Development of Bacteria sensor using Dielectrophoresis and Electropermeabilization

为了获得更高的细菌检测灵敏度，成功地将电渗透（EP）与DEPIM结合。电极释放的金属离子污染掩盖了细胞内离子释放引起的细微电导增加，通过改善脉冲电位波形成功地抑制了污染。在10^2 CFU/ml下，3 h即可定量检测出大肠杆菌，相对于不加EP的常规DEPIM提高了两个数量级。该技术是一种快速、灵敏的细菌检测方法，可以很容易地集成到Bio-MEMS或μ-TAS器件中。为了增加细菌的DEPIM或EPA-DEPIM检测的选择性，使用预先固定目标细菌特异性抗体的电极芯片演示了新的检测方案。在第一种方法中，首先通过强正DEP将所有细菌捕获到电极芯片上，通过洗涤液流动施加水动力阻力，以选择性保留可与固定化抗原结合的目标细菌。虽然通过使用抗体修饰的芯片，保留的目标细菌数量增加了，但与未修饰芯片的非特异性结合也发生了。第二种方法利用较低的DEP力，使捕集和洗涤过程可以同时完成。EPA-DEPIM比常规DEPIM更敏感，在DEP力降低的情况下，残留细菌数量明显减少。发现该方案还可以抑制非特异性细菌的结合，大大提高了对目标细菌的选择性。

Electropermeabilization (EP) was successfully incorporated with DEPIM in order to achieve higher sensitivity for bacteria detection. Contamination of metallic ions released from electrodes, which masks subtle conductance increase caused by the released intracellular ions, was successfully suppressed by improving the pulse waveform for EP. E. coli was quantitatively detected in 3 h at 10^2 CFU/ml, which was improved by two orders of magnitude relative to the conventional DEPIM without EP. The proposed technique is promising as a fast and sensitive bacteria inspection method and may be easily incorporated into Bio-MEMS or μ-TAS devices.In order to add selectivity to DEPIM or EPA-DEPIM inspection of bacteria, new inspection protocols were demonstrated using an electrode chip on which a target bacteria-specific antibody was immobilized in advance. In the first method, all bacteria were first trapped onto the electrode chip by strong positive DEP. In order to selectively retain the target bacteria, which could bind with the immobilized antigen, the hydrodynamic drag force was exerted by washing liquid flow. Although the number of retained target bacteria increased by using the antibody-modified chip, undesired non-specific binding to the unmodified chip also took place. The second method utilized lower DEP force so that trapping and washing processes could be simultaneously accomplished. A smaller number of retained bacteria under decreased DEP force was surely detected by EPA-DEPIM, which was more sensitive than the conventional DEPIM. It was found that this protocol could also suppress the non-specific bacteria binding and greatly improve the selectivity for the target bacteria.