococcus aureus. The absorption of hematoporphyrin monomethyl ether (HMME) by S. aureus was investigated using fluorescence spectroscopy. The bactericidal effects of HMME, light alone, and PDT using blue light (405 nm) on S. aureus were studied. The results indicate that the HMME uptake by S. aureus rapidly reached a certain value, then steadily increased with time in the range of 0–80 min, and thenreached a plateau at 80 min before a slow decline afterward. Without light irradiation, less than 2 μg ml⁻¹ HMME showed no bactericidal effect on S. aureus. Without HMME, blue-light at a power density of 20 mW cm⁻² had no significant bactericidal effect for 0.5 min to 10 min. When 2 μg ml⁻¹ of HMME was combined with blue-light (20 mW cm⁻²), the bactericidal effect showed a reduction of 3 log₁₀ with the extension of irradiation time. These results demonstrated that bacteria have the ability to absorb HMME, and HMME-mediated blue-light PDT can effectively kill the bacteria, which laid the foundation for blue-light PDT as a non-invasive treatment for superficial infectious diseases.

中文翻译：

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血卟啉单甲醚介导的蓝光光动力疗法对金黄色葡萄球菌的杀菌作用

光动力疗法（PDT）的实现通常使用红光作为激发源来获得更深的穿透深度。但是，对于某些浅表传染病，使用红光PDT可能会损坏其下方的正常组织。如果我们选择波长较短的光，那么PDT的效果可能会限于表面区域。这项研究评估了蓝光PDT对金黄色葡萄球菌的作用。使用荧光光谱法研究了金黄色葡萄球菌对血卟啉单甲醚（HMME）的吸收。研究了HMME，单独的光和使用蓝光（405 nm）的PDT对金黄色葡萄球菌的杀菌作用。结果表明，金黄色葡萄球菌对HMME的吸收迅速达到某个值，然后在0-80分钟的范围内随时间稳定增加，然后在80分钟达到平稳，然后缓慢下降。在没有光照射的情况下，小于2μgml ^-1 HMME对金黄色葡萄球菌没有杀菌作用。没有HMME，功率密度为20 mW cm ^-2的蓝光在0.5分钟到10分钟内没有明显的杀菌作用。当将2μgml ^-1的HMME与蓝光（20 mW cm ^-2）混合时，杀菌效果降低了3 log ₁₀随着照射时间的延长。这些结果表明细菌具有吸收HMME的能力，并且HMME介导的蓝光PDT可以有效杀死细菌，这为蓝光PDT作为浅表传染病的非侵入性治疗奠定了基础。