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We herein describe a novel lateral flow assay (LFA) to detect H 2 O 2 by utilizing self-biotinylation of G-quadruplex (G4). In this strategy, the G4 strand promotes the self-biotinylation of G4 itself in the presence of H 2 O 2 , which is then allowed to bind to the FAM-labeled complementary detector probe. The resulting biotin-labeled G4/FAM-detector probe complex is captured on the test line, producing a red-colored band during lateral flow readout. Based on this unique approach, we achieved the naked-eye detection of target H 2 O 2 at concentrations as low as 1 μM, with reliable quantification down to 0.388 μM. This method also demonstrated exceptional specificity in distinguishing H 2 O 2 from other non-target molecules. We further verified its versatile applicability by reliably identifying another biomolecule, choline, by coupling with choline oxidase, which generates H₂O₂ during oxidation. This novel LFA strategy holds great promise as a powerful point-of-care testing (POCT) platform for detecting a large spectrum of target biomolecules by employing their corresponding oxidases. [ABSTRACT FROM AUTHOR]

Functionalized few-layer borophene (FFB) was prepared using gallnut extract and coffee waste extract as natural exfoliating and stabilizing agents in an environmentally friendly ultrasonic and high shear exfoliation. Here, a facile precipitation method was employed to grow iron oxide nanoparticles doped with cerium (Ce-FeONPs) onto the surface of FFB. This intriguing combination of materials yielded Ce-FeONPs nanoparticles that exhibited exceptional peroxidase-like activity, efficiently catalyzing the conversion of 3,3′,5,5′-tetramethylbenzidine (TMB) to a blue oxidized TMB (oxTMB) in the presence of hydrogen peroxide (H 2 O 2). Additionally, the introduction of FFB contributes a reducibility effect to the catalytic oxidation of TMB, facilitating the restoration of the oxTMB to TMB. Thus, FFB-Ce-FeONPs showcase intriguing properties encompassing both oxidative and reductive characteristics, suggesting their potential as a reagent for repeated detection of H 2 O 2. Moreover, a colorimetric sensing system enabled the liner detection of H 2 O 2 spanning a concentration range from 0.08 to 1 mM, with a detection limit of 0.03 mM. Noteworthily, FFB-Ce-FeONPs demonstrated sustained efficacy over ten successive recycling cycles, as indicated by consistent slopes and observable color changes. In summary, this work reports the first application of nanoenzymes in repetitive H 2 O 2 detection. Even after ten multiple cycles, the detection limit remains virtually unaltered, underscoring the robustness and enduring effectiveness of the engineered nanomaterial. The proposed simultaneous oxidation and reduction strategies for detecting H 2 O 2 showed a commendable capability in ten cycles of H 2 O 2 detection, thus providing a promising approach in the field of H 2 O 2 detection. [ABSTRACT FROM AUTHOR]

Coronavirus disease 2019 (COVID-19) is a highly contagious illness caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), resulting in a global health crisis. The primary diagnostic method for COVID-19 is quantitative reverse transcription PCR, which is time-consuming and requires expensive instrumentation. Here, we developed an electrochemical biosensor for detecting SARS-CoV-2 biomarkers using a 3D porous polyacrylamide/polyaniline hydrogel (PPG) electrode prepared by UV photopolymerization and in situ polymerization. The electrochemical immunosensor for detecting SARS-CoV-2 N protein via the immune sandwich principle demonstrated a lower detection limit of 42 pg/mL and comparable specificity to a commercial enzyme-linked immunosorbent assay, which was additionally validated in pseudoviruses. The electrochemical sensor for hydrogen peroxide showed a low detection limit of 0.5 μM and excellent selectivity, which was further confirmed in cancer cells under oxidative stress. The biomarkers of SARS-CoV-2 were successfully detected due to the signal amplification capability provided by 3D porous electrodes and the high sensitivity of the antigen-antibody specific binding. This study introduces a novel three-dimensional electrode with great potential for the early detection of SARS-CoV-2. [ABSTRACT FROM AUTHOR]

Abstract In this work, we report a novel sensor for colorimetric and fluorometric H 2 O 2 sensing which is based on silver nanoparticles decorated and tetraphenylethene probe doped silica nanoparticles (Ag@TPE-SiO 2 NPs). A positively charged tetraphenylethene (TPE) probe is doped into silica nanoparticles, and the nanoparticles exhibit strong fluorescence emission due to aggregation-induced emission (AIE) of the TPE probe. Ag nanoparticles (AgNPs) are prepared in situ on the surface of the silica nanoparticles. AgNPs serve as a nanoquencher which can quench the AIE emission of the TPE-SiO 2 NPs efficiently. However, AgNPs can be oxidized to Ag+ by H 2 O 2 , which leads to fluorescence recovery and color fading of the Ag@TPE-SiO 2 NPs. The dual-readout strategy allows sensitive analysis of H 2 O 2. The detection limit of the fluorometric and colorimetric assay is 0.28 and 2.1 μM, respectively. And the nanosensor also shows good selectivity. In addition, analysis of H 2 O 2 in human serum and intracellular imaging of H 2 O 2 are both demonstrated. With the good analytical properties of merit, the proposed nanoprobe has a promising potential for H 2 O 2 related bioanalysis and biomedical applications. Graphical abstract fx1 Highlights • A sensor based on AgNPs decorated and TPE probe doped silica NPs was fabricated. • This dual-mode colorimetric and fluorometric sensor was employed for H 2 O 2 sensing. • The determination of H 2 O 2 in human serum was demonstrated. • The nanosensor was successfully employed for intracellular imaging of H 2 O 2. [ABSTRACT FROM AUTHOR]

Abstract: Tungsten carbide nanorods (WC NRs) are demonstrated for the first time to possess intrinsic peroxidase-like activity towards typical peroxidase substrates, such as 3, 3', 5, 5'-tetramethylbenzidine (TMB) and ο-phenylenediamine (OPD) in the presence of hydrogen peroxide (H2O2). The reactions catalyzed by these nanorods follow the Michaelis–Menten kinetics. The excellent catalytic performance of WC NRs could be attributed to their intrinsic catalytic activity to efficiently accelerate the electron-transfer process and facilitate the decomposition of H2O2 to generate more numbers of reactive oxygen species (ROS). Based upon the strong peroxidase-like activity of these WC NRs, a colorimetric sensor for H2O2 is designed, which provides good response towards H2O2 concentration over a range of 2×10−7–8×10−5 M with a detection limit of 60nM. Moreover, the peroxidase-like activities of WC NRs with TMB as the substrate are investigated in both protic and aprotic organic media, showing different colorimetric reactions from that performed in aqueous solutions. In comparison with the natural horse radish peroxidase, WC NR exhibits excellent robustness of catalytic activity and considerable reusability, thus making it a promising mimic of peroxidase catalysts. [Copyright &y& Elsevier]

The large surface, the excellent dispersion and the high degrees of sensitivity of bimetallic nanocatalysts were the attractive features of this investigation. Graphene foam (GF) was a three dimensional (3D) porous architecture consisting of extremely large surface and high conductive pathways. In this study, 3D GF was used incorporating platinum–ruthenium (PtRu) bimetallic nanoparticles as an electrochemical nanocatalyst for the detection of hydrogen peroxide (H2O2). PtRu/3D GF nanocatalyst exhibited a remarkable performance toward electrochemical oxidation of H2O2 without any additional mediator showing a high sensitivity (1023.1µAmM−1 cm−2) and a low detection limit (0.04µM) for H2O2. Amperometric results demonstrated that GF provided a promising platform for the development of electrochemical sensors in biosensing and PtRu/3D GF nanocatalyst possessed the excellent catalytic activity toward the H2O2 detection. A small particle size and a high degree of the dispersion in obtaining of large active surface area were important for the nanocatalyst for the best H2O2 detection in biosensing. Moreover, potential interference by ascorbic acid and uric acid appeared to be negligible. [ABSTRACT FROM AUTHOR]

Abstract: Here we report the derivatization of mesoporous TiO2 thin films for the preparation of H2O2 amperometric sensors. The coordination of the bifunctional ligand 1,10 phenantroline, 5,6 dione on the surface Ti(IV) ions provides open coordination sites for Fe(II) cations which are the starting point for the growth of a layer of Prussian blue polymer. The porous structure of the mesoporous TiO2 allows the growth, ion by ion of the coordination polymer. Up to four layer of Prussian blue can be deposit without losing the porous structure of the film, which results in an enhanced response of these materials as H2O2 sensors. These porous confined PB modified electrodes are robust sensors that exhibit good reproducibility, environmental stability and high sensitivity towards H2O2 detection. [ABSTRACT FROM AUTHOR]

Abstract: Biosensor performance depends on the effective functionalisation of a transducer with suitable biorecognition elements. During functionalisation, surface blocking steps are normally carried out to avoid later binding of undesirable molecules and thus guarantee biosensor specificity. However, these blocking steps may be deleterious in electrochemical systems where transduction ultimately relies on electron transfer between the electrode and a redox species in solution. This work presents a novel approach to develop improved amperometric biosensing platforms using microfabricated disk microelectrode arrays, based on the functionalisation of the inert surface surrounding the active microdisks. These devices more than doubled assay sensitivity compared to conventional biosensors produced using the same arrays. This approach benefits from three advantages: the functionalisation of a broader surface, the possibility to activate the microelectrodes immediately before detection, and access to enhanced rates of mass transport to microelectrodes that improve device sensitivity. To demonstrate this, we first studied the electrochemical behaviour of tetramethylbenzidine (TMB) at gold disk microelectrode arrays, and then used TMB as the redox mediator for the amperometric biosensing of HRP/H2O2. Down to 0.54pM H2O2 or as little as 25pM HRP were detected within 5s of enzyme activity in just 10μl of enzyme substrate solution. We postulate that microelectrode arrays may be used to develop novel electrochemical biosensing platforms that are faster and more sensitive than conventional biosensors. [Copyright &y& Elsevier]

Herein, we developed a hierarchical bio-composite sensing film by facile one-step electro-deposition of 0D enzyme-polymer nanoparticles (NPs) with 2D graphene oxide nanosheets as conductive supports and nanofillers, based on which an effective and robust enzymatic biosensor platform was constructed. Horseradish peroxidase (HRP) as a model enzyme was co-assembled with a photo-cross-linkable polypeptide of 2-hydroxyethyl methacrylate modified poly(γ-glutamic acid) (γ-PGA-HEMA), generating hybrid HRP@γ-PGA-HEMA nanoparticles (HRP@PGH NPs). Then HRP@PGH NPs and graphene oxide nanosheets (GO NSs) were simultaneously electrodeposited onto the electrode surface, obtaining a hierarchical 0D-2D bio-composite film. After subsequent electrochemical reduction of GO NSs into graphene nanosheets (GNSs) and following photo-cross-linking, the resultant nanostructured HRP@PGH/GNSs sensing film was successfully applied to construct an enzymatic biosensor for hydrogen peroxide (H 2 O 2). The biosensor exerted high sensitivity, fast response, and good stability for H 2 O 2 sensing. Satisfactory results were also demonstrated for its practical application in human serum samples, suggesting a promising application potential in biomedical diagnostics. The one-step generated 0D-2D bio-composite sensing film demonstrates synergetic effects from both the soft nanoparticles and hard conductive nanosheets, which would enlighten the innovative construction of composite nanomaterials and nanoarchitectonics for bio-sensing systems. A robust enzymatic biosensor platform was constructed based on a hierarchical bio-composite sensing film by facile one-step electro-deposition of photo-cross-linkable 0D enzyme-loaded bio-polymeric nanoparticles and 2D graphene oxide nanosheets. Image 1 • A hierarchical 0D-2D bio-composite sensing film was developed by facile one-step electro-deposition process. • The 0D-2D bio-composite film consisted of 0D enzyme-loaded polymeric nanoparticles decorating 2D graphene nanosheets. • A robust enzymatic biosensor platform was constructed with high sensitivity, fast response, and good stability. • Satisfactory analytical results in human serum samples suggests the sensor's applicability in biomedical diagnostics. [ABSTRACT FROM AUTHOR]