Sensitivity and Response Time of Polyethyleneimine Modified Impedimetric Transducer for Bacteria Detection

© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. An impedimetric transducer based on an interdigitated electrode array (IDEA) modified with polyethyleneimine was used to study interactions with bacteria present in a sample solution. Bacteria immobilization on the sensor surface affects the surface charge and produces changes in the superficial impedance. The sensor surface was chemically modified by layer-by-layer (LbL) method with oppositely charged polyelectrolyte layers by alternating polyethyleneimine (PEI) and poly(sodium 4-styrenesulfonate) (PSS). Escherichia coli gram-negative bacteria were employed as a model for sensitivity and response time evaluation. Bacteria were immobilized on IDEA with PEI-PSS-PEI multilayer taking into account the ability of PEI to react chemically with outer membrane compounds of gram-negative bacteria and thus improve purely electrostatic interactions. Detection limit of the sensor was found to be as low as 101cfu/mL in E. coli cultures with response time around 20minutes. In order to introduce a biorecognition element by bacterial detection, the lectin Concanavalin A (ConA) was deposited on IDEA surface through PEI-ConA interaction, achieving a detection limit of 104cfu/mL. The strategies developed show the possibility to achieve highly sensitive and rapid detection of bacteria using IDEA transducers.