Pathogen detection, immobilization

A special nonspecific sensor response might be due to the cross-reactivity of immobilized antibodies. Besides the analyte, an antibody can bind also other entities bearing a similar antigenic epitope, e.g. the detection of some pathogenic bacteria can be interfered by the binding of non-pathogenic bacteria with the same surface antigen. 

There are however difficulties in running multiplex PCR, and it is difficult to differentiate PCR products of approximately the same size in a multiplex PCR or PCR-RFLP gel. However DNA microarrays do not have these problems, and have been used to serotype pathogenic strains and proved to be rapid, reliable and sensitive. The approach involves the immobilization of numerous oligonucleotide DNA probes on a solid support to which fluorescence-labeled amplified target DNA is hybridized, and is a powerful tool for the detection of pathogens by virtue of high throughput, speed and sensitivity. 

Immobilized lysate antigen of E. coli 0157 H7 at different concentrations was assayed and the low detection limit was 3 gg/mL. The assay also demonstrated very good specificity different microbial lysate antigens were immobilized, including E. coli and H. pylori, and the primary and secondary antibodies were mixtures of different species. The assay time is only 25 min (the conventional lab based assay requires over 3 h) the sample consumed was less than 12 pL. While still an un-optimized chip, this lA chip shows a great potential in detecting multiple pathogen efficiently. 

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