Lectin Based Biosensor Array for Bacterial Identification and Quantitation

Biosensors consist of biochemical recognition agents, like enzymes, antibodies, nucleic acids or chemoreceptors, immobilized on the surfaces of transducers, that change the recognition event into a measurable electronic signal.  In this project, lectins are used for selective recognition of oligosaccharide structures present in bacterial surface lipopolysaccharides.  Transduction is accomplished using electrodes that detect the presence of living cells bound to the electrode surface through electrochemical respiratory cycle activity measurements.

To design the array, lectins with different saccharide recognition properties are separately bound to porous membrane disks; the disks are exposed to the cell culture, and are then placed in the wells of a screen-printed electrochemical microwell array, so that a different lectin is used in each well.  The cells bound to the membrane via the lectins are then detected electrochemically.  The pattern of electrochemical signals indicates the pattern of binding for that organism to the lectin-modified membranes, and is quite distinctly related to the species and subspecies of organism.  Using these methods, six bacterial species were readily identified, and four E. coli subspecies were also easily distinguished.

We are now extending this array to the quantitative determination of microorganisms, since the electrochemical signal magnitudes depend directly on the number of cells attached to the membranes.  The resulting arrays should be able to both identify and quantitate microorganisms.

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