Electrochemical biosensor array for the identification of microorganisms based on lectin-lipopolysaccharide recognition.

Rapid identification of bacterial strains remains a well-known problem in applied medicine and, for viable pathogens, is an important diagnostic goal. We have investigated an electrochemical biosensor array, in which transduction is based on respiratory cycle activity measurements, where the microorganism's native respiratory chain is interrupted with non-native external oxidants. The selective biochemical recognition agents employed in this study are lectins that, once immobilized, recognize and bind to cell surface lipopolysaccharides. Porous membranes with different surface properties were examined as potential immobilization supports for these lectins. Optimizations performed using concanavalin A and E. coli JM105 show that immobilization methods involving pre-activated membranes significantly reduce the time required to create a functional lectin layer on the membrane surface. Overall, we found general agreement between agglutination test results and the electrochemical assessment of lectin-cell binding. Chronocoulometric measurements were made for cells captured on lectin-modified Immunodyne ABC membranes physically affixed to Pt working electrodes. This lectin-based sensor array was exposed to viable cells of gram-negative and gram-positive bacteria as well as yeast, and chronocoulometric measurements were used to generate a pattern of responses for each organism toward each lectin. Principal component analysis was used to classify the chronocoulometric results for the different microbial strains. With this new method, six microbial species (Baccilus cereus, Staphylococcus aureus, Proteus vulgaris, Escherichia coli, Enterobacter aerogenes, Saccharomyces cerevisiae) were readily distinguished.