Selective bacteria detection using dielectrophoretic impedance measurement combined with antigen-antibody reaction

(1)采用抗原-抗体反应的选择性介电泳阻抗测量法（DEPIM）——对两种DEPIM与免疫分析法的组合进行了测试。一种方法是利用细菌的凝集来增加介电泳力。另一种方法利用抗体分子固定在微电极表面。-两种方法在初步介电泳富集后都会在电极表面留下特殊细菌。凝集或固定的细菌可以通过电极电导的残余增加来电检测。(2)介质电泳过滤器回收和富集细菌-采用多段DEP过滤器在1小时内富集细菌悬浮液30倍。- DEP过滤器富集成功地与DEPIM相结合，用于低密度的细菌检测作为预富集程序。(3)采用电渗透技术的高灵敏度DEPIM——通过对被捕获细菌施加高交流电场，观察到电导突然增加，这可能是由电渗透引起的。-对于酵母细胞，在15分钟的诊断时间内，DEPIM的灵敏度下限从10^4提高到10^2 CFU/ml。(4)碳纳米管的介电泳操作及其气体传感器应用——在正DEP力的作用下，碳纳米管被捕获并富集在微电极间隙中。在DEP捕获过程中，电极阻抗随碳纳米管数量的增加而变化。-保留碳纳米管的微电极可以检测浓度低于10ppm的氨气。

(1)Selective DEPIM (dielectrophoretic impedance measurement) using antigen-antibody reaction-Two kinds of combinations of DEPIM with immunoassay are tested. In one method, agglutination of bacteria is employed to increase dielectrophoretic force. The other method utilizes antibody molecules immobilized onto the microelectrode surface.-Both methods can leave peculiar bacteria on the electrode surface after preliminary dielectrophoretic enrichment. Agglutinated or immobilized bacteria can be electrically detected by residual increase of the electrode conductance.(2)Dielectrophoretic filter for recovery and enrichment of bacteria-The bacteria suspension was enriched by 30 times in one hour using a multi-segment DEP filter.-The DEP filter enrichment was successfully combined with DEPIM for bacteria detection at lower density as a pre-enrichment procedure.(3)High sensitive DEPIM using electropermeabilization-By applying high ac electric field to the trapped bacteria, abrupt conductance increase, which is possibly caused by electropermeabilization, is observed.-For yeast cells, the lower limit of DEPIM sensitivity is improved from 10^4 to 10^2 CFU/ml for 15 min diagnosis time.(4)Dielectrophoretic manipulation of carbon nanotubes and gas sensor application-Carbon nanotubes (CNTs) were trapped and enriched in an microelectrode gap under the action of a positive DEP force. During the DEP trapping, the electrode impedance varied as the number of CNTs increased.-The microelectrode retaining the CNTs could detect ammonia gas below 10 ppm concentration.