Nonenzymatic glucose sensor based on ultrasonic-electrodeposition of bimetallic PtM (M=Ru, Pd and Au) nanoparticles on carbon nanotubes–ionic liquid composite film

Label-free, real-time monitoring of cytochrome C drug responses in microdissected tumor biopsies with a multi-well aptasensor platform

Functional assays on intact tumor biopsies can complement genomics-based approaches for precision oncology, drug testing, and organs-on-chips cancer disease models by capturing key therapeutic response determinants, such as tissue architecture, tumor heterogeneity, and the tumor microenvironment. Most of these assays rely on fluorescent labeling, a semiquantitative method best suited for single-time-point assays or labor-intensive immunostaining analysis. Here, we report integrated aptamer electrochemical sensors for on-chip, real-time monitoring of cytochrome C, a cell death indicator, from intact microdissected tissues with high affinity and specificity. The platform features a multi-well sensor layout and a multiplexed electronic setup. The aptasensors measure increases in cytochrome C in the supernatant of mouse or human microdissected tumors after exposure to various drug treatments. Because of the sensor's high affinity, it primarily tracks rising concentrations of cytochrome C, capturing dynamic changes during apoptosis. This approach could help develop more advanced cancer disease models and apply to other complex in vitro disease models, such as organs-on-chips and organoids.

Ionogels for flexible conductive substrates and their application in biosensing

Ionogels are highly conductive gels made from ionic liquids dispersed in a matrix made of organic or inorganic materials. Ionogels are known for high ionic conductivity, flexibility, high thermal and electrochemical stability. These characteristics make them suitable for sensing and biosensing applications. This review discusses about the two main constituents, ionic liquids and matrix, used to make ionogels and effect of these materials on the characteristics of ionogels. Here, the material properties like mechanical, electrochemical and stability are discussed for both polymer matrix and ionic liquid. We have briefly described about the fabrication methods like 3D printing, sol-gel, blade coating, spin coating, aerosol jet printing etc., used to make films or coating of these ionogels. The advantages and disadvantages of each method are also briefly summarized. Finally, the last section provides a few examples of application of flexible ionogels in areas like wearables, human-machine interface, electronic skin and detection of biological molecules.

Efficient formaldehyde sensor based on PtPd nanoparticles-loaded nafion-modified electrodes

The noble metal-based electrochemical sensor design for efficient and stable formaldehyde(FA) detection is important ongoing research. In this paper, PtPd/Nafion/GCE is prepared by electrochemical cyclic voltammetry deposition method based on electrodepositing nanostructured platinum (Pt)-palladium (Pd) nanoparticles in Nafion film-coated glassy carbon electrode (GCE). The influence of deposition parameters and chemical composition (atomic ratio of Pt and Pd) on the electrochemical behaviour of PtPd/Nafion/GCE has been investigated. PtPd/Nafion/GCE displays a remarked electrocatalytic activity for the oxidation of FA and exhibits a linear relationship in the range of 10-5000μM, with a detection limit of 3.3μM in 0.1 M H2SO4solution. It is proved that the detection performance of PtPd/Nafion/GCE electrode is valuable for further application with low detection limit, wide linear range, favourable selectivity and high response.

Silver-functionalized bismuth oxide (AgBi2O3) nanoparticles for the superior electrochemical detection of glucose, NO2- and H2O2

In this study, silver-functionalized bismuth oxide (AgBi₂O₃) nanoparticles (SBO NPs) were successfully synthesized by a highly efficient hydrothermal method. The as-synthesized SBO nanoparticles were characterized using FT-IR, P-XRD, XPS, HR-SEM, and HR-TEM analytical methods. It was found that the NPs were in spherical shape and hexagonal crystal phase. The newly prepared SBO electrode was further utilized for the detection of glucose, NO₂^- and H₂O₂ by cyclic voltammetry (CV) and amperometric methods. The electrodes exhibited high sensitivity (2.153 μA mM^-1 cm^-2 for glucose, 22 μA mM^-1 cm^-2 for NO₂^- and 1.72 μA mM^-1 cm^-2 for H₂O₂), low LOD (0.87 μM for glucose, 2.8 μM for NO₂^- and 1.15 μM for H₂O₂) and quick response time (3 s for glucose, 2 s for both NO₂^- and H₂O₂ respectively). The sensor exhibited outstanding selectivity despite the presence of various interferences. The developed sensor exhibited good repeatability, reproducibility, and stability. In addition, the sensor was used to measure glucose, H₂O₂ in human serum, and NO₂^- in milk and river water samples, demonstrating its potential for use in the real sample.

Non-enzymatic electrochemical detection of creatinine based on a glassy carbon electrode modified with a Pd/Cu2O decorated polypyrrole (PPy) nanocomposite: an analytical approach

The major constraints of standard enzymatic biosensors are poor long-term storage stability and high cost. Hence, there is extensive research towards fabrication of reliable enzymeless biosensors based on nanomaterials. In this paper, we present the development of an enzymeless electrochemical biosensor for highly precise detection of creatinine. This involves the use of a simple yet effective alternative to the commonly utilized Pd/Cu₂O/PPy nanocomposite, which was characterized by different analytical methods. The present electrochemical sensor provides a wide detection range (0.1 to 150 μM), low detection limit (0.05 μM) and high sensitivity (0.207 μA), and is capable of detecting the creatinine level in human urine samples, which are inexpensive. The results are reproducible, and the sensor is stable. The sensor demonstrates good electrocatalytic activity and selectivity towards the detection of creatinine in the presence of various other similar biological entities. When compared to other existing counterparts, the electrocatalytic behaviour of the present sensor is comparable, if not better. So, the present electrochemical sensor for creatinine might be employed as a long-term diagnostic alternative.

A Nanotechnology-Based Approach to Biosensor Application in Current Diabetes Management Practices

Diabetes mellitus is linked to both short-term and long-term health problems. Therefore, its detection at a very basic stage is of utmost importance. Research institutes and medical organizations are increasingly using cost-effective biosensors to monitor human biological processes and provide precise health diagnoses. Biosensors aid in accurate diabetes diagnosis and monitoring for efficient treatment and management. Recent attention to nanotechnology in the fast-evolving area of biosensing has facilitated the advancement of new sensors and sensing processes and improved the performance and sensitivity of current biosensors. Nanotechnology biosensors detect disease and track therapy response. Clinically efficient biosensors are user-friendly, efficient, cheap, and scalable in nanomaterial-based production processes and thus can transform diabetes outcomes. This article is more focused on biosensors and their substantial medical applications. The highlights of the article consist of the different types of biosensing units, the role of biosensors in diabetes, the evolution of glucose sensors, and printed biosensors and biosensing systems. Later on, we were engrossed in the glucose sensors based on biofluids, employing minimally invasive, invasive, and noninvasive technologies to find out the impact of nanotechnology on the biosensors to produce a novel device as a nano-biosensor. In this approach, this article documents major advances in nanotechnology-based biosensors for medical applications, as well as the hurdles they must overcome in clinical practice.

Synthesis of honeycomb Ag@CuO nanoparticles and their application as a highly sensitive and electrocatalytically active hydrogen peroxide sensor material

Copper acetate/silver nitrate/polyvinylpyrrolidone was first prepared into nano-hybrid silver-doped copper oxide by electrospinning, and then nano-honeycomb particles were produced through heat-treatment. For the first time, honeycomb Ag@CuO nanoparticles were prepared by electrospinning, and a H₂O₂ sensor was constructed by modifying the carbon paste electrode (CPE) with the honeycomb Ag@CuO nanoparticles. This work performed the structural, morphological, and phase analysis of the Ag@CuO nanoparticles by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The results indicated the synthesis of Ag@CuO hybrid nanoparticles with high purity, and cyclic voltammetry and amperometry show that the Ag@CuO modified electrode has high electrocatalytic performances with fast voltammetric responses and a notably decreased overpotential compared to that of even the CuO modified CPE. In addition, the Ag/CuO-CPE based H₂O₂ sensor has the highest sensitivity of 1982.14 μA (mmol L^-1)^-1 cm^-2, the lowest detection limit of 0.01 μmol L^-1 ((S/N) = 3), and the measured linear response for H₂O₂ oxidation ranged from 0.05 μmol L^-1 to 100 μmol L^-1 and 100 μmol L^-1 to 1.5 mmol L^-1. The proposed method was applied to the determination of H₂O₂ in coconut fruit samples from canned coconut, and the satisfactory results confirmed the applicability of this sensor in practical analysis.

Recent advancement in noninvasive glucose monitoring and closed-loop management system for diabetes

Diabetes can cause many complications, which has become one of the most common diseases that may lead to death. Currently, the number of diabetics continues increasing year by year. Thus,...

Role of bioelectrochemical systems for the remediation of emerging contaminants from wastewater: A review

Bioelectrochemical systems (BESs) are a unique group of wastewater remediating technology that possesses the added advantage of valuable recovery with concomitant wastewater treatment. Moreover, due to the application of robust microbial biocatalysts in BESs, effective removal of emerging contaminants (ECs) can be accomplished in these BESs. Thus, this review emphasizes the recent demonstrations pertaining to the removal of complex organic pollutants of emerging concern present in wastewater through BES. Owing to the recalcitrant nature of these pollutants, they are not effectively removed through conventional wastewater treatment systems and thereby are discharged into the environment without proper treatment. Application of BES in terms of ECs removal and degradation mechanism along with valuables that can be recovered are discussed. Moreover, the factors affecting the performance of BES, like biocatalyst, substrate, salinity, and applied potential are also summarized. In addition, the present review also elucidates the occurrence and toxic nature of ECs as well as future recommendations pertaining to the commercialization of this BES technology for the removal of ECs from wastewater. Therefore, the present review intends to aid the researchers in developing more efficient BESs for the removal of ECs from wastewater.

NiCo-LDH nanoflake arrays-supported Au nanoparticles on copper foam as a highly sensitive electrochemical non-enzymatic glucose sensor

The detection of glucose in human blood is of great importance in the diagnosis and prevention of diabetes. In this work, we fabricated a novel electrochemical non-enzymatic glucose sensor, NiCo-LDH nanoflake arrays-supported Au nanoparticles on copper foam (NiCo-LDH@ Au/Cu) by galvanic replacement and electrodeposition methods. Owing to the synergistic effect of three-dimensional (3D) architecture of Cu foam, high electrocatalytic activity of Au nanoparticles and NiCo-LDH nanoflake arrays, the NiCo-LDH@Au/Cu electrode exhibits excellent electrocatalytic ability for glucose oxidation in NaOH solution. Under optimized conditions, the NiCo-LDH@Au/Cu electrode shows excellent activity with a linear range from 0.5 to 3000 μM at the potential of 0.50 V (vs. Ag/AgCl), a low detection limit of 0.23 μM (S/N = 3), an ultra-prompt response time of 0.5 s, and a high sensitivity of 23100 μA mM^-1 cm^-2, as well as good selectivity and stability. Furthermore, the as-fabricated non-enzymatic glucose sensor was successfully applied to the glucose detection in human serum as a promising candidate in the development of electrochemical non-enzymatic glucose sensor.

Recent Advances in Enzymatic and Non-Enzymatic Electrochemical Glucose Sensing

The detection of glucose is crucial in the management of diabetes and other medical conditions but also crucial in a wide range of industries such as food and beverages. The development of glucose sensors in the past century has allowed diabetic patients to effectively manage their disease and has saved lives. First-generation glucose sensors have considerable limitations in sensitivity and selectivity which has spurred the development of more advanced approaches for both the medical and industrial sectors. The wide range of application areas has resulted in a range of materials and fabrication techniques to produce novel glucose sensors that have higher sensitivity and selectivity, lower cost, and are simpler to use. A major focus has been on the development of enzymatic electrochemical sensors, typically using glucose oxidase. However, non-enzymatic approaches using direct electrochemistry of glucose on noble metals are now a viable approach in glucose biosensor design. This review discusses the mechanisms of electrochemical glucose sensing with a focus on the different generations of enzymatic-based sensors, their recent advances, and provides an overview of the next generation of non-enzymatic sensors. Advancements in manufacturing techniques and materials are key in propelling the field of glucose sensing, however, significant limitations remain which are highlighted in this review and requires addressing to obtain a more stable, sensitive, selective, cost efficient, and real-time glucose sensor.

Unique Nonenzymatic Glucose Sensor Using a Hollow-Shelled Triple Oxide Mn-Cu-Al Nanocomposite

Glucose monitoring devices for diabetes mellitus, which is a worldwide significant health issue, have attracted attention of many researchers. Herein, we report a hollow Mn-Cu-Al oxide nanocomposite (HMCA) by a microwave-assisted technique showing excellent sensing abilities toward glucose. Also, it possesses a superb supercapacitor activity described in our previous paper. The sensitivity value of the nanocomposite is 2.194 mA mM^-1 cm^-2 with a low detection limit of 0.43 μM (S/N = 3). The high sensitivity and low detection limit were the results of the large surface area of the nanocomposite and the redox nature of CuO and MnO₂. It shows a selective detection of glucose levels in blood serum. The hollow nanocomposite has been useful for monitoring the glucose level in blood serum and holds great potential for diabetes mellitus and clinical diagnosis.

Printable Nonenzymatic Glucose Biosensors Using Carbon Nanotube-PtNP Nanocomposites Modified with AuRu for Improved Selectivity

Nonenzymatic glucose biosensors have the potential for a more reliable in vivo functionality due to the reduced risk of biorecognition element degradation. However, these novel sensing mechanisms often are nanoparticle-based and have nonlinear responses, which makes it difficult to gauge their potential utility against more conventional enzymatic biosensors. Moreover, these nonenzymatic biosensors often suffer from poor selectivity that needs to be better addressed before being used in vivo. To address these problems, here we present an amperometric nonenzymatic glucose biosensor fabricated using one-step electrodeposition of Au and Ru nanoparticles on the surface of a carbon-nanotube-based platinum-nanoparticle hybrid in conductive polymer. Using benchtop evaluations, we demonstrate that the bimetallic catalyst of Au-Ru nanoparticles can enable the nonenzymatic detection of glucose with a superior performance and stability. Furthermore, our biosensor shows good selectivity against other interferents, with a nonlinear dynamic range of 1-19 mM glucose. The Au-Ru catalyst has a conventional linear range of 1-10 mM, with a sensitivity of 0.2347 nA/(μM mm²) ± 0.0198 (n = 3) and a limit of detection of 0.068 mM (signal-to-noise, S/N = 3). The biosensor also exhibits a good repeatability and stability at 37 °C over a 3 week incubation period. Finally, we use a modified Butler-Volmer nonlinear analytical model to evaluate the impact of geometrical and chemical design parameters on our nonenzymatic biosensor's performance, which may be used to help optimize the performance of this class of biosensors.

Recent advances of electrochemical and optical enzyme-free glucose sensors operating at physiological conditions

Diabetes is a pathological condition that requires the continuous monitoring of glucose level in the blood. Its control has been tremendously improved by the application of point-of-care devices. Conventional enzyme-based sensors with electrochemical and optical transduction systems can successfully measure the glucose concentration in human blood, but they suffer from the low stability of the enzyme. Non-enzymatic wearable electrochemical and optical sensors, with low-cost, high stability, point-of-care testing and online monitoring of glucose levels in biological fluids, have recently been developed and can help to manage and control diabetes worldwide. Advances in nanoscience and nanotechnology have enabled the development of novel nanomaterials that can be implemented for the use in enzyme-free systems to detect glucose. This review summarizes recent developments of enzyme-free electrochemical and optical glucose sensors, as well as their respective wearable and commercially available devices, capable of detecting glucose at physiological pH conditions without the need to pretreat the biological fluids. Additionally, the evolution of electrochemical glucose sensor technology and a couple of widely used optical detection systems along with the glucose detection mechanism is also discussed. Finally, this review addresses limitations and challenges of current non-enzymatic electrochemical, optical, and wearable glucose sensor technologies and highlights opportunities for future research directions.

Nanoporous Silver Submicrocubes Layer by Layer Encapsulated with Polyelectrolyte Films: Nonenzymatic Catalysis for Glucose Monitoring

This article describes the synthesis of nanoporous silver submicrocubes (Np-Ag) capped with poly(allylamine hydrochloride) PAH/poly(styrenesulfonate) PSS bilayers (Np-Ag(PAH/PSS)_n, 1 ≤ n ≤ 4) via layer-by-layer (LBL) assembly for the electrochemical glucose sensing. The consecutive LBL encapsulation of Np-Ag (average size ≈530 nm) with positively charged PAH and negatively charged PSS layers was monitored by using ζ-potential analyses, which showed that the sign of the ζ-potential became positive (+10 mV) or negative (-22 mV) depending on the charge of the encapsulating species. The thickness of two PAH/PSS bilayers on the Np-Ag was estimated to be ∼4 nm (consistent with a literature value of ∼1 nm per PAH or PSS layer) on the basis of a high-resolution transmission electron microscopy image of the Np-Ag(PAH/PSS)₂. Moreover, the high quality of the polyelectrolyte capping on Np-Ag was evidenced by the elemental mapping analysis of particles (obtained by using high-angle annular dark-field scanning transmission electron microscopy), which showed a uniform spatial distribution of C, N, and S (derived from PAH and PSS layers). Among the four different Np-Ag(PAH/PSS)n (1 ≤ n ≤ 4) electrodes, Np-Ag(PAH/PSS)₂ exhibited the highest electrocatalytic activity toward glucose because of the optimal thickness and density of its polyelectrolyte films (fabricated onto Np-Ag). The (Np-Ag(PAH/PSS)₂ electrode demonstrated a detection limit of 20 μM, a sensitivity limit of 472.15 μA mM^-1 cm^-2, and a wide range of detection for glucose at concentrations as high as 23.3 mM along with good selectivity toward glucose. The findings of this study are expected to contribute to improvements in the fabrication and stability of various particle-type catalysts on an electrode surface and to efforts to optimize the device performance using the LBL encapsulation technique.

A Hybrid Biofuel and Triboelectric Nanogenerator for Bioenergy Harvesting

Various types of energy exist everywhere around us, and these energies can be harvested from multiple sources to power micro-/nanoelectronic system and even personal electronic products. In this work, we proposed a hybrid energy-harvesting system (HEHS) for potential in vivo applications. The HEHS consisted of a triboelectric nanogenerator and a glucose fuel cell for simultaneously harvesting biomechanical energy and biochemical energy in simulated body fluid. These two energy-harvesting units can work individually as a single power source or work simultaneously as an integrated system. This design strengthened the flexibility of harvesting multiple energies and enhanced corresponding electric output. Compared with any individual device, the integrated HEHS outputs a superimposed current and has a faster charging rate. Using the harvested energy, HEHS can power a calculator or a green light-emitting diode pattern. Considering the widely existed biomechanical energy and glucose molecules in the body, the developed HEHS can be a promising candidate for building in vivo self-powered healthcare monitoring system.

Green dual-template synthesis of AgPd core-shell nanoparticles with enhanced electrocatalytic activity

A key challenge in developing an ethanol oxidation reaction is nontoxic fabrication of highly active stable and low-cost catalysts. Here we design a green synthetic strategy of AgPd bimetallic nanosphere by a dual-template cascade method. The Pd nanoshell is firstly prepared using Vapreotide acetate as a primary template, and then the Ag nanoshell acts as a secondary template for the distribution of AgPd alloy nanoparticles. The AgPd nanoparticles have core-shell structures and various sizes, and their shell thicknesses are tuned by controlling the amount of PdCl₂. The six different samples are prepared, named AgPd-1, AgPd-2, AgPd-3, AgPd-4, AgPd-5, and AgPd-6, respectively. The mass current density of AgPd-5, is higher 3.87 times that of commercial Pd/C, and exhibits the best ethanol oxidation reaction activity and long-term stability. The main reasons are that the AgPd-5 possessed excellent specific surface area due to their rough structure, and Ag can remove more CO-like species. This is the first time a Vapreotide acetate/Ag-template method has been used to synthesize a AgPd core-shell structure, which would have broad application prospects for direct ethanol fuel cells.

Towards one-step design of tailored enzymatic nanobiosensors

NP-based enzymatic biosensors were prepared by the simultaneous encapsulation of glucose and alcohol oxidases, Nafion and noble metal NPs via co-deposition from a phosphate multiple electrolyte on top of the sensor surface.

Mucilage-capped silver nanoparticles for glucose electrochemical sensing and fuel cell applications

A simple, cost-effective and green mucilage-capped silver nanoparticles (Mucilage-AgNPs) modified glassy carbon electrode (GC) composite was constructed for efficient and facile electrochemical oxidation of glucose for the first time. Mucilage-AgNPs were synthesized through the direct chemical reduction of Ag⁺ by mucilage extracted from Opuntia ficus-indica. Mucilage-AgNPs were identified and characterized using ultraviolet-visible spectroscopy, transmission electron microscopy and square wave voltammetry. Modification of the GC with AgNPs was carried out via a transfer-sticking technique with an immobilization time of 1 h. The Mucilage-AgNPs/GC composite was studied as a possible anode for glucose oxidation in a biofuel cell. The composite resulted in glucose oxidation with a current density and power density of 85.7 μA cm⁻² and 25.7 μW cm⁻², respectively. Glucose sensing using the Mucilage-AgNPs/GC composite was achieved successfully via two pathways: glucose oxidation and AgNP inhibition. The glucose oxidation-based sensor showed a lower detection limit of 0.01 mM and a linear range of 0.01 to 2.2 mM. The AgNPs inhibition-based sensor provides an indirect determination pathway of glucose with a detection limit of 0.1 mM and a linear range of 0.1 to 1.9 mM. AgNP inhibition is a novel pathway that could be used for determining a large number of organic and inorganic molecules. Overall, the Mucilage-AgNPs/GC is considered a pioneering composite for glucose sensing and fuel cell applications.

A simple, cost-effective and green mucilage-capped silver nanoparticles (Mucilage-AgNPs) modified glassy carbon electrode (GC) composite was constructed for efficient and facile electrochemical oxidation of glucose for the first time.

Superficial fabrication of gold nanoparticles modified CuO nanowires electrode for non-enzymatic glucose detection

This paper describes a low-cost facile method to construct gold (Au) nanoparticles (NPs) modified copper oxide (CuO) nanowires (NWs) electrode on copper foil for the detection of glucose. Copper foil has been converted to aligned CuO NWs arrays by sequential formation of Cu(OH)2 followed by heat treatment induced phase transformation to CuO. Au NPs are deposited on CuO NWs via simple reductive solution chemistry to impart high surface to volume ratio and enhanced catalytic activity of the resulting electrode. Structure, microstructure and morphology of Cu, Cu(OH)2 NWs, CuO NWs, and Au NPs modified CuO NWs are investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The homogeneous distribution of Au NPs (average diameter ∼12 nm) on CuO NWs (average diameter 100 nm and aspect ratio ∼20) is confirmed by high-resolution transmission electron microscopy (HRTEM), scanning transmission electron microscopy (STEM) and elemental mapping. This CuO based glucose detection method gives the highest sensitivity along with the maximum linearity range. This non-enzymatic glucose sensor based on Au modified CuO NWs electrode gives broad linearity range from 0.5 μM to 5.9 mM. The sensor exhibits sensitivity of 4398.8 μA mM-1 cm-2, lower detection limit of 0.5 μM, and very fast response time of ∼5 s. Properties of the proposed glucose sensor are also investigated in human blood and it is found that the sensor is highly accurate and reliable. In addition, higher sensitivity and lower detection limit confirm that this device is suitable for invasive detection in saliva and urine.

Exploring the potential of electroless and electroplated noble metal-semiconductor hybrids within bio- and environmental sensing

Over the last two decades, the rapid development and widespread application of nanomaterials has significantly influenced research in various fields, including analytical chemistry and biosensing technologies. In particular, the simple functionalization and tuning of noble metal nanoparticle (NP) surface chemistry resulted in the development of a series of novel biosensing platforms with quick read-out and enhanced capabilities towards specific analyte detection. Moreover, noble metal NPs possess a number of unique properties, viz. high surface-to-volume ratio and excellent spectral, optical, thermal, electrical and catalytic characteristics. This manuscript provides an elaborate review on galvanic noble metal NPs deposited onto semiconductor surfaces, from the preparation stage towards their application in biosensors and gas sensing. Two types of deposition approaches, viz. galvanic displacement/electroless and conventional electroplating, are introduced and compared. Furthermore, the analytical merit of hybrid nanomaterials towards the improvement of sensing abilities is highlighted. Finally, some limitations and challenges related to progress in the development and application of analytical devices based on electroless and electroplated noble metal NPs-semiconductor hybrids (NMNPsHs) in biochemical and environmental sensing are discussed.

Fabrication of highly effective hybrid biofuel cell based on integral colloidal platinum and bilirubin oxidase on gold support

A hybrid biofuel cell (HBFC) is explored as a low-cost alternative to abiotic and enzymatic biofuel cells. Here the HBFC provides an enzymeless approach for the fabrication of the anodic electrode while employing an enzymatic approach for the fabrication of the cathodic electrode to develop energy harvesting platform to power bioelectronic devices. The anode employed 250 μm braided gold wire modified with colloidal platinum (Au-co-Pt) and bilirubin oxidase (BODx) modified gold coated Buckypaper (BP-Au-BODx) cathode. The functionalization of the gold coated multi-walled carbon nanotube (MWCNT) structures of the BP electrodes is achieved by 3-mercaptopropionic acid surface modification to possess negatively charged carboxylic groups and subsequently followed by EDC/Sulfo-NHS (1-Ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride and N-Hydroxysulfosuccinimide) crosslinking with BODx. The integration of the BODx and gold coated MWCNTs is evaluated for bioelectrocatalytic activity. The Au-co-Pt and BP-Au-BODx exhibited excellent electrocatalytic activity towards glucose oxidation with a linear dynamic range up to 20 mM glucose and molecular oxygen reduction, respectively. The HBFC demonstrated excellent performance with the largest open circuit voltages of 0.735 V and power density of 46.31 μW/cm2 in 3 mM glucose. In addition, the HBFC operating on 3 mM glucose exhibited excellent uninterrupted operational stability while continuously powering a small electronic device. These results provide great opportunities for implementing this simple but efficient HBFC to harvest the biochemical energy of target fuel(s) in diverse medical and environmental applications.

Dual nanoenzyme modified microelectrode based on carbon fiber coated with AuPd alloy nanoparticles decorated graphene quantum dots assembly for electrochemical detection in clinic cancer samples

The development of high-efficient technologies for cancer biomarkers detection has attracted tremendous research effort for its great clinic significance. In this work, we designed a new type of flexible and robust nanohybrid microelectrode by modifying carbon fiber with dual nanoenzyme, i.e., AuPd alloy nanoparticles (AuPd-ANPs) decorated graphene quantum dots (GQDs) assembly, and explored its practical application in electrochemical sensing system for sensitive detection of cancer biomarker hydrogen peroxide (H₂O₂) in human breast cancer cells and tissue. For the preparation of dual nanoenzyme modified microelectrode, ionic liquid was used as the electrolyte for the effective electrodeposition of GQDs on carbon fiber substrate to form a close-packed assembly under a very negative potential, then the highly dense AuPd-ANPs were uniformly decorated on GQDs assembly by electrodeposition. In virtue of the structural merits and synergistic contribution of dual nanoenzyme in enhancing the electrocatalytic activity to H₂O₂, the resultant nanohybrid microelectrode exhibited good sensing performances for electrochemical detection of H₂O₂, including a high sensitivity of 371 μA cm^-2 mM^-1, a wide linear range from 1.0 μM to 18.44 mM, a low detection limit of 500 nM (a signal-to-noise ratio of 3:1), as well as good selectivity and biocompatibility, which could be used for real-time tracking H₂O₂ released from different types of human breast cells and in situ sensitive detection of H₂O₂ in clinical breast cancer tissue.

Electrochemical nonenzymatic sensing of glucose using advanced nanomaterials

An overview (with 376 refs.) is given here on the current state of methods for electrochemical sensing of glucose based on the use of advanced nanomaterials. An introduction into the field covers aspects of enzyme based sensing versus nonenzymatic sensing using nanomaterials. The next chapter cover the most commonly used nanomaterials for use in such sensors, with sections on uses of noble metals, transition metals, metal oxides, metal hydroxides, and metal sulfides, on bimetallic nanoparticles and alloys, and on other composites. A further section treats electrodes based on the use of carbon nanomaterials (with subsections on carbon nanotubes, on graphene, graphene oxide and carbon dots, and on other carbonaceous nanomaterials. The mechanisms for electro-catalysis are also discussed, and several Tables are given where the performance of sensors is being compared. Finally, the review addresses merits and limitations (such as the frequent need for working in strongly etching alkaline solutions and the need for diluting samples because sensors often have analytical ranges that are far below the glucose levels found in blood). We also address market/technology gaps in comparison to commercially available enzymatic sensors. Graphical Abstract Schematic representation of electrochemical nonenzymatic glucose sensing on the nanomaterials modified electrodes. At an applied potential, the nanomaterial-modified electrodes exhibit excellent electrocatalytic activity for direct oxidation of glucose oxidation.

Finely Composition-Tunable Synthesis of Ultrafine Wavy PtRu Nanowires as Effective Electrochemical Sensors for Dopamine Detection

Preparing Pt-based one-dimensional (1D) ultrafine nanowires with abundant structural defects/grain boundaries and exploring their novel applications have attracted great interest in real-world applications. Here we introduce an environmentally friendly, facile aqueous solution approach to directly prepare a series of sub-3.0 nm PtRu ultrafine wavy nanowires. Characterizations show that the PtRu nanowires are alloy polycrystalline structures with abundant structural defects/grain boundaries. We first introduce the as-synthesized PtRu nanowires into electrochemical biosensors for the detection of DA and find that the Pt₇Ru₃ nanowires exhibit excellent electrocatalytic activity to DA with fast response, ultralow limit of detection, and excellent selectivity at a potential of 0.3 V in 0.1 M phosphate buffered solution (pH 7.2). This study shows an effective approach to the development of ultrafine PtRu nanowires as electrocatalysts for electrochemical nonenzymatic dopamine biosensors.