College of Chemistry and Chemical Engineering, Chongqing University, Chongqing, 400044, China.
Key Principle Laboratory of Fundamental Science of Micro/Nano-Device and System Technology, Chongqing, 400044, China.
Mikrochim Acta. 2018 Feb 19;185(3):184. doi: 10.1007/s00604-017-2645-x.
The authors describe a method that can significantly improve the performance of impedimetric detection of bacteria. A multifunctional microfluidic chip was designed consisting of interdigitated microelectrodes and a micro-mixing zone with a Tesla structure. This maximizes the coating of bacterial surfaces with nanoparticles and results in improved impedimetric detection. The method was applied to the detection of Escherichia coli O157:H7 (E. coli). Silver enhancement was accomplished by coating E.coli with the cationic polymer diallyldimethylammonium chloride (PDDA) to form positively charged E. coli/PDDA complexes. Then, gold nanoparticles (AuNPs) were added, and the resulting E. coli/PDDA/AuNPs complexes were collected at interdigitated electrodes via positive dielectrophoresis (pDEP). A silver adduct was then formed on the E. coli/PDDA/AuNP complexes by using silver enhancement solutions and by using the AuNPs as catalysts. The combination of pDEP based capture and of using silver adducts reduces impedance by increasing the conductivity of the solution and the double layer capacitance around the microelectrodes. Impedance decreases linearly in the 2 × 10-2 × 10 cfu·mL E. coli concentration range, with a 500 cfu·mL detection limit. Egg shell wash samples and tap water spiked with E. coli were successfully used for validation, and this demonstrates the practical application of this method. Graphical abstract Schematic representation of the AuNP@Ag enhancement method integrated with multifunctional microfluidic chip platform for impedimetric quantitation of bacteria. The method significantly improves the performance of impedimetric detection of bacteria.
作者描述了一种可以显著提高细菌阻抗检测性能的方法。设计了一种由叉指微电极和具有特斯拉结构的微混合区组成的多功能微流控芯片。这最大限度地增加了细菌表面与纳米颗粒的涂层，并导致阻抗检测得到改善。该方法应用于检测大肠杆菌 O157:H7（E. coli）。通过用阳离子聚合物二烯丙基二甲基氯化铵（PDDA）涂覆大肠杆菌来实现银增强，从而形成带正电荷的大肠杆菌/PDDA 复合物。然后，添加金纳米颗粒（AuNPs），并通过正介电泳（pDEP）将所得的大肠杆菌/PDDA/AuNPs 复合物收集在叉指电极上。然后，通过使用银增强溶液并利用 AuNPs 作为催化剂，在大肠杆菌/PDDA/AuNP 复合物上形成银加合物。基于 pDEP 的捕获和使用银加合物的组合通过增加溶液的电导率和围绕微电极的双层电容来降低阻抗。在 2×10-2×10 cfu·mL 的大肠杆菌浓度范围内，阻抗呈线性下降，检测限为 500 cfu·mL。成功地使用鸡蛋壳洗涤样品和添加大肠杆菌的自来水进行了验证，这证明了该方法的实际应用。
