| Fiber-optic fluorescent biosensors have many advantages, including fast detection, miniaturization, flexibility, and lack of electrical contact and interference. Therefore,they are widely used in many fields, such as clinical medicine, modern athletics, foodstuff safety,and so on. In this paper, we fabricated a fiber-optic biosensor as a detecting platform, developed a choline biosensor based on choline oxidize and Ru(II) complex and a fiber-optic receptor biosensor based on competitive reactions.Choine is an important neurotransmitter in mammals. In the choline biosensor, the sensing end of the fiber is coated with Nafion film dispersed with choline oxidize and oxygen sensitive luminescent Ru(II) complex. Choline oxidize catalyzes the oxidation of choline to betaine and hydrogen peroxide while consuming oxygen. From our experiments, 10-4 mol/L choline can be detected by the sensor and the response of the fiber-optic biosensor was found to be linear to choline in the range of 10-3 mol/L～10-4 mol/L with response times less then 10 sec. The biosensor described here is a low-cost, high-performance, flexible biosensor.There are many methods to detect the dope concentration, which is a kind of small molecule. A fiber-optic dope biosensor based on competitive reactions and fluorescence detection for rapid and accurate determination of target dope concentration is introduced. From our experiments, 10-9 mol / L estrogen or testosterone can be detected by the sensor, and the response of the fiber-optic biosensor was found to be linear in the range from 10-7 mol/L～10-8 mol/L for estrogen and from 10-8～10-9 mol/L for testosterone with response times less then 0.1 s. The agarose gel films immobilized with the protein receptor are stable for more than 1 month when stored in dark under moisture-free conditions at -4℃. The biosensor described here is a low-cost, high-performance, convenient immune biosensor.
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