A Novel Potentiometric Sensor Based on 1,2-Bis(N’-benzoylthioureido)benzene and Reduced Graphene Oxide for Determination of Lead (II) Cation in Raw Milk

Graphene-based biosensors in milk analysis: A review of recent developments

Cow's milk, an excellent source of fat, protein, amino acids, vitamins and minerals, is currently one of the most consumed products worldwide. Contaminations originating from diverse sources, such as biological, chemical, and physical, cause dairy product quality problems and thus dairy-related disorders, raising public health issues. For this reason, legal authorities have deemed it necessary to classify certain contaminations in commercial milk and keep them within particular limitations; therefore, it is urgent to develop next-generation detection systems that can accurately identify just the contaminants of concern to human health. This review presents a detailed investigation of biosensors based on graphene and its derivatives, which offer superior sensitivity and selectivity, by classifying the contaminants under the headings biological, chemical, and physical, in cow's milk according to their sources. We reviewed the current status of graphene-based biosensor (GBs) technology for milk or dairy analysis, highlighting its strengths and weaknesses with the help of comparative studies, tables, and charts, and we put forward a novel perspective to handle future challenges.

Multifunctional Siloxene-Decorated Laser-Inscribed Graphene Patch for Sweat Ion Analysis and Electrocardiogram Monitoring

Potentiometric detection in complex biological fluids enables continuous electrolyte monitoring for personal healthcare; however, the commercialization of ion-selective electrode-based devices has been limited by the rapid loss of potential stability caused by electrode surface inactivation and biofouling. Here, we describe a simple multifunctional hybrid patch incorporating an Au nanoparticle/siloxene-based solid contact (SC) supported by a substrate made of laser-inscribed graphene on poly(dimethylsiloxane) for the noninvasive detection of sweat Na+ and K+. These SC nanocomposites prevent the formation of a water layer during ion-to-electron transfer, preserving 3 and 5 μV/h potential drift for the Na+ and K+ ion-selective electrodes, respectively, after 13 h of exposure. The lamellar structure of the siloxene sheets increases the SC area. In addition, the electroplated Au nanoparticles, which have a large surface area and excellent conductivity, further increased the electric double-layer capacitance at the interface between the ion-selective membranes and solid-state contacts, thus facilitating ion-to-electron transduction and ultimately improving the detection stability of Na+ and K+. Furthermore, the integrated temperature and electrocardiogram sensors in the flexible patch assist in monitoring body temperature and electrocardiogram signals, respectively. Featuring both electrochemical ion-selective and physical sensors, this patch offers immense potential for the self-monitoring of health.

Bis(thiophen-2-yl-methylene) Benzene-1, 4-Diamine as Fluorescent Probe for the Detection of Fe3+ in Aqueous Samples

A Schiff base bis(thiophen-2-yl-methylene)benzene-1, 4-diamine (L) was synthesized and used for selective and sensitive detection of Fe³⁺. L exhibited enhanced fluorescence response at excitation of 365 nm and emission wavelength of 440 nm for Fe³⁺. The formation of a 1:1 complex between L and Fe³⁺ was suggested by Job's plot by fluorescence titration and from optimized structures using Density functional theory (DFT). The fluorescence intensity was directly proportional to concentration of Fe³⁺ (R² = 0.999) with the detection limit of 3.8 × 10^-7 M and the binding constant of 1.20 × 10⁴ M^-1 at pH = 6.0. The probe was used to detect Fe³⁺ in different water samples with the percentage recovery of 99.7-103%. The interference of the other cations are < 5%.

Nanoparticles functionalized ceramic membranes: fabrication, surface modification, and performance

Membrane technologies are used intensively for desalination and wastewater treatment. Water filtration using ceramic membranes exhibited high performance compared with polymeric membranes due to various properties such as high resistance to fouling, permeability, rejection rate, and chemical stability. Recently, the performance of nanocomposite ceramic membranes was improved due to the development in nanotechnology. This article focusses on the development of porous ceramic membranes and nanomaterial functionalized ceramic membranes for water filtration applications. At the beginning, various fabrication methods of ceramic membranes were described, and the effect of surface modification techniques on the membrane intrinsic properties was reviewed. Then, the performance of nanoparticles functionalized ceramic membranes was evaluated in terms of physicochemical properties, rejection rate, and water permeability. This work can help new entrants and established researchers to become familiar with the current challenges and developments of nanoparticle-incorporated ceramic membranes for water filtration applications.

Conjugates of Curcumin with Graphene and Carbon Nanotubes: A Review on Biomedical Applications

In the last decade, the use of carbon nanotubes and graphenes has been on the rise for various nanobiotechnological applications. Owing to their special characteristics, these two nanostructures of carbon allotropes have been studied for their capacity in the detection and treatment of many diseases. On the other hand, curcumin, a well-known antioxidant and anticancer natural product, is being extensively studied for numerous medicinal applications. Interestingly, many reports have shown great potentials of conjugates of curcumin and carbon nanotubes or graphenes. These conjugates, when properly designed and functionalized with biomolecules, could represent the valuable properties of each component alone while they could be effective in overcoming the poor solubility issues of both curcumin and Carbon Nanomaterials (CNMs). In this case, curcumin conjugates with CNMs seem to be very promising in biosensing applications and the detection of many biomolecules, especially, curcumin has been reported to be very effective with these conjugates. Also, the delivery of curcumin using functionalized SWCNTs was evaluated for its ability to load and release curcumin, to protect curcumin from degradation and to enhance its solubility. It is proposed that other properties of these conjugates are still to be discovered and the interdisciplinary approaches among biology, medicine, chemistry, and material engineering will accelerate the applications of these novel materials. This review aims to summarize the findings on the applications of CNM conjugates of curcumin.

N-Hydroxysuccinimide crosslinked graphene oxide–gold nanoflower modified SPE electrode for sensitive detection of chloramphenicol antibiotic

Here we introduce a composite material that consists of graphene oxide (GO) sheets crosslinked with N-hydroxysuccinimide (NHS) and functionalized with gold nanoflowers (AuNFs). Furthermore, a screen printed electrode (SPE) modified with the introduced composite is electrochemically reduced to obtain an SPE/rGO–NHS–AuNFs electrode for sensitive and selective determination of chloramphenicol (CAP) antibiotic drug. The morphological structure of the as-prepared nanocomposite was characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy, cyclic voltammetry, Fourier-transform infrared spectroscopy and electrochemical impedance spectroscopy. The proposed sensor demonstrated excellent performance with a linear concentration range of 0.05 to 100 μM and a detection limit of 1 nM. The proposed electrode offers a high level of selectivity, stability, reproducibility and a satisfactory recovery rate for electrochemical detection of CAP in real samples such as blood serum, poultry feed, milk, eggs, honey and powdered milk samples. This further demonstrates the practical feasibility of the proposed sensor in food analysis.

Here we introduce a composite material that consists of graphene oxide (GO) sheets crosslinked with N-hydroxysuccinimide (NHS) and functionalized with gold nanoflowers (AuNFs).

The overview and perspectives of biosensors and Mycobacterium tuberculosis: A systematic review

Tuberculosis (TB) is referred to as a "consumption" or phthisis, which has been a fatal human disease for thousands of years. Mycobacterium tuberculosis (M. tb) might have been responsible for the death of more humans than any other bacterial pathogens. Therefore, the rapid diagnosis of this bacterial infection plays a pivotal role in the timely and appropriate treatment of the patients, as well as the prevention of disease spread. More than 98% of TB cases are reported in developing countries, and due to the lack of well-equipped and specialized diagnostic laboratories, development of effective diagnostic methods based on biosensors is essential for this bacterium. In this review, original articles published in English were retrieved from multiple databases, such as PubMed, Scopus, Google Scholar, Science Direct, and Cochrane Library during January 2010-October 2019. In addition, the reference lists of the articles were also searched. Among 109 electronically searched citations, 42 articles met the inclusion criteria. The highest potential and wide usage of biosensors for the diagnosis of M. tb and its drug resistance belonged to DNA electrochemical biosensors (isoniazid and rifampin strains). Use of biosensors is expanding for the detection of resistant strains of anti-TB antibiotics with high sensitivity and accuracy, while the speed of these sensory methods is considered essential as well. Furthermore, the lowest limit of detection (0.9 fg/ml) from an electrochemical DNA biosensor was based on graphene-modified iron-oxide chitosan hybrid deposited on fluorine tin oxide for the MPT64 antigen target. According to the results, the most common methods used for M. tb detection include acid-fast staining, cultivation, and polymerase chain reaction (PCR). Although molecular techniques (e.g., PCR and real-time PCR) are rapid and sensitive, they require sophisticated laboratory and apparatuses, as well as skilled personnel and expertise in the commentary of the results. Biosensors are fast, valid, and cost-efficient diagnostic method, and the improvement of their quality is of paramount importance in resource-constrained settings.

Rapid and label-free electrochemical DNA biosensor based on a facile one-step electrochemical synthesis of rGO-PPy-(L-Cys)-AuNPs nanocomposite for the HTLV-1 oligonucleotide detection

Human T cell leukemia virus type 1 (HTLV-1) as the first human retrovirus is currently a serious endemic health challenge. Despite the use of assorted molecular or serological assays for HTLV-1 detection, there are several limitations due to the lack of a confirmatory test that may affect the accuracy of the results. Herein, a novel label-free biosensor for the detection of HTLV-1 Tax gene has been reported. An electrochemical facile ecofriendly synthesis method has been demonstrated based on a synthesis of nanocomposite of reduced graphene oxide, polypyrrole, and gold nanoparticles (rGO-PPy-(l-Cys)-AuNPs) deposited on the surface of screen-printed carbon electrode. Electrochemical techniques were used to characterize and study the electrochemical behavior of the rGO-PPy-(l-Cys)-AuNPs, which exhibited a stable reference peak at 0.21 V associated with hybridization forms by applying the differential pulse voltammetry. The designed DNA biosensor presented a wide linear range from 0.1 fM to 100 µM and a low detection limit of 20 atto-molar. The proposed biosensor presented in this study provides outstanding selectivity, sensitivity, repeatability, and reproducibility.

Recent advances in solid-contact ion-selective electrodes: functional materials, transduction mechanisms, and development trends

This article presents a comprehensive overview of recent progress in the design and applications of solid-contact ion-selective electrodes (SC-ISEs).

The role of curcumin and its derivatives in sensory applications

Curcumin has recently attracted much attention due to the wide range of its physiological actions such as anti-tumor, anti-inflammatory, anti-thrombotic, anti-diabetic and anti-microbial effects. This phytochemical can be used as a sensing material for the detection of chemicals due to its optical properties as a fluorescent polyphenol. Curcumin and its derivatives can make complexes with many cations such as Cu²⁺, Fe²⁺, Hg²⁺, Pt²⁺, Re³⁺ and Al³⁺via bearing 1,3-diketones with keto-enol isomerization. The complexation of curcumin with certain metal ions leads to its solubility in water and producing various hues of colors as well as cytotoxic and antimicrobial effects. Curcumin can also form complexes with certain metal ions and thus serve as a chelating agent for anions such as ClO^-, CN^-, F^- and S^2-. Moreover, conjugation of curcumin with some organic compounds such as cysteine and poly-glycerol acrylate provides an efficient fluorescence detection system for picric acid and 2-vinyl pyridine in aqueous media. In this review, we focused on curcumin as a key element in a membrane composition of chemical sensors. In addition, the latest sensing platforms based on curcumin and its derivatives are briefly described.

Health Risk Assessment for Human Exposure to Trace Metals and Arsenic via Consumption of Hen Egg Collected from Largest Poultry Industry in Iran

The relative contribution of foodstuffs to intake of heavy metal is still equivocal, and thus, available data are rare. Here, the concentration of ten heavy metals and arsenic were measured in the content of hen egg from five strains of commercial laying hens to evaluate contamination level and potential health risk among local and international consumers in Iran. The estimated daily intake (EDI) of all heavy metals was significantly lower than the provisional tolerable daily intake (PTDI) and respective tolerable daily intake (TDI). The non-carcinogenic and carcinogenic risk values for eating eggs were in the safe range for all consumers, indicating that the no health risk for consumers due to the daily intake of either arsenic or heavy metals. Therefore, intake of heavy metal exposure through the consumption of commercial egg product in Iran is completely safe for both national and international consumers.

Graphene-derived nanomaterials as recognition elements for electrochemical determination of heavy metal ions: a review

This review (with 155 refs.) summarizes the progress made in the past few years in the field of electrochemical sensors based on graphene-derived materials for the determination of heavy metal ions. Following an introduction of this field and a discussion of the various kinds of modified graphenes including graphene oxide and reduced graphene oxide, the review covers graphene based electrodes modified (or doped) with (a) heteroatoms, (b) metal nanoparticles, (c) metal oxides, (d) small organic molecules, (e) polymers, and (f) ternary nanocomposites. Tables are provided that afford an overview of representative methods and materials for fabricating electrochemical sensors. Furthermore, sensing mechanisms are discussed. A concluding section presents new perspectives, opportunities and current challenges. Graphical Abstract Schematic illustration of electrochemical sensor for heavy metal ion sensing based on heteroatom-doped graphene, metal-modified graphene, metal-oxide-modified graphene, organically modified graphene, polymer-modified graphene, and ternary graphene based nanocomposites.

Depth profiling X-ray photoelectron spectroscopy and atomic force microscopy of Cd(ii)- and Pb(ii)-selective electrodes based on nano metal sulfides

This research involved constructing and studying plastic membrane Cd(ii)- and Pb(ii)-ion selective electrodes of the coated wire type based on nanoparticles of CdS and PbS as ionophores, respectively. The electrodes exhibited average linear concentration ranges of 1.0 × 10⁻⁶ to 1.0 × 10⁻² and 9.6 × 10⁻⁷ to 1.0 × 10⁻² M, average detection limits of 8.6 × 10⁻⁷ and 5.8 × 10⁻⁷ M, pH ranges of 2.2–5.8 and 2.9–5.9, and average calibration graph slopes of 28.56 and 28.81 mV per concentration decade, respectively. Both electrodes showed high selectivity towards many inorganic cations. Depth profiling X-ray photoelectron spectroscopy of fresh and expired membranes proved that: (a) the nanoparticles were homogeneously dissolved in the polymeric network and (b) the limitation of the life span of the plastic membrane was due to leaching of the active ingredient from the membrane surface to the bathing solution. The topography of fresh, active, and expired membranes as imaged by atomic force microscopy revealed the formation of a gel layer at the surface of the active electrode and drastic deformation of the expired membrane's surface.

Nanoparticles of CdS and PbS as ionophres for plastic membrane metal cations electrodes.

Air-Stable Black Phosphorus Devices for Ion Sensing

Black phosphorus (BP) is one of the most attractive graphene analogues, and its properties make it a promising nanomaterial for chemical sensing. However, mono- and few-layer BP flakes are reported to chemically degrade rapidly upon exposure to ambient conditions. Therefore, little is known about the performance and sensing mechanism of intrinsic BP, and chemical sensing of intrinsic BP with acceptable air stability remains only theoretically explored. Here, we experimentally demonstrated the first air-stable high-performance BP sensor using ionophore coating. Ionophore-encapsulated BP demonstrated significantly improved air stability. Its performance and sensing mechanism for trace ion detection were systematically investigated. The BP sensors were able to realize multiplex ion detection with superb selectivity, and sensitive to Pb(2+) down to 1 ppb. Additionally, the time constant for ion adsorption extracted was only 5 s. The detection limit and response rate of BP were both superior to those of graphene based sensors. Moreover, heavy metal ions can be effectively detected over a wide range of concentration with BP conductance change following the Langmuir isotherm for molecules adsorption on surface. The simplicity of this ionophore-encapsulate approach provides a route for achieving air-stable intrinsic black phosphorus sensors that may stimulate further fundamental research and potential applications.

Integrated ecological risk assessment of dioxin compounds

Current ecological risk assessment (ERA) schemes focus mainly on bioaccumulation and toxicity of pollutants in individual organisms. Ecological models are tools mainly used to assess ecological risks of pollutants to ecosystems, communities, and populations. Their main advantage is the relatively direct integration of the species sensitivity to organic pollutants, the fate and mechanism of action in the environment of toxicants, and life-history features of the individual organism of concern. To promote scientific consensus on ERA schemes, this review is intended to provide a guideline on short-term ERA involving dioxin chemicals and to identify key findings for exposure assessment based on policies of different agencies. It also presents possible adverse effects of dioxins on ecosystems, toxicity equivalence methodology, environmental fate and transport modeling, and development of stressor-response profiles for dioxin-like chemicals.

Nanocomposites of nitrogen-doped graphene decorated with a palladium silver bimetallic alloy for use as a biosensor for methotrexate detection

Pd₁Ag₁/NG–GCE is a promising platform for the highly sensitive electrochemical detection of MTX.

A novel potentiometric self-plasticizing polypyrrole sensor based on a bidentate bis-NHC ligand for determination of Hg(ii) cation

In this approach, a new potentiometric self-plasticizing polypyrrole sensor was constructed based on a bidentate bis-NHC ligand for the purpose of Hg²⁺cation determination.