Sensivity and response of modified impedimetric transducer for bacteria toxins detection

Abstract

In this work, an impedimetric transducer based on a three dimensional interdigitated electrode array (3D-IDEA) was used to study interactions with gram-negative bacteria endotoxins from Escherichia coli in a sample solution. Bacteria endotoxins mainly belong to a lipopolysaccharide (LPS) chemical class. LPS immobilization on the sensor surface affects the surface charge and produces changes in the superficial resistance which is possible to detect using impedance spectroscopy technique. The sensor surface was chemically modified with polyethilenimine (PEI) or epoxysilane. As a biorecognition element for bacterial endotoxin detection, lectin Concanavalin A (ConA) was deposited on the IDEA surface through PEI-ConA or epoxysilane-ConA interactions. To prevent non-specific adsorption of LPS different ways of surface blocking were studied. However, different types of blocking agents tested did not permit to enhance the specificity of the sensor. The best results on selective detection of LPS were achieved by modifying surface with Concanavalin A – Glycogen multilayers. Detection limit of the sensor with PEI-(ConA-Gly)2-ConA was found to be as low as 1μgLPS/mL in E. coli endotoxins with response time around 20 minutes. The sensor responses follow the Langmuir adsorption curve (type I) and can be perfectly fitted by Hill’s equation.