Abstract
The evolution of optical fiber technology has revolutionized a variety of fields, from optical transmission to environmental monitoring and biomedicine, given their unique properties and versatility. For biosensing purposes, the light guided in the fiber core is exposed to the surrounding media where the analytes of interest are detected by different techniques, according to the optical fiber configuration and biofunctionalization strategy employed. These configurations differ in manufacturing complexity, cost and overall performance. The biofunctionalization strategies can be carried out directly on bare fibers or on coated fibers. The former relies on interactions between the evanescent wave (EW) of the fiber and the analyte of interest, whereas the latter can comprise plasmonic methods such as surface plasmon resonance (SPR) and localized SPR (LSPR), both originating from the interaction between light and metal surface electrons. This review presents the basics of optical fiber immunosensors for a broad audience as well as the more recent research trends on the topic. Several optical fiber configurations used for biosensing applications are highlighted, namely uncladded, U-shape, D-shape, tapered, end-face reflected, fiber gratings and special optical fibers, alongside practical application examples. Furthermore, EW, SPR, LSPR and biofunctionalization strategies, as well as the most recent advances and applications of immunosensors, are also covered. Finally, the main challenges and an outlook over the future direction of the field is presented.
Highlights
Since the 1970s, when the extraordinary revolution in optical fiber (OF) technology took place, extensive research has been dedicated to this area
This means that optical fibers can be used in a variety of fields ranging from environmental monitoring [3] to biomedical diagnosis [4] and food safety [5], since these waveguides present high flexibility and compactness, as well as the ability for remote measurement [6] and immunity to electromagnetic interference [7]
The grating period defines the wavelength configuration represents a great advantage this context.inUncladded, and of the light that is reflected, and the periodicinperturbations the sensors D-shaped based on fiform of an ber Bragg gratings (FBGs) tapered geometries result in small sized biosensors, usually interrogated in transmission, that can be used in miniaturized photonic chips
Summary
Since the 1970s, when the extraordinary revolution in optical fiber (OF) technology took place, extensive research has been dedicated to this area. The bioreceptor is the element responsible to provide a specific biorecognition event for a target analyte, whereas the transducer transforms this biochemical reaction in a measurable signal that is processed by the signal processor They can be classified according to the biorecognition element, which can be based on catalytic (enzymes, cells or tissues) [15] or affinity interactions, namely antibodies (ABs) or nucleic acids [16]. The purpose of this review is to outline the different geometries and configurations used in optical fiber biosensors over the years and provide information about biofunctionalization strategies and their working principles, including EW and SPR/LSPR with. The purpose of this review is to outline the different geometries and configurations used in optical fiber biosensors over the years and provide information about biofunctionalization strategies and theiraworking including EW and SPR/LSPR with is referreference to plasmonic materials.
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