Now, a label-free biosensor has been defined as “to detect a whole biologically active molecule in real time”. Also, the specificity and sensitivity common to all assays must apply. To be precise, to be fast, to be small, to be integrated and less cost….. Is it possible? In this talk, several results for improving the sensitivity, the specificity and the dynamic range of a label-free optical fiber biosensor will be discussed.
First, a tapered optical fiber refractometer and biosensor modifying their unclad region with the coating of SiO2 and gold nanospheres will be compared to show that the combination of nanosphere-induced absorption and scattering losses and multimode propagation of tapered fiber gives a way to increase its detection range. Second, the results of ultrasensitive label-free detection of cardiac troponin I with optical microfiber coupler is shown when it works around the turning point. The detection limit with a concentration as low as 2fg/mL can be achieved using the proposed immunosensor. This kind of immunosensor has great application potential for biomarkers detection due to its characteristics as simple scheme, fast response and ease to miniaturation.Finally, the Fano and some other extraordinary effects by tapered optical fiber coupled WGMs will be discussed. The functions of several special modes may help to take the challenges of selectivity for plasma detection.
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