A disposable fiber optic SPR probe for immunoassay.

Immunoassay can be divided into two aspects, one is immobilization of antibodies for the efficient detection of corresponding antigens, and the other is immobilization of antigens to search for antibodies which work against them. In this paper, we demonstrated these two aspects of immunoassay by using the disposable fiber optic biosensors based on surface plasmon resonance (SPR) through surface decoration with half-antibody fragments, which has been scarcely ever reported to the best of our knowledge. We first fabricated the fiber optic SPR biosensor which consists of one gold film coated single-mode fiber sandwiched by two multimode fibers. Then, we decorated the fiber optic SPR biosensors with antibody fragments and antigen fragments, respectively, and compared the specific detection performances of these two kinds of sensors. After surface decoration with half-antibody fragments, the antigen-decorated fiber probe has a demonstrated sensitivity and limit of detection of 0.9771nm/(μg/mL) and 0.1 μg/mL, respectively, which improves by 10 times compared with the performance of the antibody-decorated fiber probe. Additionally, the selective detection results indicate that our proposed biosensor can be employed as a reliable antigen detector or an effective antibody filter. Our proposed sensor has the advantages of miniaturization, low cost, simple usage, label-free detection, high efficiency and sensitivity, and can effectively avoid cross-contamination caused by reuse. Given the reliable and clean detection method for immunoassay, our work should open a new window for the utilization of miniaturized fiber optic sensors in biochemical sensing.