Advanced nanomaterials for use in electrochemical and optical immunoassays of carcinoembryonic antigen. A review

This review (with 196 refs.) covers the state of the art in electrochemical and optical immunoassays for the carcinoembryonic antigen (CEA). In essence, it has sections on (a) frequently applied principles and types of CEA immunoassays; (b) aspects of sensor fabrication including immunological and immobilization procedures and the proper choice of nanomaterials; (c) electrochemical immunoassays, with subsections on assays based on the use of nanoparticles and other nanomaterials (such as conducting polymers and graphenes); (d) optical immunoassays based on the use of nanoparticles such as quantum dots, gold nanoparticles, upconversion nanoparticles, graphenes and their derivatives; (d) lateral flow and lab-on-a-chip (microfluidic) immunoassays; and (e) on multiplexed electrochemical and optical immunoassays with and without labels. Examples for applications to real samples are given. A final section discusses current limitations and trends in terms of sensing schemes and nanomaterials. 

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Graphical abstract A key to develop nanodevices with high performance for immunoassay applications is to explore advanced functional nanomaterials. This review focus on practical aspects trying to give the readers useful insights that should be considered such as the choice of the advanced nanomaterials to be used, the best methods/techniques in immunesensing of CEA.

     

An electrochemical sensor for pesticide assays based on carbon nanotube-enhanced acetycholinesterase activity

There has been urgent demand for rapid, sensitive and cost-effective pesticide assay technologies due to the global attention of environmental and food-safety problems. Acetycholinesterase (AChE)-based electrochemical sensors have attracted significant interest toward this goal. In this contribution, we introduced multiwalled carbon nanotubes (MWNTs) into our sensor design, where they played dual enhancement roles; first is that MWNTs loaded on glassy carbon (GC) electrodes significantly increase surface areas, facilitating the electrochemical polymerization of prussian blue (PB), a redox mediator for the electrochemical oxidation of the enzymatic product, thiocholine (TCh). Second, MWNTs enhance the enzymatic activity of AChE, as manifested by the decreased Michaelis-Menten constant (K(m)). As a result of these two important enhancement factors offered by MWNTs, our electrochemical pesticide sensor exhibited rapid response and high sensitivity toward the detection of a series of pesticides. Moreover, we demonstrated that this sensor was stable, reproducible and selective enough for detection in real samples.     

Solid-phase extraction techniques based on nanomaterials for mycotoxin analysis: An overview for food and agricultural products

Mycotoxin contamination is a globally concerned problem for food and agricultural products since it may directly or indirectly induce severe threats to human health. Sensitive and selective screening is an efficient strategy to prevent or reduce human and animal exposure to mycotoxins. However, enormous challenges exist in the determination of mycotoxins, arising from complex sample matrices, trace-level analytes, and the co-occurrence of diverse mycotoxins. Appropriate sample preparation is essential to isolate, purify, and enrich mycotoxins from complicated matrices, thus decreasing sample matrix effects and lowering detection limits. With the cross-disciplinary development, new solid-phase extraction strategies have been exploited and integrated with nanotechnology to meet the challenges of mycotoxin analysis. This review summarizes the advance and progress of solid-phase extraction techniques as the methodological solutions for mycotoxin analysis. Emphases are paid on nanomaterials fabricated as trapping media of solid-phase extraction techniques, including carbonaceous nanoparticles, metal/metal oxide-based nanoparticles, and nanoporous materials. Advantages and limitations are discussed, along with the potential prospects.     

Impedance methods for electrochemical sensors using nanomaterials

This article presents an overview of electrochemical sensors that employ nanomaterials and utilize electrochemical impedance spectroscopy for analyte detection. The most widely utilized nanomaterials in impedance sensors are gold (Au) nanoparticles and carbon nanotubes (CNTs). Au nanoparticles have been employed in impedance sensors to form electrodes from nanoparticle ensembles and to amplify impedance signals by forming nanoparticle-biomolecule conjugates in the solution phase. CNTs have been employed for impedance sensors within composite electrodes and as nanoelectrode arrays. The advantages of nanomaterials in impedance sensors include increased sensor surface area, electrical conductivity and connectivity, chemical accessibility and electrocatalysis.     

基于纳米材料的电化学免疫传感器在传染性病原体POCT中的应用

传染性病原体POCT对于及时有效控制传染病尤为关键。相比于传统检测方法,基于电化学免疫传感器的传染性病原体检测具有快速、灵敏、准确、易于小型化和集成化等优势,尤其适用于传染病POCT。新兴的纳米材料因其独特的理化性质可用于修饰传感器界面或作为生物分子的固载基质以及信号标记物等,有助于构建出高选择性和高灵敏度的电化学免疫传感器。在本文中,我们着重阐述了不同结构的纳米材料修饰的电化学免疫传感器在传染性病原体POCT检测中的应用,进一步介绍了基于纳米材料的电化学免疫传感器与不同检测技术联用在传染性病原体POCT中的应用,并对其发展前景做出了展望。     

Topical advances in nanomaterials based electrochemical sensors for resorcinol detection

The ever-increasing environmental pollution is a severe threat to the ecosystem’s healthy sustainability, and therefore environmental monitoring of these pollutants has become a burning issue throughout the world. In recent years, cost-effective, selective, portable, sensitive, and rapid sensing devices must be developed in urgent need. Advancement in nanotechnology has urged the use of different types of nanomaterials as an excellent electrode material to amplify the electrochemical detection in terms of long-term stability and electrocatalytic activity of the electrochemical sensors in addition to fulfill the aforementioned desires. This review article intimates significant advancement in developing the enzymatic and non-enzymatic electrochemical sensors based on different nanomaterials for the detection of resorcinol (RS) in the absence or presence of other phenolic compounds. This also concludes the current associated challenges as well as future perspectives for the analysis of RS in the environment. There is plethora of reported articles on RS sensors, but this review mainly discusses the selective reports on the applications of RS sensors.     

Recent trends and advances in microbial electrochemical sensing technologies: An overview

Microbial electrochemical systems utilize the electrochemical interaction between microorganisms and electrode surfaces to convert chemical energy into electrical energy, offering a promise as technologies for wastewater treatment, bioremediation, and biofuel production. Recently, growing research attention has been devoted to the development of microbial electrochemical sensrs as biosensing platforms. Microbial electrochemical sensors are a type of microbial electrochemical technology (MET) capable of sensing through the anodic or the cathodic electroactive microorganisms and/or biofilms. Herein, we review and summarize the recent advances in the design of microbial electrochemical sensing approaches with a specific overview and discussion of anodic and cathodic microbial electrochemical sensor devices, highlighting both the advantages and disadvantages. Particular emphasis is given on the current trends and strategies in the design of low-cost, convenient, efficient, and high performing METs with different biosensing applications, including toxicity monitoring, pathogen detection, corrosion monitoring, as well as measurements of biological oxygen demand, chemical oxygen demand, and dissolved oxygen. The conclusion provides perspectives and an outlook to understand the shortcomings in the design, development status, and sensing applications of microbial electrochemical platforms. Namely, we discuss key challenges that limit the practical implementation of METs for sensing purposes and deliberate potential solutions, necessary developments, and improvements in the field.     

Nickel-cermet electrodes for high-temperature electrochemical devices made using nanomaterials

Characteristics of nickel-cermet anodes obtained from weakly aggregated NiO nanopowders made by wire electric blasting (NiO/WEB) were studied. Electrodes made of NiO/WEB nanopowders have low sheet resistance (<0.1 Ohm) and high electrochemical activity (R _η = 0.06–0.09 Ohm cm² at 850–900°C). Prolonged studies of symmetric cells of the (0.9H₂ + 0.1H₂O) Ni-SSZ + CeO₂/YSZ/CeO₂ + Ni-SSZ (0.9H₂ + 0.1H₂O) type at the temperature of 850°C showed that the electrodes preserve sufficiently high activity (R _η < 0.1 Ohm cm²) for 1000 h. Using a NiO-WEB powder allows not performing presynthesis of nickel-cermet and decreasing the anode baking temperature to 1200°C.     

Miniaturized optical chemosensor for flow-based assays

A cost-effective, highly compact, and versatile optoelectronic device constructed of two ordinary light emitting diodes compatible with optosensing films has been developed. This fibreless device containing chemoreceptor, semiconductor light source, and detector integrated in a miniaturized flow-through cell of low microliter internal volume works as a complete photometric chemical sensor suitable for detection in flow analysis. The operation of the developed device under nonstationary programmable-flow conditions offered by sequential injection analysis has been demonstrated using Prussian Blue film as a model optical chemoreceptor. The unique spectroelectrochemical properties of the sensing material enable its use for optical sensing of redox species, whereby ascorbic acid and hydrogen peroxide have been chosen as model analytes. The reported SI-sensor system features fast and reproducible determination of both analytes in the submillimolar range of concentrations. The construction concept demonstrated in this work can be easily applied to other kinds of optical sensors based on absorbance sensing films.     

Significance of nanomaterials in electrochemical sensors for nitrate detection: A review

Nanomaterial-enabled electrochemical sensors are designed as an economical, efficient, and user-friendly analytical tool for on-site and routine nitrate analysis over a wide range of environmental samples. The remarkable advances and tunable attributes of nanomaterials have greatly improved the analytical performance of electrochemical nitrate sensors. In this review, a comprehensive elucidation of the recent advances in nanomaterial-based electrochemical nitrate sensors is presented. The review firstly provides a general introduction, followed by typical electrochemical sensing methods. The next two sections detail various nanomaterials, including graphene derivatives, carbon nanotubes/fibers, metal/bimetal/metal oxide nanoparticles, and conducting polymers for modifying electrodes in enzymatic and non-enzymatic electrochemical nitrate sensors. Finally, the perspectives and current challenges in achieving real-world applications of nanomaterial-based electrochemical nitrate sensors are outlined.     

An overview of a sustainable approach to the biosynthesis of AgNPs for electrochemical sensors

Mother nature furnishes various sources to synthesize nanomaterial’s with different geometry, size, and functionality. In this outline, we aimed to discuss the biological source-mediated fabrication of Ag NPs because of their easy handling, yields, and economical and non-toxicity. The literature reveals that different plant species, fungi, and bacteria can employ biosynthesis, enabling the fabrication of nanoparticles with different features, notably size, geometry, and morphology. The exact mechanisms have not been understood well, even though it is trusted that bio-sourced is responsible for this process. The method of synthesis can be influenced by pH, concentration, time, and biomass. The optimized biosynthesized AgNPs can employ in various domains like sensors, nanomedicine, environmental pollution etc., The main objective of the paper is to elaborate on the biosynthesized AgNPS in electrochemical sensing and its surface modifications. Furthermore, these electroanalytical techniques are to be used for real-time sampling to allow the selective detection of the target analyte.     

An introduction to bismuth film electrode for use in cathodic electrochemical detection

A new electrode surface design, the bismuth film electrode (BiFE), is presented as a promising alternative to mercury and other solid electrodes for direct cathodic electrochemical detection of organic compounds. The preparation of the BiFE, involving an ex situ electroplating of metallic bismuth onto a glassy carbon (GC) substrate electrode, was optimised. The useful negative potential windows of the BiFE in the pH range 1 (−0.2 to −0.8 V vs Ag/AgCl) to 10 (−0.2 to −1.5 V) were determined. The reproducibility of measuring 2-nitrophenol as a model compound (relative standard deviation, r.s.d., n=10) was found to be 0.5% at the same BiFE, and 1.0% at successive newly prepared BiFEs. No polishing or any other pre-treatment of the substrate GC surface was required prior to re-plating of a new Bi film. The BiFE showed similar or even favourable voltammetric behaviour when compared to mercury and bare GC electrodes, and was successfully tested for amperometric detection under hydrodynamic conditions. The results revealed that BiFE is an attractive new non-mercury metallic electrode particularly suitable for cathodic electrochemical detection in flow analytical systems.     

An electrochemical and optical anion chemosensor based on tripodal tris(ferrocenylurea)

A neutral tripodal tris(ferrocenylurea) anion receptor has been designed that can electrochemically and optically recognize sulfate and phosphate anions. The binding of the tetrahedral anion induced distinct cathodic shifts of the ferrocene/ferrocenium redox couple in chloroform, whereas the UV/Vis spectrum of the receptor showed an increase in the d–d transition band upon addition of sulfate ions. Furthermore, the anion complexes (TBA)₂ ? [SO₄?L] ? H₂O ( 1 ) and TBA[F?L] ( 2 ; TBA=tetrabutylammonium ion) were isolated. Crystal structural analyses showed that the receptor in the two 1:1 (host/guest) complexes encapsulated sulfate or fluoride ions in the tripodal cavity through multiple hydrogen bonds. ¹H NMR spectroscopic and ESI mass‐spectrometric analysis revealed strong sulfate and fluoride binding in solution.     

An overview of the electrochemical reduction of oxygen at carbon-based modified electrodes

We present an overview of the electrochemical reduction of oxygen in water, focussing on carbon-based and modified carbon electrodes. This process is of importance for gas sensing, in fuel cells and in the electrosynthesis of hydrogen peroxide.     

Review on applications of carbon nanomaterials for simultaneous electrochemical sensing of environmental contaminant dihydroxybenzene isomers

Carbonaceous nanostructures stand out as an excellent electrode material to enhance the electrocatalytic, electroconductivity, and long-term stability of the electrochemical sensor in recent years. This review article focus on the important advancement in developing carbonaceous nanomaterials-based electrochemical sensors for simultaneous electrochemical sensing (binary and ternary mixtures) of environmental contaminants dihydroxybenzene isomers. The fabrication of electrochemical sensors such as graphene/carbon nanotubes hybrid composite, graphene/ carbon nanotubes supported nanomaterials, mesoporous carbon, carbon nanofiber, carbon nano-fragment and biochar modified electrode was presented coupled with suitable applications. This review discussed the selective reports on the application of dihydroxybenzene sensors during the period from 2015 to 2020.     

Recent advances in optical detection of dopamine using nanomaterials

This review (with 121 references) gives a summary on recent advances in the use of nanomaterials for the optical determination of dopamine. It includes a brief overview of the clinical significance of dopamine followed by a discussion on the recent advances in various nanomaterial-based distinctive optical spectroscopic methods such as (a) colorimetry and spectrophotometry, (b) surface-enhanced Raman spectroscopy (SERS), (c) fluorescence spectrometry, and (d) electrochemiluminescence (ECL) spectrometry. All sections are further divided into subsections based on the type of nanomaterial used, and their advantages and disadvantages are discussed. A discussion on the validity of the nanomaterial-based optical detection of dopamine for human samples is also included. This review concludes with highlights of current challenges of nanomaterial-based optical sensors and an outlook on future perspectives.

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Graphical abstract Schematic of the use of various nanomaterials in the detection of dopamine based on colorimetry, spectrophotometry, surface-enhanced Raman spectroscopy, fluorescence and electrochemiluminescence.

     

Carbon nanomaterials and metallic nanoparticles-incorporated electrochemical sensors for small metabolites: Detection methodologies and applications

Detection of small metabolite biomarkers at different concentrations could be powerfully used for disease diagnosis and progression. To enhance detection capabilities, nanomaterials possessing excellent optical and electrochemical properties have been integrated into a wide range of sensing or detection platforms. This review will highlight recent developments in creating electrochemical sensors alongside biosensors using carbon nanomaterials and metallic nanoparticles that target small metabolites. Moreover, electrochemical sensors having different detection strategies toward metabolites (such as amino acids, amino acid–derived neurotransmitters, vitamins, adenosine triphosphate, and purine derivatives) will be discussed. Finally, certain challenging issues and future aspects of nanomaterials-integrated electrochemical sensors for small metabolites will be discussed.