Introduction: Nanoparticle solutions have been studied to improve antimicrobial effect. The aim of this study was to develop, characterize, and evaluate the in vitro and in vivo antiseptic efficacy of 0.25% aqueous-based chlorhexidine nanoemulsion (NM-Cl 0.25% w/v).
Methods: The NM-Cl 0.25% w/v (2.5mg/mL) and free chlorhexidine nanoemulsion (FCN; same composition of NM-Cl without the molecule of chlorhexidine) were synthetized by the spontaneous emulsification method. Characterization analyses of physical and chemical properties were performed. The NM-Cl 0.25% w/v was compared with chlorhexidine 0.5% alcohol base (CS-Cl 0.5%) in vitro studies (microdilution study and kill curve study), and in vivo study (antisepsis of rats dorsum). Kruskal–Wallis test was used between groups and inside the same group, at different sample times and the Mann–Whitney test was performed when difference was detected.
Results: The NM-Cl 0.25% w/v presented adequate physicochemical characteristics for a nanoemulsion, revealing a more basic pH than FCN and difference between zeta potential of NM-Cl 0.25% w/v and FCN. The NM-Cl 0.25% w/v and CS-Cl 0.5% solutions were more effective on Gram-positive than on Gram-negative bacteria (p≤ 0.05). NM-Cl 0.25% w/v presented upper antiseptic effect in the microdilution study and residual antiseptic effect was maintained for a longer time when compared to CS-Cl 0.5% (kill curve study). The four-fold (minimal inhibitory concentration) of NM-Cl 0.25% were the formulations with most durable effect within those tested, presenting residual effect until T6 for both bacteria. In the in vivo study, both formulations (NM-Cl 0.25% w/v and CS-Cl 0.5%) had a reduction of the microorganisms in the skin of the rats (p< 0.0001) not revealing any difference between the formulations at different times, showing the antiseptic effect of NM-Cl (p≤ 0.05).
Conclusion: Both in vitro and in vivo experiments demonstrated that NM-Cl showed promising future as an antiseptic for cutaneous microbiota.

Keywords: antisepsis, cutaneous microbiota, nanoformulation, nanotechnology


中文翻译：

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洗必泰纳米乳：一种新的防腐剂配方

简介：已经研究了纳米颗粒溶液以提高抗菌效果。本研究的目的是开发、表征和评估 0.25% 水基洗必泰纳米乳 (NM-Cl 0.25% w/v) 的体外和体内防腐效果。
方法：通过自发乳化法合成了 NM-Cl 0.25% w/v (2.5mg/mL) 和游离洗必泰纳米乳 (FCN; 相同成分的 NM-Cl 不含洗必泰分子)。进行了物理和化学性质的表征分析。NM-Cl 0.25% w/v 与氯己定 0.5% 醇碱 (CS-Cl 0.5%) 在体外研究（微量稀释研究和杀灭曲线研究）和体内研究（大鼠背部防腐）进行了比较。Kruskal-Wallis 检验用于组间和同一组内，在不同的采样时间，当检测到差异时进行 Mann-Whitney 检验。
结果：NM-Cl 0.25% w/v 对纳米乳液表现出足够的物理化学特性，显示出比 FCN 更碱性的 pH 值以及 NM-Cl 0.25% w/v 和 FCN 之间的 zeta 电位差异。NM-Cl 0.25% w/v 和 CS-Cl 0.5% 溶液对革兰氏阳性菌比对革兰氏阴性菌更有效（p≤ 0.05)。NM-Cl 0.25% w/v 在微量稀释研究中表现出较高的防腐效果，与 CS-Cl 0.5%（杀灭曲线研究）相比，残留的防腐效果保持更长的时间。NM-Cl 0.25% 的四倍（最小抑制浓度）是在那些测试中具有最持久效果的制剂，在 T6 之前对两种细菌都呈现残留效果。在体内研究中，两种制剂（NM-Cl 0.25% w/v 和 CS-Cl 0.5%）均减少了大鼠皮肤中的微生物（p < 0.0001），未显示不同制剂在不同环境下的任何差异次，显示 NM-Cl 的防腐效果 ( p ≤ 0.05)。
结论：体外和体内实验都表明，NM-Cl 作为皮肤微生物群的防腐剂具有广阔的前景。

关键词：抗菌，皮肤微生物群，纳米制剂，纳米技术