Label-free fiber optical biosensor has a promising prospect in “point-of-care” (POC) test for disease diagnosis. A sensitive label-free fiber-optic based immunosensor for quantitative Cardiac Troponin I (cTn-I) testing has been proposed by using a phase-shifted Bragg grating directly inscribed in microfiber. The fine notch signal in the grating spectrum remarkably enhances the ability of the sensor in detecting an extremely small amount of immune binding events, which is essential for AMI diagnosis at very early stage. A cTn-I concentration of 6 pg/mL is enough to arouse the response of the sensor with high specificity. According to the log-linear range of the concentration between 0.1-10 ng/mL, measurements with shorter detection time are analyzed to demonstrate the potential of the sensor in the fast screen of the high-risk patients. The proposed sensing probe is compact and feasible, easy to handle, fabricate and network, making itself a competitive candidate in POC diagnosis of AMI.
We have developed a chip-scale optofluidic sensor for biomolecular detection, by tapering laterally aligned silica microfiber and capillary to form a modal interferometer. With the pre-immobilization of DNA probes, the sensor is capable of selectively detecting single-stranded microRNA-let7a (molecular weight: 6.5 k) by measuring the spectral shift of the interferometric spectrum. A log-linear response from 2 nM to 20 μM and a minimum detectable concentration of 212 pM (1.43 ng/mL) have been achieved. The sensor is promising for future diagnosis applications due to its high sensitivity, resistance to environmental perturbations, improved portability, and intrinsic connection to fiber optic measurement.