Division of Chemistry & Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371, Singapore.
Chemistry. 2013 Jun 17;19(25):8227-35. doi: 10.1002/chem.201300824. Epub 2013 Apr 29.
Graphene, a class of two-dimensional carbon nanomaterial, has attracted extensive interest in recent years, with a significant amount of research focusing on graphene oxides (GOs). They have been primed as potential candidates for biomedical applications such as cell labeling and drug delivery, thus the toxicity and behavior of graphene oxides in biological systems are fundamental issues that need urgent attention. The production of GO is generally achieved through a top-down route, which includes the usage of concentrated H₂SO₄ along with: 1) concentrated nitric acid and KClO₃ oxidant (Hoffmann); 2) fuming nitric acid and KClO₃ oxidant (Staudenmaier); 3) concentrated phosphoric acid with KMnO₄ (Tour); or 4) sodium nitrate for in-situ production of nitric acid in the presence of KMnO₄ (Hummers). It has been widely assumed that the properties of these four GOs produced by using the above different methods are roughly similar, so the methods have been used interchangeably. However, several studies have reported that the toxicity of graphene-related nanomaterials in biological systems may be influenced by their physiochemical properties, such as surface functional groups and structural defects. In addition, considering how GOs are increasingly used in the field of biomedicine, we are interested to see how the oxygen content/functional groups of GOs can impact their toxicological profiles. Since in-vitro testing is a common first step in assessing the health risks related with engineered nanomaterials, the cytotoxicity of the GOs prepared by the four different oxidative treatments was investigated by measuring the mitochondrial activity in adherent lung epithelial cells (A549) by using commercially available viability assays. The dose-response data was generated by using two assays, the methylthiazolyldiphenyl-tetrazolium bromide (MTT) assay and the water-soluble tetrazolium salt (WST-8). From the viability data, it is evident that there is a strong dose-dependent cytotoxic response resulting from the four GO nanomaterials tested after a 24 h exposure, and it is suggested that there is a correlation between the amounts of oxygen content/functional groups of GOs with their toxicological behavior towards the A549 cells.
石墨烯是一种二维碳纳米材料，近年来引起了广泛的关注，大量研究集中在氧化石墨烯（GO）上。它们已被视为生物医学应用的潜在候选材料，如细胞标记和药物输送，因此氧化石墨烯在生物系统中的毒性和行为是需要紧急关注的基本问题。GO 的生产通常采用自上而下的方法，包括使用浓 H₂SO₄ 以及：1）浓硝酸和 KClO₃ 氧化剂（Hoffmann）；2）发烟硝酸和 KClO₃ 氧化剂（Staudenmaier）；3）浓磷酸和 KMnO₄（Tour）；或 4）在存在 KMnO₄ 的情况下用硝酸钠原位生产硝酸（Hummers）。人们普遍认为，使用上述不同方法生产的这四种 GO 的性质大致相似，因此这些方法可以互换使用。然而，有几项研究报告称，生物系统中与石墨烯相关的纳米材料的毒性可能受到其物理化学性质的影响，例如表面官能团和结构缺陷。此外，考虑到 GO 在生物医学领域的应用日益广泛，我们很想知道 GO 中的氧含量/官能团如何影响其毒理学特征。由于体外测试是评估工程纳米材料相关健康风险的常见第一步，因此通过使用市售的活力测定法测量贴壁肺上皮细胞（A549）中的线粒体活性来研究通过四种不同氧化处理制备的 GO 的细胞毒性。通过使用两种测定法，即甲基噻唑二苯基四唑溴化物（MTT）测定法和水溶性四唑盐（WST-8），生成剂量-反应数据。从活力数据可以明显看出，在 24 小时暴露后，四种 GO 纳米材料测试均表现出强烈的剂量依赖性细胞毒性反应，并且 GO 中的氧含量/官能团的数量与其对 A549 细胞的毒理学行为之间存在相关性。
