A perfusion-based micro opto-fluidic system (PMOFS) with GNP signal enhancement for continuously in-situ immune sensing

This paper proposes a novel design of a reusable biosensor for in-situ and continuous protein detection. The sensing probe was practiced by the integration of a fiber optic interferometry (FOI) sensor accommodated in a micro opto-fluidic chip covered with a microdialysis membrane and surface regeneration mechanism for regenerable detection. Gold-nanoparticles (GNPs) labeled anti-rabbit IgG was used to enhance the protein conjugation signal due to an elongated optical path length by GNPs layer, providing extended interference fringe shift for signal enhancement. On the other hand, surface regeneration of the sensor was realized through local pH level manipulation by employing a photoactivable molecule, o-Nitrobenzaldehyde (o-NBA), for the elution of immune complex. Experimental results showed the o-NBA elution method can keep the pH variation to be limited close to the neighboring region of the sensor surface, providing a self-contained sensing system. In-situ immune detection and surface regeneration of the sensing probe was achieved successfully for two identical cycles on the same sensing probe, and 10ng/ml of detection limit can be approached.