Portable Enzyme-Paper Biosensors Based on Redox-Active CeO2 Nanoparticles

Cerium oxide nanoparticles in wound care: a review of mechanisms and therapeutic applications

Skin wound healing is a complex and tightly regulated process. The frequent occurrence and reoccurrence of acute and chronic wounds cause significant skin damage to patients and impose socioeconomic burdens. Therefore, there is an urgent requirement to promote interdisciplinary development in the fields of material science and medicine to investigate novel mechanisms for wound healing. Cerium oxide nanoparticles (CeO2 NPs) are a type of nanomaterials that possess distinct properties and have broad application prospects. They are recognized for their capabilities in enhancing wound closure, minimizing scarring, mitigating inflammation, and exerting antibacterial effects, which has led to their prominence in wound care research. In this paper, the distinctive physicochemical properties of CeO2 NPs and their most recent synthesis approaches are discussed. It further investigates the therapeutic mechanisms of CeO2 NPs in the process of wound healing. Following that, this review critically examines previous studies focusing on the effects of CeO2 NPs on wound healing. Finally, it suggests the potential application of cerium oxide as an innovative nanomaterial in diverse fields and discusses its prospects for future advancements.

The applications of nanozymes in cancer therapy: based on regulating pyroptosis, ferroptosis and autophagy of tumor cells

Nanozymes are nanomaterials with catalytic properties similar to those of natural enzymes, and they have recently been collectively identified as a class of innovative artificial enzymes. Nanozymes are widely used in various fields, such as biomedicine, due to their high catalytic activity and stability. Nanozymes can trigger changes in reactive oxygen species (ROS) levels in cells and the activation of inflammasomes, leading to the programmed cell death (PCD), including the pyroptosis, ferroptosis, and autophagy, of tumor cells. In addition, some nanozymes consume glucose, starving cancer cells and thus accelerating tumor cell death. In addition, the electric charge of the structure and the catalytic activity of nanozymes are sensitive to external factors such as light and electric and magnetic fields. Therefore, nanozymes can be used with different therapeutic methods, such as chemodynamic therapy (CDT), photodynamic therapy (PDT) and sonodynamic therapy (SDT), to achieve highly efficient antitumor effects. Many cancer therapies induce tumor cell death via the pyroptosis, ferroptosis, and autophagy of tumor cells mediated by nanozymes. We review the mechanisms of pyroptosis, ferroptosis, and autophagy in tumor development, as well as the potential application of nanozymes to regulate pyroptosis, ferroptosis, and autophagy in tumor cells.

Detection and Quantification of Nanoparticle-Induced Intracellular ROS in Live Cells by Laser Scanning Confocal Microscopy

All living organisms utilise reactive oxygen species (ROS) for essential cellular functions, the majority of which involve signal transduction pathways, such as enzyme regulation, cell growth and differentiation signalling, and inflammation mediation. Increased ROS in cancer cells can be caused by abnormalities in the tumor environment. However, using fluorescence microscopy to detect and quantify ROS changes in biological systems is difficult for several reasons: (1) lack of specificity of ROS-sensitive probes, (2) high turnover of ROS species, (3) rapid decrease in ROS fluorescence with time, and (4) detection and quantification techniques with insufficient sensitivity. Existing approaches to ROS measurement using confocal microscopy imaging focus solely on ROS detection rather than quantification. A novel fluorescence-based ROS detection and quantification technique has been developed for the purpose of resolving the limitations of existing methods. In general, ROS is detected by fluorescence using instrumentation such as flow cytometry and laser scanning confocal microscopy. However, these approaches confirm only the presence or absence of ROS; they are not quantitative, which is essential for therapeutic applications. In the newly developed technique, cerium-based ROS-generating nanoparticles have been used to elevate the ROS in HT-1080 fibrosarcoma cells. The elevated ROS levels are detected using an H2DCFDA fluorescence probe, which is used widely for this application, and captured as digital images using a 488 nm fluorescence channel. Quantification of the ROS is achieved using script in MATLAB software to convert the fluorescence intensities to numerical values. Thus, this technique nearly simultaneously integrates both detection and quantification of the ROS, which provides the statistical justification necessary to support therapeutic translation.

Cerium Oxide Nanoparticles and Their Efficient Antibacterial Application In Vitro against Gram-Positive and Gram-Negative Pathogens

In this study, the antibacterial activity of cerium oxide nanoparticles on two Gram-negative and three Gram-positive foodborne pathogens was investigated. CeO₂ nanoparticles (CeO₂ nps) were synthesized by a Wet Chemical Synthesis route, using the precipitation method and the Simultaneous Addition of reactants (WCS–SimAdd). The as-obtained precursor powders were investigated by thermal analysis (TG–DTA), to study their decomposition process and to understand the CeO₂ nps formation. The composition, structure, and morphology of the thermally treated sample were investigated by FTIR, Raman spectroscopy, X-ray diffraction, TEM, and DLS. The cubic structure and average particle size ranging between 5 and 15 nm were evidenced. Optical absorption measurements (UV–Vis) reveal that the band gap of CeO₂ is 2.61 eV, which is smaller than the band gap of bulk ceria. The antioxidant effect of CeO₂ nps was determined, and the antibacterial test was carried out both in liquid and on solid growth media against five pathogenic microorganisms, namely Escherichia coli, Salmonella typhimurium, Listeria monocytogenes, Staphylococcus aureus, and Bacillus cereus. Cerium oxide nanoparticles showed growth inhibition toward all five pathogens tested with notable results. This paper highlights the perspectives for the synthesis of CeO₂ nps with controlled structural and morphological characteristics and enhanced antibacterial properties, using a versatile and low-cost chemical solution method.

Arsenate reductase from Thermus thermophilus conjugated to polyethylene glycol-stabilized gold nanospheres allow trace sensing and speciation of arsenic ions

Water sources pollution by arsenic ions is a serious environmental problem all around the world. Arsenate reductase enzyme (TtArsC) from Thermus thermophilus extremophile bacterium, naturally binds arsenic ions, As(V) and As (III), in aqueous solutions. In this research, TtArsC enzyme adsorption onto hybrid polyethylene glycol-stabilized gold nanoparticles (AuNPs) was studied at different pH values as an innovative nanobiosystem for metal concentration monitoring. Characterizations were performed by UV/Vis and circular dichroism spectroscopies, TEM images and in terms of surface charge changes. The molecular interaction between arsenic ions and the TtArsC-AuNPs nanobiosystem was also monitored at all pH values considered by UV/Vis spectroscopy. Tests performed revealed high sensitivities and limits of detection equal to 10 ± 3 M^-12 and 7.7 ± 0.3 M^-12 for As(III) and As(V), respectively.

A Sub-30 mpH Resolution Thin Film Transistor-Based Nanoribbon Biosensing Platform

We present a complete biosensing system that comprises a Thin Film Transistor (TFT)-based nanoribbon biosensor and a low noise, high-performance bioinstrumentation platform, capable of detecting sub-30 mpH unit changes, validated by an enzymatic biochemical reaction. The nanoribbon biosensor was fabricated top-down with an ultra-thin (15 nm) polysilicon semiconducting channel that offers excellent sensitivity to surface potential changes. The sensor is coupled to an integrated circuit (IC), which combines dual switched-capacitor integrators with high precision analog-to-digital converters (ADCs). Throughout this work, we employed both conventional pH buffer measurements as well as urea-urease enzymatic reactions for benchmarking the overall performance of the system. The measured results from the urea-urease reaction demonstrate that the system can detect urea in concentrations as low as 25 μM, which translates to a change of 27 mpH, according to our initial pH characterisation measurements. The attained accuracy and resolution of our system as well as its low-cost manufacturability, high processing speed and portability make it a competitive solution for applications requiring rapid and accurate results at remote locations; a necessity for Point-of-Care (POC) diagnostic platforms.