From challenge to opportunity: Revolutionizing the monitoring of emerging contaminants in water with advanced sensors

Emerging contaminants in water represent long-term and unpredictable threats to both environmental and human health due to their persistence and bioaccumulation. Current research predominantly focuses on their removal rather than sustained monitoring. This review comprehensively investigates advanced sensor technologies for detecting these contaminants in water, critically evaluating biosensors, optical sensors, electrochemical sensors, and nanomaterial sensors. Elucidating the operational principles, performance metrics such as detection thresholds, and the pros and cons of their practical applications, the review addresses a significant research gap in environmental monitoring. Moreover, it enhances understanding of sensor effectiveness, which in turn guides researchers in selecting the right sensor types for various environmental scenarios. Furthermore, by emphasizing the integration of nanotechnology and the standardization of evaluation protocols, it promotes the development of robust, deployable sensing solutions. Ultimately, this leads to the proposal of a strategic framework aimed at significantly improving the detection capabilities of emerging contaminants and supporting the preservation of environmental health.

Electrochemical investigations and antimicrobial activity of Au nanoparticles photodeposited on titania nanoparticles

Titanium oxide nanopowder (TiO2 NPs) was synthesized via anodization in 0.7 M perchloric acid then annealed in nitrogen at 450 °C for 3 h to prepared the Titanium Oxide Nitrogen annealed nanoparticles (TiO2 NPs-N2) powder as catalytic support. Using a photodeposition process, gold was added with isopropanol as a sacrificial donor and H[AuCl4] acid, producing gold nanoparticles on nitrogen-annealed titanium oxide nanoparticles (Au-NPs on TiO2-NPs-N2). The mass loading of Au NPs was 2.86 × 10-4 (g/cm2). TEM images of Au NPs on TiO2-NPs-N2 suggest circular particles with a tendency to agglomerate. Cyclic voltammetry (CV) was used to investigate the electrocatalytic performance of the Au NPs/TiO2-NPs-N2 catalysts in ferrocyanide, KOH, and H2SO4, and the results were compared to those of a polycrystalline Au electrode that is readily accessible in the market. In KOH, H2SO4, and (2 M KOH + 0.1 M glycerol) solutions, the Au NPs/TiO2-NPs-N2 electrode displayed a startlingly high electrocatalytic performance. Using CV, the electrocatalytic oxygen reduction reaction (ORR) of Au NPs/TiO2-NPs-N2 and Au-NPs against glycerol oxidation in basic media was studied. The results indicated that Au NPs/TiO2-NPs-N2 is a promising support material for improving the electrocatalytic activity for acidic and basic oxidation. The electrode made of Au NPs/TiO2-NTs-N2 has steady electrocatalytic activity and may be reused repeatedly. TiO2 NPs and Au NPs/TiO2NPs-N2 showed satisfactory antibacterial activity against some human pathogenic bacteria using the disc diffusion method.

Eco-friendly monitoring of triclosan as an emerging antimicrobial environmental contaminant utilizing electrochemical sensors modified with CNTs nanocomposite transducer layer

Environmental appearance of antimicrobials due to frequent use of personal care products as recommended by WHO can cause serious flare-up of antimicrobial resistance. In this work, three eco-friendly microfabricated copper solid-state sensors were developed for measuring triclosan in water. Multi-walled carbon nanotubes were incorporated in sensor 2 and 3 as hydrophobic conductive inner layer. Meanwhile, β-cyclodextrin was incorporated in sensor 3 as an ionophore for selective binding of TCS in presence of interfering compounds. The obtained linear responses of sensors 1, 2 and 3 were (1 × 10- 8-1 × 10- 3 M), (1 × 10- 9-1 × 10- 3 M) and (1 × 10- 10- 1 × 10- 3 M), respectively. Limit of detection was 9.87 × 10- 9 M, 9.62 × 10- 10 M, and 9.94 × 10- 11 M, respectively. The miniaturized sensors were utilized for monitoring of triclosan in water samples.

Alternative methods of monitoring emerging contaminants in water: a review

Anthropogenic activities have steadily increased the release of emerging contaminants (ECs) in aquatic bodies, and these ECs may have adverse effects on humans even at their trace (μg L^-1) levels. Their occurrence in wastewater systems is more common, and the current wastewater treatment facilities are inefficient in eliminating many of such persistent ECs. "Gold standard" techniques such as chromatography, mass spectrometry, and other high-resolution mass spectrometers are used for the quantification of ECs of various kinds, but they all have significant limitations. This paper reviews the alternative methods for EC detection, which include voltammetry, potentiometry, amperometry, electrochemical impedance spectroscopy (EIS) based electrochemical methods, colorimetry, surface-enhanced Raman spectroscopy (SERS), fluorescence probes, and fluorescence spectroscopy-based optical techniques. These alternative techniques have several advantages over conventional techniques, including low sample volume, excludes solid phase extraction procedure, high sensitivity, selectivity, portability, reproducibility, rapidity, low cost, and the ability to monitor ECs in real time. This review summarises each of the alternative methods for detecting ECs in water samples and their respective limits of detection (LODs). The sensitivity of each technique varied depending on the type of EC measured, type of electrochemical probe and electrode, substrates, type of nanoparticle (NP), the physicochemical parameters of water samples tested, and more. Nevertheless, this paper also focuses on some of the current challenges encountered by these alternative methods in monitoring ECs.

Graphene oxide-based nanomaterials for the treatment of pollutants in the aquatic environment: Recent trends and perspectives - A review

Graphene oxide can be used to store energy, as electrodes and purify industrial and domestic wastewater as photocatalysts and adsorbents because of its remarkable thermal, electrical, and chemical capabilities. Toward understanding graphene oxide (GO) based nanomaterials considering the background factors, the present review study investigated their characteristics, preparation methods, and characterization processes. The removal of contaminants from wastewater has recently been a focus of attention for materials based on GO. Progress in GO synthesis and surface modification has shown that they can be used to immobilize enzymes. It is possible to immobilize enzymes with varying characteristics on graphene-oxide-based substrates without sacrificing their functioning, thus developing a new environmental remediation platform utilizing nano biocatalysts. GO doping and co-doping with a variety of heterogeneous semiconductor-based metal oxides were included in a brief strategy for boosting GO efficiency. A high band-gap material was also explored as a possibility for immobilization, which shifts the absorption threshold to the visible range and increases photoactivity. For water treatment applications, graphene-based nanomaterials were used in Fenton reactions, photocatalysis, ozonation, photo electrocatalysis, photo-Fenton, and a combination of photon-Fenton and photocatalysis. Nanoparticles made from GO improved the efficiency of composite materials when used for their intended applications. As a result of the analysis, prospects and improvements are clear, especially when it comes to scaling up GO-based wastewater treatment technologies.

Effect of Triclosan and Silver Nanoparticles on DNA Damage Investigated with DNA-Based Biosensor

Triclosan (TCS) is a broad-spectrum antimicrobial agent widely used in personal care, healthcare, and clinical practice. One of the most important aspects of toxicological profiling of compounds is their interaction with DNA. In human cells, TCS causes a significant reduction in DNA methylation. The involvement of TCS in chromosomal aberrations, DNA damage, and strand breaks, as well as DNA damage from TCS degradation products, was reported. AgNPs share similarities with TCS in terms of antimicrobial properties, enter the body after exposure, and are used even together with TCS in oral care products. Therefore, their mutual effect on the DNA is of interest. In this study, the electrochemical behavior of TCS on a glassy carbon electrode (GCE) and the biosensor with salmon sperm dsDNA (DNA/GCE), DNA damage by TCS present in phosphate buffer solution pH 7.4 and an additional effect of the immobilized AgNP layer on such DNA damage have been investigated. Two different sizes of AgNPs (about 15 and 37 nm) were tested. Using square-wave voltammetric signals of nucleobases, the portion of survived DNA was 64% in the presence of 15 nm AgNPs compared to 55% in its absence. The protective effect of AgNPs on DNA against TCS-induced DNA damage was found.

Polyoxometalate Functionalized Sensors: A Review

Polyoxometalates (POMs) are a class of metal oxide complexes with a large structural diversity. Effective control of the final chemical and physical properties of POMs could be provided by fine-tuning chemical modifications, such as the inclusion of other metals or non-metal ions. In addition, the nature and type of the counterion can also impact POM properties, like solubility. Besides, POMs may combine with carbon materials as graphene oxide, reduced graphene oxide or carbon nanotubes to enhance electronic conductivity, with noble metal nanoparticles to increase catalytic and functional sites, be introduced into metal-organic frameworks to increase surface area and expose more active sites, and embedded into conducting polymers. The possibility to design POMs to match properties adequate for specific sensing applications turns them into highly desirable chemicals for sensor sensitive layers. This review intends to provide an overview of POM structures used in sensors (electrochemical, optical, and piezoelectric), highlighting their main functional features. Furthermore, this review aims to summarize the reported applications of POMs in sensors for detecting and determining analytes in different matrices, many of them with biochemical and clinical relevance, along with analytical figures of merit and main virtues and problems of such devices. Special emphasis is given to the stability of POMs sensitive layers, detection limits, selectivity, the pH working range and throughput.

Sensitive and selective determination of triclosan using visual spectroscopy

Triclosan is a commonly used biocide effective against bacterial and fungal infections. However, its overuse in pharmaceutical and personal care products has resulted in its abundance in the natural environment. The detection of triclosan by visual spectroscopy can be carried out using the azo-coupling reaction of diazonium complexes. However, the reaction is also common to other phenolic compounds and aromatic amines, posing significant challenge. In this work, we investigate the azo-coupling reaction of triclosan and several commonly occurring analogous compounds to develop an improved spectroscopic method for the selective determination of triclosan without interference. We find that the azo-coupling reaction between the diazotized derivative and the phenolic compounds is highly dependent on the pH of the reaction media. At pH 7.2, the absorbance of the azo dye product of triclosan shows a peak at 452 nm which has minimal interference from other phenolic azo-dye products with the exception of naphthol. Naphthol shows an interference corresponding to 58% of the analytical signal of equimolar triclosan concentration. To overcome this, we develop an analytical model for the simultaneous determination of triclosan and naphthol from mixed solutions of the compounds. A linear calibration plot from 1.7 to 34 µM was obtained for both triclosan and naphthol with limit-of-detection (LOD) of 0.62 µM and 1.03 µM respectively. The developed protocol was tested for the analysis of water samples collected from various environmental sources spiked with different concentrations of triclosan and naphthol. The samples were enriched by solid-phase-extraction which allowed a 50-fold enhancement in detection of triclosan. The average relative recovery of triclosan in real samples was found to be 98.6% .

In situ monitoring of triclosan in environmental water with subnanomolar detection limits using eco-friendly electrochemical sensors modified with cyclodextrins

The environmental emergence of unexpected contaminants has gained the attention of the scientific community. A broad spectrum antimicrobial compound named triclosan (TCS) was detected in the environment as an emerging contaminant. Owing to its inherent toxicity, we have proposed eco-friendly potentiometric liquid state sensors to be used for monitoring and quantifying TCS in environmental water samples. The proposed sensors have been optimized by modifying the inner filling solution using hydrophilic 2-hydroxypropyl β-cyclodextrin as a complexing agent to be capable of minimizing the trans-membrane ion flux and hence improving the selective and sensitive determination of TCS in environmental matrices with low LOD values. The obtained linear response of the optimized sensor was (1 × 10^-9 to 1 × 10^-5 M) compared to the control sensor (1 × 10^-8 to 1 × 10^-4 M). The obtained limit of detection (LOD) value was found to be 9.86 × 10^-10 M compared to 9.78 × 10^-9 M of the control sensor. The modification of the inner filling solution of the sensor with 2-hydroxypropyl β-cyclodextrin improves not only its sensitivity but also its response time to be only 5 seconds. The electrical performance of the proposed sensor was evaluated following IUPAC recommendations. Both the pH and temperature effects were studied and optimized. Two different greenness assessment tools, Analytical Eco-scale and Green Procedure Index, were adopted upon the evaluation of the proposed sensors' greenness.

Plant-Based Natural Dye-Stimulated Visible-Light Reduction of GO and Physicochemical Factors Influencing the Production of Oxidizing Species by a Synthesized (rGO)/TiO2 Nanocomposite for Environmental Remediation

Here, we report our findings related to the structural and photocatalytic considerations that influence the speed of electron-hole separation in semiconductor photocatalysis in the presence of reduced graphene oxide. A comparison of the exterior properties required for the degradation of the dye methylene blue and drug amoxicillin (C₁₆H₁₉N₃O₅S) as a probe by the synthesized photocatalyst reduced graphene oxide (rGO)/TiO₂ nanowire with graphene oxide and reduced graphene oxide; TiO₂ alone reveals that TiO₂ is significantly influenced by three factors: (1) rGO interactions with TiO₂ in terms of electron and hole transfer, (2) mode of reduction strategies adopted for reducing graphene oxide, and (3) production of OH^• by the catalyst used. This work provides a thorough insight into the smooth, encouraging, and environment-friendly way developed for synthesizing reduced graphene oxide (rGO). The indigo dye-stimulated visible-light reduction methodology not only gives us an easy light-assisted reduction technique but also leads to new ways to get photoactive carbon-based titania semiconductor nanocomposites. Inspired by advances taking place in materials science as well as nanotechnology, we sought to develop improved photocatalytic materials by modifications to anatase TiO₂ through which opportunities to improve the performance of photocatalytic pollutant treatment may emerge.

The electrochemical immunosensor for detection of prostatic specific antigen using quince seed mucilage-GNPs-SNPs as a green composite

Prostatic specific antigen (PSA) is known as a biomarker of prostate cancer. In males, prostate cancer is ranked second as leading cause of death out of more than 200 different cancer types1. As a result, early detection of cancer can cause a significant reduction in mortality. PSA concentration directly is related to prostate cancer, so normal serum concentrations in healthy means are 4 ng and above 10 ng as abnormal concentration. Therefore, PSA determination is important to cancer progression. In this study, a free label electrochemical immunosensor was prepared based on a new green platform for the quantitative detection of the PSA. The used platform was formed from quince seed mucilage containing green gold and silver nanoparticles and synthesized by the green method (using Calendula officinalis L. extract). The quince mucilage biopolymer was used as a sub layer to assemble nanoparticles and increase the electrochemical performance. This nanocomposite was used to increase the antibody loading and accelerate the electron transfer, which can increase the biosensor sensitivity. The antibodies of the PSA biomarker were successfully incubated on the green platform. Under the optimal conditions, the electrochemical impedance spectroscopy (EIS) was proportional to the PSA biomarker concentration from 0.1 pg mL^-1 to 100 ng mL^-1 with low limit of detection (0.078 pg mL^-1). The proposed green immunosensor exhibited high stability and reproducibility, which can be used for the quantitative assay of the PSA biomarker in clinical analyses. The results of real sample analysis presented another tool for the PSA biomarker detection in physiologic models.

Polyoxometalates in Analytical Sciences

Polyoxometalates (POMs) have been used for spectrophotometric determinations of silicon and phosphorus under acidic conditions, referred to as the molybdenum yellow method and molybdenum blue method, respectively. Many POMs are redox active and exhibit fascinating but complicated voltammetric responses. These compounds can reversibly accommodate and release many electrons without exhibiting structural changes, implying that POMs can function as excellent mediators and can be applied to sensitive determination methods based on catalytic electrochemical reactions. In addition, some rare-earth-metal-incorporated POMs exhibit fluorescence, which enables sensitive determination by the enhancement and quenching of fluorescence intensities. In this review, various analytical applications of POMs are introduced, mainly focusing on papers published after 2000, except for the molybdenum yellow method and molybdenum blue method.

Confinement of PMo12 in hollow SiO2-PMo12@rGO nanospheres for high-performance lithium storage

High-performance lithium storage was achieved by the confinement of PMo12 in hollow SiO2-PMo12@rGO nanocomposites.

Nanomaterial-based electrochemical sensors and biosensors for the detection of pharmaceutical compounds

The surging growth of the pharmaceutical industry is a result of the rapidly increasing human population, which has inevitably led to new biomedical and environmental issues. Aside from the quality control of pharmaceutical production and drug delivery, there is an urgent need for precise, sensitive, portable, and cost-effective technologies to track patient overdosing and to monitor ambient water sources and wastewater for pharmaceutical pollutants. The development of advanced nanomaterial-based electrochemical sensors and biosensors for the detection of pharmaceutical compounds has garnered immense attention due to their advantages, such as high sensitivity and selectivity, real-time monitoring, and ease of use. This review article surveys state-of-the-art nanomaterials-based electrochemical sensors and biosensors for the detection and quantification of six classes of significant pharmaceutical compounds, including anti-inflammatory, anti-depressant, anti-bacterial, anti-viral, anti-fungal, and anti-cancer drugs. Important factors such as sensor/analyte interactions, design rationale, fabrication, characterization, sensitivity, and selectivity are discussed. Strategies for the development of high-performance electrochemical sensors and biosensors tailored toward specific pharmaceuticals are highlighted to provide readers and scientists with an extensive toolbox for the detection of a wide range of pharmaceuticals. Our aims are two-fold: (i) to inspire readers by further elucidating the properties and functionalities of existing nanomaterials for the detection of pharmaceuticals; and (ii) to provide examples of the potential opportunities that these devices have for the advanced sensing of pharmaceutical compounds toward safeguarding human health and ecosystems on a global scale.

Polydopamine/graphene/MnO2 composite-based electrochemical sensor for in situ determination of free tryptophan in plants

The in vivo detection of small active molecules in plant tissues is essential for the development of precision agriculture. Tryptophan (Trp) is an important precursor material for auxin biosynthesis in plants, and the detection of Trp levels in plants is critical for regulating the plant growth process. In this study, an electrochemical plant sensor was fabricated by electrochemically depositing a polydopamine (PDA)/reduced graphene oxide (RGO)-MnO₂ nanocomposite onto a glassy carbon electrode (GCE). PDA/RGO-MnO₂/GCE exhibited high electrocatalytic activity for the oxidation of Trp owing to the combined selectivity of PDA and catalytic activity of RGO-MnO₂. To address the pH variability of plants, a reliable Trp detection program was proposed for selecting an appropriate quantitative detection model for the pH of the plant or plant tissue of interest. Therefore, a series of linear regression curves was constructed in the pH range of 4.0-7.0 using the PDA/RGO-MnO₂/GCE-based sensor. In this pH range, the linear detection range of Trp was 1-300 μM, the sensitivity was 0.39-1.66 μA μM^-1, and the detection limit was 0.22-0.39 μM. Moreover, the practical applicability of the PDA/RGO-MnO₂/GCE-based sensor was successfully demonstrated by determining Trp in tomato fruit and juice. This sensor stably and reliably detected Trp levels in tomatoes in vitro and in vivo, demonstrating the feasibility of this research strategy for the development of electrochemical sensors for measurements in various plant tissues.

Non-enzymatic sensor for determination of glucose based on PtNi nanoparticles decorated graphene

Diabetes has become a universal epidemic in recent years. Herein, the monitoring of glucose in blood is of importance in clinical applications. In this work, PtNi alloy nanoparticles homogeneously dispersed on graphene (PtNi alloy-graphene) was synthesized as a highly effective electrode material for glucose detection. Based on the modified PtNi alloy-graphene/glass carbon (PtNi alloy-graphene/GC) electrode, it is found that the PtNi alloy-graphene/GC electrode exhibited excellent electrocatalytic performance on glucose oxidation. Furthermore, the results from amperometric current–time curve show a good linear range of 0.5–15 mM with the limit of detection of 16 uM (S/N = 3) and a high sensitivity of 24.03 uAmM⁻¹ cm⁻². On account of the good selectivity and durability, the modified electrode was successfully applied on glucose detection in blood serum samples.

Fabrication of bacteriochlorin shell/gold core nanoparticles for the sensitive determination of trichlosan using differential pulse voltammetry

The triclosan contamination in daily life has attracted great attention, and there is rare electroanalytical assay based on π-system dyes. In this work, a facile preparation and electroanalytical application of an organic dispersion containing bacteriochlorin dyes (LS11) and gold nanoparticles (AuNPs) was proposed. The organic-inorganic hybrid nanocomposites were characterized by transmission electron microscope (TEM) showing a core-shell structure with a uniform layer of dye molecules. The as-prepared nanocomposites were successfully coated onto glassy carbon electrodes, and the surface characteristics of the top most layer of the modified electrodes were examined by atomic force microscopy (AFM), field emission scanning electron microscopy (FE-SEM) and water contact angle experiments. The nanocomposite film-modified electrodes exhibited good electrochemical activity towards oxidation of triclosan. The oxidation of adsorbed triclosan occurred at a reduced overpotential, and the anodic current responses under a pre-concentration step prior to the potential scan were used for quantitative analysis. A good linear relationship from 0.01 μM to 0.5 μM was obtained using differential pulse voltammetry. The sensitivity and detection limit (S/N = 3) were 23.69 μA μM^-1 and 0.03 μM, respectively. The proposed assay was applied to detect triclosan in two personal hygiene products using standard addition method, and the results showed good recoveries that ranged from 96.6% to 101.5% and from 99.3% to 103.8% for a toothpaste sample and a hand wash sample, respectively. A reference HPLC-UV method was used to evaluate the proposed electroanalytical method, and a good agreement was achieved.

Binding of Leishmania spp with gold nanoparticles supported polyethylene glycol and its application for the sensitive detection of infectious photogenes in human plasma samples: A novel biosensor

The management of pathogen detection using a rapid and cost-effective method presents a major challenge to the biological safety of the world. The field of pathogen detection is nascent and therefore, faces a dynamic set of challenges as the field evolves. Visceral leishmaniasis (VL), or kala-azar is the most severe form of leishmaniasis. Delay to the accurate diagnosis and treatment is likely to lead to fatality. The reliable, fast and sensitive detection is closely linked to safe and effective treatment of Leishmania spp. Despite several routine and old method for sensitive and specificity detection of Leishmania spp, there is highly demand for developing modern and powerfully system. In this study a novel ultra-sensitive DNA-based biosensor was prepared for detection of Leishmania spp. For the first time, the specific and thiolated sequences of the Leishmania spp genome (5'-SH-[CH2 ]6 ATCTCGTAAGCAGATCGCTGTGTCAC-3') were recognized by electrochemical methods. Also, selectivity of the proposed bioassay was examined by three sequences that were mismatched in 1, 2, and 3 nucleotides. The linear range (10-6 to 10-21 M) and limit of detection (LLOQ = 1 ZM) obtained are remarkable in this study. Also, simple and cost-effective construction of genosensors was another advantage of the proposal DNA-based assay. The experimental results promise a fast and simple method in detection of kala-azar patients with huge potential of the nanocomposite-based probe for development of ideal biosensors.

Synthesis, characterization and anticancer activity in vitro evaluation of novel dicyanoaurate (I)-based complexes

Molecular structures containing gold, such as auranofin, have been extensively studied in the diagnosis and treatment of many diseases, including cancer treatment. The pharmacological properties of the newly synthesized unique gold-ligand structures have been reported for different cancer cell lines. However, findings on bishydeten-metal salt complexes with gold are rare. In this work, the synthesis of five novel cyanide-bridged coordination compounds having the closed formulae [Ni(bishydeten)][Au(CN)₂]₂ (1), [Cu(bishydeten)][Au(CN)₂]₂ (2), [Zn(bishydeten)₂Au₃(CN)₄][Au₂(CN)₃] (3), [Cd(bishydeten)_0,5]₂[Au(CN)₂]₄.2H₂O (4), and [Cd(bishydeten)₂][Au(CN)₂]₂ (5) (where bisyhdeten = N,N-bis(2-hydroxyethyl)ethylene diamine), and their characterization by elemental, infrared, ESI-MS, X-ray (for 2) and thermic measurement methods were performed. Complexes 1 and 3 are thermally more stable than the other three complexes. For these, pharmacological adequacies were also tested. The nucleic acid and protein binding affinities of the Au (I) compounds were also estimated by spectroscopic and electrophoretic techniques. Au (I) complexes were identified as strong chemotherapeutic with mild cytotoxicity, and they demonstrated a dose-dependent inhibition on the growth of cancer cells with IC50 at 0.11 to 0.47 μM. Investigation of mechanisms of action on cells revealed that Au (I) compounds managed to inhibit cell migration and led to a decrease in cytoskeletal proteins such as CK7 and CK20. However, Au (I) compounds failed to inhibit DNA topoisomerase I. Overall, and we suggest that potent antiproliferative activity, mild cytotoxicity, good solubility, and micromolar dosage of Au (I) compounds containing bisyhdeten-metal derivatives render them the potential focus of further studies as chemotherapeutic agents.

2D Mesoporous Channels of PMO; a Platform for Cluster-Like Pt Synthesis and Catalytic Activity in Nitrophenol Reduction

Thiourea-bridged organosiloxane is used to synthesize a periodic mesoporous organosilica (PMO). Since this PMO has an S-enriched surface, owing to thiourea functional groups, it exhibits strong coordination toward Pt ions, and it shows a high tunability in the Pt nanoparticles size. This hybrid mesoporous material is employed as a catalyst in the efficient reduction reaction of 4-nitrophenol to 4-aminophenol at room temperature in an aqueous media.

An electrochemical sensor based on chitosan capped with gold nanoparticles combined with a voltammetric electronic tongue for quantitative aspirin detection in human physiological fluids and tablets

Inflammatory diseases increase has recently sparked the research interest for drugs diagnostic tools development. At therapeutic doses, acetylsalicylic acid (ASA or aspirin) is widely used for these diseases' treatment. ASA overdoses can however give rise to adverse side effects including ulcers, gastric damage. Hence, development of simple, portable and sensitive methods for ASA detection is desirable. This paper reports aspirin analysis in urine, saliva and pharmaceutical tablet using an electrochemical sensor and a voltammetric electronic tongue (VE-Tongue). The electrochemical sensor was fabricated by self-assembling chitosan capped with gold nanoparticles (Cs + AuNPs) on a screen-printed carbon electrode (SPCE). It exhibits a logarithmic-linear relationship between its response and the ASA concentration in the range between 1 pg/mL and 1 μg/mL. A low detection limit (0.03 pg/mL), good selectivity against phenol and benzoic acid interference, and successful practical application were demonstrated. Qualitative analysis was performed using the VE-Tongue based unmodified metal electrodes combined with two chemometric approaches to classify urine samples spiked with different aspirin concentrations. Partial least squares (PLS) method provided prediction models obtained from the data of both devices with a regression correlation coefficient R² = 0.99. Correspondingly, the SPCE/(Cs + AuNPs) electrochemical sensor and VE-Tongue could be viable tools for biological analysis of drugs.

Perspective on chymotrypsin detection

Chymotrypsin is one of the most extensively known proteases participating in the pathogenesis of various diseases, which can be used in drug discovery and clinical diagnosis.

Simultaneous recognition of cysteine and cytosine using thiophene-based organic nanoparticles decorated with Au NPs and bio-imaging of cells

Biomolecules like cysteine and cytosine play a significant role in many physiological processes, and their unusual level in biological systems can lead to many diseases including cancer. Indeed, the need for selective detection of these moieties by a fluorescence probe is imperative. Thus, thiophene based Schiff N,N'-bis(thiophene-2-ylmethylene)thiophenemethane (BMTM) was synthesized and then characterized using several analytical techniques before converting it into organic nanoparticles (ONPs). Then, fluorescent organic inorganic nanohybrids (FONs) were obtained after decorating ONPs with AuNPs to yield BMTM-Au-ONPs (FONPs). The morphology of the particles, analyzed using a Transmission Electron Microscope (TEM), shows that AuNPs were embedded with low density organic matter (ONPs). FONPs were employed to recognize cysteine and cytosine simultaneously. No interference was observed from other moieties such as guanine, uracyl, NADH, NAD, ATP, and adenine during the detection. It means that the intensity of the fluorescence signal was significantly changed (enhanced for cytosine and quenched for cysteine). So, FONPs were used to detect cysteine and cytosine in real samples, like Saccharomyces cerevisiae cells. As expected, no considerable fluorescence signal for cysteine was observed, while for cytosine, strong fluorescence signals were detected in the cells. DFT was used to explain the interaction of FONPs with cysteine or cytosine.

Carbon Paste Modified Electrode as Powerful Sensor Approach Determination of Food Contaminants, Drug Ingredients, and Environmental Pollutants: A Review

Background:

Application of electrochemical sensors for analysis of food, biological and water polluting compounds helps to speed up their analysis in the real samples. Electrochemical sensors with low cost, fast response and portable ability are a better choice compared to traditional methods for analysis of electro-active compounds such as HPLC. Therefore, in recent years, many analytical scientists have suggested this type of analytical method for analysis of food, biological compounds and water pollutants.

Objective:

Due to low cost, easy modification and low non-faradic current, the carbon paste electrode is a suitable choice as a working electrode in the electrochemical and especially voltammetric analysis. On the other hand, modification of carbon paste electrode can improve the quality of the sensor for the analysis of electroactive compounds at nanomolar level.

Electroanalysis of Catecholamine Drugs using Graphene Modified Electrodes

Background:

Catecholamine drugs are a family of electroactive pharmaceutics, which are widely analyzed through electrochemical methods. However, for low level online determination and monitoring of these compounds, which is very important for clinical and biological studies, modified electrodes having high signal to noise ratios are needed. Numerous materials including nanomaterials have been widely used as electrode modifies for these families during the years. Among them, graphene and its family, due to their remarkable properties in electrochemistry, were extensively used in modification of electrochemical sensors.

Objective:

In this review, working electrodes which have been modified with graphene and its derivatives and applied for electroanalyses of some important catecholamine drugs are considered.

Fluorescence Optosensing of Triclosan by Upconversion Nanoparticles with Potassium Permanganate

It is greatly significant to develop a simple and rapid sensing method for triclosan (TCS) because it is a widely used and a chronically toxic compound that adversely affects biological organisms and human health. This paper presents the design and development of a novel simple optosensor that uses carboxylic group-functionalized NaYF₄:Yb³⁺/Er³⁺ upconversion nanoparticles (UCNPs) coated with potassium permanganate (KMnO₄). The sensor enables the rapid, non-autofluorescence, sensitive, and selective detection of TCS based on the "turn off-on fluorescence" technique through fluorescence resonance energy transfer. Under an near-infrared radiation excitation (980 nm), the "turn-off fluorescence" process involves the transfer of fluorescence resonance energy between the UCNPs and KMnO₄, whereas the "turn-on fluorescence" process occurs when KMnO₄ is reduced in the presence of TCS. TCS was detected by recovering the green emission of UCNPs. Under optimized conditions, the resulting sensor offered an excellent response to TCS with 0.2 μM of a limit of detection. The developed sensor showed higher selectivity to TCS than other phenolic compounds. Moreover, the analytical performance of the proposed probe was practically demonstrated to successfully monitor trace levels of TCS in samples of tap water and personal care products. The developed simple and sensitive method may offer a new approach for determining TCS in environmental applications.

Simultaneous Colorimetric Detection of a Variety of Salmonella spp. in Food and Environmental Samples by Optical Biosensing Using Oligonucleotide-Gold Nanoparticles

Optical biosensors for rapid detection of significant foodborne pathogens are steadily gaining popularity due to its simplicity and sensitivity. While nanomaterials such as gold nanoparticles (AuNPs) are commonly used as signal amplifiers for optical biosensors, AuNPs can also be utilized as a robust biosensing platform. Many reported optical biosensors were designed for individual pathogen detection in a single assay and have high detection limit (DL). Salmonella spp. is one of the major causative agents of foodborne sickness, hospitalization and deaths. Unfortunately, there are around 2,000 serotypes of Salmonella worldwide, and rapid and simultaneous detection of multiple strains in a single assay is lacking. In this study, a comprehensive and highly sensitive simultaneous colorimetric detection of nineteen (19) environmental and outbreak Salmonella spp. strains was achieved by a novel optical biosensing platform using oligonucleotide-functionalized AuNPs. A pair of newly designed single stranded oligonucleotides (30-mer) was displayed onto the surface of AuNPs (13 nm) as detection probes to hybridize with a conserved genomic region (192-bases) of ttrRSBCA found on a broad range of Salmonella spp. strains. The sandwich hybridization (30 min, 55°C) resulted in a structural formation of highly stable oligonucleotide/AuNPs-DNA complexes which remained undisturbed even after subjecting to an increased salt concentration (2 M, final), thus allowing a direct discrimination via color change of target (red color) from non-target (purplish-blue color) reaction mixtures by direct observation using the naked eye. In food matrices (blueberries and chicken meat), nineteen different Salmonella spp. strains were concentrated using immunomagnetic separation and then simultaneously detected in a 96-well microplate by oligonucleotide-functionalized AuNPs after DNA preparation. Successful oligonucleotide/AuNPs-DNA hybridization was confirmed by gel electrophoresis while AuNPs aggregation in non-target and control reaction mixtures was verified by both spectrophotometric analysis and TEM images. Results showed that the optical AuNP biosensing platform can simultaneously screen nineteen (19) viable Salmonella spp. strains tested with 100% specificity and a superior detection limit of <10 CFU/mL or g for both pure culture and complex matrices setups. The highly sensitive colorimetric detection system can significantly improve the screening and detection of viable Salmonella spp. strains present in complex food and environmental matrices, therefore reducing the risks of contamination and incidence of foodborne diseases.

Electrochemical sensor based on molecularly imprinted polymer for sensitive triclosan detection in wastewater and mineral water

Triclosan (TCS) is a topical antiseptic widely used in different cosmetic products. It is also a common additive in many antimicrobial household consumables. Over a certain concentration, it becomes risky for human and environmental health. This work describes the development of an electrochemical sensor based on molecularly imprinted polymer (MIP), assembled on screen-printed gold electrode (Au-SPE), dedicated to the TCS detection in environmental water sources. To achieve this goal, an acrylamide/bisacrylamide solution was polymerized after linking TCS with the carboxylic polyvinyl chloride (PVC-COOH) layer onto the Au-SPE. The sensor device fabrication and its retention capabilities were characterized through cyclic voltammetry (CV), differential pulse voltammetry (DPV), electrochemical impedance spectroscopy (EIS), atomic force microscopy (AFM) and Fourier transform infrared (FTIR) spectroscopy. As control experiment, negligible responses were obtained during the non-imprinted polymer (NIP) test. The sensor could effectively detect TCS avoiding interferences of structural similar substances like 2,4,6-trichlorophenol and catechol. Under optimal conditions, the sensor responses were found logarithmic in the concentration range from 0.1 to 1000 pg mL^-1. Indeed, compared with reported works, this sensor exhibits lower detection limit (LOD) and quantification limit (LOQ) of 0.23 and 0.78 pg mL^-1, respectively. The developed sensor was effectively applied to wastewater samples for TCS detection and displayed satisfactory performances. Moreover, the different wastewater samples, regarding their TCS contents, were correctly classified by using principal component analysis (PCA) technique. Correspondingly, this work has demonstrated a cheap, simple and effective sensing platform for TCS detection thus making it a promising tool for future evolution of accurate and reliable environmental analysis.