Phage-coated paramagnetic beads as selective and specific capture system for biosensor applications

M13 bacteriophage, engineered to express specific and selective peptides on its capsid proteins, can be used as a good substitute for antibodies in recognition of specific targets showing at the same time thermal and mechanical resistance, strength and stability in the presence of different organic solvents and compounds. Magnetic beads are useful tools to identify, separate and concentrate specific target in solution. These are usually coated either with antibodies, which are sensitive to chemical and physical changes, or peptides that are laborious and expensive to produce. In this work we proposed a phage-based biosensor model for capture and identification of specific bacteria in a liquid sample. Commercial fluorescent paramagnetic beads were functionalized with the entire 9mer-M13 phage clone selected towards the pathogen Pseudomonas aeruginosa. Phage probes covalently linked to beads were capable to capture bacteria in suspension. Complexes of phage-coated beads and bacteria were specifically identified using an optical detection system based on the double coloring of non-specifically stained bacteria as well as of beads own fluorescence.