Division of Chemistry & Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore 637371, Singapore.
Nanoscale. 2014 Jan 21;6(2):1173-80. doi: 10.1039/c3nr05275c.
Graphene and its family of derivatives possess unique and remarkable physicochemical properties which make them valuable materials for applications in many areas like electronics, energy storage and biomedicine. In response to the possibility of its large-scale manufacturing as commercial products in the future, an investigation was conducted to determine the cytotoxicity of one particular family of graphene derivatives, the halogenated graphenes, for the first time. Halogenated graphenes were prepared through thermal exfoliation of graphite oxide in gaseous chlorine, bromine or iodine atmospheres to yield chlorine- (TRGO-Cl), bromine- (TRGO-Br) and iodine-doped graphene (TRGO-I) respectively. 24 h exposure of human lung carcinoma epithelial cells (A549) to the three halogenated graphenes and subsequent cell viability assessments using methylthiazolyldiphenyl-tetrazolium bromide (MTT) and water-soluble tetrazolium salt (WST-8) assays revealed that all the halogenated graphenes examined are rather cytotoxic at the concentrations tested (3.125 μg mL(-1) to 200 μg mL(-1)) and the effects are dose-dependent, with TRGO-Cl reducing the cell viability to as low as 25.7% at the maximum concentration of 200 μg mL(-1). Their levels of cytotoxicity can be arranged in the order of TRGO-Cl > TRGO-Br > TRGO-I, and it is suggested that the amount of halogen present in the graphene material is the determining factor for the observed trend. Control experiments were carried out to test for possible nanomaterial-induced interference as a consequence of reaction between the halogenated graphenes and the viability markers (MTT/WST-8 reagent) or binding of the formazan products under cell-free conditions. The data obtained eliminate the probability of significant influence by these interferents as the change in the normalized percentage of formazan formed is relatively small and thorough washings were performed prior to the viability assessments to reduce the amount of halogenated graphenes that could eventually interact with the MTT/WST-8 assays. More studies need to be carried out in the future to complement the results obtained in this initial study in an attempt to develop a better understanding of the health hazards that the halogenated graphenes pose.
石墨烯及其衍生物具有独特而显著的物理化学性质，这使得它们成为许多领域（如电子、储能和生物医学）应用的有价值材料。为了应对未来大规模商业化生产的可能性，我们首次对一类特定的石墨烯衍生物，卤化石墨烯，进行了细胞毒性研究。卤化石墨烯是通过在氯气、溴气或碘气气氛中热剥离氧化石墨制备的，分别得到氯掺杂石墨烯（TRGO-Cl）、溴掺杂石墨烯（TRGO-Br）和碘掺杂石墨烯（TRGO-I）。将三种卤化石墨烯暴露于人类肺癌上皮细胞（A549）中 24 小时，然后通过甲基噻唑基二苯基四唑溴盐（MTT）和水溶性四唑盐（WST-8）测定细胞活力，结果表明，在所测试的浓度（3.125μg/mL 至 200μg/mL）下，所有测试的卤化石墨烯都具有相当的细胞毒性，且作用呈剂量依赖性，在最大浓度 200μg/mL 下，TRGO-Cl 将细胞活力降低至低至 25.7%。它们的细胞毒性水平可以按照 TRGO-Cl > TRGO-Br > TRGO-I 的顺序排列，并且可以认为石墨烯材料中卤素的存在量是观察到的趋势的决定因素。进行了对照实验以测试由于卤化石墨烯与活力标记物（MTT/WST-8 试剂）之间的反应或在无细胞条件下形成的甲臜产物的结合而可能引起的纳米材料诱导的干扰。获得的数据消除了这些干扰物的显著影响的可能性，因为形成的甲臜的归一化百分比的变化相对较小，并且在进行活力评估之前进行了彻底的洗涤以减少最终可能与 MTT/WST-8 测定相互作用的卤化石墨烯的量。未来需要进行更多的研究，以补充本初步研究中的结果，试图更好地了解卤化石墨烯带来的健康危害。
