Non-enzymatic Biosensor Research Articles

Effect of Hydrogen Plasma Treatment on the Sensitivity of ZnO Based Electrochemical Non-Enzymatic Biosensor.

Information on vitamin C-ascorbic acid (AA)-content is important as it facilitates the provision of dietary advice and strategies for the prevention and treatment of conditions associated with AA deficiency or excess. The methods of determining AA content include chromatographic techniques, spectrophotometry, and electrochemical methods of analysis. In the present work, an electrochemical enzyme-free ascorbic acid sensor for a neutral medium has been developed. The sensor is based on zinc oxide nanowire (ZnO NW) arrays synthesized via low-temperature chemical deposition (Chemical Bath Deposition) on the surface of an ITO substrate. The sensitivity of the electrochemical enzyme-free sensor was found to be dependent on the process treatments. The AA sensitivity values measured in a neutral PBS electrolyte were found to be 73, 44, and 92 µA mM-1 cm-2 for the ZnO NW-based sensors of the pristine, air-annealed (AT), and air-annealed followed by hydrogen plasma treatment (AT+PT), respectively. The simple H-plasma treatment of ZnO nanowire arrays synthesized via low-temperature chemical deposition has been shown to be an effective process step to produce an enzyme-free sensor for biological molecules in a neutral electrolyte for applications in health care and biomedical safety.

The Dual-Response-Single-Amplification Fluorescent Nanomachine for Tumor Imaging and Gastric Cancer Diagnosis.

Gastric cancer (GC) is one of the most common tumors worldwide and is the leading cause of tumor-related mortality. Traditional biomarkers and screening methods cannot meet the clinical demands. There is an urgent need for highly sensitive diagnostic markers as well as accurate quantification methods for early gastric cancer (EGC) screening. Here a dual-target cooperatively responsive fluorescent nanomachine by the innovative application of two targets─responsive strand migration system with a single-amplification-cycle element was developed for the simultaneous detection of GC biomarkers miR-5585-5p and PLS3 mRNA, which were selected by next-generation sequencing and RT-qPCR. It was also an RNA extraction-free, PCR-free, and nonenzymatic biosensor to achieve tumor cell imaging and serum diagnosis. Requiring only a 20 μL serum sample and 20 min incubation time, the nanomachine achieved an ultrasensitive detection limit of fM level with a broad linear range from fM to nM. More importantly, a higher AUC value (0.884) compared to the clinically used biomarker CA 72-4 was obtained by the nanomachine to distinguish GC patients successfully. Notably, for the key concerns of diagnosis of EGC patients, the nanomachine also achieved a satisfactory AUC value of 0.859. Taken together, this work has screened and obtained multiple biomarkers and developed a fluorescent nanomachine for combination diagnosis of GC, providing an ingenious design of a functionalized DNA nanomachine and a feasible strategy for the transformation of serum biomarkers into clinical diagnosis.

Non-enzymatic amperometric biosensor with anchored Ni nanoparticles for urinary glucose quantification

In a one-step approach, Nickel nanoparticles of <200 nm in diameter were electrodeposited on the surface of laser-induced graphene using the chronoamperometry technique to develop a sensitive, flexible nonenzymatic sensor for detecting glucose in urine. The prepared sensor prototype exhibited remarkable catalytic activity toward the glucose oxidation with a response time of <3 s, sensitivity of 5796.18 μAmM−1 cm−2, a linear range of 12 μM-1.5 mM, and a detection limit of 0.0152 μM. It detected glucose in human urine samples with high reliability of 98.5 % and showed excellent anti-interference ability for glucose sensing. This prototype can form the basis for wearable sensors to detect glucose in a range of concentrations because of the developed sensor's excellent performance, durability, and lifespan.

Review: Electrochemical biosensors based on ZnO nanostructures

In the last few decades’ electrochemical biosensors have witnessed vast developments due to the broad range of different applications, including health care and medical diagnosis, environmental monitoring and assessment, food industry, and drug delivery. Integration of nanostructured material with different disciplines and expertise of electrochemistry, solid-state physics, material science, and biology has offered the opportunity of a future generation of highly rapid, sensitive, stable, selective, and novel electrochemical biosensor devices. Among metal oxide nanomaterials, ZnO nanostructures are one of the most important nanomaterials in today’s nanotechnology research. Such nanostructures have been studied intensely not only for their extraordinary structural, optical, and electronic properties but also for their prominent performance in diverse novel applications such as photonics, optics, electronics, drug delivery, cancer treatment, bio-imaging, etc. However, functionality of these nanomaterials is eventually dictated by the capability to govern their properties including shape, size, position, and crystalline structure on the nanosized scale. This review aims to update the outstanding advancement in the developments of the enzymatic and non-enzymatic biosensors using a different structure of ZnO nanomaterials. After a coverage of the basic principles of electrochemical biosensors, we highlight the basic features of ZnO as a potential anticancer agent. focused attention gives to functionalized biosensors based on ZnO nanostructures for detecting biological analytes, such as glucose, cholesterol, L-lactic acid, uric acid, metal ions, and pH.

Facile colorimetric smartphone-based biosensor for rapid detection of organophosphorus pesticides residues in environment using the aptamer-enhanced oxidase activity of octahedral Ag2O particles

The long-term and excessive use of organophosphorus pesticides (OPs) leads to hazardous residues in the environment, which threatens human health to a considerable extent. Colorimetric methods can quickly and readily identify pesticide residue, but they still have various challenges in accuracy and stability. Herein, a smartphone-assisted and non-enzymatic colorimetric biosensor was constructed for rapid monitoring of multiple OPs based on the enhanced effect of aptamer on the catalytic ability of octahedral Ag2O. It was demonstrated that the aptamer sequence could enhance the affinity of colloidal Ag2O to chromogenic substrates, and accelerate the generation of oxygen radicals such as superoxide radical (·O2−) and singlet oxygen (1O2) from dissolved oxygen, thereby significantly increasing the oxidase activity of octahedral Ag2O. The color change of the solution can be easily converted to the corresponding RGB values by a smartphone for quantitative and rapid detection of multiple OPs. Hence, the smartphone-based and visual biosensor of multiple OPs was acquired with limit of detection of 10 μg L−1, 28 μg L−1 and 40 μg L−1 for isocarbophos, profenofos and omethoate, respectively. The colorimetric biosensor also exhibited good recoveries in several environmental and biological samples, showing that it may have broad application prospects for detecting OPs residues.

Tailored Fabrication of Defect-Rich Ion Implanted CeO2-x Nanoflakes for Electrochemical Sensing of H2O2

As an alternative to H2O2 enzymatic biosensing devices, non-enzymatic CeO2-based biosensors have shown improved sensibility, robustness, and shelf lives. The redox capability in CeO2 and rapid switching between its oxidation states facilitate the formation of structural vacancy defects that serve as active sites. This work reports a novel approach for synthesis of defect-rich CeO2-x-based nanoflakes using a controllable electrochemical-based deposition at low temperatures (45°−65 °C) followed by low-energy ion implantation. Among the nanoflakes, Mo-implanted CeO2-x exhibited outstanding sensitivity of 4.96 × 10−5 A·mM−1 cm−2 within the linear range of 0.05–10 mM. Moreover, the ion-implanted samples yielded high sensing stability and electronic conductivity. The former was achieved through the multi-valence charge transfer between Ce and the implanted ions that caused the reduction of Gibbs free energies required for the formation/retention of the defects. The latter was due to the narrowing of the electronic bandgap of CeO2-x by creation of defect-induced midgap states.

Fibers/Textiles-Based Flexible Sweat Sensors: A Review

With the rise of smart textiles, fibers/textiles-based sensors are being applied in various situations, such as healthcare, green energy, and environmental monitoring. The field of health monitoring mainly involves the detection of human secretions (such as sweat, saliva, urine, and excrement). Among them, sweat is extensive and closely related to human health, so it is receiving more and more attention. Various sensors are used for sweat detection, but fiber/textile-based flexible sensors have unique advantages and thus have emerged as an important branch. So, this Review aims to 1) explain the physiological mechanism of sweating and metabolites; 2) introduce the advantages of fibers/textiles as the substrate of sweat sensors; 3) outline different kinds of fibers/textiles-based flexible sweat sensors (enzymatic biosensors, non-enzymatic biosensors, ion-selective sensors, and others) and explain their working principle; 4) summarize the applications of such sensors in different fields (physical condition monitoring, power supply, drug monitoring, mental state monitoring, etc.). Moreover, the opportunities and challenges of flexible fiber/textile-based sweat sensors will also be discussed. This Review will help promote the diversified development of sweat sensors, which is significant for manufacturing advanced sweat detection and diagnostic systems.

Nonenzymatic Flexible Wearable Biosensors for Vitamin C Monitoring in Sweat.

Nutritional status monitoring plays an important role in the maintenance of human health and disease prevention. Monitoring the intake of vitamins can support the improvement of diet behavior. In this work, a polyaniline (PANI) film-based nonenzymatic electrochemical sensor was prepared to track the vitamin C level in sweat. The PANI film was modified with organic acids (ethylformic acid, malic acid, tartaric acid, and phytic acid). The phytic acid-modified PANI film based on sensor has a wide detection range (0.5-500 μmol·L-1), high sensitivity (665.5 and 326.2 μA·(mmol·L-1)-1·cm-2), and low detection limit (0.17 μmol·L-1) toward vitamin C in sweat. The phytate enhances the band transport between PANI chains, which increases the electrical conductivity of the film to improve the electrochemical properties of the sensor. In addition, we monitored changes of vitamin C levels in human body after taking vitamin C pills by detecting sweat or saliva. The ability to track the pharmacological profile demonstrates the potential of PANI film-based sensors for applications in personalized nutritional intake and tracking. And a simple and portable vitamin C detection system was developed to improve the practicability of the sensor. This work provides an idea for the application of wearable electrochemical sensing devices in nutrition guidance.

Facile green microwave-assisted synthesis of silver-chitosan nanoparticle for antioxidant, antibacterial, and non-enzymatic biosensor for dopamine detection

Facile green microwave-assisted synthesis of silver-chitosan nanoparticle for antioxidant, antibacterial, and non-enzymatic biosensor for dopamine detection

Development of a miniaturised potentiostat for urea detection using the LMP91000

In this report, we develop a low-cost cyclic voltammetry platform for electrochemical analyses based on the LMP91000 integrated circuit (IC). The proposed system can be suitable to detect chemicals of interest in food safety or biology. The system includes three main blocks: the electrodes, electrochemical measuring circuit, and data acquisition. An algorithm was also built to process and display the data on the screen. Experiments are carried out with a standard redox solution containing Fe(II)/Fe(III) 5 mM and KCl 0.1 mM to evaluate system performance and make comparisons to the commercial potentiostat. The results show that the obtained signals from the proposed system and the commercial potentiostat device are similar. With applications of the miniaturised potentiostat, a non-enzymatic electrochemical biosensor for urea detection was fabricated on cobalt sulphide materials (CoS) synthesized via a microwave assisted method. The sensing performance for urea was determined by changing the oxidation potential peak of 100 mV. The sensor had a linear range from 1-8 mM corresponding to the urea concentration in blood. The sensor sensitivity was comparable (7.5 μAmM-1cm-2) to some previous publications. With the achieved results, the proposed system demonstrates potential in urea detection and can be a prototype to develop a commercial device for point-of-care testing in the future.

Electrospun nanofibers for extraction of thymoquinone from Nigella-Stevia prior to detection using electrochemical biosensor based on GCE/rGO/CuO

Thymoquinone (TQ) is the main constituent of Nigella sativa that has some effects on the treatment of many illnesses such as cancer and kidney diseases. Electrospun nanofibers with polyvinyl chloride/ethylene vinyl acetate latex/electrochemically (reduced graphene oxide/polypyrrole)/Silybum marianum inflorescence extract (PVC/EVA/(rGO/Ppy)/SM) were first prepared, and then TQ was extracted from black seed with using these nanofibers as a sorbent. Finally, TQ was detected with the construction of a simple nonenzymatic electrochemical biosensor using copper (II) oxide nanoparticles/reduced graphene oxide/glassy carbon electrode (CuO/rGO/GCE). Factors affecting TQ adsorption/desorption, time and potential values for constructed biosensor were optimized by methods such as design-expert 12.0 and one-at-a-time (OAT). The morphology of PVC/EVA/(rGO/Ppy)/SM nanofibers and rGO/CuO nanocomposites was characterized. Finally, the electrochemical biosensor was put into human blood serum samples and the standard addition method was applied with the spike of TQ to them. The linear range and detection limit reached 50–1000 μM and 4.85 μM, respectively (S/N = 3).

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.

High-performance enzyme-free glucose and hydrogen peroxide sensors based on bimetallic AuCu nanoparticles coupled with multi-walled carbon nanotubes

Interest in designing and manufacturing non-enzymatic biosensors is growing which stimulates the increased research efforts to explore innovative nanocomposites with highly catalytic activity. Here, the development of high-performance non-enzymatic glucose and hydrogen peroxide (H2O2) sensors based on bimetallic AuCu nanoparticles coupled with multi-walled carbon nanotubes (AuCu@MWCNTs) was achieved in this work. They were investigated by the cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and chronoamperometry (CA) methods separately. Benefiting from the synergistic effects of AuCu@MWCNTs, the proposed biosensors exhibited excellent performance such as low detection limits (1.3 nM for glucose, 0.1 nM for H2O2), broad linear ranges (8 nM-60 mM for glucose, 1 nM-4 mM for H2O2) and high sensitivities (362.3 μA·mM−1·cm−2 for glucose, 1335 μA·mM−1·cm−2 for H2O2). Besides, the AuCu@MWCNTs based electrodes provided excellent stability, repeatability and reproducibility. Based on the outstanding performance, they exhibited good reliability and accuracy in the detection of glucose in goat serum samples and real-time monitoring of H2O2 released by living cells. The present work suggests that the fabricated biosensor holds great potential for non-enzymatic glucose determination and real-time quantitative detection of H2O2 in biomedical applications.

Growth of non-enzymatic cholesterol biosensor using TiO2 decorated graphene oxide with bare GCE and PPy-GCE

In this work, we report an electrochemical cholesterol biosensor based on cholesterol oxidase(ChOx) enzyme immobilized on TiO2- nanoparticles – reduced graphene oxide(rGO) – polypyrrole (PPy) nanocomposite modified electrode.The electrochemical properties of GCE modified PPy (PPy-GCE) were studied using CV (Cyclic Voltammetry) and DPV (Differential Pulse Voltammetry). The developed sensor exhibited piecewise linearity from 0.1 μM to 1 μM and from 1 μM to 600 μM with the sensitivity of 61.665 and 0.1466 (2 mA mM × cm) respectively. The limit of detection of the sensor was found to be 32 nm.

Flexible electrochemical sensor for highly sensitive and selective non-enzymatic detection of creatinine via electrodeposited copper over polymelamine formaldehyde.

A non-enzymatic electrochemical biosensor was developed for highly sensitive detection of creatinine using copper nanoparticles supported over polymelamine formaldehyde. The synergy between the electrodeposited copper nanoparticles over the highly porous polymer (eCu-PMF) provided a greener platform to boost up the electron transport at the electrode electrolyte interface by eliminating the role of redox species as well as interference of major interferents like glucose, dopamine, and ascorbic acid in physiological media 0.1 M PBS (pH 7.4). The proposed sensor exhibited a wide detection range of 100 fM-60 mM with high sensitivities of 0.320 mA nM-1 cm-2 and 3.8 mA nM-1 cm-2. Moreover, the sensor was applied to real samples of serum creatinine and recoveries of 97 to 114% were found. Additionally, a paper-based flexible screen-printed electrode was fabricated which displayed an excellent activity with the same detection range of 100 fM-60 mM and long-term storage stability of 15 days.

Highly Selective and Sensitive Non-enzymatic Glucose Biosensor Based on Polypyrrole-Borophene Nanocomposite

In this study, a non-enzymatic glucose sensor composed of two-dimensional (2D) borophene-decorated polypyrrole (PPy) nanocomposites (NCs) was developed. The PPy-borophene NCs were prepared using a low-cost sonication method. The sensing performance of the PPy-borophene NCs was investigated by the cyclic voltammetry (CV) technique against various biomolecules such as glucose, maltose, lactose, fructose, and urea. According to the electrochemical results, it was observed that in the glucose concentration range of 1.5 to 24 mM within a voltammetric cycle of 1 min, the PPy-based sensor and PPy-borophene NCs-based sensor exhibited sensitivities of 11.88 μAmM−1 cm−2 and 213.42 μAmM−1 cm−2, respectively. The detection limits of the PPy-based and PPy-borophene NCs-based sensors were determined to be 0.5 µM and 0.04 µM, respectively. Furthermore, selectivity measurement results revealed that the proposed non-enzymatic biosensor has remarkably good sensitivity and high selectivity, indicating that common biomolecules (glucose, maltose, lactose, fructose, and urea) could be captured by the sensor. Consequently, it was proven that the proposed biosensor could be a potential device for diabetes diagnosis.

Iron Oxide Nanoparticles: A Review on the Province of Its Compounds, Properties and Biological Applications

Materials science and technology, with the advent of nanotechnology, has brought about innumerable nanomaterials and multi-functional materials, with intriguing yet profound properties, into the scientific realm. Even a minor functionalization of a nanomaterial brings about vast changes in its properties that could be potentially utilized in various applications, particularly for biological applications, as one of the primary needs at present is for point-of-care devices that can provide swifter, accurate, reliable, and reproducible results for the detection of various physiological conditions, or as elements that could increase the resolution of current bio-imaging procedures. In this regard, iron oxide nanoparticles, a major class of metal oxide nanoparticles, have been sweepingly synthesized, characterized, and studied for their essential properties; there are 14 polymorphs that have been reported so far in the literature. With such a background, this review's primary focus is the discussion of the different synthesis methods along with their structural, optical, magnetic, rheological and phase transformation properties. Subsequently, the review has been extrapolated to summarize the effective use of these nanoparticles as contrast agents in bio-imaging, therapeutic agents making use of its immune-toxicity and subsequent usage in hyperthermia for the treatment of cancer, electron transfer agents in copious electrochemical based enzymatic or non-enzymatic biosensors and bactericidal coatings over biomaterials to reduce the biofilm formation significantly.

Development of single-use thin film electrodes based on Zn2SnO4 on In2O3:SnO2 substrates with their biosensing applications

Dopamine (DA) has a significant impact on the emergence and treatment of certain diseases (e.g., Alzheimer’s and Parkinson’s diseases). Therefore, monitoring of DA is important, and using biosensors is a favorable option instead of time-consuming and expensive conventional methods. In biosensor manufacturing, thin films have become a rapidly emerging field. In this study, a non-enzymatic electrochemical biosensor based on thin film electrodes is developed for monitoring DA levels. The thin film electrodes (ZTO/ITO) are developed by deposition of Zn 2 SnO 4 (ZTO) on In 2 O 3 :SnO 2 (ITO) substrates by magnetron sputtering. 3-aminopropyltriethoxysilane (APTES) is used to modify the surface of these electrodes. Physical, optical, and structural properties of the electrodes are determined by applying surface profilometry, UV-VIS-NIR spectrophotometry, X-ray diffraction (XRD), and scanning electron microscopy (SEM) measurements. According to these measurements, it has been observed that the ZTO/ITO combination has a higher optical transmission value than the bare ITO, depending on the deposition time and the oxygen concentration used during ZTO deposition. In addition, the ITO thin film has a crystalline structure, while the ZTO thin film has an amorphous structure and both thin films have a good surface morphology. As electrochemical analysis, cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and differential pulse voltammetry (DPV) measurements are performed. As a result of CV and EIS measurements, a remarkable change (63.54%) was observed after applying APTES modification onto the surface of ZTO/ITO electrode, and the ones obtained by DPV showed successful detection of DA by APTES modified ZTO/ITO. In addition, the experiments in the presence of interferences such as ascorbic acid (AA), uric acid (UA), bovine serum albumin (BSA), and fish sperm double-stranded DNA (fsDNA) show that the electrodes can be successfully applied for voltammetric determination of DA. The detection limit of DA was estimated to be 0.013 µM in the range of DA between 0.1 – 1 µM, and sensitivity was calculated and found to be 11.057 μA μg −1 mL cm −2 , which means ZTO/ITO electrodes have a good sensitivity. • ZTO/ITO thin film electrodes are fabricated by DC magnetron sputtering. • Surface of the ZTO/ITO electrodes are modified with APTES. • Single-use transparent APTES/ZTO/ITO electrodes are used for voltammetric detection of dopamine (DA). • APTES/ZTO/ITO electrodes have been used for the first time for detection of DA. • APTES/ZTO/ITO electrodes provided a low detection limit and good selectivity on DA detection.

Non-enzymatic electrochemiluminescence biosensor for ultrasensitive detection of ochratoxin A based on efficient DNA walker

Ochratoxin A (OTA) with high toxicity represents a serious threat to the agriculture and food chain, consequently to human health. Herein, a simple electrochemiluminescence (ECL) biosensor was constructed for ultrasensitive detection of OTA based on mercaptopropionic acid templated Au nanoclusters (Au NCs) as intensive signal probe and a non-enzymatic 2D DNA walking machine as the effective amplification strategy. Specifically, the target related bipedal DNA walker efficiently moved along 2D DNA tracks through toehold-mediated DNA strand displacement, which triggered abundant signal probes for combining to the DNA tracks. Moreover, the Au NCs could exhibit strong ECL emission due to fast electron transfer from massive Au-S electronic pathways under the electrochemical excitation. Thus, the biosensor possessed significant ECL response for achieving ultrasensitive detection toward OTA with low detection limit of 3.19 fg/mL. Impressively, the sensing platform was also applied to detect OTA from edible oils, exhibiting great application potential in food analysis.

Nanostructured Cu2O deposited on TiO2 nanotube arrays for ultra-sensitive non-enzymatic glucose electrochemical biosensor

Nanostructured Cu2O deposited on TiO2 nanotube arrays for ultra-sensitive non-enzymatic glucose electrochemical biosensor