Biopanning is a technique used to select peptides or antibodies that bind to a target of interest using affinity selection. Phage are engineered to display a peptide of interest and captured by conjugating to a desired target. Unbound phage are washed from the surface and, finally, the bound phage are eluted to obtain the desired high-affinity phage clones which can then be used to create further display libraries.

The FO-SPR probes of the White FOx are ideally suited for this procedure. The user-friendly dip-in, fluidics-free setup offers a simple protocol for the binding, washing and elution steps, and the binding affinity, association and dissociation kinetics of the phage can be measured in real time.

Bacteriophage kinetic affinity analysis

Generating phage with high affinity to a product is an essential step in the development and production of many proteins and antibodies. A method that can both select the phage with highest affinities and also measure the binding and dissociation kinetics is highly valuable in the efficient design of these applications. However, typical methods for measuring binding kinetics rely on microfluidics and are prone to clogging by phage particles.

The FOx BIOSYSTEMS platform was used to select phage with high affinity for eGFP in order to study the affinity and binding kinetics of phage displaying peptide libraries in a microfluidic-free, dip-in experiment. A clear correlation was demonstrated between the SPR binding parameters and the expression density of the target protein and two phage clones with dissociation constants in the femtomolar range were found.

Affinity selection of phage fiber-optic SPR. Phage expressing eGFP receptors on coat proteins were selected based on their affinity for eGFP. Furthermore, differential SPR signals were obtained when the eGFP receptor was expressed on the P3 (A) or P8 (B) protein due to the difference in protein density on the phage surface.

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