Wang Jiong, Zhao Yun, Ma Fen-Xiang, Wang Kang, Wang Feng-Bing, Xia Xing-Hua
State Key Laboratory of Analytical Chemistry for Life Science, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210093, China.
J Mater Chem B. 2013 Mar 14;1(10):1406-1413. doi: 10.1039/c2tb00454b. Epub 2013 Jan 22.
Surface modification has been proved to be one of the effective strategies for enhancing the properties of graphene sheets. When a non-covalent modification method is appropriately designed, novel opportunities for better performance of graphene nanosheets can be expected since this strategy can tailor the properties of graphene while its natural structure is retained. This paper introduces a simple route to prepare a highly biocompatible, stable and conductive graphene hybrid modified by poly-l-lysine (PLL) for biosensors using the non-covalent strategy. Results show that PLL adopts a random conformation with the nonpolar parts exposed to outside since its side chains are positively charged under neutral conditions. This conformation allows the strong adhesion of PLL to graphene surface via the hydrophobic interaction between butyl chains of PLL and graphene surface, cation-π interaction of protonated amine groups on PLL with the π electrons in graphene, and electrostatic interaction between the protonated amine groups on PLL and the negatively charged carboxyl groups remaining on graphene. All these interactions make the resultant PLL-G hybrid stable and dispersible in aqueous solutions. The resultant hybrid is then used to construct high performance biosensors. As demonstration, hemoglobin (Hb) carrying negative charges can be easily immobilized on the hybrid via electrostatic interactions with the positively charged lysine side chains of PLL modified on graphene surface, forming the Hb@PLL-G bionanocomposite. The immobilized protein retains its native structure and exhibits reversible direct electrochemistry. The Hb@PLL-G based enzymatic electrochemical biosensor shows excellent catalytic activity toward its substrate hydrogen peroxide. Its electrochemical response shows the linear dependence of hydrogen peroxide concentration in a range between 10 μM and 80 μM with a detection limit of 0.1 μM. The apparent Michaelis-Menten constant is calculated as 0.0753 mM, demonstrating the significant catalytic ability of the protein. The present strategy can be extended to modify other carbon materials and the resultant nanocomposites are promising for construction of biosensors, bioelectronics and biofuel cells.
表面改性已被证明是增强石墨烯片性能的有效策略之一。当合理设计非共价改性方法时，有望为石墨烯纳米片带来更好性能的新机遇，因为该策略可在保留石墨烯天然结构的同时调整其性能。本文介绍了一种简单的路线，采用非共价策略制备由聚-L-赖氨酸（PLL）改性的具有高生物相容性、稳定性和导电性的石墨烯杂化物用于生物传感器。结果表明，PLL呈无规构象，其侧链在中性条件下带正电荷，非极性部分暴露于外部。这种构象使得PLL通过PLL的丁基链与石墨烯表面之间的疏水相互作用、PLL上质子化胺基团与石墨烯中π电子的阳离子-π相互作用以及PLL上质子化胺基团与石墨烯上残留的带负电荷羧基之间的静电相互作用，牢固地粘附在石墨烯表面。所有这些相互作用使得所得的PLL-G杂化物在水溶液中稳定且可分散。然后将所得杂化物用于构建高性能生物传感器。作为示例，带负电荷的血红蛋白（Hb）可通过与石墨烯表面改性的PLL带正电荷的赖氨酸侧链的静电相互作用轻松固定在杂化物上，形成Hb@PLL-G生物纳米复合材料。固定化的蛋白质保留其天然结构并表现出可逆的直接电化学。基于Hb@PLL-G的酶促电化学生物传感器对其底物过氧化氢显示出优异的催化活性。其电化学响应表明过氧化氢浓度在10μM至80μM范围内呈线性依赖关系,检测限为0.1μM。表观米氏常数计算为0.0753 mM，表明该蛋白质具有显著的催化能力。本策略可扩展到修饰其他碳材料，所得纳米复合材料有望用于构建生物传感器、生物电子学和生物燃料电池。
