Abstract
This paper proposes a needle-type biosensor for immunological application, which combines the abilities of real-time monitoring, in-situ measurement and high sensitivity, by adopting gold-nanoparticles (GNPs) coated with antibody to enhance the signal of Fabry-Perot (F-P) interferometry in an optic fiber sensing system. Strong reflection induced by larger index mismatch and longer optical path from GNPs-protein conjugation are suggested to attribute most to the signal enhancement in F-P interference shift. The experiments carry out the monitoring of immuno-sensing in real-time by the employment of rabbit IgG conjugate to GNPs-anti-rabbit IgG. And the detection limit was demonstrated to approach 0.17 nM (∼25.5 ng/ml), which was three orders of magnitude better than those of the traditional fiber-based F-P biosensors. Besides, the reproducibility of the sensor has been tested through at least three cycles of detection/surface- regeneration process and demonstrated a reasonable consistency. The relationship between the concentrations of GNPs-antibody and F-P spectrum shift has also been characterized. The time-constant of this sensor to complete one cycle of biomolecule-detection and surface-regeneration can be as low as 4 minutes. © 2007 IEEE.