Monodispersed gold nanoparticles entrapped in ordered mesoporous carbon/silica nanocomposites as xanthine oxidase mimic for electrochemical sensing of xanthine

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.

MIL-101(Cr) molecular cage anchored on 2D Ti3C2TX MXene nanosheets as high-performance electrochemical sensing platform for detection of xanthine

A new electrochemical sensing material based on the MIL-101(Cr) molecular cage anchored on 2D Ti₃C₂T_X-MXene nanosheets was prepared by using the in situ growth molecular engineering strategy. The sensing material was characterized by using different methods such as SEM, XRD, and XPS. The electrochemical sensing performance of MIL-101(Cr)/Ti₃C₂T_x-MXene was studied by DPV, CV, EIS, and other techniques. The electrochemical tests showed that the linear range of the modified electrode for xanthine (XA) detection was 1.5-73.0 μM and 73.0-133.0 μM, the detection limit was 0.45 μM (working potential of + 0.71 V vs. Ag/AgCl), and the performance is superior compared with the reported enzyme-free modified electrodes for detecting XA. The fabricated sensor has high selectivity and stability. It has good practicability in serum analysis with recoveries of 96.58-103.27% and a relative standard deviation (RSD) of 3.58-4.32%.

Silica nanoparticles: Biomedical applications and toxicity

Silica nanoparticles (SiNPs) are composed of silicon dioxide, the most abundant compound on Earth, and are used widely in many applications including the food industry, synthetic processes, medical diagnosis, and drug delivery due to their controllable particle size, large surface area, and great biocompatibility. Building on basic synthetic methods, convenient and economical strategies have been developed for the synthesis of SiNPs. Numerous studies have assessed the biomedical applications of SiNPs, including the surface and structural modification of SiNPs to target various cancers and diagnose diseases. However, studies on the in vitro and in vivo toxicity of SiNPs remain in the exploratory stage, and the toxicity mechanisms of SiNPs are poorly understood. This review covers recent studies on the biomedical applications of SiNPs, including their uses in drug delivery systems to diagnose and treat various diseases in the human body. SiNP toxicity is discussed in terms of the different systems of the human body and the individual organs in those systems. This comprehensive review includes both fundamental discoveries and exploratory progress in SiNP research that may lead to practical developments in the future.

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.

A Review on Metal- and Metal Oxide-Based Nanozymes: Properties, Mechanisms, and Applications

Since the ferromagnetic (Fe3O4) nanoparticles were firstly reported to exert enzyme-like activity in 2007, extensive research progress in nanozymes has been made with deep investigation of diverse nanozymes and rapid development of related nanotechnologies. As promising alternatives for natural enzymes, nanozymes have broadened the way toward clinical medicine, food safety, environmental monitoring, and chemical production. The past decade has witnessed the rapid development of metal- and metal oxide-based nanozymes owing to their remarkable physicochemical properties in parallel with low cost, high stability, and easy storage. It is widely known that the deep study of catalytic activities and mechanism sheds significant influence on the applications of nanozymes. This review digs into the characteristics and intrinsic properties of metal- and metal oxide-based nanozymes, especially emphasizing their catalytic mechanism and recent applications in biological analysis, relieving inflammation, antibacterial, and cancer therapy. We also conclude the present challenges and provide insights into the future research of nanozymes constituted of metal and metal oxide nanomaterials.

A sandwich-configuration electrochemiluminescence immunoassay based on Cu2O@OMC-Ru nanocrystals and OMC-MoS2 nanocomposites for determination of alpha-fetoprotein

A sandwich-format electrochemiluminescence (ECL) immunosensor has been developed for alpha-fetoprotein (AFP) detection based on the use of ordered mesoporous carbon-molybdenum disulfide (OMC-MoS₂) as a sensor platform and cuprous oxide @ ordered mesoporous carbon-Ru(bpy)₃²⁺ (Cu₂O@OMC-Ru) composites as signal tags. OMC alongside MoS₂ plays a synergistic role in improving the electrochemical performance of the electrode in the electron transfer process. The uniform cubic-shaped Cu₂O@OMC-Ru nanocrystals display excellent luminous efficiency, with a signal amplification strategy of OMC-MoS₂ synergistic enhancement and Cu₂O@OMC which is capable of immobilizing more Ru(bpy)₃²⁺ serving as a tracing tag to label antibodies. A detectable ECL emission at a Cu₂O@OMC-Ru nanocrystals modified electrode is initiated at an applied voltage of +1.15 V (scanning range: 0-1.2 V), in the presence of the tripropylamine (TPA) as coreactant. With the increase in AFP concentration, the loading of Cu₂O@OMC-Ru at the electrode increases. Afterward, the ECL detection of AFP shows a wide linear range from 0.1 pg/mL to 10 ng/mL with a correlation coefficient of 0.9964 and a detection limit of 0.011 pg/mL (S/N = 3) under the optimal experimental conditions. The recoveries were in the range 91.2-97.1% with RSD varying from 4.8 to 8.5%. Overall, the novel immunosensor has been successfully applied to the analysis of human serum samples, indicating a great potential for application in clinical diagnostics.

Multimodal/Multifunctional Nanomaterials in (Bio)electrochemistry: Now and in the Coming Decade

Multifunctional nanomaterials, defined as those able to achieve a combined effect or more than one function through their multiple functionalization or combination with other materials, are gaining increasing attention in the last years in many relevant fields, including cargo targeted delivery, tissue engineering, in vitro and/or in vivo diseases imaging and therapy, as well as in the development of electrochemical (bio)sensors and (bio)sensing strategies with improved performance. This review article aims to provide an updated overview of the important advances and future opportunities exhibited by electrochemical biosensing in connection to multifunctional nanomaterials. Accordingly, representative aspects of recent approaches involving metal, carbon, and silica-based multifunctional nanomaterials are selected and critically discussed, as they are the most widely used multifunctional nanomaterials imparting unique capabilities in (bio)electroanalysis. A brief overview of the main remaining challenges and future perspectives in the field is also provided.