Impedance endothelial cell biosensor for lipopolysaccharide detection

It is important to analyse endothelial cell adherence for the development of biomedical devices of antithrombogenic vascular grafts. Endothelial cells must be firmly attached to the biomaterials when cells are seeded in order to create a natural lining. Polystyrene (PS) is presented as a reproducible implant model substrate for studying cell-material interactions. Polystyrene was deposited as a thin layer on a thiol functionalised gold electrode. Fibronectin, a protein promoting the endothelial cell adhesion was then adsorbed on PS surface. The different steps of this multilayer assembly were characterized by Electrochemical Impedance Spectroscopy (EIS). The charge transfer resistance and the capacitance of the total layer were modified at each step in agreement with the electrical properties of each layer. The electrical properties of the confluent layer of endothelial cells were determined: (i) a charge transfer resistance of 2 k Omega cm(-2) shows no large defects in the cell layer, (ii) as the cells attach and spread on the gold electrode, the impedance increases. EIS was used for testing behaviour of endothelial cells on substrate coated by fibronectin layer and in presence of cytotoxicants such as lipopolysaccharide (LPS). The impedance measurement may be a valuable method for the assessment of mechanisms of decreased endothelial barrier function occurring with inflammatory mediators. The results indicate that LPS causes a dose-dependent decrease in impedance of the endothelial cell monolayer, indicating widening of the paracellular pathways and increasing vascular endothelial permeability. This study is an increasing trend towards the development of impedimetric biosensors and designing cell sensor arrays for toxic and drug detection. (c) 2007 Elsevier B.V. All rights reserved.