A Ratiometric Fiber Optic Sensor Based on CdTe QDs Functionalized with Glutathione and Mercaptopropionic Acid for On-Site Monitoring of Antibiotic Ciprofloxacin in Aquaculture Water

Human serum albumin directed formation of cadmium telluride quantum dots: Applications in biosensing, anti-bacterial activities and cell cytotoxicity measurements

Although cadmium-based quantum dots (QDs) are highly promising candidates for numerous biological applications, their intrinsic toxicity limits their pertinency in living systems. Surface functionalization of QDs with appropriate molecules could reduce the toxicity level. Herein, we have synthesized the smaller sized (1-5 nm) aqueous-compatible biogenic CdTe QDs using human serum albumin (HSA) as a surface passivating agent via a greener approach. HSA-functionalized CdTe QDs have been explored in multiple in vitro sensing and biological applications, namely, (1) sensing, (2) anti-bacterial and (3) anti-cancer properties. Using CdTe-HSA QDs as a fluorescence probe, a simple fluorometric method has been developed for highly sensitive and selective detection of blood marker bilirubin and hazardous Hg2+ ion with a limit of detection (LOD) of 3.38 and 0.53 ng/mL, respectively. CdTe-HSA QDs also acts as a sensor for standard antibiotics, tetracycline and rifampicin with LOD values of 41.34 and 114.99 ng/mL, respectively. Nano-sized biogenic CdTe-HSA QDs have shown promising anti-bacterial activities against both gram-negative, E. coli and gram-positive, E. faecalis strains confirming more effectiveness against E. faecalis strains. The treatment of human cervical cancer cell lines (HeLa cells) with the synthesized QDs reflected the proficient cytotoxic properties of QDs.

Highly Coupled Seven-Core Fiber for Ratiometric Anti-Phase Sensing

A ratiometric fiber optic temperature sensor based on a highly coupled seven-core fiber (SCF) is proposed and experimentally demonstrated. A theoretical analysis of the SCF's sinusoidal spectral response in transmission configuration is presented. The proposed sensor comprises two SCF devices exhibiting anti-phase transmission spectra. Simple fabrication of the devices is shown by just splicing a segment of a 2 cm long SCF between two single-mode fibers (SMFs). The sensor proved to be robust against light source fluctuations, as a standard deviation of 0.2% was registered in the ratiometric measurements when the light source varied by 12%. Its low-cost detection system (two photodetectors) and the range of temperature detection (25 °C to 400 °C) make it a very attractive and promising device for real industrial applications.

Novel biocompatible and sensitive visual sensor based on aggregation-induced emission for on-site detection of radioactive uranium in water and live cell imaging

In consideration of the severe hazards of radioactive uranium pollution, the rapid assessment of uranium in field and in vivo are urgently needed. In this work a novel biocompatible and sensitive visual fluorescent sensor based on aggregation-induced emission (AIE) was designed for onsite detection of UO₂²⁺ in complex environmental samples, including wastewater from Uranium Plant, river water and living cell. The AIE-active sensor (named as TPA-SP) was prepared with a "bottom-up" strategy by introducing a trianiline group (TPA) with a single-bond rotatable helix structure into the salicylaldehyde Schiff-base molecule. The photophysical properties, cytotoxicity test, recognition mechanism and the analytical performance for the detection of UO₂²⁺ in actual water samples and cell imaging were systematically investigated. TPA-SP exhibited high sensitivity and selectivity toward UO₂²⁺ as well as outstanding anti-interference ability against large equivalent of different ions in a wide effective pH range. A good linear relationship in the UO₂²⁺ concentration range of 0.05-1 μM was obtained with a low limit of detection (LOD) of 39.4 nM (9.38 ppb) for uranium detection. The prepared visual sensor showed great potential for fast risk assessment of uranium pollution in environmental systems. In addition, our results also indicated that the TPA-SP exhibited very low cytotoxicity in cells and demonstrated great potential for uranium detection in vivo.

Progress in Plasmonic Sensors as Monitoring Tools for Aquaculture Quality Control

Aquaculture is an expanding economic sector that nourishes the world's growing population due to its nutritional significance over the years as a source of high-quality proteins. However, it has faced severe challenges due to significant cases of environmental pollution, pathogen outbreaks, and the lack of traceability that guarantees the quality assurance of its products. Such context has prompted many researchers to work on the development of novel, affordable, and reliable technologies, many based on nanophotonic sensing methodologies. These emerging technologies, such as surface plasmon resonance (SPR), localised SPR (LSPR), and fibre-optic SPR (FO-SPR) systems, overcome many of the drawbacks of conventional analytical tools in terms of portability, reagent and solvent use, and the simplicity of sample pre-treatments, which would benefit a more sustainable and profitable aquaculture. To highlight the current progress made in these technologies that would allow them to be transferred for implementation in the field, along with the lag with respect to the most cutting-edge plasmonic sensing, this review provides a variety of information on recent advances in these emerging methodologies that can be used to comprehensively monitor the various operations involving the different commercial stages of farmed aquaculture. For example, to detect environmental hazards, track fish health through biochemical indicators, and monitor disease and biosecurity of fish meat products. Furthermore, it highlights the critical issues associated with these technologies, how to integrate them into farming facilities, and the challenges and prospects of developing plasmonic-based sensors for aquaculture.

Liquid-Core Hydrogel Optical Fiber Fluorescence Probes

This paper first reports a liquid-core hydrogel optical fiber fluorescence probe. It is composed of a liquid core, a high-refractive-index hydrogel fiber core, and a low-refractive-index hydrogel fiber cladding, which is completely different from many existing optical fiber fluorescence probes. The sensing solution with sensitive materials is sealed as a liquid core, and it can sufficiently react with small-molecule targets penetrating through the hydrogel fiber cladding and core, thus inducing variations in the fluorescence signals. These fluorescence signals can be localized and transmitted within the probe and finally collected and quantified for target detection. This proposed probe can be simply and rapidly fabricated and reused, and it was proven to have high sensitivity, accuracy, and selectivity in practical applications. Therefore, this liquid-core hydrogel optical fiber fluorescence probe will enable a novel sensing platform for small-molecule analyte detection that faces on-site detection challenges.

Improving the Sensitivity of Nanofibrous Membrane-Based ELISA for On-Site Antibiotics Detection

An ultrasensitive and portable colorimetric enzyme-linked immunosorbent assay (ELISA) sensor for antibiotics was fabricated by immobilizing antibodies inside the largely porous and highly hydrophilic nanofibrous membranes. Different from regular electrospun nanofibrous membranes where antibodies may frequently be blocked by the heterogeneous porous structure and sterically crowded loaded on the surface, the controlled microporous structure and increased hydrophilicity of nanofibrous membranes could improve the diffusion properties of antibodies, reduce the sterically crowding effect, and dramatically improve the sensitivity of the membrane-based ELISA. The limitation of detection (LOD) for chloramphenicol (CAP) reached 0.005 ng/mL, around 200 times lower than the conventional paper-based ELISA, making quantitative analysis and portable on-site detection achievable via the use of smartphones. The successful design and fabrication of the nanofibrous membrane-based ELISA with novel features overcome the structural drawbacks of regular electrospun nanofibrous membranes and provide new paths to develop highly sensitive on-site detection of hazardous chemical agents.