Signal-enhanced multi-core fiber-based WaveFlex biosensor for ultra-sensitive xanthine detection

In this work, we introduce a novel multimode fiber (MMF) - seven core fiber (SCF) - MMF (MCM) optical fiber biosensor, also known as the WaveFlex biosensor (plasma wave assisted fiber biosensor), based on localized surface plasmon resonance (LSPR) for qualitative detection of xanthine. Xanthine is a purine base widely distributed in human blood and tissues, and commonly used as an indicator for various disease detections. The MCM sensor incorporates a tapered optical fiber structure, fabricated using the combiner manufacturing system (CMS), and is designed with SCF and MMF. By effectively harnessing LSPR, the sensor boosts the attachment points of biomolecules on the probe surface through immobilized tungsten disulfide (WS2)-thin layers, gold nanoparticles (AuNPs), and carbon nitride quantum dots (C3N-QDs). The functionalization of xanthine oxidase (XO) on the sensing probe further enhances the sensor's specificity. The proposed WaveFlex biosensor exhibits a remarkable sensitivity of 3.2 nm/mM and a low detection limit of 96.75 µM within the linear detection range of 100 - 900 µM. Moreover, the sensor probe demonstrates excellent reusability, reproducibility, stability, and selectivity. With its sensitivity, biocompatibility, and immense potential for detecting human serum and fish products, this WaveFlex biosensor presents a promising platform for future applications.

A ratiometric SERS sensor with one signal probe for ultrasensitive and quantitative monitoring of serum xanthine

Xanthine can be converted into uric acid, and a high concentration of xanthine in the human body can cause many diseases. Therefore, it is important to develop a sensitive, simple, and reliable approach for measuring xanthine in biological liquids. Hence, a ratiometric surface-enhanced Raman spectroscopy (SERS) sensing strategy with one signal probe was exploited for reliable, sensitive, and quantitative monitoring of serum xanthine. 3-Mercaptophenylboronic acid (3-MPBA) was used as a typical reference with a Raman peak at 996 cm-1. First, 3-MPBA was bound to gold nanoflowers@silica (GNFs@Si) through Au-S bonds. Xanthine oxidase (XOD) catalyzed the oxidation of xanthine into H2O2 on GNFs@Si. Afterward, the obtained H2O2 further reduced 3-MPBA to 3-hydroxythiophenol (3-HTP) accompanied by the emergence of a new Raman peak at 883 cm-1. Meanwhile, the Raman intensity at 996 cm-1 remained constant. Therefore, the ratio of I883/I996 increased with the increasing of xanthine concentration, thus realizing quantitative detection of xanthine. As a result, a ratiometric SERS sensor for the detection of xanthine was proposed with a detection limit of 5.7 nM for xanthine. The novel ratiometric SERS sensor provides a new direction for analyzing other biomolecules with high sensitivity and reliability.

Tungsten-based Nanomaterials in the Biomedical Field: A Bibliometric Analysis of Research Progress and Prospects

Tungsten-based nanomaterials (TNMs) with diverse nanostructures and unique physicochemical properties have been widely applied in the biomedical field. Although various reviews have described the application of TNMs in specific biomedical fields, there are still no comprehensive studies that summarize and analyze research trends of the field as a whole. To identify and further promote the development of biomedical TNMs, a bibliometric analysis method is used to analyze all relevant literature on this topic. First, general bibliometric distributions of the dataset by year, country, institute, referenced source, and research hotspots are recognized. Next, a comprehensive review of the subjectively recognized research hotspots in various biomedical fields, including biological sensing, anticancer treatments, antibacterials, and toxicity evaluation, is provided. Finally, the prospects and challenges of TNMs are discussed to provide a new perspective for further promoting their development in biomedical research.

Ultrafast synthesized monometallic nanohybrids as an efficient quencher and recognition antenna of upconversion nanoparticles for the detection of xanthine with enhanced sensitivity and selectivity

Upconversion nanoparticles (UCNPs) have shown great promise in bioanalytical applications owing to their excellent optical properties. Generally, most analytical applications are based on the fluorescence resonance energy transfer (FRET) principle to quench the fluorescence of UCNPs. However, each UCNP contains thousands of emission center ions, and most of them exceed the FRET critical distance, which hinders FRET efficiency and leads to a low signal-to-background ratio (SBR). Herein, a novel nanoprobe for the detection of Xanthine (XA) based on inner filter effects (IFE) and cascade signal amplification strategy was constructed by decorating UCNP with trypsin-chymotrypsin-stabilized gold nanoparticles-gold nanoclusters (Try-chy-AuNPs-AuNCs) monometallic nanohybrids. The Try-chy-AuNPs-AuNCs prepared by ultrafast (3 min) and green synthesis method have efficient upconversion fluorescence quenching ability (the quenching efficiency up to 90.9%), which can effectively improve the SBR of the probe, so as to improve the sensitivity. In addition, the Try-chy-AuNPs-AuNCs have a unique spatial structure, which can effectively prevent the interaction between large-size biothiol (glutathione) and the probe, thus improving its selectivity. Besides, combined with the excellent optical performance of UCNPs and cascaded signal amplification strategy, the sensitivity of the probe can be further improved. Under the optimized conditions, the linear response range of the probe was obtained from 0.05 to 50 μM, 0.06-80 μM and with the low detection limit of 22.6 nM and 26.3 nM for H₂O₂ and XA, respectively. Meanwhile, the developed method has been further applied to the detection of XA in human serum with satisfactory results.