Specific Detection of Aquaporin-2 Using Plasmonic Tilted Fiber Grating Sensors

Aquaporin-2 (AQP2) has been identified as one of the most important biomarkers for nephrotic syndrome analysis. Here we propose and experimentally demonstrate a surface Plasmon resonance (SPR) reflective fiber-based biosensor for label-free specific detection of the urinary AQP2 with high resolution. The biosensor utilizes a tilted fiber Bragg grating with a 50 nm gold coating to excite SPR for the detection of refractive indices change at the fiber surface and the surroundings. The sensor works with very controllable cross-sensitivities because the core mode is temperature dependent but insensitive to surrounding refractive index. This label-free sensing system takes advantage of the specific functionalization of the sensor with AQP2 antibody, which has a high specificity to the target protein. The intensity variation of a selected plasmonic resonance caused by the specific capture of urinary AQP2 enables us to clearly differentiate between healthy and nephropathic samples in a few minutes, with the limit of detection up to 1.5 ng/ml.