Relevance of the Spectral Analysis Method of Tilted Fiber Bragg Grating-Based Biosensors: A Case-Study for Heart Failure Monitoring

Detection of NT-proBNP Using Optical Fiber Back-Reflection Plasmonic Biosensors

Heart failure (HF) is a clinical entity included in cardiovascular diseases affecting millions of people worldwide, being a leading cause of hospitalization of older adults, and therefore imposing a substantial economic burden on healthcare systems. HF is characterized by dyspnea, fatigue, and edema associated with elevated blood levels of natriuretic peptides, such as N Terminal pro-B-type Natriuretic Peptide (NT-proBNP), for which there is a high demand for point of care testing (POCT) devices. Optical fiber (OF) biosensors offer a promising solution, capable of real-time detection, quantification, and monitoring of NT-proBNP concentrations in serum, saliva, or urine. In this study, immunosensors based on plasmonic uncladded OF tips were developed using OF with different core diameters (200 and 600 µm). The tips were characterized to bulk refractive index (RI), anddetection tests were conducted with NT-proBNP concentrations varying from 0.01 to 100 ng/mL. The 200 µm sensors showed an average total variation of 3.6 ± 2.5 mRIU, an average sensitivity of 50.5 mRIU/ng·mL-1, and a limit of detection (LOD) of 0.15 ng/mL, while the 600 µm sensors had a response of 6.1 ± 4.2 mRIU, a sensitivity of 102.8 mRIU/ng·mL-1, and an LOD of 0.11 ng/mL. Control tests were performed using interferents such as uric acid, glucose, and creatinine. The results show the potential of these sensors for their use in biological fluids.

Multifunctional Integration of Optical Fibers and Nanomaterials for Aircraft Systems

Smart sensing for aeronautical applications is a multidisciplinary process that involves the development of various sensor elements and advancements in the nanomaterials field. The expansion of research has fueled the development of commercial and military aircrafts in the aeronautical field. Optical technology is one of the supporting pillars for this, as well as the fact that the unique high-tech qualities of aircrafts align with sustainability criteria. In this study, a multidisciplinary investigation of airplane monitoring systems employing optical technologies based on optical fiber and nanomaterials that are incorporated into essential systems is presented. This manuscript reports the multifunctional integration of optical fibers and nanomaterials for aircraft sector discussing topics, such as airframe monitoring, flight environment sensing (from temperature and humidity to pressure sensing), sensors for navigation (such as gyroscopes and displacement or position sensors), pilot vital health monitoring, and novel nanomaterials for aerospace applications. The primary objective of this review is to provide researchers with direction and motivation to design and fabricate the future of the aeronautical industry, based on the actual state of the art of such vital technology, thereby aiding their future research.

Applications of Optical Fiber in Label-Free Biosensors and Bioimaging: A Review

Biosensing and bioimaging are essential in understanding biological and pathological processes in a living system, for example, in detecting and understanding certain diseases. Optical fiber has made remarkable contributions to the biosensing and bioimaging areas due to its unique advantages of compact size, immunity to electromagnetic interference, biocompatibility, fast response, etc. This review paper will present an overview of seven common types of optical fiber biosensors and optical fiber-based ultrasound detection in photoacoustic imaging (PAI) and the applications of these technologies in biosensing and bioimaging areas. Of course, there are many types of optical fiber biosensors. Still, this paper will review the most common ones: optical fiber grating, surface plasmon resonance, Sagnac interferometer, Mach-Zehnder interferometer, Michelson interferometer, Fabry-Perot Interferometer, lossy mode resonance, and surface-enhanced Raman scattering. Furthermore, different optical fiber techniques for detecting ultrasound in PAI are summarized. Finally, the main challenges and future development direction are briefly discussed.

Phase interrogation of plasmonic tilted fiber Bragg grating biosensors through the Jones formalism

Gold-coated tilted fiber Bragg gratings (TFBG) are refined plasmonic biosensors, highly sensitive to surrounding refractive index (RI) changes. Their interrogation usually relies on insertion loss measurements for single input polarized light, limiting the set of exploitable features. To overcome this limitation, we trigger the Jones formalism to retrieve the polarization enabling optimized plasmonic excitation for both phase and amplitude measurements. We present an experimental phase shift with a sensitivity as high as 45835^°/RIU and further assess this approach to HER2 proteins sensing at 1µg/ml. We compare this angular modality with the one relying on the insertion loss using a quality factor that takes the shift as well as the dispersion into account. This strengthens its relevance in terms of precision for ultra-small RI variations.