Analyte peptidomimetics selected from phage display peptide libraries: a systematic strategy for the development of environmental immunoassays.

Due to their simplicity, speed, low cost, and specificity, immunoassays have become a useful tool for the analysis of environmental pollutants. Once the anti-hapten antibodies are produced, the same hapten or a related molecule is conjugated to a tracer enzyme or coating protein to set up the assay. Here we report the use of peptides that mimic the analyte as advantageous substitutes of competing haptens. These peptides, which open opportunities for innovation in the development of tracer reagents, can be selected from phage display libraries in a straightforward systematic manner. The concept was proven using assays for the herbicides molinate and atrazine as model systems. Several characteristics of the selection process that may affect the final assay were analyzed, such as the phage coat proteins fused to the peptide, the use of linear or constrained peptide libraries, the effect of the concentration of analyte used during the selection process, and the use of monoclonal or polyclonal antibodies as selector molecules. In all cases we found that the selected peptides performed with improved sensitivity as compared with the chemical hapten conventional assays, showing an analogous cross-reactivity pattern. Interestingly, the phage particles perform as robust and highly standardized assay reagents, and due to their filamentous repetitive structure, they function as sensitive multienzymatic reporters.