Nanomaterial-based electrochemical sensors for arsenic - A review

Functionalized Chiral Materials for Use in Chiral Sensors

Chirality represents a fundamental attribute within living systems and is a pervasive phenomenon in the natural world. The identification and analysis of chiral materials within natural environments and biological systems hold paramount importance in clinical, chemical, and biological sciences. Within chiral analysis, there is a burgeoning focus on developing chiral sensors exhibiting exceptional selectivity, sensitivity, and stability, marking it as a forefront area of research. In the past decade (2013-2023), approximately 1990 papers concerning the application of various chiral materials in chiral sensors have been published. Biological materials and nanomaterials have important applications in the development of chiral sensors, which accounting for 26.67% and 45.24% of the material-related applications in these sensors, respectively; moreover, the development of chiral nanomaterials is closely related to the development of portable and stable chiral sensors. Natural chiral materials, utilized as selective recognition units, are combined with carriers characterized by good physical and chemical properties through functionalization to form various functional chiral materials, which improve the recognition efficiency of chiral sensors. In this article, from the perspective of biological materials, polymer materials, nanomaterials, and other functional chiral materials, the applications of chiral sensors are summarized and the research prospects of chiral sensors are discussed.

A facile approach for selective detection of arsenite ions using plasmonic behaviour of silver nanoparticles

A specific reagent/aptamer-free easy redox strategy between silver(I) moieties present in a citrate-stabilized colloidal silver nanoparticle (NP) system and arsenite ions is described that enables plasmonic change of AgNPs for the selective quantification of arsenite ions in the range of 0 to 30 μM with a low limit of quantification value of 50 nM (5.3 ppb).

Recent advances in nanobiosensors for sustainable healthcare applications: A systematic literature review

The need for novel healthcare treatments and drugs has increased due to the expanding human population, detection of newer diseases, and looming pandemics. The development of nanotechnology offers a platform for cutting-edge in vivo non-invasive monitoring and point-of-care-testing (POCT) for rehabilitative disease detection and management. The advancement and uses of nanobiosensors are currently becoming more common in a variety of scientific fields, such as environmental monitoring, food safety, biomedical, clinical, and sustainable healthcare sciences, since the advent of nanotechnology. The identification and detection of biological patterns connected to any type of disease (communicable or not) have been made possible in recent years by several sensing techniques utilizing nanotechnology concerning biosensors and nanobiosensors. In this work, 2218 articles are drawn and screened from six digital databases out of which 17 were shortlisted for this review by using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) technique. As a result, this study uses a systematic methodology to review some recently developed extremely sensitive nanobiosensors, along with their biomedical, point-of-care diagnostics (POCD), or healthcare applications and their capabilities, particularly for the prediction of some fatal diseases based on a few of the most recent publications. The potential of nanobiosensors for medicinal, therapeutic, or other sustainable healthcare applications, notably for ailments diagnostics, is also recognized as a way forward in the manifestation of future trends.

Nanomaterials-based aptasensors: An efficient detection tool for heavy-metal and metalloid ions in environmental and biological samples

In light of potential risks of heavy metal exposure, diverse aptasensors have been developed through the combination of aptamers with nanomaterials for the timely and efficient detection of metals in environmental and biological matrices. Aptamer-based sensors can benefit from multiple merits such as heightened sensitivity, facile production, uncomplicated operation, exceptional specificity, enhanced stability, low immunogenicity, and cost-effectiveness. This review highlights the detection capabilities of nanomaterial-based aptasensors for heavy-metal and metalloid ions based on their performance in terms of the basic quality assurance parameters (e.g., limit of detection, linear dynamic range, and response time). Out of covered studies, dendrimer/CdTe@CdS QDs-based ECL aptasensor was found as the most sensitive option with an LOD of 2.0 aM (atto-molar: 10-18 M) detection for Hg2+. The existing challenges in the nanomaterial-based aptasensors and their scientific solutions are also discussed.

A Nanograss Boron and Nitrogen Co-Doped Diamond Sensor Produced via High-Temperature Annealing for the Detection of Cadmium Ions

The high-performance determination of heavy metal ions (Cd2+) in water sources is significant for the protection of public health and safety. We have developed a novel sensor of nanograss boron and nitrogen co-doped diamond (NGBND) to detect Cd2+ using a simple method without any masks or reactive ion etching. The NGBND electrode is constructed based on the co-doped diamond growth mode and the removal of the non-diamond carbon (NDC) from the NGBND/NDC composite. Both the enlarged surface area and enhanced electrochemical performance of the NGBND film are achievable. Scanning electron microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, cyclic voltammetry, electrochemical impedance spectroscopy, and differential pulse anodic stripping voltammetry (DPASV) were used to characterize the NGBND electrodes. Furthermore, we used a finite element numerical method to research the current density near the tip of NGBND. The NGBND sensor exhibits significant advantages for detecting trace Cd2+ via DPASV. A broad linear range of 1 to 100 μg L-1 with a low detection limit of 0.28 μg L-1 was achieved. The successful application of this Cd2+ sensor indicates considerable promise for the sensitive detection of heavy metal ions.

Revealing the solid-solution interface interference behaviors between Cu2+ and As(III) via partial peak area analysis of simulations and experiments

The mutual interference in the sensing detection of heavy metal ions (HMIs) is considerably serious and complex. Besides, the co-existed ions may change the stripping peak intensity, shape and position of the target ion, which partly makes peak current analysis inaccurate. Herein, a promising approach of partial peak area analysis was proposed firstly to research the mutual interference. The interference between two species on their electrodeposition processes was investigated by simulating different kinetics parameters, including surface coverage, electro-adsorption, -desorption rate constant, etc. It was proved that the partial peak area is sensitive and regular to these interference kinetics parameters, which is favorable for distinctly identifying different interferences. Moreover, the applicability of the partial peak area analysis was verified on the experiments of Cu2+, As(III) interference at four sensing interfaces: glassy carbon electrode, gold electrode, Co3O4, and Fe2O3 nanoparticles modified electrodes. The interference behaviors between Cu2+ and As(III) relying on solid-solution interfaces were revealed and confirmed by physicochemical characterizations and kinetics simulations. This work proposes a new descriptor (partial peak area) to recognize the interference mechanism and provides a meaningful guidance for accurate detection of HMIs in actual water environment.

Emerging nanotechnology backed formulations for the management of atopic dermatitis

Atopic dermatitis is a prevalent chronic skin inflammation affecting 2.1 to 4.1% of adults globally. The complexity of its pathogenesis and the relapsing nature make it challenging to treat. Current treatments follow European Academy of Dermatology and Venerology guidelines, but advanced cases with recurring lesions lack effective therapies. To address this gap, researchers are exploring nanotechnology for targeted drug delivery. Nanoparticles offer benefits such as improved drug retention, stability, controlled release and targeted delivery through the disrupted epidermal barrier. This integrated review evaluates the current state of AD treatment and highlights the potential of novel nano-formulations as a promising approach to address the disease.

Magnetite interaction with arsenic during sorptive removal from groundwater: a mechanistic study

A magnetic mixed iron oxide, magnetite (Fe₃O₄), was synthesized in the laboratory and characterized before its use as sorbent for arsenic removal. The characterization techniques used were X-ray diffraction (XRD), specific surface area, zeta potential and particle size measurements. The sorbent was applied for arsenic removal, without any pre or post treatment, from groundwater. The efficiency of sorption can only be improved by understanding the sorbent-sorbate interaction. For onsite monitoring of the sorbent-sorbate interaction, an electrochemical investigation using cyclic voltammetry (CV) measurement was developed. The study confirmed that the sorption of As(III) on Fe₃O₄ is dynamic (reversible) whereas that of As(V) is static (irreversible) in nature. Detailed investigation after the sorption was carried out utilizing X-ray photoelectron spectroscopy (XPS) measurement. The complexation of As(III)-Fe₃O₄ and As(V)-Fe₃O₄ without any redox transformation was evident from the XPS data. By careful examination of the results, a mechanism of arsenic removal by Fe₃O₄ was proposed.

Detection of organic arsenic based on acid-base stable coordination polymer

Organic arsenic, usually found in animal feed and livestock farm wastewater, is a carcinogenic and life-threatening substance. Hence, for the rapid and sensitive detection of organic arsenic, the development of new fluorescent sensors is quite essential. Here, an acid-base stable coordination polymer (HNU-62) was constructed by the introduction of hydrophobic fluorescence ligand, which can be used as a highly selective sensor for the detection of roxarsone (ROX) in water. The limit of detection (LOD) of HNU-62 for ROX was 4.5 × 10^-6 M. Furthermore, HNU-62 also exhibits good anti-interference and recyclability, which can be used in detecting ROX in real samples of pig feed. This work provides an alternative approach for the construction of water-stable coordination polymer-based fluorescence sensors.

The Role of Silver Nanoparticles in Electrochemical Sensors for Aquatic Environmental Analysis

With rapidly increasing environmental pollution, there is an urgent need for the development of fast, low-cost, and effective sensing devices for the detection of various organic and inorganic substances. Silver nanoparticles (AgNPs) are well known for their superior optoelectronic and physicochemical properties, and have, therefore, attracted a great deal of interest in the sensor arena. The introduction of AgNPs onto the surface of two-dimensional (2D) structures, incorporation into conductive polymers, or within three-dimensional (3D) nanohybrid architectures is a common strategy to fabricate novel platforms with improved chemical and physical properties for analyte sensing. In the first section of this review, the main wet chemical reduction approaches for the successful synthesis of functional AgNPs for electrochemical sensing applications are discussed. Then, a brief section on the sensing principles of voltammetric and amperometric sensors is given. The current utilization of silver nanoparticles and silver-based composite nanomaterials for the fabrication of voltammetric and amperometric sensors as novel platforms for the detection of environmental pollutants in water matrices is summarized. Finally, the current challenges and future directions for the nanosilver-based electrochemical sensing of environmental pollutants are outlined.

Detection of Phenylarsine Oxide in Drinking Water Using an Impedimetric Electrochemical Sensor with Gelatin-Based Solid Electrolyte Enriched with Mercaptoethanol: A Novel Prospective Green Biosensor Methodology

A simple, inexpensive, rapid, and label-free detection of phenylarsine oxide (PAO) in the field is a significant and unmet need because of its fatally acute and chronic effects on human health. A simple, fast, sensitive, and relatively low-cost arsenic detection system with an eco-friendly sensor could fill this gap. To monitor arsenic in situ, a reliable, portable impedimetric electrochemical sensor is the most suitable platform, which is real-time, fast, low-cost, and easy to design and use and has high sensitivity at low detection limits in the nanogram per mL range. The detection system in this study has a patent-applied green sensor with minimum harm to nature and the potential to dissolve in nature. The electrode containing 15 mL of distilled water (DIW) + 2 g gelatin + 1.75 g glycerol was determined to be the most suitable for determining the amount of inorganic arsenic in the range of 1-100 ng/mL using a gelatin-based solid electrochemical sensor enriched with 2-mercaptoethanol. Impedance measurements were performed to analyze the stability of the sensor in both deionized water and drinking water, as well as for arsenic detection. Among the procedures examined, the procedure prepared with 15 mL DIW + 2 g glycerol + 1.75 g gelatin resulted in the best stability in aqueous medium and in sensitivity with resistance changes (-ΔR _ct (%)) of 12% (±0.62%), 26% (±2.3%), and 40% (±3.8%) for the concentrations of 1, 10, and 100 ng/mL PAO in drinking water, respectively. With this detection methodology, there is the potential to detect not only arsenic but also other heavy metals in waters and different biomarkers in human fluids.

Nanomaterials-based electrochemical sensors for the detection of natural antioxidants in food and biological samples: research progress

Antioxidants are healthy substances that are beneficial to the human body and exist mainly in natural and synthetic forms. Among many kinds of antioxidants, the natural antioxidants have great applications in many fields such as food chemistry, medical care, and clinical application. In recent years, many efforts have been made for the determination of natural antioxidants. Nano-electrochemical sensors combining electrochemistry and nanotechnology have been widely used in the determination of natural antioxidants due to their unique advantages. Therefore, a large number of nanomaterials such as metal oxide, carbon materials, and conducting polymer have attracted much attention in the field of electrochemical sensors due to their good catalytic effect and stable performance. This review mainly introduces the construction of electrochemical sensors based on different nanomaterials, such as metallic nanomaterials, metal oxide nanomaterials, carbon nanomaterials, metal-organic frameworks, polymer nanomaterials, and other nanocomposites, and their application to the detection of natural antioxidants, including ascorbic acid, phenolic acids, flavonoid, tryptophan, citric acid, and other natural antioxidants. In the end, the limitations of the existing nano-sensing technology, the latest development trend, and the application prospect for various natural antioxidant substances are summarized and analyzed. We expect that this review will be helpful to researchers engaged in electrochemical sensors.

Nanoinspired Biocompatible Chemosensors: Progress toward Efficient Prognosis of Arsenic Poisoning

Diagnosing heavy metals poisoning in human beings is of paramount importance. In this work, we present the design of a biocompatible Fe_xNi_(1-x)O hierarchical nanostructure-based sensor for ultraselective detection of arsenate (As(V)) ions in biological environments (e.g., body fluids, blood plasma, etc.). A novel iron doping technique was employed to fabricate the nanostructures rich with Fe cores to induce ultraselectivity toward arsenates. These nanostructures were used as dispersed markers and thin films deposited on Si/SiO₂ substrates to support in vivo and in vitro detection of As(V) ions. The device demonstrated excellent sensitivity with a maximum response of 64.7% (for 1000 ppm As(V) ions) with a limit of detection of 1 ppb in blood plasma. The sensor's response time (τ_r) was 5 s with 95.48% recovery with a maximum error of ±0.549% after three washes. The device showed excellent response stability for 63 days with a maximum error of ±1.27%. The sensor devices were highly reproducible, with a maximum variation of ±0.6% in response for a batch of four devices. Due to Fe doping, the nanostructures in suspension demonstrated as arsenate markers with excellent cytocompatibility (with dosage up to 1 mg/mL) for human umbilical vein endothelial cells and 3T3 fibroblasts (LDH < 120 and cell viability ∼80%) till 48 h of incubation. The sensing mechanism suggested that the nanostructures not only detect arsenates but also prevent their substantial reduction to arsenites under anoxic environments. Thus, the sensors may show considerable progress toward early arsenate detection in living systems.

Cell-free arsenic biosensors with applied nanomaterials: critical analysis

Arsenic is a ubiquitously found metalloid in our ecosystem because of natural and anthropogenic activities. People exposed to a higher level of arsenic become susceptible to several disorders, including cancer. According to current statistics, the population chronically exposed to arsenic has surpassed 200 million. Therefore, its detection in our environment is of great importance. There are many analytical techniques for the assessment of arsenic in different kinds of environmental samples. Among these techniques, the biosensor is considered a convenient platform and a widely applied analytical device for rapid qualitative and quantitative analysis in the field of environmental monitoring, food safety, and disease diagnosis. Today, there is a trend of including nanomaterials in sensors and biosensors because it empowers researchers to explore new arsenic detection methods and to enhance their analytical capabilities. In this review article, we summarized the latest developments in arsenic biosensors in particular with emphasis on the works based on cell-free approaches that are protein/enzyme-based, DNA-based, and aptamer-based utilizing various transduction platforms. In the meantime, we compared the capabilities that were related to these cell-free arsenic biosensors. This review article also highlights the development and application of novel nanomaterials for arsenic detection.

Low-cost electrochemical detection of arsenic in the groundwater of Guanajuato state, central Mexico using an open-source potentiostat

Arsenic is a carcinogenic groundwater contaminant that is toxic even at the parts-per-billion (ppb) level and its on-site determination remains challenging. Colorimetric test strips, though cheap and widely used, often fail to give reliable quantitative data. On the other hand, electrochemical detection is sensitive and accurate but considerably more expensive at the onset. Here, we present a study on arsenic detection in groundwater using a low-cost, open-source potentiostat based on Arduino technology. We tested different types of gold electrodes (screen-printed and microwire) with anodic stripping voltammetry (ASV), achieving low detection limits (0.7 μg L^-1). In a study of arsenic contaminated groundwaters in Mexico, the microwire technique provides greater accuracy than test strips (reducing the median error from -50% to +2.9%) and greater precision (reducing uncertainties from ±25% to ±4.9%). Most importantly, the rate of false negatives versus the World Health Organisation’s 10 μg L^-1 limit was reduced from 50% to 0% (N = 13 samples). Arsenic determination using open-source potentiostats may offer a low-cost option for research groups and NGOs wishing to perform arsenic analysis in-house, yielding superior quantitative data than the more widely used colorimetric test strips.

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...

Carbon Nanomaterial-Based Drug Sensing Platforms Using State-of-the- Art Electroanalytical Techniques

Background:

Currently, nanotechnology and nanomaterials are considered as the most popular and outstanding research subjects in scientific fields ranging from environmental studies to drug analysis. Carbon nanomaterials such as carbon nanotubes, graphene, carbon nanofibers etc. and non-carbon nanomaterials such as quantum dots, metal nanoparticles, nanorods etc. are widely used in electrochemical drug analysis for sensor development. Main aim of drug analysis with sensors is developing fast, easy to use and sensitive methods. Electroanalytical techniques such as voltammetry, potentiometry, amperometry etc. which measure electrical parameters such as current or potential in an electrochemical cell are considered economical, highly sensitive and versatile techniques.

Methods:

Most recent researches and studies about electrochemical analysis of drugs with carbon-based nanomaterials were analyzed. Books and review articles about this topic were reviewed.

Results:

The most significant carbon-based nanomaterials and electroanalytical techniques were explained in detail. In addition to this; recent applications of electrochemical techniques with carbon nanomaterials in drug analysis was expressed comprehensively. Recent researches about electrochemical applications of carbon-based nanomaterials in drug sensing were given in a table.

Conclusion:

Nanotechnology provides opportunities to create functional materials, devices and systems using nanomaterials with advantageous features such as high surface area, improved electrode kinetics and higher catalytic activity. Electrochemistry is widely used in drug analysis for pharmaceutical and medical purposes. Carbon nanomaterials based electrochemical sensors are one of the most preferred methods for drug analysis with high sensitivity, low cost and rapid detection.

Electrical and Electrochemical Sensors Based on Carbon Nanotubes for the Monitoring of Chemicals in Water-A Review

Carbon nanotubes (CNTs) combine high electrical conductivity with high surface area and chemical stability, which makes them very promising for chemical sensing. While water quality monitoring has particularly strong societal and environmental impacts, a lot of critical sensing needs remain unmet by commercial technologies. In the present review, we show across 20 water monitoring analytes and 90 references that carbon nanotube-based electrochemical sensors, chemistors and field-effect transistors (chemFET) can meet these needs. A set of 126 additional references provide context and supporting information. After introducing water quality monitoring challenges, the general operation and fabrication principles of CNT water quality sensors are summarized. They are sorted by target analytes (pH, micronutrients and metal ions, nitrogen, hardness, dissolved oxygen, disinfectants, sulfur and miscellaneous) and compared in terms of performances (limit of detection, sensitivity and detection range) and functionalization strategies. For each analyte, the references with best performances are discussed. Overall, the most frequently investigated analytes are H+ (pH) and lead (with 18% of references each), then cadmium (14%) and nitrite (11%). Micronutrients and toxic metals cover 40% of all references. Electrochemical sensors (73%) have been more investigated than chemistors (14%) or FETs (12%). Limits of detection in the ppt range have been reached, for instance Cu(II) detection with a liquid-gated chemFET using SWCNT functionalized with peptide-enhanced polyaniline or Pb(II) detection with stripping voltammetry using MWCNT functionalized with ionic liquid-dithizone based bucky-gel. The large majority of reports address functionalized CNTs (82%) instead of pristine or carboxyl-functionalized CNTs. For analytes where comparison is possible, FET-based and electrochemical transduction yield better performances than chemistors (Cu(II), Hg(II), Ca(II), H2O2); non-functionalized CNTs may yield better performances than functionalized ones (Zn(II), pH and chlorine).

Evidences on As(III) and As(V) interaction with iron(III) oxides: Hematite and goethite

Arsenic, which is ubiquitous in nature, was found associated with iron oxides in soils and sediments. Our interest was to utilize the same mechanism for the sorptive removal of arsenic from groundwater. The iron(III) oxides: hematite, goethite, were synthesized, characterized and sorption studies of arsenic [As(III) and As(V)] were carried out in batch mode. For studying the evidence of the interaction between arsenic and iron oxide during the process of sorption, a new electrochemical method was developed. Differential pulse voltammetry (DPV) study indicated that the sorbed arsenic species is redox active on the surface of the sorbent. X-ray photoelectron spectroscopy (XPS) measurement was performed for confirmation of the changes occurring to the oxidation states of iron as well as arsenic after the sorption. XPS studies confirmed that the behavior of arsenic species on hematite/goethite was similar and occurs via a partial redox reaction. During sorption of As(III), a partial oxidation occurs resulting in As(V) species, simultaneously the Fe(III) present in the iron oxide gets reduced to Fe(II). However, during the sorption of As(V), there occurs a Fe(II) oxidation followed by As(V) reduction. Based on the results, a mechanistic scheme for sorption of arsenic on iron(III) oxides as sorbents was proposed.

Electrochemical Mini-Platform with Thread based Electrodes for Interference Free Arsenic Detection

Herein, a fully integrated thread/textile-based electrochemical sensing device has been demonstrated. A hydrophilic conductive carbon thread, chemically modified with gold nanoparticles through an electrodeposition process, was used as a working electrode (WE). The hydrophilic thread coated with Ag/AgCl and an unmodified bare hydrophilic thread were used as reference electrode (RE) and counter electrode (CE) respectively. The device was fabricated with hydrophilic conductive carbon threads supported by capillary tubes and these integrated electrodes were placed in a 2 mL glass vial. The physico-chemical characterization of the working electrode was carried out using SEM (scanning electron microscopy) and X-ray photoelectron spectroscopy (XPS). Furthermore, the fabricated sensing platform, was tested for electrochemical sensing of arsenic. The electrocatalytic oxidation activity of arsenic in the designed platform was investigated via cyclic voltammetry (CV) and square wave Voltammetry (SWV). An oxidation peak at -0.4 V corresponding to the oxidation of arsenic was obtained. Scan rate effect was performed using CV analysis and the diffusion coefficient was found to be 2.478×10-10 with a regression coefficient of R2 = 0.9647. Further, concentration effect was accomplished in the linear range 0.4 μM to 60 μM. The limit of detection was obtained as 0.416 μM. For the practical application, effect of interference from other chemicals and real sample analysis from the tap water and blood serum sample was carried out which gave remarkable recovery values.

Challenges and potential solutions for nanosensors intended for use with foods

Nanotechnology-adapted detection technologies could improve the safety and quality of foods, provide new methods to combat fraud and be useful tools in our arsenal against bioterrorism. Yet despite hundreds of published studies on nanosensors each year targeted to the food and agriculture space, there are few nanosensors on the market in this area and almost no nanotechnology-enabled methods employed by public health agencies for food analysis. This Review shows that the field is currently being held back by technical, regulatory, political, legal, economic, environmental health and safety, and ethical challenges. We explore these challenges in detail and provide suggestions about how they may be surmounted. Strategies that may have particular effectiveness include improving funding opportunities and publication venues for nanosensor validation, social science and patent landscape studies; prioritizing research and development of nanosensors that are specifically designed for rapid analysis in non-laboratory settings; and incorporating platform cost and adaptability into early design decisions.

Flagellin-based electrochemical sensing layer for arsenic detection in water

Regular monitoring of arsenic concentrations in water sources is essential due to the severe health effects. Our goal was to develop a rapidly responding, sensitive and stable sensing layer for the detection of arsenic. We have designed flagellin-based arsenic binding proteins capable of forming stable filament structures with high surface binding site densities. The D3 domain of Salmonella typhimurium flagellin was replaced with an arsenic-binding peptide motif of different bacterial ArsR transcriptional repressor factors. We have shown that the fusion proteins developed retain their polymerization ability and have thermal stability similar to that of wild-type filament. The strong arsenic binding capacity of the monomeric proteins was confirmed by isothermal titration calorimetry (ITC), and dissociation constants (K_d) of a few hundred nM were obtained for all three variants. As-binding fibers were immobilized on the surface of a gold electrode and used as a working electrode in cyclic voltammetry (CV) experiments to detect inorganic arsenic near the maximum allowable concentration (MAC) level. Based on these results, it can be concluded that the stable arsenic-binding flagellin variant can be used as a rapidly responding, sensitive, but simple sensing layer in a field device for the MAC-level detection of arsenic in natural waters.

0D/2D heteronanostructure-integrated bimetallic CoCu-ZIF nanosheets and MXene-derived carbon dots for impedimetric cytosensing of melanoma B16-F10 cells

A novel heterogeneous architecture has been constructed integrating two-dimensional (2D) bimetallic CoCu-zeolite imidazole framework (CoCu-ZIF) and zero-dimensional (0D) Ti₃C₂T_x MXene-derived carbon dots (CDs) (represented by CoCu-ZIF@CDs). The prepared CoCu-ZIF@CDs were further explored as sensitive layer for anchoring B16-F10 cell-targeted aptamer strands and detecting B16-F10 cells from the biological environment. Basic characterization showed that CDs were homogeneously embedded within CoCu-ZIF NSs owing to their π-π stacking interaction, leading to outstanding fluorescence performance of the 0D/2D CoCu-ZIF@CD nanohybrid. As such, the CoCu-ZIF@CD-based cytosensor was applied to detect living B16-F10 cells through electrochemical techniques and cell imaging. Compared with CoCu-ZIF- and CD-based cytosensors, the constructed CoCu-ZIF@CD-based one showed superior sensing performance, with an extremely low limit of detection (LOD) of 33 cells∙mL^-1 and a wide range of suspension concentration of 1 × 10²-1 × 10⁵ cells∙mL^-1 B16-F10 cells. The developed cytosensor also demonstrated excellent detection performance, including cell imaging properties, good selectivity, high stability, and good reproducibility. By anchoring other probe molecules, the constructed CoCu-ZIF@CD-based biosensor can be extensively explored for early diagnosis of other analytes, thereby widening the applications of porous organic frameworks in biosensing and biomedical fields. A novel sensing system for melanoma B16-F10 cells based on a novel CoCu-ZIF@CD nanohybrid has been developed. The CoCu-ZIF@CDs-based cytosensor displayed an extremely low limit of detection (LOD) of 33 cells∙mL^-1 within the wide range of B16-F10 cell concentration from 1 × 10² to 1 × 10⁵ cells∙mL^-1, accompanying with cell imaging properties, good selectivity, high stability, and well reproducibility.

Recent development of chromogenic and fluorogenic chemosensors for the detection of arsenic species: Environmental and biological applications

Due to biological and environmental significance of highly toxic arsenic species, the design, synthesis and development of chemosensors for arsenic species has been a very active research field in recent times. In this review, we summarize recent works on the sensing mechanisms employed by fluorometric/colorimetric chemosensors and their applications in arsenic detection. Various types of sensing strategies can be categorized into six types including (i) chemosensors based on hydrogen bonding interactions; (ii) aggregation induced emission (AIE) based chemosensors; (iii) chemodosimetric approach (reaction-based chemosensors); (iv) metal coordination-based sensing strategy; (v) chemosensors based on metal complex displacement approach and (vi) metal complex as chemosensor. All these sensing strategies are very much simple and sensitive for use in the design of arsenic selective chromogenic and fluorogenic probes.

Self-assembling thermostable chimeras as new platform for arsenic biosensing

The correct immobilization and orientation of enzymes on nanosurfaces is a crucial step either for the realization of biosensors, as well as to guarantee the efficacy of the developed biomaterials. In this work we produced two versions of a chimeric protein, namely ArsC-Vmh2 and Vmh2-ArsC, which combined the self-assembling properties of Vmh2, a hydrophobin from Pleurotus ostreatus, with that of TtArsC, a thermophilic arsenate reductase from Thermus thermophilus; both chimeras were heterologously expressed in Escherichia coli and purified from inclusion bodies. They were characterized for their enzymatic capability to reduce As(V) into As(III), as well as for their immobilization properties on polystyrene and gold in comparison to the native TtArsC. The chimeric proteins immobilized on polystyrene can be reused up to three times and stored for 15 days with 50% of activity loss. Immobilization on gold electrodes showed that both chimeras follow a classic Langmuir isotherm model towards As(III) recognition, with an association constant (KAsIII) between As(III) and the immobilized enzyme, equal to 650 (± 100) L mol-1 for ArsC-Vmh2 and to 1200 (± 300) L mol-1 for Vmh2-ArsC. The results demonstrate that gold-immobilized ArsC-Vmh2 and Vmh2-ArsC can be exploited as electrochemical biosensors to detect As(III).

Miniaturized electrochemical biosensor based on whole-cell for heavy metal ions detection in water

The heavy metals pollution represents one of the important issues in the environmental field since it is involved in many pathologies from cancer, neurodegenerative, and metabolic diseases. We propose an innovative portable biosensor for the determination of traces of trivalent arsenic (As(III)) and bivalent mercury (Hg(II)) in water. The system implements a strategy combining two advanced sensing modules consisting in (a) a whole cell based on engineered Escherichia coli as selective sensing element towards the metals and (b) an electrochemical miniaturised silicon device with three microelectrodes and a portable reading system. The sensing mechanism relies on the selective recognition from the bacterium of given metals producing the 4-aminophenol redox active mediator detected through a cyclic voltammetry analysis. The miniaturized biosensor is able to operate a portable, robust, and high-sensitivity detection of As(III) with a sensitivity of 0.122 µA ppb^-1 , LoD of 1.5 ppb, and a LoQ of 5 ppb. The LoD value is one order of magnitude below of the value indicated to WHO to be dangerous (10 μg/L). The system was proved to be fully versatile being effective in the detection of Hg(II) as well. A first study on Hg(II) showed sensitivity value of 2.11 µA/ppb a LOD value of 0.1 ppb and LoQ value of 0.34 ppb. Also in this case, the detected LOD was 10 times lower than that indicated by WHO (1 ppb). These results pave the way for advanced sensing strategies suitable for the environmental monitoring and the public safety.

Nano-Enabled sensors for detection of arsenic in water

The elevated cases of arsenic contamination reported across the globe have made its early detection and remediation an active area of research. Although, the World Health Organisation has set the maximum provisional value for arsenic in drinking water at 10 parts per billion, yet concentrations as high as 5000 parts per billion are still reported. In human beings, chronic arsenic exposure can culminate into lethal diseases such as cancer. Thus, there is a need for urgent emergence of efficient and reliable detection system. This paper offers an overview of the state-of-art knowledge on current arsenic detection mechanisms. The central agenda of this paper is to develop an understanding into the nano-enabled methods for arsenic detection with an emphasis on strategic fabrication of nanostructures and the modulation of nanomaterial chemistry in order to strengthen the knowledge into novel nano-enabled solutions for arsenic contamination. Towards the end prospects for arsenic detection in water are also prompted.

Interfacing DNA with Gold Nanoparticles for Heavy Metal Detection

The contamination of heavy metals (e.g., Hg, Pb, Cd and As) poses great risks to the environment and human health. Rapid and simple detection of heavy metals of considerable toxicity in low concentration levels is an important task in biological and environmental analysis. Among the many convenient detection methods for heavy metals, DNA-inspired gold nanoparticles (DNA-AuNPs) have become a well-established approach, in which assembly/disassembly of AuNPs is used for colorimetric signaling of the recognition event between DNA and target heavy metals at the AuNP interface. This review focuses on the recent efforts of employing DNA to manipulate the interfacial properties of AuNPs, as well as the major advances in the colorimetric detection of heavy metals. Beginning with the introduction of the fundamental aspects of DNA and AuNPs, three main strategies of constructing DNA-AuNPs with DNA binding-responsive interface are discussed, namely, crosslinking, electrostatic interaction and base pair stacking. Then, recent achievements in colorimetric biosensing of heavy metals based on manipulation of the interface of DNA-AuNPs are surveyed and compared. Finally, perspectives on challenges and opportunities for future research in this field are provided.

Ultrathin quasi-hexagonal gold nanostructures for sensing arsenic in tap water

Monodispersed colloidal gold nanoparticles (AuNPs) were synthesized by an easy, cost-effective, and eco-friendly method. The AuNPs were mostly quasi-hexagonal in shape with sizes ranging from 15 to 18 nm. A screen-printed electrode modified with AuNPs (AuNPs/SPE) was used as an electrochemical sensor for the detection of As(iii) in water samples. The mechanistic details for the detection of As(iii) were investigated and an electrochemical reaction mechanism was proposed. Under the optimal experimental conditions, the sensor was highly sensitive to As(iii), with a limit of detection of 0.11 μg L⁻¹ (1.51 nM), which is well below the regulatory limit of 10 μg L⁻¹ established by the United States Environmental Protection Agency and the World Health Organization. The sensor responses were highly stable, reproducible, and linear over the As(iii) concentration range of 0.075 to 30 μg L⁻¹. The presence of co-existing heavy metal cations such as lead, copper, and mercury did not interfere with the sensor response to As(iii). Furthermore, the voltammogram peaks for As(iii), lead, copper, and mercury were sufficiently separate for their potential simultaneous measurement, and at very harsh acidic pH it may be possible to detect As(v). The AuNPs/SPE could detect As(iii) in tap water samples at near-neutral pH, presenting potential possibilities for real-time, practical applications.

Monodispersed colloidal gold nanoparticles (AuNPs) were synthesized by an easy, cost-effective, and eco-friendly method for electrochemical detection of As(iii).

A competitive coordination-based immobilization-free electrochemical biosensor for highly sensitive detection of arsenic(v) using a CeO2-DNA nanoprobe

We developed a competitive coordination-based immobilization-free electrochemical biosensor for highly sensitive and selective detection of arsenic(v) using a CeO₂-DNA nanoprobe, which effectively circumvented complicated modification procedures and successfully achieved arsenic(v) determination in natural water samples.

Electrochemical aptasensors based on the gold nanostructures

Electrochemical aptasensors as novel diagnostic tools have attracted sufficient research interest in biomedical sciences. In this review, recent leading trends about gold (Au) nanostructures based electrochemical aptasensors have been collected, reviewed, and compared. Here, the considered electrochemical aptasensors were categorized based on the analytes and diagnostic techniques. Pharmaceutical analytes and biomolecules were reviewed in a separate section consisting of a variety of antibiotics, analgesics, and other biomolecules. Various aptasensors have also measured toxins, ions, and hazardous chemicals, and the findings of them have also been reviewed. Many aptasensors have been designed to detect different disease biomarkers that will play an essential role in the future of early diagnosis of diseases. Pathogen microorganisms have been considered as the analyte in several designed electrochemical aptasensors in recent researches, and their results have been reviewed and discussed as another section. Important aspects considered in the review of the mentioned aptasensors were the type of analyte, features of the aptamer as the biorecognition element, type of Au nanostructures, diagnostic technique, diagnostic mechanism, detection range and the limit of detection (LOD). In the last section, an in-depth analysis has been provided based on the crucial features of all included aptasensors.

Multiwalled Carbon Nanotubes-CeO2 Nanorods: A "Nanonetwork" Modified Electrode for Detecting Trace Rifampicin

Herein, a "nanonetwork" modified electrode was fabricated based on multiwalled carbon nanotubes and CeO₂ nanorods. Scanning electron microscopy, X-ray powder diffraction and zeta potential were employed to characterize this electrode. Multiwalled carbon nanotubes negatively charged and CeO₂ nanorods positively charged form "nanonetwork" via electrostatic interaction. The performance of the CeO₂ nanorods-based electrode remarkably improved due to the introduction of multiwalled carbon nanotubes. The detection of rifampicin (RIF) was used as a model system to probe this novel electrode. The results showed a significant electrocatalytic activity for the redox reaction of RIF. Differential pulse voltammetry was used to detect rifampicin, the reduction peak current of rifampicin linear with the logarithm of their concentrations in the range of 1.0 × 10^-13-1.0 × 10^-6 mol/L, The linear equation is i_p = 6.72 + 0. 46lgc, the detect limit is 3.4 × 10^-14 mol/L (S/N = 3). Additionally, the modified electrode exhibits enduring stability, excellent reproducibility, and high selectivity. This strategy can be successfully used to detect trace rifampicin in samples with satisfactory results.