Surface Plasmon Resonance Biosensor Based On Tilted Fiber Bragg Grating

With the rapid development of bioinformatics since the mid-20 th century, all kinds of biomedical issue have attracted our attention together with the biosensor technology. A surface plasmon resonance based on tilted fiber Bragg grating being(TFBG-SPR) used as the light guiding medium have been proposed and experimental demonstrated, which has been a wide range application by the function of the cost-effective and relatively simple-to-implement platform that has been proved significant value by the property of rapid, without labeling, real-time, high sensitivity.In this paper, the application of SPR based on fiber, which is different from the prism configuration, has been introduced with hybrid new instrument of TFBG. According to the coupled-mode theory, the TFBG coupling principle as well as its cladding modes polarization property has been clearly explained, meanwhile, we could also know its response to the surrounding refractive index change. After debating the phase-match condition and internal relationship of dispersion between cladding mode and surface plasmon wave, the thickness of the sliver coating on the surface of the fiber is precisely controlled at 15 nm(thinner than normal case by 45 nm), which provides the support for the both of leaky mode penetrating the metal layer and surface plasmon resonance in transmission spectrum.Based on the theoretical and manufacture method, two main applications for biomedicine are proposed:(1) The monitoring of the intracellular density in cell changes responding to drug and environmental factors: for convenience, this phenomenon is named as “density alteration in non-physiological cells”(DANCE). Human acute leukemia cells with different intracellular densities, which were incubated with retinoic acid for 48 hr, at 0, 8, 16 μg/m L, “DANCE up”(decrease in intracellular density) was observed with increasing of the drug concentration, were clearly discriminated in-situ by using the differential transmission spectrum between two orthogonal polarizations for the last guided mode resonance before “cut-off”, with an amplitude variation sensitivity of 1.4×104 d B/RIU and a limit of detection of 2×10-5 RIU. With the presence of drugs, the surface-RI falls resulting from the decrease the cell densities,which might provide a potential way to verify the hypothesis for DANCE.(2) The monitoring of the Aquaporin in the rats urine: after tail vein injection by adriamycin in healthy rats, the expression of Aquaporin-2 in kidney arise dramatically and so does it excrete in urine which could be used as a criteria for detecting the recovery from a traditional Chinese medicine therapy named Zhen Wu Tang. A new method has been proposed by using SPR biosensor based on TFBG with ultra-thin sliver-coating, which investigates the surface RI change of the biosensor when the entire protein link to the surface of the fiber with help of fibronectin and provides the support for surface plasmon resonance together with “cut-off” resonance in transmission spectrum simultaneously. Both of these two resonances show extremely high sensitivities but inverse amplitude responses to the bio-sample interaction, with an amplitude variation sensitivity of ~8098.3d B/RIU. By further validation, the BCA and ELISA method were applied to verify that the climb of total amount of protein in urine induce the rise of the surface RI, meanwhile, except the AQP2, the other component remain stable, which reveals the fact that the AQP2 can be quantitatively detected by monitoring the surface RI change.