Insulator-based (electrodeless) dielectrophoresis (iDEP) is an innovative approach in which the nonuniform electric field needed to drive DEP is produced by insulators, avoiding problems associated with the use of electrodes. Live and dead Escherichia coli were concentrated and selectively released by applying stepped DC voltages across a microchannel containing an array of insulating posts etched in glass. The only electrodes present were two platinum wires placed in the inlet and outlet reservoirs, producing mean electric fields of up to 200 V/mm across the insulators. The cells were labeled with Syto 9 and propidium iodide and imaged through a fluorescent microscope. Cell trapping and release were controlled by modifying the relative responses of electrokinesis and DEP by adjusting the magnitude of the applied voltage. Dead cells were observed to have significantly lower dielectrophoretic mobility than live cells, whereas the electrokinetic mobilities of live and dead cells were indistinguishable. The locations of the bands of differentially trapped cells were consistent with predictions. In addition, cells were selectively trapped and concentrated against backgrounds of 1- and 0.2-μm carboxylate-modified polystyrene particles. This first application of iDEP for simultaneous live/dead bacteria separation and concentration illustrates its potential as a front-end method for bacterial analysis.
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机译:基于绝缘体的(无电极)介电电泳(iDEP)是一种创新方法,其中驱动DEP所需的非均匀电场由绝缘体产生,避免了与电极使用相关的问题。通过在微通道上施加阶梯状的直流电压来浓缩活生和死亡的大肠杆菌,并选择性地释放它们,该微通道包含一系列在玻璃中蚀刻的绝缘柱。仅有的电极是放在入口和出口储液罐中的两条铂金丝,在绝缘子上产生的平均电场高达200 V / mm。用Syto 9和碘化丙啶标记细胞,并通过荧光显微镜成像。通过调节电动势和DEP的相对响应(通过调节施加电压的大小)来控制细胞的捕获和释放。观察到死细胞比活细胞具有明显更低的介电泳迁移率,而活细胞和死细胞的电动迁移率却难以区分。差异捕获细胞带的位置与预测一致。另外,细胞被选择性地捕获并在1-和0.2-μm羧酸盐改性的聚苯乙烯颗粒的背景下浓缩。 iDEP在同时进行活/死细菌分离和浓缩中的首次应用说明了其作为细菌分析前端方法的潜力。
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