Hollow sphere nickel sulfide nanostructures-based enzyme mimic electrochemical sensor platform for lactic acid in human urine

Surface engineered gold nanodendrites decorated flexible carbon fiber-based electrochemical sensor platform for sensitive detection of L-Cysteine in serum and urine samples

In this work, highly dispersed gold nanodendrites (Au NDs) decorated flexible carbon fiber electrode (Au NDs@FCF electrode) were fabricated by facile, green, and one-step electrochemical deposition protocol and utilized for the direct electrochemical determination of L-Cysteine (L-Cys). The prepared Au NDs@FCF electrodes were characterized by SEM, HR-TEM, XRD, XPS, CV, and EIS towards the dimensions, surface morphological traits, crystalline nature, chemical composition, and electrochemical catalytic oxidation towards L-Cys and electrochemical active surface area (ECASA) of the Au NDs. The developed Au NDs@FCF electrode demonstrates an enzyme mimics electrocatalytic efficiency towards the oxidation of L-Cys at the operating potential of 0.82 V (vs Ag/AgCl) with a lower experimental detection limit of 0.16 nM, higher sensitivity of ∼50.2 μA μM-1 cm-2, and a wide concentration ranges from 100 to 3000 nM with a correlation coefficient of R2 = 0.996. In addition, the developed Au NDs@FCF electrode has exhibited excellent selectivity with various anti-interferences such as glucose, dopamine, uric acid, Na+, Mg2+, Ca2+, high reproducibility, and repeatability with RSD of 2.3 %. The Au NDs@FCF electrode demonstrates outstanding electrocatalytic oxidation and a rapid sensing response time of ∼3 s. The current Au NDs@FCF electrode achieving the successful detection of L-Cys in practical human serum and urine samples highlights its potential application in biomedical diagnostics. This advancement indicates that the sensor can effectively operate in real-world conditions, offering a valuable tool for medical professionals to monitor L-Cys levels in patients accurately.

Recent Advances in MOF-Based Materials for Biosensing Applications

Metal-organic frameworks (MOFs) or coordination polymers have gained enormous interest in recent years due to their extraordinary properties, including their high surface area, tunable pore size, and ability to form nanocomposites with various functional materials. MOF materials possess redox-active properties that are beneficial for electrochemical sensing applications. Furthermore, the tunable pore size and high surface area improve the adsorption or immobilization of enzymes, which can enhance the sensitivity and selectivity for specific analytes. Additionally, MOF-derived metal sulfides, phosphides, and nitrides demonstrate superior electrical conductivity and structural stability, ideal for electrochemical sensing. Moreover, the functionalization of MOFs further increases sensitivity by enhancing electrode-analyte interactions. The inclusion of carbon materials within MOFs enhances their electrical conductivity and reduces background current through optimized loading, preventing agglomeration and ensuring uniform distribution. Noble metals immobilized on MOFs offer improved stability and catalytic performance, providing larger surface areas and uniform nanoparticle dispersion. This review focuses on recent developments in MOF-based biosensors specifically for glucose, dopamine, H2O2, ascorbic acid, and uric acid sensing.

Flexible Nanostructured NiS-Based Electrochemical Biosensor for Simultaneous Detection of DNA Nucleobases

Herein, we demonstrate a one-step, scalable, solution-processed method for the growth of nickel sulfide (NiS) nanostructures using single-source precursors (SSPs) on a flexible substrate as a versatile framework for simultaneous detection of four DNA nucleobases. The as-grown NiS nanostructures exhibit a broad bandgap range and spherical morphology with high surface area and significant porosity, as confirmed by SEM, TEM, and BET surface area analysis. Consequently, the NiS/Ni-foam electrode exhibited remarkable electrochemical performance toward the oxidation of A, G, T, and C due to its large surface area, high electrode activity, and efficient electron transfer capacity. Under the optimum conditions, the electrode demonstrated selective and simultaneous detection of all four nucleobases over a wide linear range from 200 to 1000 μM for A and G, and 50 to 500 μM for T and C, with a low limit of detection of 159 μM for A, 147.6 μM for G, 16.8 μM for T, and 45.9 μM for C, along with high sensitivity of 1.2 × 10-4 A M-1 for A, 6.1 × 10-4 A M-1 for G, 1.2 × 10-3 A M-1 for T, and 3.0 × 10-4 A M-1 for C. The as-fabricated electrode revealed excellent reproducibility and stability toward nucleobase detection and demonstrated a reliable DPV response under different bending and twisting conditions. For immediate practical application, NiS/Ni-foam was utilized to quantify the concentration of all nucleobases in calf thymus and Escherichia coli (E. coli) DNA, resulting in a (G + C)/(A + T) ratio of 0.79 and 1.10, respectively. This simple, cost-effective, and flexible NiS/Ni-foam electrode paves the way for the development of non-invasive, wearable biosensors for potential applications in early disease detection.

Willow catkin template synthesis of NiS@NSC hollow tubes for highly sensitive dual-function electrochemical detection of acetaminophen and Cu2

Public health and environmental well-being have become increasingly threatened by the contamination of pharmaceuticals and heavy metal ions. This study focuses on addressing this critical issue by developing a novel electrochemical sensor for the dual-functional detection of acetaminophen (AP) and Cu2+. Utilizing willow catkins as a biomass template, a hollow tubular NiS@NSC composite was prepared by simple nickel salt impregnation combined with calcination and sulfurization. A highly sensitive dual-functional electrochemical sensor was thus constructed that can detect both acetaminophen (AP) and Cu2+. By examining its electrochemical properties, the sensor achieves an impressive detection limit of 1.33 pM for AP, with a linear range of 4.00 pM ~ 0.15 mM. The sensor can also detect Cu2+, with a detection limit of 1.04 µM, and a linear range of 3.13 µM ~ 0.66 mM. The sensor also exhibits strong resistance to interference, and good repeatability and stability. In addition, the sensor has demonstrated good performance in actual sample analysis, including the detection of AP in serum and Cu2+ in wastewater. This excellent electrochemical sensing performance is mainly attributed to the synergistic effect of its unique tubular structure and highly conductive N, S co-doped carbon. This results in the sensor exhibiting minimal charge transfer resistance, an extensive electrochemically active surface area, and a high density of active sites.

Fates and models for exposure pathways of pyrethroid pesticide residues: A review

Pyrethroids (PYs) are widely applied pesticides whose residues pose potential health risks. This review describes current knowledge on PY chemical properties, usage patterns, environmental and food contamination, and human exposure models. It evaluates life cycle assessment (LCA), chemical alternatives assessment (CAA), and high-throughput screening (HTS) as tools for pesticide policy. Despite efforts to mitigate PY presence, their pervasive residues in the environment and food persist. And the highest concentrations ranged from 54,360 to 80,500 ng/L in water samples from agricultural fields. Food processing techniques variably reduce PY levels, yet no method guarantees complete elimination. This review provides insights into the fates and exposure pathways of PY residues in agriculture and food, and highlights the necessity for improved PY management and alternative practices to safeguard health and environment.

Nanozyme-Enhanced Electrochemical Biosensors: Mechanisms and Applications

Nanozymes, as innovative materials, have demonstrated remarkable potential in the field of electrochemical biosensors. This article provides an overview of the mechanisms and extensive practical applications of nanozymes in electrochemical biosensors. First, the definition and characteristics of nanozymes are introduced, emphasizing their significant role in constructing efficient sensors. Subsequently, several common categories of nanozyme materials are delved into, including metal-based, carbon-based, metal-organic framework, and layered double hydroxide nanostructures, discussing their applications in electrochemical biosensors. Regarding their mechanisms, two key roles of nanozymes are particularly focused in electrochemical biosensors: selective enhancement and signal amplification, which crucially support the enhancement of sensor performance. In terms of practical applications, the widespread use of nanozyme-based electrochemical biosensors are showcased in various domains. From detecting biomolecules, pollutants, nucleic acids, proteins, to cells, providing robust means for high-sensitivity detection. Furthermore, insights into the future development of nanozyme-based electrochemical biosensors is provided, encompassing improvements and optimizations of nanozyme materials, innovative sensor design and integration, and the expansion of application fields through interdisciplinary collaboration. In conclusion, this article systematically presents the mechanisms and applications of nanozymes in electrochemical biosensors, offering valuable references and prospects for research and development in this field.

Enzyme-free electrochemical sensor platforms based on transition metal nanostructures for clinical diagnostics

The detection of emergent biomarkers is of key significance in numerous clinical, biological, and biomedical fields. Specifically, the design and development of potent electrochemical lactic acid and glucose sensing platforms are especially in great demand in a variety of industries, including those involved in clinical analysis, biomedicine, biological, food, cosmetics, pharmaceuticals, leather, sports, and chemical industries. Nanostructured transition metal-derived materials have opened the door to electrochemical sensors and biosensors due to their advantages of high surface-to-volume ratio, surface reaction activity, catalytic activity, and strong adsorption capability. The primary aim of the present minireview is to highlight the advancement of enzyme-free electrochemical sensor platforms based on transition metal-derived nanostructures with high electrocatalytic activity and sensing performance towards lactic acid and glucose in practical samples. The preparation approaches, structural and composition monitoring, fabrication of sensing electrodes, catalytic activity, sensing performance in real samples, and the exploration of sensing mechanisms are majorly concentrated on in most of our recent research studies. Moreover, state-of-the-art transition metal-derived nanostructure-derived electrochemical sensor platforms, critical comparison of the analytical performance of the sensor platforms, and the future perspectives of the enzyme-free electrochemical sensor for clinical diagnostics are described.

Recent Advances in Wearable Biosensors for Non-Invasive Detection of Human Lactate

Lactate, a crucial product of the anaerobic metabolism of carbohydrates in the human body, is of enormous significance in the diagnosis and treatment of diseases and scientific exercise management. The level of lactate in the bio-fluid is a crucial health indicator because it is related to diseases, such as hypoxia, metabolic disorders, renal failure, heart failure, and respiratory failure. For critically ill patients and those who need to regularly control lactate levels, it is vital to develop a non-invasive wearable sensor to detect lactate levels in matrices other than blood. Due to its high sensitivity, high selectivity, low detection limit, simplicity of use, and ability to identify target molecules in the presence of interfering chemicals, biosensing is a potential analytical approach for lactate detection that has received increasing attention. Various types of wearable lactate biosensors are reviewed in this paper, along with their preparation, key properties, and commonly used flexible substrate materials including polydimethylsiloxane (PDMS), polyethylene terephthalate (PET), paper, and textiles. Key performance indicators, including sensitivity, linear detection range, and detection limit, are also compared. The challenges for future development are also summarized, along with some recommendations for the future development of lactate biosensors.

Gold Nanoclusters Dispersed on Gold Dendrite-Based Carbon Fibre Microelectrodes for the Sensitive Detection of Nitric Oxide in Human Serum

Herein, gold nanoclusters (Au NC) dispersed on gold dendrite (Au DS)-based flexible carbon fibre (AuNC@AuDS|CF) microelectrodes are developed using a one-step electrochemical approach. The as-fabricated AuNC@AuDS|CF microelectrodes work as the prospective electrode materials for the sensitive detection of nitric oxide (NO) in a 0.1 M phosphate buffer (PB) solution. Carbon microfibre acts as an efficient matrix for the direct growth of AuNC@AuDS without any binder/extra reductant. The AuNC@AuDS|CF microelectrodes exhibit outstanding electrocatalytic activity towards NO oxidation, which is ascribed to their large electrochemical active surface area (ECSA), high electrical conductivity, and high dispersion of Au nanoclusters. As a result, the AuNC@AuDS|CF microelectrodes attain a rapid response time (3 s), a low limit of detection (LOD) (0.11 nM), high sensitivity (66.32 µA µM cm^-2), a wide linear range (2 nM-7.7 µM), long-term stability, good reproducibility, and a strong anti-interference capability. Moreover, the present microsensor successfully tested for the discriminating detection of NO in real human serum samples, revealing its potential practicability.

Nanomaterials-based portable electrochemical sensing and biosensing systems for clinical and biomedical applications

Miniaturized electrochemical sensing systems are employed in day-to-day uses in the several area from public health to scientific applications. A variety of electrochemical sensor and biosensor systems may not be effectively employed in real-world diagnostic laboratories and biomedical industries due to their limitation of portability, cost, analytical period, and need of skilled trainer for operating devices. The design of smart and portable sensors with high sensitivity, good selectivity, rapid measurement, and reusable platforms is the driving strength for sensing glucose, lactate, hydrogen peroxide, nitric oxide, mRNA, etc. The enhancement of sensing abilities of such sensor devices through the incorporation of both novel sensitive nanomaterials and design of sensor strategies are evidenced. Miniaturization, cost and energy efficient, online and quantitative detection and multiple sensing ability are the beneficial of the nanostructured-material-based electrochemical sensor and biosensor systems. Owing to the discriminating catalytic action, solidity and biocompatibility for designing sensing system, nanoscale materials empowered electrochemical detection systems are accomplished of being entrenched into/combined with portable or miniaturized devices for specific applications. In this review, the advance development of portable and smart sensing/biosensing systems derived from nanoscale materials for clinical and biomedical applications is described.

Graphical Abstract

A facile chemical synthesis of nanoflake NiS2 layers and their photocatalytic activity

A single-phase and crystalline NiS2 nanoflake layer was produced by a facile and novel approach consisting of a two-step growth process. First, a Ni(OH)2 layer was synthesized by a chemical bath deposition approach using a nickel precursor and ammonia as the starting solution. In a second step, the obtained Ni(OH)2 layer was transformed into a NiS2 layer by a sulfurization process at 450 °C for 1 h. The XRD analysis showed a single-phase NiS2 layer with no additional peaks related to any secondary phases. Raman and X-ray photoelectron spectroscopy further confirmed the formation of a single-phase NiS2 layer. SEM revealed that the NiS2 layer consisted of overlapping nanoflakes. The optical bandgap of the NiS2 layer was evaluated with the Kubelka-Munk function from the diffuse reflectance spectrum (DRS) and was estimated to be around 1.19 eV, making NiS2 suitable for the photodegradation of organic pollutants under solar light. The NiS2 nanoflake layer showed photocatalytic activity for the degradation of phenol under solar irradiation at natural pH 6. The NiS2 nanoflake layer exhibited good solar light photocatalytic activity in the photodegradation of phenol as a model organic pollutant.

A photonic crystal fiber-based fluorescence sensor for simultaneous and sensitive detection of lactic acid enantiomers

A photonic crystal fiber (PCF)–based fluorescence sensor is developed for rapid and sensitive detection of lactic acid (LA) enantiomers in serum samples. The sensor is fabricated by chemical binding dual enzymes on the inner surface of the PCF with numerous pore structures and a large specific surface area, which is suitable to be utilized as an enzymatic reaction carrier. To achieve simultaneous detection of l-LA and d-LA, the PCF with an aldehyde-activated surface is cut into two separate pieces, one of which is coated with l-LDH/GPT enzymes and the other with d-LDH/GPT enzymes. By being connected and carefully aligned to each other by a suitable sleeve tube connector, the responses of both l-LA and d-LA sensors are determined by laser-induced flourescence (LIF) detection. With the aid of enzyme-linked catalytic reactions, the proposed PCF sensor can greatly improve the sensitivity and analysis speed for the detection of LA enantiomers. The PCF sensor exhibits a low limit of detection of 9.5 μM and 0.8 μM, and a wide linear range of 25–2000 μM and 2–400 μM for l-LA and d-LA, respectively. The sensor has been successfully applied to accurate determination of LA enantiomers in human serum with satisfactory reproducibility and stability. It is indicated that the present PCF sensors would be used as an attractive analytical platform for quantitative detection of trace-amount LA enantiomers in real biological samples, and thus would play a role in disease diagnosis and clinical monitoring in point-of-care testing.

Gold dispersed hierarchical flower-like copper oxide microelectrodes for the sensitive detection of glucose and lactic acid in human serum and urine

Herein, we report self-supported gold dispersed copper oxide microflowers (Au@CuO MFs) on copper microelectrodes (CME) as a sensitive platform for the sensing of glucose and lactic acid in human serum...

Non-Enzymatic Glucose Detection Based on NiS Nanoclusters@NiS Nanosphere in Human Serum and Urine

Herein, we report a non-enzymatic electrochemical glucose sensing platform based on NiS nanoclusters dispersed on NiS nanosphere (NC-NiS@NS-NiS) in human serum and urine samples. The NC-NiS@NS-NiS are directly grown on nickel foam (NF) (NC-NiS@NS-NiS|NF) substrate by a facile, and one-step electrodeposition strategy under acidic solution. The as-developed nanostructured NC-NiS@NS-NiS|NF electrode materials successfully employ as the enzyme-mimic electrocatalysts toward the improved electrocatalytic glucose oxidation and sensitive glucose sensing. The NC-NiS@NS-NiS|NF electrode presents an outstanding electrocatalytic activity and sensing capability towards the glucose owing to the attribution of great double layer capacitance, excessive electrochemical active surface area (ECASA), and high electrochemical active sites. The present sensor delivers a limit of detection (LOD) of ~0.0083 µM with a high sensitivity of 54.6 µA mM-1 cm-2 and a wide linear concentration range (20.0 µM-5.0 mM). The NC-NiS@NS-NiS|NF-based sensor demonstrates the good selectivity against the potential interferences and shows high practicability by glucose sensing in human urine and serum samples.