Abstract
The article reviews the current status of label-free integrated optical biosensors focusing on the evolution over the years of their analytical performance. At first, a short introduction to the evanescent wave optics is provided followed by detailed description of the main categories of label-free optical biosensors, including sensors based on surface plasmon resonance (SPR), grating couplers, photonic crystals, ring resonators, and interferometric transducers. For each type of biosensor, the detection principle is first provided followed by description of the different transducer configurations so far developed and their performance as biosensors. Finally, a short discussion about the current limitations and future perspectives of integrated label-free optical biosensors is provided.
Highlights
Starting more than 50 years ago from the report of Clark and Lyons [1], biosensors have been the subject of intensive research efforts, and of numerous attempts of commercial exploitation aiming to overcome the limitations of classical analytical systems and provide solutions for on-site determinations
The portable systems so far that have been developed based on optical transduction principles are lacking in analytical sensitivity compared to the respective laboratory systems, a fact that restricts to a great extent the potential applications
Apart from the quest for outstanding analytical performance, effort has been devoted to the realization of multiplexed determinations due to the inherent advantage of optical biosensors of reduced cross-over signals as opposed to electrochemical ones [6,7]. This has led to efforts towards applying them for sensing of multiple targets simultaneously, which can help their spread in diverse fields, including the commercial market [6,7,8]
Summary
Starting more than 50 years ago from the report of Clark and Lyons [1], biosensors have been the subject of intensive research efforts, and of numerous attempts of commercial exploitation aiming to overcome the limitations of classical analytical systems and provide solutions for on-site determinations. Portable systems are no longer restricted to electrochemical transducers, for which miniaturization of both the sensing element and the instrumentation is more straightforward compared to other transducers, but has been extended to optical ones, the miniaturization of which is hindered by the need to use external light sources and detectors Despite these advances, the portable systems so far that have been developed based on optical transduction principles are lacking in analytical sensitivity compared to the respective laboratory systems, a fact that restricts to a great extent the potential applications. Apart from the quest for outstanding analytical performance, effort has been devoted to the realization of multiplexed determinations due to the inherent advantage of optical biosensors of reduced cross-over signals as opposed to electrochemical ones [6,7] This has led to efforts towards applying them for sensing of multiple targets simultaneously (multiplexed sensing), which can help their spread in diverse fields, including the commercial market [6,7,8]. Monolithically integrated broad-band interferometric transducers will be presented in more detail, and the review will conclude with a comparison of the presented sensors and a brief discussion about the future of integrated optical transducers
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