Development of an optical fiber SPR sensor for living cell activation

Surface plasmon resonance (SPR) sensors provide a useful means to study the interactions of biological molecules and the reaction of living cells on a sensor chip. However, conventional SPR sensors are bulky, expensive and complicated to use as common diagnostic equipment. In this study, we developed a relatively small and simple SPR system, using optical fibers of 250 μm diameter to detect the activation of living cells attached to the fiber tip. For this system, the core of 200 μm diameter with 1 cm length of an optical fiber was coated by gold film with 50 nm thickness to cause plasmon resonance. The light provided by a white LED and attenuated due to a SPR phenomenon in the sensor part was detected and analyzed using a spectrum detector. The difference in solvents with various refractive indexes and protein-bindings to the sensor tip was detected with sufficient sensitivity. Moreover, it detected a sustained increase of AR in a real-time manner, when RBL-2H3 mast cells were fixed onto the fiber tip and stimulated by an antigen. This small fiber SPR system might serve as a useful tool for various clinical examinations either within or outside the body.