Background: Endotoxin-free engineered nanoparticle suspensions are imperative for their successful applications in the field of nanomedicine as well as in the investigations in their toxicity. Gold nanoparticles are known to interfere with various in vitro assays due to their optical properties and potential for surface reactivity. In vitro endotoxin testing assays are known to be susceptible to interference caused by the sample being tested.

Objective: This study aimed to identify a preferred assay for the testing of endotoxin contamination in gold nanoparticle suspensions.

Methods: The interference by gold nanoparticles on three assays namely, the commonly used limulus amebocyte lysate chromogenic assay, the limulus amebocyte lysate gel-clot method, and the less common recombinant Factor C (rFC) assay, was tested.

Results: Possible interference could be observed with all three assays. The interference with the absorbance- based chromogenic assay could not be overcome by dilution; whilst the qualitative nature of the gel-clot assay excluded the possibility of distinguishing between a false positive result due to enhancement of the sensitivity of the assay, and genuine endotoxin contamination. However, interference with the rFC assay was easily overcome through dilution.

Conclusion: The rFC assay is recommended as an option for endotoxin contamination detection in gold nanoparticle suspensions.

背景：无内毒素工程纳米颗粒悬浮液对于其在纳米医学领域的成功应用及其毒性研究至关重要。已知金纳米颗粒由于其光学性质和表面反应潜力而会干扰各种体外测定。已知体外内毒素测试测定法容易受到由待测样品引起的干扰的影响。

目的：本研究旨在确定一种检测金纳米颗粒悬浮液中内毒素污染的优选方法。

方法：测试了金纳米颗粒对三种测定的干扰，即常用的变形细胞裂解物显色法，变形细胞凝胶凝结法和较不常见的重组因子C（rFC）测定。

结果：三种测定均可观察到可能的干扰。稀释不能克服对基于吸光度的生色测定法的干扰。而凝胶凝块测定的定性性质排除了区分由于测定灵敏度提高而导致的假阳性结果和真正的内毒素污染的可能性。但是，通过稀释很容易克服对rFC分析的干扰。

结论：建议将rFC分析作为金纳米颗粒悬浮液中内毒素污染检测的一种选择。