Bacteriophages are interesting entities on the border of biology and chemistry. In nature, they are bacteria parasites, while, after genetic manipulation, they gain new properties, e.g., selectively binding proteins. Owing to this, they may be applied as recognition elements in biosensors. Combining bacteriophages with different transducers can then result in the development of innovative sensor designs that may revolutionize bioanalytics and improve the quality of medical services. Therefore, here, we review the use of bacteriophages, or peptides from bacteriophages, as new sensing elements for the recognition of biomarkers and the construction of the highly effective diagnostics tools.

Phage-derived affinity peptides have become widespread thanks to their easy selection via phage display. Interactions between a target protein and its specific peptide are similar to those between antibodies and antigens. The strength of these noncovalent complexes may be described by the dissociation constant (K d ). In this paper, protein-specific peptides are exposed on the pIII protein present in the M13 bacteriophage virion with up to five copies. Therefore, one phage particle can bind from one to five ligands. Here, we discuss the dependences between phagedisplayed peptides and their ligands in solution using a model system based on troponin T (TnT) binding phages. Moreover, a method of calculating K d values from ELISA experiments was developed and is presented. The determined K d values are in the picomolar range.