Electrochemically Deposited Pd–Pt and Pd–Au Codeposits on Graphite Electrodes for Electrocatalytic H2O2 Reduction

Nuclear matrix protein 22 in bladder cancer

Bladder cancer (BC) is ranked as the ninth most common malignancy worldwide, with approximately 570,000 new cases reported annually and over 200,000 deaths. Cystoscopy remains the gold standard for the diagnosis of BC, however, its invasiveness, cost, and discomfort have driven the demand for the development of non-invasive, cost-effective alternatives. Nuclear matrix protein 22 (NMP22) is a promising non-invasive diagnostic tool, having received FDA approval. Traditional methods for detecting NMP22 require a laboratory environment equipped with specialized equipment and trained personnel, thus, the development of NMP22 detection devices holds substantial potential for application. In this review, we evaluate the NMP22 sensors developed over the past decade, including electrochemical, colorimetric, and fluorescence biosensors. These sensors have enhanced detection sensitivity and overcome the limitations of existing diagnostic methods. However, many emerging devices exhibit deficiencies that limit their potential clinical use, therefore, we propose how sensor design can be optimized to enhance the likelihood of clinical translation and discuss the future applications of NMP22 as a legacy biomarker, providing insights for the design of new sensors.

Potential Biomedical Applications of Terbium-Based Nanoparticles (TbNPs): A Review on Recent Advancement

The scientific world is increasingly focusing on rare earth metal oxide nanomaterials due to their consequential biological prospects, navigated by breakthroughs in biomedical applications. Terbium belongs to rare earth elements (lanthanide series) and possesses remarkably strong luminescence at lower energy emission and signal transduction properties, ushering in wide applications for diagnostic measurements (i.e., bioimaging, biosensors, fluorescence imaging, etc.) in the biomedical sectors. In addition, the theranostic applications of terbium-based nanoparticles further permit the targeted delivery of drugs to the specific site of the disease. Furthermore, the antimicrobial properties of terbium nanoparticles induced via reactive oxygen species (ROS) cause oxidative damage to the cell membrane and nuclei of living organisms, ion release, and surface charge interaction, thus further creating or exhibiting excellent antioxidant characteristics. Moreover, the recent applications of terbium nanoparticles in tissue engineering, wound healing, anticancer activity, etc., due to angiogenesis, cell proliferation, promotion of growth factors, biocompatibility, cytotoxicity mitigation, and anti-inflammatory potentials, make this nanoparticle anticipate a future epoch of nanomaterials. Terbium nanoparticles stand as a game changer in the realm of biomedical research, proffering a wide array of possibilities, from revolutionary imaging techniques to advanced drug delivery systems. Their unique properties, including luminescence, magnetic characteristics, and biocompatibility, have redefined the boundaries of what can be achieved in biomedicine. This review primarily delves into various mechanisms involved in biomedical applications via terbium-based nanoparticles due to their physicochemical characteristics. This review article further explains the potential biomedical applications of terbium nanoparticles with in-depth significant mechanisms from the individual literature. This review additionally stands as the first instance to furnish a "single-platted" comprehensive acquaintance of terbium nanoparticles in shaping the future of healthcare as well as potential limitations and overcoming strategies that require exploration before being trialed in clinical settings.

Operando Scanning Electrochemical Probe Microscopy during Electrocatalysis

Scanning electrochemical probe microscopy (SEPM) techniques can disclose the local electrochemical reactivity of interfaces in single-entity and sub-entity studies. Operando SEPM measurements consist of using a SEPM tip to investigate the performance of electrocatalysts, while the reactivity of the interface is simultaneously modulated. This powerful combination can correlate electrochemical activity with changes in surface properties, e.g., topography and structure, as well as provide insight into reaction mechanisms. The focus of this review is to reveal the recent progress in local SEPM measurements of the catalytic activity of a surface toward the reduction and evolution of O₂ and H₂ and electrochemical conversion of CO₂. The capabilities of SEPMs are showcased, and the possibility of coupling other techniques to SEPMs is presented. Emphasis is given to scanning electrochemical microscopy (SECM), scanning ion conductance microscopy (SICM), electrochemical scanning tunneling microscopy (EC-STM), and scanning electrochemical cell microscopy (SECCM).

Electrodes and electrocatalysts for electrochemical hydrogen peroxide sensors: a review of design strategies

H₂O₂ sensing is required in various biological and industrial applications, for which electrochemical sensing is a promising choice among various sensing technologies. Electrodes and electrocatalysts strongly influence the performance of electrochemical H₂O₂ sensors. Significant efforts have been devoted to electrode nanostructural designs and nanomaterial-based electrocatalysts. Here, we review the design strategies for electrodes and electrocatalysts used in electrochemical H₂O₂ sensors. We first summarize electrodes in different structures, including rotation disc electrodes, freestanding electrodes, all-in-one electrodes, and representative commercial H₂O₂ probes. Next, we discuss the design strategies used in recent studies to increase the number of active sites and intrinsic activities of electrocatalysts for H₂O₂ redox reactions, including nanoscale pore structuring, conductive supports, reducing the catalyst size, alloying, doping, and tuning the crystal facets. Finally, we provide our perspectives on the future research directions in creating nanoscale structures and nanomaterials to enable advanced electrochemical H₂O₂ sensors in practical applications.

Functional Nucleic Acid Nanomaterials: Development, Properties, and Applications

Functional nucleic acid (FNA) nanotechnology is an interdisciplinary field between nucleic acid biochemistry and nanotechnology that focuses on the study of interactions between FNAs and nanomaterials and explores the particular advantages and applications of FNA nanomaterials. With the goal of building the next-generation biomaterials that combine the advantages of FNAs and nanomaterials, the interactions between FNAs and nanomaterials as well as FNA self-assembly technologies have established themselves as hot research areas, where the target recognition, response, and self-assembly ability, combined with the plasmon properties, stability, stimuli-response, and delivery potential of various nanomaterials can give rise to a variety of novel fascinating applications. As research on the structural and functional group features of FNAs and nanomaterials rapidly develops, many laboratories have reported numerous methods to construct FNA nanomaterials. In this Review, we first introduce some widely used FNAs and nanomaterials along with their classification, structure, and application features. Then we discuss the most successful methods employing FNAs and nanomaterials as elements for creating advanced FNA nanomaterials. Finally, we review the extensive applications of FNA nanomaterials in bioimaging, biosensing, biomedicine, and other important fields, with their own advantages and drawbacks, and provide our perspective about the issues and developing trends in FNA nanotechnology.

Highly dispersive Pt-Pd nanoparticles on graphene oxide sheathed carbon fiber microelectrodes for electrochemical detection of H2O2 released from living cells

We report a facile strategy for the synthesis of surfactant-free, small and highly dispersive Pt-Pd nanoparticles on graphene oxide (Pt-Pd NPs/GO) by an electroless deposition method, which is sheathed on carbon fiber microelectrodes (CFMs) as an electrochemical sensing platform for highly sensitive and selective detection of hydrogen peroxide (H₂O₂) released from the living cells. GO serves as the reducing agent and stabilizer for electroless deposition of Pd NPs on the surface of GO owing to its low work function (4.38 eV) and highly conjugated electronic structure. The obtained Pd NPs/GO have a relatively high work function (4.64 eV), and thereby could be used as stabilizer for synthesis of surfactant-free, small and highly dispersive Pt-Pd NPs/GO by chemical reduction of K₂PtCl₄. The obtained Pt-Pd NPs have a uniform size of 4.0 ± 0.6 nm on the surface of GO. Moreover, the Pt-Pd NPs/GO sheathed CFMs exhibit an excellent electrocatalytic activity for the reduction of H₂O₂ with a low detection limit of 0.3 μM and good selectivity. These good properties enable the modified microelectrode to detect the H₂O₂ released from living cells.

AuCu xO-Embedded Mesoporous CeO2 Nanocomposites as a Signal Probe for Electrochemical Sensitive Detection of Amyloid-Beta Protein

A sandwich-type electrochemical immunosensor for detecting amyloid-beta protein was fabricated based on Au NP-functionalized reduced graphene oxide (Au@rGO) as an effective sensing platform and AuCu _xO-embedded mesoporous CeO₂ (AuCu _xO@m-CeO₂) nanocomposites as the catalytic matrix. The AuCu _xO@m-CeO₂ composites were obtained by adjusting the amount of m-CeO₂ in the reaction to expose enormous active sites. Also, AuCu _xO@m-CeO₂ was applied as a matrix to immobilize antibodies by forming bridged bonds between m-CeO₂ and carboxyl functional groups of antibodies without additional agents. Furthermore, AuCu _xO with prominent catalytic activities dramatically improved the performance of the fabricated immunosensor. Also, the morphology, structure, and electronic state of the surface were characterized by SEM, XRD, TEM, and XPS. In addition, the immunosensor demonstrated a wide linear range of 100 fg mL^-1 to 10 ng mL^-1. This study may provide a way for sensitively detecting various biomarkers.

Nanomaterials based optical and electrochemical sensing of histamine: Progress and perspectives

Histamine is known to be a principal causative agent associated with marine food poisoning outbreaks worldwide, which is typically formed in the contaminated food by decarboxylation of histidine by bacterial histidine decarboxylase. Upon quantification of histamine in different food products, one can comment on the quality of the food and use it as an indicator of the good manufacturing practices and the state of preservation. The United States Food and Drug Administration (FDA) has established 50 ppm (50 mg/kg) of histamine as the chemical index for fish spoilage. Consumption of foods containing histamine higher than the permissible limit can cause serious health issues. Several methods have been developed for the determination of histamine in a variety of food products. The conventional methods for histamine detection such as thin layer chromatography, capillary zone electrophoresis, gas chromatography, colorimetry, fluorimetry, ion mobility spectrometry, high-performance liquid chromatography, and enzyme-linked immunosorbent assay (ELISA), are being used for sensitive and selective detection of histamine. However, there are a number of disadvantages associated with the conventional techniques, such as multi-step sample processing and requirement of expensive sophisticated instruments, which restrict their applications at laboratory level only. In order to address the limitations associated with the traditional methods, new approaches have been developed by various research groups. Current advances in nanomaterial-based sensing of histamine in different food products have shown significant measurement accuracy due to their high sensitivity, specificity, field deployability, cost and ease of operation. In this review, we have discussed the development of nanomaterials-based histamine sensing assays/strategies where the detection is based on optical (fluorescence, surface enhanced Raman spectroscopy (SERS), localized surface plasmon resonance) and electrochemical (impedimetric, voltammetry, potentiometric, etc.). Further, the advantages, disadvantages and future scope of the nanomaterials-based histamine sensor research are highlighted.

Hollow PtPdRh Nanocubes with Enhanced Catalytic Activities for In Vivo Clearance of Radiation-Induced ROS via Surface-Mediated Bond Breaking

Catalytic nanomaterials can be used extrinsically to combat diseases associated with a surplus of reactive oxygen species (ROS). Rational design of surface morphologies and appropriate doping can substantially improve the catalytic performances. In this work, a class of hollow polyvinyl pyrrolidone-protected PtPdRh nanocubes with enhanced catalytic activities for in vivo free radical scavenging is proposed. Compared with Pt and PtPd counterparts, ternary PtPdRh nanocubes show remarkable catalytic properties of decomposing H₂ O₂ via enhanced oxygen reduction reactions. Density functional theory calculation indicates that the bond of superoxide anions breaks for the energetically favorable status of oxygen atoms on the surface of PtPdRh. Viability of cells and survival rate of animal models under exposure of high-energy γ radiation are considerably enhanced by 94% and 50% respectively after treatment of PtPdRh nanocubes. The mechanistic investigations on superoxide dismutase (SOD) activity, malondialdehyde amount, and DNA damage repair demonstrate that hollow PtPdRh nanocubes act as catalase, peroxidase, and SOD analogs to efficiently scavenge ROS.

Fabrication of novel nitrogen-doped graphene-hollow AuPd nanoparticle hybrid films for the highly efficient electrocatalytic reduction of H2O2

Hollow AuPd (hAuPd) alloy nanoparticles (NPs) were prepared through simultaneous reduction of HAuCl4 and Na2PdCl4 using Co NPs as sacrificial template (i.e., reductant). Then, the hAuPd NPs were assembled on nitrogen-doped graphene (NG) to prepare an NG-hAuPd hybrid film. The obtained NG-hAuPd composite showed higher electrocatalytic activity toward the reduction of H2O2, compared with graphene-hAuPd hybrid, NG-solid AuPd hybrid, and hAuPd NPs. The enhanced performance was related to the hollow structure of hAuPd NPs and the synergistic effect between NG and hAuPd NPs. Under optimum conditions, the NG-hAuPd hybrid film showed a linear response to H2O2 in the range of 0.1-20 μM, with a sensitivity of 5095.5 μA mM(-1) cm(-2)and a comparable detection limit of 0.02 μM (S/N = 3). These results demonstrated that the NG-hAuPd composite was a promising electrocatalytic material for constructing sensors, etc.

A sensitive electrochemical immunosensor for the detection of squamous cell carcinoma antigen by using PtAu nanoparticles loaded on TiO2colloidal spheres as labels

A sensitive sandwich-type electrochemical immunosensor for detection of squamous cell carcinoma antigen (SCCA) was developed by using PtAu nanoparticles loaded on TiO₂colloidal spheres (PtAu/TiO₂) as secondary-antibody (Ab₂) labels.

Versatile biosensing platform for DNA detection based on a DNAzyme and restriction-endonuclease-assisted recycling

On the basis of a DNAzyme and a restriction-endonuclease-assisted target recycling strategy using Pd-Au alloy nanocrystals to immobilize probe DNA on an electrode and catalyze the reduction of H2O2 which amplified signal and promoted the detection sensitivity, a versatile biosensing platform for DNA detection was proposed. Using p53 and oral cancer genes as models, hemin/G-quadruplex simultaneously acted as a reduced nicotinamide adenine dinucleotide (NADH) oxidase and a horseradish peroxidase (HRP)-mimicking DNAzyme, and a versatile DNA biosensor was designed for the first time based on the good electrocatalytic activity of Pd-Au alloy nanocrystals. Hemin/G-quadruplex catalyzed the reduction of H2O2, which was generated from NADH in the presence of O2, to produce an electrochemical signal when thionine functioned as the electron mediator. Moreover, the nicking endonuclease N.BstNB I caused the target DNA to cycle for multiple rounds and further amplified the electrochemical response. This versatile DNA biosensor exhibited linear ranges for the detection of p53 and oral cancer genes from 0.1 fmol L(-1) to 0.1 nmol L(-1) and 0.1 fmol L(-1) to 1 nmol L(-1), respectively. The detection limits, established as 3σ, were estimated to be 0.03 and 0.06 fmol L(-1) for the p53 and oral cancer genes, respectively. The as-prepared biosensor could discriminate mismatched sequences, indicating a satisfactory selectivity and validating the feasibility of the proposed strategy. More importantly, simply by changing the helper DNA, this versatile DNA biosensor could detect different target DNA species, which could create a new avenue for the potential diagnosis of cancer.

Co3O4 nanowires supported on 3D N-doped carbon foam as an electrochemical sensing platform for efficient H2O2 detection

Using a simple hydrothermal procedure and a subsequent annealing treatment, one-dimensional (1D) cobalt oxide nanowires (Co3O4-NWs) with tunable size have been successfully in situ fabricated on a three-dimensional (3D) carbon foam (CF) network. By changing the hydrothermal treatment time (0.5, 1, or 2 h) at 180 °C, size-controlled Co3O4 nanowires can be formed on the CF. Scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM) measurements showed that nanoporous Co3O4 nanowires grew uniformly on the 3D carbon framework. Because of the 3D porous architecture and the high conductivity of the carbon foam skeleton, the obtained composites are characterized by fast mass transport, large surface area and high electronic conductivity, which make them very promising electrochemical sensing materials. Among the studied composites, the Co3O4-NWs/CF hydrothermally treated for 1 h exhibited the lowest detection limit (1.4 μM) and the largest linear ranges (0.01-1.4 mM) with a sensitivity of 230 nA μM(-1) cm(-2) for H2O2 detection. The present study shows that metal oxides supported on 3D carbon materials present a class of promising sensing platform for the electrochemical detection of H2O2.

Pd-Au Electrocatalysts for Hydrogen Evolution Reaction at Neutral pH

Pd-Au codeposits with different ratio of both metals were electrodeposited on carbon felt, characterized by scanning electron microscopy, and investigated as electrocatalysts towards hydrogen evolution reaction in neutral phosphate buffer solution. The quantities of the produced hydrogen gas with different electrocatalysts, estimated from data obtained by chronoamperometry, were confirmed by mass spectrometry analysis. The highest hydrogen evolution rate was achieved with the electrocatalysts, produced from electrolyte with equal Pd and Au content.