Nonenzymatic amperometric sensor for hydrogen peroxide released from living cancer cells based on hierarchical NiCo2O4-CoNiO2 hybrids embedded in partially reduced graphene oxide

Ni Nanoparticles on the Reduced Graphene Oxide Surface Synthesized in Supercritical Isopropanol

Nanocomposites based on ferromagnetic nickel nanoparticles and graphene-related materials are actively used in various practical applications such as catalysis, sensors, sorption, etc. Therefore, maintaining their dispersity and homogeneity during deposition onto the reduced graphene oxide substrate surface is of crucial importance to provide the required product characteristics. This paper demonstrates a new, reproducible method for preparing a tailored composite based on nickel nanoparticles on the reduced graphene oxide surface using supercritical isopropanol treatment. It has been shown that when a graphene oxide film with previously incorporated Ni2+ salt is treated with isopropanol at supercritical conditions, nickel (2+) is reduced to Ni (0), with simultaneous deoxygenation of the graphene oxide substrate. The resulting composite is a solid film exhibiting magnetic properties. XRD, FTIR, Raman, TEM, and HRTEM methods were used to study all the obtained materials. It was shown that nickel nanoparticles on the surface of the reduced graphene oxide had an average diameter of 27 nm and were gradually distributed on the surface of reduced graphene oxide sheets. The data obtained allowed us to conduct a reconnaissance discussion of the mechanism of composite fabrication in supercritical isopropanol.

Sensorization of microfluidic brain-on-a-chip devices: Towards a new generation of integrated drug screening systems

Brain-on-a-chip (BoC) devices show typical characteristics of brain complexity, including the presence of different cell types, separation in different compartments, tissue-like three-dimensionality, and inclusion of the extracellular matrix components. Moreover, the incorporation of a vascular system mimicking the blood-brain barrier (BBB) makes BoC particularly attractive, since they can be exploited to test the brain delivery of different drugs and nanoformulations. In this review, we introduce the main innovations in BoC and BBB-on-a-chip models, especially focusing sensorization: electrical, electrochemical, and optical biosensors permit the real-time monitoring of different biological phenomena and markers, such as the release of growth factors, the expression of specific receptors/biomarkers, the activation of immune cells, cell viability, cell-cell interactions, and BBB crossing of drugs and nanoparticles. The recent improvements in signal amplification, miniaturization, and multiplication of the sensors are discussed in an effort to highlight their benefits versus limitations and delineate future challenges in this field.

Enhancing electrochemical sensing through the use of functionalized graphene composites as nanozymes

Graphene-based nanozymes possess inherent nanomaterial properties that offer not only a simple substitute for enzymes but also a versatile platform capable of bonding with complex biochemical environments. The current review discusses the replacement of enzymes in developing biosensors with nanozymes. Functionalization of graphene-based materials with various nanoparticles can enhance their nanozymatic properties. Graphene oxide functionalization has been shown to yield graphene-based nanozymes that closely mimic several natural enzymes. This review provides an overview of the classification, current state-of-the-art development, synthesis routes, and types of functionalized graphene-based nanozymes for the design of electrochemical sensors. Furthermore, it includes a summary of the application of functionalized graphene-based nanozymes for constructing electrochemical sensors for pollutants, drugs, and various water and food samples. Challenges related to nanozymes as electrocatalytic materials are discussed, along with potential solutions and approaches for addressing these shortcomings.

Metal Oxides Nanomaterials and Nanocomposite-Based Electrochemical Sensors for Healthcare Applications

Wide-ranging research efforts have been directed to prioritize scientific and technological inventions for healthcare monitoring. In recent years, the effective utilization of functional nanomaterials in various electroanalytical measurements realized a rapid, sensitive, and selective detection and monitoring of a wide range of biomarkers in body fluids. Owing to good biocompatibility, high organic capturing ability, strong electrocatalytic activity, and high robustness, transition metal oxide-derived nanocomposites have led to enhancements in sensing performances. The aim of the present review is to describe key advancements of transition metal oxide nanomaterials and nanocomposites-based electrochemical sensors, along with current challenges and prospects towards the development of a highly durable and reliable detection of biomarkers. Moreover, the preparation of nanomaterials, electrode fabrication, sensing mechanism, electrode-bio interface, and performance of metal oxides nanomaterials and nanocomposite-based sensor platforms will be described.

Facile preparation of urchin-like NiCo2O4 microspheres for efficient hydrogen peroxide detection

The fabricated NiCo2O4 microspheres acted as excellent sensors for H2O2, with much better performance than the reported NiCo2O4-based H2O2 sensors.

0D/2D heteronanostructure-integrated bimetallic CoCu-ZIF nanosheets and MXene-derived carbon dots for impedimetric cytosensing of melanoma B16-F10 cells

A novel heterogeneous architecture has been constructed integrating two-dimensional (2D) bimetallic CoCu-zeolite imidazole framework (CoCu-ZIF) and zero-dimensional (0D) Ti₃C₂T_x MXene-derived carbon dots (CDs) (represented by CoCu-ZIF@CDs). The prepared CoCu-ZIF@CDs were further explored as sensitive layer for anchoring B16-F10 cell-targeted aptamer strands and detecting B16-F10 cells from the biological environment. Basic characterization showed that CDs were homogeneously embedded within CoCu-ZIF NSs owing to their π-π stacking interaction, leading to outstanding fluorescence performance of the 0D/2D CoCu-ZIF@CD nanohybrid. As such, the CoCu-ZIF@CD-based cytosensor was applied to detect living B16-F10 cells through electrochemical techniques and cell imaging. Compared with CoCu-ZIF- and CD-based cytosensors, the constructed CoCu-ZIF@CD-based one showed superior sensing performance, with an extremely low limit of detection (LOD) of 33 cells∙mL^-1 and a wide range of suspension concentration of 1 × 10²-1 × 10⁵ cells∙mL^-1 B16-F10 cells. The developed cytosensor also demonstrated excellent detection performance, including cell imaging properties, good selectivity, high stability, and good reproducibility. By anchoring other probe molecules, the constructed CoCu-ZIF@CD-based biosensor can be extensively explored for early diagnosis of other analytes, thereby widening the applications of porous organic frameworks in biosensing and biomedical fields. A novel sensing system for melanoma B16-F10 cells based on a novel CoCu-ZIF@CD nanohybrid has been developed. The CoCu-ZIF@CDs-based cytosensor displayed an extremely low limit of detection (LOD) of 33 cells∙mL^-1 within the wide range of B16-F10 cell concentration from 1 × 10² to 1 × 10⁵ cells∙mL^-1, accompanying with cell imaging properties, good selectivity, high stability, and well reproducibility.

Electrochemical Detection of H2O2 Released from Prostate Cancer Cells Using Pt Nanoparticle-Decorated rGO–CNT Nanocomposite-Modified Screen-Printed Carbon Electrodes

In this study, we fabricated platinum nanoparticles (PtNP)-decorated, porous reduced graphene oxide (rGO)–carbon nanotube (CNT) nanocomposites on a PtNP-deposited screen-printed carbon electrode (PtNP/rGO–CNT/PtNP/SPCE) for detection of hydrogen peroxide (H2O2), which is released from prostate cancer cells LNCaP. The PtNP/rGO–CNT/PtNP/SPCE was fabricated by a simple electrochemical deposition and co-reduction method. In addition, the amperometric response of the PtNP/rGO–CNT/PtNP/SPCE electrode was evaluated through consecutive additions of H2O2 at an applied potential of 0.2 V (vs. Ag pseudo-reference electrode). As a result, the prepared PtNP/rGO–CNT/PtNP/SPCE showed good electrocatalytic activity toward H2O2 compared to bare SPCE, rGO–CNT/SPCE, PtNP/SPCE, and rGO–CNT/PtNP/SPCE. In addition, the PtNP/rGO–CNT/PtNP/SPCE electrode exhibited a sensitivity of 206 μA mM−1·cm−2 to H2O2 in a linear range of 25 to 1000 μM (R2 = 0.99). Moreover, the PtNP/rGO–CNT/PtNP/SPCE electrode was less sensitive to common interfering substances, such as ascorbic acid, uric acid, and glucose than H2O2. Finally, real-time monitoring of H2O2 released from LNCaP cells was successfully performed by this electrode. Therefore, we expect that the PtNP/rGO–CNT/PtNP/SPCE can be utilized as a promising electrochemical sensor for practical nonenzymatic detection of H2O2 in live cells or clinical analysis.