Phage-based label-free biomolecule detection in an opto-fluidic ring resonator

We have developed a sensitive and inexpensive opto-fluidic ring resonator (OFRR) biosensor using phage as a receptor for analyte detection. Phages have distinct advantages over antibodies as biosensor receptors. First, affinity selection from large libraries of random peptides displayed on phage provides a generic method of discovering receptors for detecting a wide range of analytes with high specificity and sensitivity. Second, phage production can be less complicated and less expensive than antibody production. Third, phages withstand harsh environments, reducing the environmental limitations and enabling regeneration of the biosensor surface. In this work, filamentous phage R5C2, displaying peptides that bind streptavidin specifically, was employed as a model receptor to demonstrate the feasibility of a phage-based OFRR biosensor. The experimental detection limit was approximately 100 pM streptavidin and the Kd(apparent) is 25 pM. Specificity was verified using the RAP 5 phage, which is not specific to streptavidin, as the negative control. Sensing surface regeneration results show that the phage maintained functionality after surface regeneration, which greatly improves the sensors’ reusability. The phage-based OFRR biosensor will become a promising platform for universal biomolecule detection with high sensitivity, low cost, and good reusability.