Benhal Prateek, Chase J Geoffrey, Gaynor Paul, Oback Björn, Wang Wenhui
Department of Mechanical Engineering, University of Canterbury, Christchurch, New Zealand.
Lab Chip. 2014 Aug 7;14(15):2717-27. doi: 10.1039/c4lc00312h. Epub 2014 Jun 16.
The precise rotation of suspended cells is one of the many fundamental manipulations used in a wide range of biotechnological applications such as cell injection and enucleation in nuclear transfer (NT) cloning. Noticeably scarce among the existing rotation techniques is the three-dimensional (3D) rotation of cells on a single chip. Here we present an alternating current (ac) induced electric field-based biochip platform, which has an open-top sub-mm square chamber enclosed by four sidewall electrodes and two bottom electrodes, to achieve rotation about the two axes, thus 3D cell rotation. By applying an ac potential to the four sidewall electrodes, an in-plane (yaw) rotating electric field is generated and in-plane rotation is achieved. Similarly, by applying an ac potential to two opposite sidewall electrodes and the two bottom electrodes, an out-of-plane (pitch) rotating electric field is generated and rolling rotation is achieved. As a prompt proof-of-concept, bottom electrodes were constructed with transparent indium tin oxide (ITO) using the standard lift-off process and the sidewall electrodes were constructed using a low-cost micro-milling process and then assembled to form the chip. Through experiments, we demonstrate rotation of bovine oocytes of ~120 μm diameter about two axes, with the capability of controlling the rotation direction and the rate for each axis through control of the ac potential amplitude, frequency, and phase shift, and cell medium conductivity. The maximum observed rotation rate reached nearly 140° s⁻¹, while a consistent rotation rate reached up to 40° s⁻¹. Rotation rate spectra for zona pellucida-intact and zona pellucida-free oocytes were further compared and found to have no effective difference. This simple, transparent, cheap-to-manufacture, and open-top platform allows additional functional modules to be integrated to become a more powerful cell manipulation system.
悬浮细胞的精确旋转是广泛应用于生物技术领域的众多基本操作之一，比如在核移植（NT）克隆中的细胞注射和去核操作。在现有的旋转技术中，明显缺乏的是在单个芯片上对细胞进行三维（3D）旋转。在此，我们展示了一种基于交变电流（ac）感应电场的生物芯片平台，该平台有一个顶部开口的亚毫米方形腔室，由四个侧壁电极和两个底部电极包围，以实现绕两个轴的旋转，即3D细胞旋转。通过向四个侧壁电极施加交流电势，产生一个平面内（偏航）旋转电场并实现平面内旋转。同样，通过向两个相对的侧壁电极和两个底部电极施加交流电势，产生一个平面外（俯仰）旋转电场并实现滚动旋转。作为一个快速的概念验证，底部电极采用标准剥离工艺用透明氧化铟锡（ITO）构建，侧壁电极采用低成本微铣削工艺构建，然后组装形成芯片。通过实验，我们展示了直径约120μm的牛卵母细胞绕两个轴的旋转，能够通过控制交流电势的幅度、频率、相移以及细胞培养基的电导率来控制每个轴的旋转方向和速率。观察到的最大旋转速率接近140° s⁻¹，而持续旋转速率可达40° s⁻¹。进一步比较了有透明带完整和无透明带的卵母细胞的旋转速率谱，发现没有显著差异。这个简单、透明、制造成本低且顶部开口的平台允许集成额外的功能模块，从而成为一个更强大的细胞操作系统。
