Conducting polymer and multi-walled carbon nanotubes nanocomposites based amperometric biosensor for detection of organophosphate

Ultrasensitive detection of holoTC for analysis of Vitamin B12 levels using Ag2MoO4 deposited PEDOT sensing platform

Vitamin B12 is an essential micronutrient required for the proper functioning of the human body. Vitamin B12 deficiency is primarily causative of various neurolological disorders alongwith recurrence of oral ulcers and burning sensations which are early signs of condition such as pernicious anemia. Other complications associated with Vitamin B12 deficiency include risk of heart failure due to anemia, risk of developing autoimmune disorders and gastric cancer. Therefore, to obstruct these communal health issues, early detection of Vit B12 is highly needed. However, screening of vitamin B12 insufficiency is hindered by the low sensitivity of the conventional vitamin B12 test. Holotranscobalamin (holoTC) is an early indicator of the negative vitamin B12 balance as it is the first protein to decline in the serum. We report a novel impedimetric immunosensor based on flower-like poly (3,4-ethylenedioxythiophene) (PEDOT) nanostructural film impregnated with silver molybdate nanoparticles (Ag2MoO₄ NPs) deposited on fluorine-doped tin oxide electrode. The prepared electrodes were characterized by Field emission scanning electron microscopy (FE-SEM) with energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), and electrochemical studies. The activated anti-holoTC antibody was immobilized and optimized to capture the target in a response time of 15 min. The electrochemical performance of the sensor was carried out by using the electrochemical impedance spectroscopy technique (EIS) and a good linear relationship between ΔRct and holoTC was obtained in the range from 0.1 pg mL-1 to 100 ng mL-1 with a detection limit of 0.093 pg mL-1. The proposed sensor was successfully applied in human serum samples for holoTC detection. The experimental results showed that the immunosensor is highly selective towards holoTC and presented an acceptable stability of 20 days with reproducibility RSD ≤4%. To the best of our knowledge, this is the first developed electrochemical immunosensor for holoTC detection.

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.

Soy protein isolate/kappa-carrageenan/cellulose nanofibrils composite film incorporated with zenian essential oil-loaded MOFs for food packaging

Edible films applied in food packaging must possess excellent inhibitory and mechanical properties. Protein-based films exhibit a high capacity for film formation and offer good gas barrier properties. However, they have weak mechanical and water barrier characteristics. The objective of this research was to develop active composite films based on reinforced soy protein isolate (SPI)/Kappa-carrageenan (K) with varying concentrations of bacterial cellulose nanofibrils (BCN). Increasing the BCN concentration improved the morphological, structural, mechanical, water vapor barrier, and moisture content properties. In comparison to the pure SPI film (S), the film with a high BCN concentration demonstrated a significant decrease in WS (22.98 ± 0.78 %), MC (21.72 ± 0.68 %), WVP (1.22 ± 0.14 g mm-1 S-1 Pa-1 10-10), and EAB (57.77 ± 5.25 %) properties. It should be emphasized that there was no significant alteration in the physicomechanical properties of the optimal film (SKB0.75) containing Zenian-loaded metal-organic frameworks (ZM). However, it substantially enhanced the thermal stability of this film, which can be attributed to the strong interfacial interactions between polymer chains and ZM. Furthermore, the ZM films inhibited the growth of pathogenic bacteria and increased the DPPH antioxidant activity. Thus, SKB0.75-ZM2 films can be utilized as practical components in food packaging.

A Novel Electrochemical Biosensor Based on Polyaniline-Embedded Copper Oxide Nanoparticles for High-Sensitive Paraoxon-Ethyl (PE) Detection

This paper proposes a fabrication of a hyper-sensitive amperometric biosensor for paraoxon-ethyl (PE) detection. In this developed biosensor, polyaniline (PANI) and copper oxide (CuO)-based nanocomposite is used as a sensing platform. The homogeneous distribution of CuO onto the PANI matrix enhances the surface area and conductivity of the nanocomposite. Additionally, the PANI produces a compatible environment for enzyme immobilization, which further enhances the rate of electron transfer. For biosensor fabrication, the nanocomposite is deposited electrophoretically onto the ITO glass substrate and immobilization of acetylcholinesterase (AChE) enzyme is conducted onto the fabricated electrode surface. The results validate good reproducibility, good stability, and high selectivity of the fabricated biosensor (AChE/PANI@CuO/ITO). The inhibition rate of paraoxon-ethyl (PE) is recorded in the concentration range of 1-200 nM with a low limit of detection of 0.096 nM or 96 pM. The sensitivity of the developed biosensor is found to be 49.86 µA(nM)^-1. The developed biosensor is further successfully accomplished for the detection of PE in real samples like rice and pulse.

Citrate and glutathione capped gold nanoparticles for electrochemical immunosensing of atrazine: Effect of conjugation chemistry

Recently, the exposure of pesticides/herbicides to the living organisms is increased especially due to agricultural malpractices and industrial processes. In particular, the exposure of pesticides/herbicides (e.g., atrazine) can impart several harsh effects on the human health. The development of efficient detection systems can be crucial in monitoring the atrazine in water and food/plant products, which can be decisive in controlling the deadly exposures of atrazine. Herein, we have developed electrochemical immunosensors for atrazine by employing monoclonal anti-atrazine antibody conjugated gold nanoparticles. Two types of gold nanoparticles (i.e., citrate and glutathione (GSH)-capped AuNPs) were used to modify gold working electrode and utilized for the development of atrazine immunosensors. The conjugation of immunoprobe on working electrode was especially designed to obtain stable and efficient sensing signals. The nanosensing immunoprobes fabricated using citrate-AuNPs and GSH-AuNPs exhibited comparable responses for a wide linear working range of 50 ng/L- 30 μg/L with limit of detection (LOD) values of 0.08 and 0.06 ng/L for atrazine, respectively.

Recent Advances in Nanomaterial-Based Biosensors for Pesticide Detection in Foods

Biosensors are a simple, low-cost, and reliable way to detect pesticides in food matrices to ensure consumer food safety. This systematic review lists which nanomaterials, biorecognition materials, transduction methods, pesticides, and foods have recently been studied with biosensors associated with analytical performance. A systematic search was performed in the Scopus (n = 388), Web of Science (n = 790), and Science Direct (n = 181) databases over the period 2016–2021. After checking the eligibility criteria, 57 articles were considered in this study. The most common use of nanomaterials (NMs) in these selected studies is noble metals in isolation, such as gold and silver, with 8.47% and 6.68%, respectively, followed by carbon-based NMs, with 20.34%, and nanohybrids, with 47.45%, which combine two or more NMs, uniting unique properties of each material involved, especially the noble metals. Regarding the types of transducers, the most used were electrochemical, fluorescent, and colorimetric, representing 71.18%, 13.55%, and 8.47%, respectively. The sensitivity of the biosensor is directly connected to the choice of NM and transducer. All biosensors developed in the selected investigations had a limit of detection (LODs) lower than the Codex Alimentarius maximum residue limit and were efficient in detecting pesticides in food. The pesticides malathion, chlorpyrifos, and paraoxon have received the greatest attention for their effects on various food matrices, primarily fruits, vegetables, and their derivatives. Finally, we discuss studies that used biosensor detection systems devices and those that could detect multi-residues in the field as a low-cost and rapid technique, particularly in areas with limited resources.

Recent developments in conducting polymers: applications for electrochemistry

Scientists have categorized conductive polymers as materials having strongly reversible redox behavior and uncommon combined features of plastics and metal. Because of their multifunctional characteristics, e.g., simplistic synthesis, acceptable environmental stability, beneficial optical, electronic, and mechanical features, researchers have largely considered them for diverse applications. Therefore, their capability of catalyzing several electrode reactions has been introduced as one of their significant features. A thin layer of the conducting polymer deposited on the substrate electrode surface can augment the electrode process kinetics of several solution species. Such electrocatalytic procedures with modified conducting polymer electrodes can create beneficial utilization in diverse fields of applied electrochemistry. This review article explores typical recent applications of conductive polymers (2016–2020) as active electrode materials for energy storage applications, electrochemical sensing, and conversion fields such as electrochemical supercapacitors, lithium-ion batteries, fuel cells, and solar cells.

Scientists have categorized conductive polymers as materials having strongly reversible redox behavior and uncommon combined features of plastics and metal.

Monocrotophos detection with a bienzyme biosensor based on ionic-liquid-modified carbon nanotubes

Acetylcholinesterase (AChE) biosensor technology is widely applied in the detection of organophosphate pesticides in agricultural production via the inhibition of AChE activity by organophosphates. However, the AChE electrode has some drawbacks, such as low stability and high overpotential. Combining the advantages of multiwalled carbon nanotubes (MWCNTs) and ionic liquids, we constructed a novel bienzyme electrode [Cl/iron porphyrin (FePP)-modified MWCNTs/AChE/glassy carbon electrode], which included AChE and mimetic oxidase FePP. In this electrode, FePP is covalently bound to the AChE carrier via ionic liquid for increased electrode sensitivity and stability. Under optimal conditions, this novel biosensor has a monocrotophos detection limit of 3.2 × 10-11 mol/L and good recovery of 89-104%. After 5 weeks of storage at 4 °C, the oxidation current was 97.8% of its original value. The biosensor has high stability and sensitivity for monocrotophos detection and is a promising device for monitoring food safety. Graphical abstract The complete synthesis process of Cl/FePP-MWCNTs/AChE/GCE.

Recent Developments in Enzyme, DNA and Immuno-Based Biosensors

Novel sensitive, rapid and economical biosensors are being developed in a wide range of medical environmental and food applications. In this paper, we review some of the main advances in the field over the past few years by discussing recent studies from literature. A biosensor, which is defined as an analytical device consisting of a biomolecule, a transducer and an output system, can be categorized according to the type of the incorporated biomolecule. The biomolecules can be enzymes, antibodies, ssDNA, organelles, cells etc. The main biosensor categories classified according to the biomolecules are enzymatic biosensors, immunosensors and DNA-based biosensors. These sensors can measure analytes produced or reduced during reactions at lower costs compared to the conventional detection techniques. Numerous types of biosensor studies conducted over the last decade have been explored here to reveal their key applications in medical, environmental and food industries which provide comprehensive perspective to the readers. Overviews of the working principles and applications of the reviewed sensors are also summarized.

Soluble soybean polysaccharide/TiO2 bionanocomposite film for food application

In the current study, a set of biodegradable soybean polysaccharide (SSPS) nanocomposites containing different ratios of TiO2 nanoparticles was characterized as new packaging system. X-ray diffraction (XRD) measurement showed that the crystalline structure of the TiO2 nanoparticles remained intact in the polysaccharide matrix and the surface of nanocomposites containing 1-3% TiO2 was observed morphologically uniform under scanning electron microscopy (SEM). Dynamic mechanical thermal analysis revealed that the magnitude of storage modulus was 3.62-fold higher in SPSS/TiO2 nanocomposites containing 7 wt.% of TiO2 than control SSPS indicating improvement in the physical properties of the film supposed to be utilized for food packaging. With respect to the concern over the safety of these nanocomposites, inductively coupled plasma-optical emission spectroscopy (ICP-OES) showed that no TiO2 was detected in bread samples covered by SSPS/TiO2 film and stored for 6 months. Similarly, the nanocomposite films only released a minuscule amount (21.05 ± 0.054 ppm) of TiO2 in water. TiO2 nanoparticles were found in the plasma membrane of epithelial cell line after long-term exposure (10-day) of these cells to large amounts of the free nanoparticles. SSPS/TiO2 nanocomposites showed excellent antimicrobial activity against Staphylococcus aureus PTCC 1431 (ATCC 25923), while neither anti-cancerous nor pro-cancerous activity was observed for these nanocomposites denoting their neutrality with respect to cancer suppression or progression in gastrointestinal tract. In conclusion, SSPS/TiO2 nanocomposites could be a promising packaging system for food industries' objective regarding their physical characteristics, low rate of Ti transition, and low health risk.

Nanomaterials-based enzyme electrochemical biosensors operating through inhibition for biosensing applications

In recent years great progress has been made in applying nanomaterials to design novel biosensors. Use of nanomaterials offers to biosensing platforms exceptional optical, electronic and magnetic properties. Nanomaterials can increase the surface of the transducing area of the sensors that in turn bring an increase in catalytic behaviors. They have large surface-to-volume ratio, controlled morphology and structure that also favor miniaturization, an interesting advantage when the sample volume is a critical issue. Biosensors have great potential for achieving detect-to-protect devices: devices that can be used in detections of pollutants and other treating compounds/analytes (drugs) protecting citizens' life. After a long term focused scientific and financial efforts/supports biosensors are expected now to fulfill their promise such as being able to perform sampling and analysis of complex samples with interest for clinical or environment fields. Among all types of biosensors, enzymatic biosensors, the most explored biosensing devices, have an interesting property, the inherent inhibition phenomena given the enzyme-substrate complex formation. The exploration of such phenomena is making remarkably important their application as research and applied tools in diagnostics. Different inhibition biosensor systems based on nanomaterials modification has been proposed and applied. The role of nanomaterials in inhibition-based biosensors for the analyses of different groups of drugs as well as contaminants such as pesticides, phenolic compounds and others, are discussed in this review. This deep analysis of inhibition-based biosensors that employ nanomaterials will serve researchers as a guideline for further improvements and approaching of these devices to real sample applications so as to reach society needs and such biosensor market demands.

Chitosan-iron oxide nanocomposite based electrochemical aptasensor for determination of malathion

An electrochemical aptasensor based on chitosan-iron oxide nanocomposite (CHIT-IO) film deposited on fluorine tin Oxide (FTO) was developed for the detection of malathion. Iron oxide nanoparticles were prepared by co-precipitation method and characterized by Transmission electron microscopy and UV-Visible spectroscopy. The biotinylated DNA aptamer sequence specific to the malathion was immobilized onto the iron oxide doped-chitosan/FTO electrode by using streptavidin as linking molecule. Various characterization studies like Field Emission-Scanning Electron Microscopy (FE-SEM), Fourier Transform Infrared Spectroscopy (FT-IR), and Electrochemical studies were performed to attest the successful fabrication of bioelectrodes. Experimental parameters like aptamer concentration, response time, stability of electrode and reusability studies were optimized. Aptamer immobilized chitosan-iron oxide nanocomposite (APT/SA/CHIT-IO/FTO) bioelectrodes exhibited LOD of about 0.001 ng/mL within 15 min and spike-in studies revealed about 80-92% recovery of malathion from the lettuce leaves and soil sample.