Novel electrochemical non-enzymatic glucose sensor based on 3D Au@Pt core–shell nanoparticles decorated graphene oxide/multi-walled carbon nanotubes composite

Efficient Nonenzymatic Electrochemical Detection of Glucose Using CuO Nanoparticles@CNT-Wrapped Graphene Oxide Composite Electrode

A highly sensitive and stable nonenzymatic glucose biosensor has been developed via composite materials composed of CuO and graphene oxide (GO)/carbon nanotube (CNT) nanohybrid (CuO/GO/CNTs). Copper oxide nanoparticle(NP)-modified CNTs were stacked via graphene sheets and synthesized through hydrothermal method, providing a larger surface area with boosted catalytic activity for efficient mass and electron passage, respectively. Scanning electron microscopy (SEM) and energy-dispersive x-ray (EDX) spectroscopy have been used to investigate the morphology and composition of as-prepared nanohybrids, whereas x-ray diffraction (XRD) patterns provide information about the crystal structure and lattice parameters. Fabricated nanohybrid was used as electrode material to develop the nonenzymatic glucose biosensor, which exhibited better performance with a linear dynamic range from 0.06 to 0.74 mM, a high sensitivity of 328 mA mM-1 cm-2 and a low detection limit of up to 0.033 mM with a fast response time of 2 s. Although the stability and reusability of the fabricated electrode have been tested. The limit of detection was determined by using the traditional formula LOD = (SNR × σ)/Slope. The outcomes recommend the synthesized novel structured nanohybrid as a promising material possessing significant impact for flexible and wearable biosensing applications.

Core-shell Au@Ag NPs-based SERS-LFIA for the simultaneous quantitation of PEDV and PoRVA on site

Porcine epidemic diarrhea virus (PEDV) and porcine group A rotavirus (PoRVA) are predominant pathogens responsible for infectious diarrhea in porcine. Co-infections of PEDV and PoRVA have become a common situation in porcine farms in recent years, which increases the severity of the diarrhea disease and makes the accurate diagnosis more difficult. Rapid quantitation of PEDV and PoRVA is of great significance for the guarantee of disease control. In this study, a 4-mercaptobenzoic acid (MBA) modified core-shell Au@Ag nanoparticles (Au@MBA@Ag NPs) based lateral flow immunochromatography (LFIA) with dual-signal modes of visual observation and surface-enhanced Raman scattering (SERS) signal analysis was developed for the rapid and sensitive detection of PEDV and PoRVA. The established SERS-LFIA was capable of simultaneous quantitation of PEDV and PoRVA in porcine fecal samples within 20 min, with visual limits of detection (LODs) of 6.25 × 102 TCID50/mL and 7.42 × 102 copies/μL for PEDV and PoRVA, respectively. The LODs based on Raman signals were as low as 8.01 × 101 TCID50/mL and 3.19 × 102 copies/μL for PEDV and PoRVA, respectively, which were more than two orders of magnitude lower than the conventional colloidal gold (AuNPs) based colorimetric immunochromatography. Additionally, the SERS-LFIA exhibited no cross-reactivity with other prevalent pathogens and was highly repeatability, with a coefficient of variation (CV) of less than 15 %. When detecting clinical samples, the overall compliance of the SERS-LFIA with RT-PCR results was 93.3 %. Thus, the developed SERS-LFIA showed great potential for field applications on the rapid diagnosis of PEDV and PoRVA infection.

Recent progress on nanomaterial-based electrochemical sensors for glucose detection in human body fluids

In the modern age, half of the population is facing various chronic illnesses due to glucose maintenance in the body, major causes of fatality and inefficiency. The early identification of glucose plays a crucial role in medical treatment and the food industry, particularly in diabetes diagnosis. In the past few years, non-enzymatic electrochemical glucose sensors have received a lot of interest for their ability to identify glucose levels accurately. Electrochemical biosensors are developing as a propitious solution for personalized health monitoring due to their accuracy, specificity, and affordability. This review article provides an observation of a variety of non-enzymatic glucose sensor resources, such as carbon nanomaterials, noble metals gold and silver, transition metal and their oxides, and porous material composites. Moreover, basic knowledge of the reaction mechanism of enzymatic and nonenzymatic glucose sensors are outlined and recent advancements in glucose sensors applications to various human body biofluids such as sweat, tears, urine, saliva, and blood are presented. Finally, this review summarizes electrochemical sensors for glucose detection in human body fluids, the challenges they faced, and their solutions.

A Hierarchical Core-Shell Structure of NiO@Cu2O-CF for Effective Non-Enzymatic Electrochemical Glucose Detection

Non-enzymatic glucose detection is an effective strategy to control the blood glucose level of diabetic patients. A novel hierarchical core-shell structure of nickel hydroxide shell coated copper hydroxide core based on copper foam (Ni(OH)2@Cu(OH)2-CF) was fabricated and derived from NiO@Cu2O-CF for glucose sensing. Cyclic voltammetry and amperometry experiments have demonstrated the efficient electrochemical catalysis of glucose under alkaline conditions. The measurement displays that the fabricated sensor exhibits a detection scale of 0.005-4.5 mM with a detection sensitivity of 4.67 µA/µM/cm2. It has remarkable response/recovery times in respect of 750 μM glucose (1.0 s/3.5 s). Moreover, the NiO@Cu2O-CF shows significant selectivity, reliable reproducibility and long-term stability for glucose determination, suggesting it is a suitable candidate for further applications.

MicroRNA Triggered Dimerization of DNA Tetrahedron for Enhanced Biosensing Performance of Solid-State Nanochannels Functionalized with MoS2 Nanosheets

Solid-state nanochannels (SSN) have great development potential as a biosensing interface. The integration of two-dimensional nanomaterials with nanochannels endows SSN with diverse properties, including distinguishing DNA nanostructures. In this study, by modifying MoS2 nanosheets, the outer surface of SSN could be endowed with robust adsorption properties for single-stranded DNA. Therefore, DNA tetrahedrons connected with single-stranded DNA could remain on the SSN surface, whereas DNA tetrahedron dimers with full double-stranded structures formed by the presence of target microRNA cannot be retained on the surface of nanochannels. The change in the DNA nanostructure generated by the target recognition process could cause variations of steric hindrance and electrostatic repulsion on the surface of the SSN. The variations were reflected by the free diffusion flux of [Fe(CN)6]3-. Then, the sensitive electrochemical detection method for microRNA was established, and the detection limit of the method for microRNA-31 was as low as 0.5 fM. The study provided a promising approach for the ultrasensitive detection of biomarkers, thereby offering potential means for early diagnosis of the related diseases.

Construction of a self-reporting molecularly-imprinted electrochemical sensor based on CuHCF modified by rGNR-rGO for the detection of zearalenone

A self-reporting molecularly-imprinted electrochemical sensor is prepared for the detection of Zearalenone (ZEA). Firstly, the reduced graphene nanoribbons and reduced graphene oxide (rGNR-rGO) were simultaneously modified onto a glassy carbon electrode (GCE) to improve the sensor's sensitivity. After electrodepositing copper nanoparticles onto the rGNR-rGO/GCE, cyclic voltammetry scanning was performed in potassium ferrocyanide solution, and copper hexacyanoferrate (CuHCF) was deposited onto rGNR-rGO/GCE to further improve the sensor's sensitivity while giving it self-reporting capability. Then, molecularly-imprinted polymer films were prepared on the CuHCF/rGNR-rGO/GCE to ensure the selectivity of the sensor. It is found that the linear range of ZEA detection by the constructed sensor is 0.25-500 ng·mL -1, with a detection limit of 0.09 ng·mL -1. This sensor shows the merits of good selectivity, high sensitivity and accurate detection, providing a great possibility for the precise detection of low concentration ZEA in food.

Advances of Transition Metal-Based Electrochemical Non-enzymatic Glucose Sensors for Glucose Analysis: A Review

Glucose concentration is a crucial parameter for assessing human health. Over recent years, non-enzymatic electrochemical glucose sensors have drawn considerable attention due to their substantial progress. This review explores the common mechanism behind the transition metal-based electrocatalytic oxidation of glucose molecules through classical electrocatalytic frameworks like the Pletcher model and the Hydrous Oxide-Adatom Mediator model (IHOAM), as well as the redox reactions at the transition metal centers. It further compiles the electrochemical characterization techniques, associated formulas, and their ensuing conclusions pertinent to transition metal-based non-enzymatic electrochemical glucose sensors. Subsequently, the review covers the latest advancements in the field of transition metal-based active materials and support materials used in non-enzymatic electrochemical glucose sensors in the last decade (2014-2023). Additionally, it presents a comprehensive classification of representative studies according to the active metal catalysts components involved.

Molecularly imprinted polymers-aptamer electrochemical sensor based on dual recognition strategy for high sensitivity detection of chloramphenicol

In this paper, an electrochemical sensor based on a dual recognition strategy of molecularly imprinted polymers (MIPs) and aptamer (Apt) has been designed for the high sensitivity detection of chloramphenicol (CAP). Here, MIPs and Apt have provided dual recognition sites to greatly improve the specific recognition ability of the sensor. Chitosan-multi-walled carbon nanotubes (CS-MWNTs) and AuNPs (gold nanoparticles) have been used for their excellent electrical conductivity. When CAP existed in the detection environment, the imprinted cavities with specific recognition ability bound to CAP through forces such as hydrogen bonds. It hindered the rate of electron transfer and resulted in a decrease in current value. Quantitative detection of CAP could be achieved after analyzing the relationship between the concentration of CAP and the change of current value. After optimizing the experimental parameters, the detection range of the sensor was 10-8 g/L-10-2 g/L with the limit of detection of 3.3 × 10-9 g/L, indicating that the sensor had a high practical application potential.

Biosensors based on core-shell nanoparticles for detecting mycotoxins in food: A review

Mycotoxins are toxic metabolites produced by fungi in the process of infecting agricultural products, posing serious threat to the health of human and animals. Thus, sensitive and reliable analytical techniques for mycotoxin detection are needed. Biosensors equipped with antibodies or aptamers as recognition elements and core-shell nanoparticles (NPs) for the pre-treatment and detection of mycotoxins have been extensively studied. By comparison with monocomponent NPs, core-shell nanostructures exhibit unique optical, electric, magnetic, plasmonic, and catalytic properties due to the combination of functionalities and synergistic effects, resulting in significant improvement of sensing capacities in various platforms, such as surface-enhanced Raman spectroscopy, fluorescence, lateral flow immunoassay and electrochemical sensors. This review focused on the development of core-shell NPs based biosensors for the sensitive and accurate detection of mycotoxins in food samples. Recent developments were categorised and summarised, along with detailed discussion of advantages and shortcomings. The future potential of utilising core-shell NPs in food safety testing was also highlighted.

Carbon nanotubes: a powerful bridge for conductivity and flexibility in electrochemical glucose sensors

The utilization of nanomaterials in the biosensor field has garnered substantial attention in recent years. Initially, the emphasis was on enhancing the sensor current rather than material interactions. However, carbon nanotubes (CNTs) have gained prominence in glucose sensors due to their high aspect ratio, remarkable chemical stability, and notable optical and electronic attributes. The diverse nanostructures and metal surface designs of CNTs, coupled with their exceptional physical and chemical properties, have led to diverse applications in electrochemical glucose sensor research. Substantial progress has been achieved, particularly in constructing flexible interfaces based on CNTs. This review focuses on CNT-based sensor design, manufacturing advancements, material synergy effects, and minimally invasive/noninvasive glucose monitoring devices. The review also discusses the trend toward simultaneous detection of multiple markers in glucose sensors and the pivotal role played by CNTs in this trend. Furthermore, the latest applications of CNTs in electrochemical glucose sensors are explored, accompanied by an overview of the current status, challenges, and future prospects of CNT-based sensors and their potential applications.

Eco-friendly fabrication of nonenzymatic electrochemical sensor based on cobalt/polymelamine/nitrogen-doped graphitic-porous carbon nanohybrid material for glucose monitoring in human blood

The design and development of eco-friendly fabrication of cost-effective electrochemical nonenzymatic biosensors with enhanced sensitivity and selectivity are one of the emerging area in nanomaterial and analytical chemistry. In this aspect, we developed a facile fabrication of tertiary nanocomposite material based on cobalt and polymelamine/nitrogen-doped graphitic porous carbon nanohybrid composite (Co-PM-NDGPC/SPE) for the application as a nonenzymatic electrochemical sensor to quantify glucose in human blood samples. Co-PM-NDGPC/SPE nanocomposite electrode fabrication was achieved using a single-step electrodeposition method under cyclic voltammetry (CV) technique under 1 M NH₄Cl solution at 20 constitutive CV cycles (sweep rate 20 mV/s). Notably, the fabricated nonenzymatic electroactive nanocomposite material exhibited excellent electrocatalytic sensing towards the quantification of glucose in 0.1 M NaOH over a wide concentration range from 0.03 to 1.071 mM with a sensitive limit of detection 7.8 μM. Moreover, the Co-PM-NDGPC nanocomposite electrode with low charge transfer resistance (Rct∼81 Ω) and high ionic diffusion indicates excellent stability, reproducibility, and high sensitivity. The fabricated nanocomposite materials exhibit a commendable sensing response toward glucose molecules present in the blood serum samples recommends its usage in real-time applications.

An Amperometric Biomedical Sensor for the Determination of Homocysteine Using Gold Nanoparticles and Acetylene Black-Dihexadecyl Phosphate-Modified Glassy Carbon Electrode

A novel nanocomposite film composed of gold nanoparticles and acetylene black-dihexadecyl phosphate was fabricated and modified on the surface of a glassy carbon electrode through a simple and controllable dropping and electropolymerization method. The nanocomposite film electrode showed a good electrocatalytic response to the oxidation of homocysteine and can work as an amperometric biomedical sensor for homocysteine. With the aid of scanning electron microscopy, energy dispersive X-ray technology and electrochemical impedance spectroscopy, the sensing interface was characterized, and the sensing mechanism was discussed. Under optimal conditions, the oxidation peak current of homocysteine was linearly increased with its concentration in the range of 3.0 µmol/L~1.0 mmol/L, and a sensitivity of 18 nA/(μmol/L) was obtained. Furthermore, the detection limit was determined as 0.6 µmol/L, and the response time was detected as 3 s. Applying the nanocomposite film electrode for monitoring the homocysteine in human blood serum, the results were satisfactory.

CuO/Cu/rGO nanocomposite anodic titania nanotubes for boosted non-enzymatic glucose biosensors

Highly arranged porous anodic titania (TiO2) nanotube arrays (ATNT) were fruitfully fabricated by the anodization of Ti foil in an ammonium fluoride electrolyte.

Nonenzymatic Glucose Sensor Based on Porous Co3O4 Nanoneedles

Herein, porous Co3O4 nanoneedle arrays were synthesized on nickel (Ni) foam (Co3O4 NNs/NF) by one-step hydrothermal method. Some electrochemical methods were used to investigate its nonenzymatic glucose sensing performance in alkaline solution. The results show that the sensitivity of Co3O4 NNs/NF electrode to glucose is 4570 μA mM-1 cm-2. The linear range is 1 μM-0.337 mM, and the detection limit is 0.91 μM ( $S/N=3$ ). It also displays good selectivity and repeatability for glucose. The good electrochemical sensing performance of Co3O4 NNs/NF based sensor for glucose can be attributed to interconnected porous structure and large specific surface area of Co3O4.

Functionalized Platinum Nanoparticles with Biomedical Applications

Functionalized platinum nanoparticles have been of considerable interest in recent research due to their properties and applications, among which they stand out as therapeutic agents. The functionalization of the surfaces of nanoparticles can overcome the limits of medicine by increasing selectivity and thereby reducing the side effects of conventional drugs. With the constant development of nanotechnology in the biomedical field, functionalized platinum nanoparticles have been used to diagnose and treat diseases such as cancer and infections caused by pathogens. This review reports on physical, chemical, and biological methods of obtaining platinum nanoparticles and the advantages and disadvantages of their synthesis. Additionally, applications in the biomedical field that can be utilized once the surfaces of nanoparticles have been functionalized with different bioactive molecules are discussed, among which antibodies, biodegradable polymers, and biomolecules stand out.

Strategies, advances, and challenges associated with the use of graphene-based nanocomposites for electrochemical biosensors

Graphene is an intriguing two-dimensional honeycomb-like carbon material with a unique basal plane structure, charge carrier mobility, thermal conductivity, wide electrochemical spectrum, and unusual physicochemical properties. Therefore, it has attracted considerable scientific interest in the field of nanoscience and bionanotechnology. The high specific surface area of graphene allows it to support high biomolecule loading for good detection sensitivity. As such, graphene, graphene oxide (GO), and reduced GO are excellent materials for the fabrication of new nanocomposites and electrochemical sensors. Graphene has been widely used as a chemical building block and/or scaffold with various materials to create highly sensitive and selective electrochemical sensing microdevices. Over the past decade, significant advancements have been made by utilizing graphene and graphene-based nanocomposites to design electrochemical sensors with enhanced analytical performance. This review focus on the synthetic strategies, as well as the structure-to-function studies of graphene, electrochemistry, novel multi nanocomposites combining graphene, limit of detection, stability, sensitivity, assay time. Finally, the review describes the challenges, strategies and outlook on the future development of graphene sensors technology that would be usable for the internet of things are also highlighted.