| Biosensor technology has important research value and application requirements in disease diagnosis, drug development, environmental monitoring and other fields. Exploring sensing mechanism, developing novel sensor, and broadening the biomedical sensing application have become the urgent demand to the related industry development. The employment of new material- fiber has brought fresh vitality to modern biological sensing technology. Different from other functional materials, optical fiber has the advantages of small size, high sensitivity, anti-interference, security and good biocompatibility, thus fiber has become one of the most rapidly developing sensing medium in recent two decades. The realization of high sensitivity, high specificity, label-free optical fiber of "in vivo‖ biomedical detection technologies, and the development of integrated fiber optic biomedical sensors, have become the research focus and developing direction in this field.In this paper, microfiber Bragg grating and single tapered fiber-optic interferometer is uesd as the a conversion element of the biosensor, and the sensitive biological membrane on the surface of the fiber is used as a recognition element. The measured biological information can be efficiently converted to optical signal for detecting identification with high refractive index(RI) sensitivity and high specific recognition ability. Different from complex pretreatment process of traditional labeled sensors, the above two kinds of optical microfiber devices directly measure biological samples by strong evanescent field, and sensing probe has the characteristic of compact design, flexible structure and so on. These devices provide a new approach for high resolution, label free, in vivo detection of biomedical sensing.The main content of the thesis is as follows:(1) A fiber-optic biosensor with microfiber Bragg grating for in-situ DNA hybridizationThe mechanism of DNA sequence hybridization is detecting high specific target DNA in the test sample by a known DNA sequence. Microfiber Bragg grating is high-efficiently fabricated by 193 nm excimer laser combined with the phase mask. The specific recognition of microfiber grating biological probe is manufactured by adsorption method. The minimum detectable concentration of 0.5μM and the repeated measurement results are reliably obtained. At the same time, the nonspecific response of DNA hybridization with microfiber Bragg grating has been experimentally demonstrated. We propose the relative wavelength separation to eliminate temperature cross-sensitivity problem of DNA hybridization(2) A fiber-optic biosensor with single tapered fiber-optic interferometer aptasensor forin-situ thrombin detectionBased on thrombin and thrombin aptamers with high specificity and strong affinity, single tapered fiber-optic interferometer aptasensor for thrombin detection has been proposed. The microfiber biological probe with specific recognition is achieved by the covalent bonding method to modify thrombin aptamer. Then the tests for target thrombin detection with different concentrations are operated, with the lowest detectable concentration of 0.1μM. Specific response in the serum close to the actual situation is researched further and gets good results. Finally, we choose pepsin for the non-specific test, because of its molecular weight corresponding to thrombin. The used device is drawn and tapered by heating method using a butane flame brushing. The RI sensitivity of this device is 1660 nm/RIU, and it has a low coefficient of temperature response. The device is designed as ―U-shaped‖ sensing probe mechanically to simply stabilize the test system of biosensing measurement.(3) Breast cancer antigen immunosensor based on tapered fiber-optic interferometerBased on immunosensing mechanism of high specificity of breast cancer marker antigen with corresponding antibody, the properties of the sensitive biological membrane will chang with specific reaction. The specific recognition of microfiber biological immune-probe is achieved by the covalent bonding method. Then the tests for breast cancer biomarkers HER2 antigen detection with different concentrations are operated. The feasibility of the biosensor has been verified in the early diagnosis of breast cancer detection... |
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