Impedimetric detection of bacteria by using a microfluidic chip and silver nanoparticle based signal enhancement

Abstract

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.

Recent Advances in (Bio)Chemical Sensors for Food Safety and Quality Based on Silver Nanomaterials

“…High specificity of the modified Au electrode was proven towards C. sakazaki , MRSA, S. albus , L. easei and S. flexneri . In the second report, encapsulation of negatively charged E. coli surface with positively charged poly(dimethyldiallylammonium chloride) (PDDA) enabled the connection between bacteria and nanogold particles ( 84 ). Silver enhancement reaction resulted in the formation of E. coli /PDDA/AuNP@Ag complex, which improved the performance of a novel microfluidic chip for the impedimetric detection of bacteria.…”

Recent advances in magnetic nanoparticle-based microfluidic devices for the pretreatment of pathogenic bacteria

“…After bacteria–MNP complexes are separated from a sample solution, various devices, such as optical, electrochemical, and magnetoresistance sensors, can be employed to detect target bacteria [ 49 – 51 ]. Detailed detection methods have already been discussed in numerous review papers [ 52 – 55 ]. The most sensitive detection method employs optical probes, such as gold nanoparticles, fluorescent dyes, and quantum dots [ 37 , 56 , 57 ].…”

Impedance-Based Detection of Bacteria

“…In many cases, signal amplification methods can greatly improve LODs and linear detection ranges. There are a variety of strategies for signal amplification, ranging from enzymatic methods to those involving nanoparticle-coated cells …”