Department of Chemical Engineering, University of Waterloo, 200 University Avenue West, Waterloo, Ontario, CanadaN2L 3G1.
Nanoscale. 2019 Feb 7;11(6):2999-3012. doi: 10.1039/c8nr08397e.
Biological molecules have promising potential to exfoliate graphite and produce biocompatible graphene nano-materials for biomedical applications. Here, a systematic design of a histidine-rich lipidated peptide sequence is presented that simultaneously exfoliates graphite flakes and functionalizes the resulting graphene nanosheets (∼150 nm lateral size) with long-term dispersion stability in aqueous solution (>8 months). The details of peptide/peptide and peptide/graphite interactions are probed using various microscopy, spectroscopy and molecular dynamics simulation methods. The results show that histidine and stearic acid interact with the graphite surface through π-π stacking and hydrophobic forces, respectively. Surface-assisted assembly of peptide molecules is then initiated via hydrogen bonds between deprotonated histidine segments, and a textured peptide nano-structure is formed. The work of adhesion between the peptide and graphite is found to be high enough to promote exfoliation of graphite flakes through layer-by-layer peeling of graphene nanosheets. The positively charged arginine in the peptide is exposed outward, and is responsible for the stable dispersion. The peptide molecules are sufficiently small, presenting the possibility to insert into and increase the spacing between the graphitic layers for enhanced exfoliation. The peptide-functionalized graphene nanosheets not only show great biocompatibility with cells in vitro, but also enhance cancer drug uptake by the cells.
生物分子具有剥离石墨并生成用于生物医学应用的生物相容的石墨烯纳米材料的巨大潜力。在这里，设计了一种组氨酸丰富的脂质化肽序列，该序列同时剥离石墨薄片，并使得到的石墨烯纳米片（横向尺寸约为 150nm）功能化，在水溶液中具有长期的分散稳定性（>8 个月）。使用各种显微镜、光谱和分子动力学模拟方法研究了肽/肽和肽/石墨相互作用的细节。结果表明，组氨酸和硬脂酸分别通过π-π堆积和疏水相互作用与石墨表面相互作用。然后，通过去质子化组氨酸段之间的氢键，起始肽分子的表面辅助组装，形成具有纹理的肽纳米结构。发现肽和石墨之间的粘附功足够高，可以通过逐层剥离石墨烯纳米片来促进石墨薄片的剥离。肽中的带正电荷的精氨酸暴露在外部，负责稳定的分散。肽分子足够小，有可能插入并增加石墨层之间的间距，从而增强剥离效果。肽功能化的石墨烯纳米片不仅在体外与细胞具有很好的生物相容性，而且还增强了细胞对癌症药物的摄取。
