PfHRP2 detection using plasmonic optrodes: performance analysis

Insulin biotrapping using plasmofluidic optical fiber chips: A benchmark

Plasmonic optical fiber-based biosensors are currently in their early stages of development as practical and integrated devices, gradually making their way towards the market. While the majority of these biosensors operate using white light and multimode optical fibers (OFs), our approach centers on single-mode OFs coupled with tilted fiber Bragg gratings (TFBGs) in the near-infrared wavelength range. Our objective is to enhance surface sensitivity and broaden sensing capabilities of OF-based sensors to develop in situ sensing with remote interrogation. In this study, we comprehensively assess their performance in comparison to the gold-standard plasmonic reference, a commercial device based on the Kretschmann-Raether prism configuration. We present their refractive index sensitivity and their capability for insulin sensing using a dedicated microfluidics approach. By optimizing a consistent surface biotrapping methodology, we elucidate the dynamic facets of both technologies and highlight their remarkable sensitivity to variations in bulk and surface properties. The one-to-one comparison between both technologies demonstrates the reliability of optical fiber-based measurements, showcasing similar experimental trends obtained with both the prismatic configuration and gold-coated TFBGs, with an even enhanced limit of detection for the latter. This study lays the foundation for the detection of punctual molecular interactions and opens the way towards the detection of spatially and temporally localized events on the surface of optical probes.

Dual-Mode Comb Plasmonic Optical Fiber Sensing

Surface plasmon (SP) excitation in metal-coated tilted fiber Bragg gratings (TFBGs) has been a focal point for highly sensitive surface biosensing. Previous efforts focused on uniform metal layer deposition around the TFBG cross section and temperature self-compensation with the Bragg mode, requiring both careful control of the core-guided light polarization and interrogation over most of the C + L bands. To circumvent these two important practical limitations, we studied and developed an original platform based on partially coated TFBGs. The partial metal layer enables the generation of dual-comb resonances, encompassing highly sensitive (TM/EH mode families) and highly insensitive (TE/HE mode families) components in unpolarized transmission spectra. The interleaved comb of insensitive modes acts as wavelength and power references within the same spectral region as the SP-active modes. Despite reduced fabrication and measurement complexity, refractometric accuracy is not compromised through statistical averaging over seven individual resonances within a narrowband window of 10 nm. Consequently, measuring spectra over 60 nm is no longer needed to compensate for small temperature or power fluctuations. This sensing platform brings the following important practical assets: (1) a simpler fabrication process, (2) no need for polarization control, (3) limited bandwidth interrogation, and (4) maintained refractometric accuracy, which makes it a true game changer in the ever-growing plasmonic sensing domain.

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.

From Whispering Gallery Mode Resonators to Biochemical Sensors

Optical biosensors are frontrunners for the rapid and real-time detection of analytes, particularly for low concentrations. Among them, whispering gallery mode (WGM) resonators have recently attracted a growing focus due to their robust optomechanical features and high sensitivity, measuring down to single binding events in small volumes. In this review, we provide a broad overview of WGM sensors along with critical advice and additional "tips and tricks" to make them more accessible to both biochemical and optical communities. Their structures, fabrication methods, materials, and surface functionalization chemistries are discussed. We propose this reflection under a pedagogical approach to describe and explain these biochemical sensors with a particular focus on the most recent achievements in the field. In addition to highlighting the advantages of WGM sensors, we also discuss and suggest strategies to overcome their current limitations, leaving room for further development as practical tools in various applications. We aim to provide new insights and combine different knowledge and perspectives to advance the development of the next generation of WGM biosensors. With their unique advantages and compatibility with different sensing modalities, these biosensors have the potential to become major game changers for biomedical and environmental monitoring, among many other relevant target applications.

Preliminary insight into the potential antiplasmodial activity and cytotoxicity of Bufo bufo and Incilius alvarius poison

The rise and spread of resistant Plasmodium falciparum strains are responsible for an increase in therapeutic failures in many of the regions endemic with malaria. The need for new therapeutic candidates is now more urgent than ever. Animal venoms have long been considered as interesting resources to exploit in terms of potential therapeutic candidates. Among these, the cutaneous secretions of toads constitute a rich and diverse source of bioactive molecules. We focused on two different species: Bufo bufo and Incilius alvarius. The dried secretions underwent a solvent-based extraction and were submitted to a systematic bio-guided fractionation approach using preparative thin-layer chromatography. Initial crude extracts were tested in vitro for their antiplasmodial activity. Based on these results, only crude extracts displaying IC₅₀ < 100 μg/mL were considered for further fractionation. All extracts and fractions, including those that did not display antiplasmodial properties, were characterized by chromatographic (LC-UV/MS) and spectrometric techniques (HRMS). Antiplasmodial activity was evaluated in vitro using a chloroquine-sensitive strain (3D7) and a resistant one (W2). Toxicity was assessed on normal human cells for the samples displaying IC₅₀ < 100 μg/mL. Crude extracts from Bufo bufo secretions exhibited no appreciable antiplasmodial activities. However, the methanol and dichloromethane extracts from Incilius alvarius secretions gave IC₅₀ of (34 ± 4) μg/mL and (50 ± 1) μg/mL respectively when tested on W2 strain. No significant effect was observed on 3D7. This poison would warrant further investigation in terms of its antiplasmodial potential. Following preliminary characterization, it was revealed that the fractions of interest contained mainly bufotoxins, bufagins and alkaloids.

Aptamer-Based Technologies for Parasite Detection

Centuries of scientific breakthroughs have brought us closer to understanding and managing the spread of parasitic diseases. Despite ongoing technological advancements in the detection, treatment, and control of parasitic illnesses, their effects on animal and human health remain a major concern worldwide. Aptamers are single-stranded oligonucleotides whose unique three-dimensional structures enable them to interact with high specificity and affinity to a wide range of targets. In recent decades, aptamers have emerged as attractive alternatives to antibodies as therapeutic and diagnostic agents. Due to their superior stability, reusability, and modifiability, aptamers have proven to be effective bioreceptors for the detection of toxins, contaminants, biomarkers, whole cells, pathogens, and others. As such, they have been integrated into a variety of electrochemical, fluorescence, and optical biosensors to effectively detect whole parasites and their proteins. This review offers a summary of the various types of parasite-specific aptamer-based biosensors, their general mechanisms and their performance.

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.

Review of Microdevices for Hemozoin-Based Malaria Detection

Despite being preventable and treatable, malaria still puts almost half of the world's population at risk. Thus, prompt, accurate and sensitive malaria diagnosis is crucial for disease control and elimination. Optical microscopy and immuno-rapid tests are the standard malaria diagnostic methods in the field. However, these are time-consuming and fail to detect low-level parasitemia. Biosensors and lab-on-a-chip devices, as reported to different applications, usually offer high sensitivity, specificity, and ease of use at the point of care. Thus, these can be explored as an alternative for malaria diagnosis. Alongside malaria infection inside the human red blood cells, parasites consume host hemoglobin generating the hemozoin crystal as a by-product. Hemozoin is produced in all parasite species either in symptomatic and asymptomatic individuals. Furthermore, hemozoin crystals are produced as the parasites invade the red blood cells and their content relates to disease progression. Hemozoin is, therefore, a unique indicator of infection, being used as a malaria biomarker. Herein, the so-far developed biosensors and lab-on-a-chip devices aiming for malaria detection by targeting hemozoin as a biomarker are reviewed and discussed to fulfil all the medical demands for malaria management towards elimination.

Recent Advances in Biomedical Photonic Sensors: A Focus on Optical-Fibre-Based Sensing

In this invited review, we provide an overview of the recent advances in biomedical photonic sensors within the last five years. This review is focused on works using optical-fibre technology, employing diverse optical fibres, sensing techniques, and configurations applied in several medical fields. We identified technical innovations and advancements with increased implementations of optical-fibre sensors, multiparameter sensors, and control systems in real applications. Examples of outstanding optical-fibre sensor performances for physical and biochemical parameters are covered, including diverse sensing strategies and fibre-optical probes for integration into medical instruments such as catheters, needles, or endoscopes.