Biofunctionalization strategies for optical fiber grating immunosensors

Optical fiber sensors are of growing interest in biomedical applications, especially for early diagnosis and in situ assays. Their intrinsic properties bring numerous assets for the detection of low concentrations of analytes, such as easy light injection and the possibility to obtain remote and real-time interrogation of very low amounts of analytes. Among the different optical fiber configurations, tilted fiber Bragg gratings (TFBGs) manufactured in the core of telecommunication-grade optical fibers are known to be highly-sensitive and temperature-compensated refractometers, as they couple light to the surrounding medium. In our work, we have used different strategies to turn them into label-free (plasmonic) immunosensors. Bare and gold-sputtered configurations were biofunctionalized with antibodies and aptamers, aiming at the detection of cancer biomarkers. In this paper, we review the biofunctionalization processes that can be used in these different cases and discuss the obtained performances. For the most sensitive configuration, we report an experimental limit of detection of 10(-12) g/mL in laboratory settings.