Probing Macrophage Activity with Carbon-Nanotube Sensors
Probing Macrophage Activity with Carbon-Nanotube Sensors
复制标题
DOI：
10.1002/smll.200900823
复制
发表时间：
2009-11-16
期刊：
影响因子：
13.3
通讯作者：
Dekker, Cees
中科院分区：
文献类型：
--
作者：
Heller, Iddo;Smaal, Wiljan T. T.;Dekker, Cees
基于单个单壁碳纳米管（SWNT）的电子传感器提供了一个极好的机会，以扩展现有的一套可用于单细胞研究的多功能高灵敏度探针的纳米尺寸的电探针。单壁碳纳米管已被证明可以作为纳米级电化学传感器和静电场效应晶体管（FET）传感器。[1-3]在活细胞内和周围发生的生物过程通常仅具有静电和/或电化学性质，因此可以潜在地用SWNT传感器探测。重要的是，单壁碳纳米管具有准维圆柱形几何形状。[4]单壁碳纳米管的长度为几微米，可以跨越单个细胞，而其直径为一纳米，直接与单个蛋白质的大小相当。与目前具有与单细胞相当的横向尺寸的电探针相比，[5] SWNT探针可以具有更高的空间分辨率，并且在接触或刺穿单细胞膜时施加大大减少的物理扰动。在这里，我们提出了我们的第一个研究单壁碳纳米管传感器作为电探针询问单个巨噬细胞和探针细胞活性。作为免疫系统的一部分，巨噬细胞可以在称为吞噬作用的过程中摄取和消化病原体。[5]我们用抗体包裹SWNT传感器以刺激巨噬细胞附着、摄取并试图消化传感器。在吞噬过程中，发生了许多过程，包括抗体与膜结合受体的结合、细胞形态的变化、pH值的变化和细胞毒性分子的产生。通过在电解质门控晶体管配置中使用抗体涂覆的SWNT，[6]我们的目标是通过同时监测晶体管电导（FET信号）的变化和电化学电流（EC信号）的变化来实时跟踪吞噬过程。将SWNT悬挂在基底上方以允许细胞和SWNT之间的紧密接触。[7]我们目前的实验显示FET和EC细胞粘附后的反应，这表明成功检测细胞活性。然而，在所制造的布局中的单壁碳纳米管传感器的性能不是最佳的：我们发现悬浮的、接触钝化的单壁碳纳米管晶体管的FET信号通常是不稳定的，并且在单壁碳纳米管电极处的电化学反应被抑制。我们表明，单壁碳纳米管的电化学信号的检测可以增强时，涂覆有催化铂纳米粒子。最后，我们讨论了单壁碳纳米管作为电探针研究单细胞的前景。图1a显示了用于研究巨噬细胞活性检测的实验装置布局。我们用的是接触钝化的悬挂式单壁碳纳米管[8，9]通过光刻限定电接触化学气相沉积（CVD）生长的SWNT的Cr/Au电极，在氧化的硅晶片上制造SWNT晶体管。打开聚甲基丙烯酸甲酯（PMMA）钝化层中的窗口以部分暴露SWNT，[9]之后使用缓冲HF蚀刻将SWNT悬浮在SiO2衬底上方。[7]SWNT的悬浮段允许巨噬细胞吞噬SWNT。虽然吞噬SWNT的细胞的确切几何形状是未知的，但由于器件布局的原因，SWNT传感器的吞噬作用需要SWNT的不完全吞噬。这种布局的变化将在后面讨论。将具有SWNT器件的衬底放置在珀耳帖元件顶部的自制流动池中，以将温度保持在约37 ° C。那个...
Electronic sensors based on individual single-walled carbon nanotubes (SWNTs) provide an excellent opportunity to expand the existing set of electrical probes available for single-cell studies with a versatile high-sensitivity probe of nanometer dimension. SWNTs have been shown to function both as nanoscale electrochemical sensors and as electrostatic fieldeffect-transistor (FET) sensors.[1–3] The biological processes occurringinandaroundlivingcellsarecommonlyofelectrostatic and/or electrochemical nature, and can thus potentially be probed with SWNT sensors. Importantly, SWNTs have a quasione-dimensional cylindrical geometry.[4] With a length of several micrometers, a SWNT can span a single cell, while its diameter is of the order of one nanometer, directly comparable to the size of single proteins. In comparison with current electrical probes that have lateral dimensions comparable to single cells,[5] SWNT probes can have a higher spatial resolution and impose a largely reduced physical perturbation when in contact with or puncturing through the membrane of a single cell. Here we present our first studies of SWNT sensors as electrical probes to interrogate single macrophage cells and probe cellular activity. As part of the immune system, macrophages can ingest and digest pathogens in a process known as phagocytosis.[5] We coat SWNT sensors with antibodies to stimulate macrophages to attach to, ingest, and attempt to digest the sensors. During phagocytosis a multitude of processes occur, including binding of antibodies to membrane-bound receptors, changes in cell morphology, pH changes, and the production of cytotoxic molecules. By employing antibody-coated SWNTs in an electrolyte-gated transistor configuration,[6] we aim to follow the process of phagocytosis in real-time by simultaneously monitoring both changes in transistor conductance (FET signal) and changes in the electrochemical current (EC signal). The SWNTs are suspended above the substrate to allow close contact between the cell and the SWNT.[7] We present experiments that display FET and EC responses after cell adhesion, which suggests successful detection of cellular activity. The performance of the SWNT sensors in an as-fabricated layout is, however, not optimal: we find that the FET signal of suspended, contactpassivated SWNT transistors is often unstable and that electrochemical reactions at the SWNT electrodes are suppressed. We show that the detection of electrochemical signals from single cells can be enhanced when the SWNT is coated with catalytic platinum nanoparticles. Finally, we discuss the prospects of SWNTs as electrical probes to study single cells. Figure 1a shows the experimental device layout used to study the detection of macrophage activity. We use a SWNT in a contact-passivated, suspended layout.[8, 9] SWNT transistors are fabricated on oxidized silicon wafers by lithographically defining Cr/Au electrodes that electrically contact chemicalvapor-deposition (CVD)-grown SWNTs. Windows in a poly (methyl methacrylate)(PMMA) passivation layer are opened up to partially expose the SWNTs,[9] after which a buffered HF etch is used to suspend the SWNT above the SiO2 substrate.[7] The suspended segment of the SWNT allows the macrophage cell to engulf the SWNT. Although the exact geometry of the cell engulfing the SWNT is not known, phagocytosis of the SWNT sensor entails an incomplete swallowing of the SWNT due to the device layout. Variations to this layout are discussed later. The substrate with SWNT devices is placed in a homebuilt ffow-cell on top of a Peltier element to maintain the temperature at about 37 8C. The …