Objective

This study aimed to test the efficacy of photodynamic inactivation (PDI) mediated by curcumin with EDTA against Streptococcus mutans in planktonic suspension using blue LED light.

Methods

Antibacterial activity of curcumin and EDTA was evaluated by determination of their minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC). The fractional inhibitory concentration index (FICI) was used to estimate the synergistic effect of various combination ratios of curcumin and EDTA against S. mutans. Cultures of S. mutans (18 h, 37 °C, 5% C0₂) were prepared to test the effect of curcumin-mediated PDI (50 μM and 500 μM) with or without 0.4% EDTA and 40 s of light-activation with blue light. EDTA and each concentration of curcumin were also tested individually. Chlorhexidine (0.2%), was used as positive control. Planktonic suspensions were also analyzed by viable colony counts (VCC), confocal laser scanning microscopy (CLSM), transmission electron microscopy (TEM), and polymerase chain reaction (PCR).

Results

The MIC values of curcumin and EDTA were 5 mM and 0.125% respectively. FICI showed a synergistic interaction between curcumin and EDTA. All the combinations with curcumin and blue LED light resulted in a complete inactivation of the S. mutans and CLSM confirms these results, TEM showed morphological changes produced by the PDI. No damage on DNA structure was detected by PCR.

Significance

Curcumin-mediated PDI with EDTA using a blue light, shows a strong inhibitory effect against S. mutans in planktonic culture. Because of the unspecific target mechanism, it could be a promising technique for disinfection of dental tissues.

中文翻译：

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姜黄素与EDTA联用对变形链球菌的光动力学灭活作用

目的

这项研究旨在测试使用姜黄素与EDTA介导的光动力灭活（PDI）对蓝光LED浮游悬浮液中变形链球菌的功效。

方法

通过测定姜黄素和EDTA的最小抑菌浓度（MIC）和最小杀菌浓度（MBC）来评估其抗菌活性。使用分数抑制浓度指数（FICI）来评估姜黄素和EDTA的各种配比对变形链球菌的协同作用。变形链球菌的培养（18 h，37°C，5％C0 ₂制备了），以测试姜黄素介导的PDI（50μM和500μM）在有或没有0.4％EDTA的情况下以及蓝光激活40 s的效果。EDTA和姜黄素的每种浓度也分别进行了测试。洗必泰（0.2％）用作阳性对照。还通过活菌落计数（VCC），共聚焦激光扫描显微镜（CLSM），透射电子显微镜（TEM）和聚合酶链反应（PCR）分析了浮游生物悬浮液。

结果

姜黄素和EDTA的MIC值分别为5 mM和0.125％。FICI显示姜黄素和EDTA之间具有协同作用。姜黄素和蓝色LED灯的所有组合均导致变形链球菌完全失活，CLSM证实了这些结果，TEM显示PDI产生了形态变化。通过PCR未检测到对DNA结构的破坏。

意义

姜黄素介导的PDI与EDTA一起使用蓝光，在浮游文化中显示出对变形链球菌的强抑制作用。由于目标机制的不确定性，它可能是一种有前途的牙科组织消毒技术。