Synthesis of Surface Molecularly Imprinted Poly(methacrylic acid-hemin) on Carbon Nanotubes for the Voltammetric Simultaneous Determination of Antioxidants from Lipid Matrices and Biodiesel

Overview and trends in electrochemical sensors, biosensors and cellular antioxidant assays for oxidant and antioxidant determination in food

Screening and quantifying antioxidants from food samples, their antioxidant activity, as well as the assessment of food oxidation is critical, not only for ensuring food quality and safety, but also to understand and relate these parameters to the shelf life, sensory attributes, and health aspects of food products. For this purpose, several methods have been developed and used for decades, which regardless of their effectiveness, present a certain number of drawbacks mainly related to extensive sample preparation and technical complexity, time requirements, and the use of hazardous chemicals. Electrochemical sensors and biosensors are gaining popularity in food analysis due to their high sensitivity, specificity, rapid response times, and potential for miniaturisation and portability. Furthermore, other modern methods using whole living cells such as the cellular antioxidant activity assay, the antioxidant power 1 assay, and the catalase-like assays, may interpret more realistic antioxidant results rather than just reporting the ability to scavenge free radicals in isolated systems with extrapolation to reality. This paper provides an overview of electrochemical sensors, biosensors, and cellular antioxidant assays, and reviews the latest advancements and emerging trends in these techniques for determining oxidants and antioxidants in complex food matrices. The performances of different strategies are described for each of these approaches to provide insights into the extent to which these methods can be exploited in the field and inspire new research to fill the current gaps.

Trends in pulse voltammetric techniques applied to foodstuffs analysis: The food additives detection

Food additives are chemical compounds intentionally added during foodstuff production to control technological functions, such as pH, viscosity, stability (color, flavor, taste, and odor), homogeneity, and loss of nutritional value. These compounds are fundamental in inhibition the degradation process and prolonging the shelf life of foodstuffs. However, their inadequate employment or overconsumption can adversely affect consumers' health with the development of allergies, hematological, autoimmune, and reproductive disorders, as well as the development of some types of cancer. Thus, the development and application of simple, fast, low-cost, sensitivity, and selectivity analytical methods for identifying and quantifying food additives from various chemical classes and in different foodstuffs are fundamental to quality control and ensuring food safety. This review presents trends in the detection of food additives in foodstuffs using differential pulse voltammetry and square wave voltammetry, the main pulse voltammetric techniques, indicating the advantages, drawbacks, and applicability in food analysis. Are discussed the importance of adequate choices of working electrode materials in the improvements of analytical results, allowing reliable, accurate, and inexpensive voltammetric methods for detecting these compounds in foodstuffs samples.

A ratiometric electrochemical sensing strategy based on the self-assembly of Co NC/CNT and methylene blue for effective detection of the food additive tert-butylhydroquinone

It is crucial to achieve accurate and rapid detection of tert-butylhydroquinone (TBHQ) in the field of food safety, for the excessive addition of TBHQ in food is harmful to human health and evil to the environment and aquatic life. Therefore, researchers have done a lot of work on signal amplification through nanomaterials to achieve TBHQ detection, but the conventional single-signal detection strategy results in limited accuracy. In this work, an innovative and facile ratiometric electrochemical sensor for TBHQ detection was built based on advanced nanomaterial complexes carbon nanotube-encapsulated Co/nitrogen-doped carbon (Co NC/CNT) and selected internal reference signal methylene blue (MB) enhancing the accuracy by offering effective self-calibration. A linear relationship between the net peak current ratio between TBHQ and MB (ΔI (TBHQ)/ΔI (MB)) and the TBHQ concentration was obtained under the optimal experimental conditions, with two linear ranges of 0.1-20 μM and 20-100 μM and a limit of detection (LOD) of 0.054 μM (S/N = 3). Benefiting from the synergistic effects between Co NC and CNT and the ratiometric sensing strategy, the as-designed sensor for TBHQ detection showcased excellent selectivity, repeatability, reproducibility, stability, and satisfactory applicability in real edible oil samples.

Development of novel nanocomposite-modified photoelectrochemical sensor based on the association of bismuth vanadate and MWCNT-grafted-molecularly imprinted poly(acrylic acid) for dopamine determination at nanomolar level

This study proposes the development of a new photoelectrochemical (PEC) sensor for the determination of dopamine (DA) at nanomolar levels. The PEC sensor was based on a physical mixture of bismuth vanadate (BiVO4) with nanocomposite molecularly imprinted poly(acrylic acid) (MIP-AA) grafted onto MWCNTox by using the surface-controlled radical polymerization strategy with an INIFERTER reagent. XRD, diffuse reflectance spectroscopy (DRE), SEM, TEM, and TGA were employed to characterize the materials. Photoelectrochemical analyses were carried out with GCE/BiVO4/MIP-AA sensor under visible light using a potential of 0.6 V, phosphate buffer (0.1 mol L-1) at pH 7.0, and modifying the GCE with a film composed of monoclinic BiVO4 at 3.5 mg mL-1 and nanocomposite MIP prepared with acrylic acid (MIP-AA) at 0.1 mg mL-1. The proposed method using the GCE/BiVO4/MIP-AA sensor presented a limit of detection (LOD) of 2.9 nmol L-1, a linear range from 9.7 to 150 nmol L-1 and it was successfully applied for analysis of DA in urine samples using external calibration curve yielding recovery values of 90-105%. Additionally, the proposed PEC sensor allowed DA determination without interference from uric acid, ascorbic acid, epinephrine, norepinephrine, and other unwanted interferences.

A novel molecularly imprinted electrochemical sensor for the ultrasensitive detection of tert-butylhydroquinone in edible oils

Tert-butylhydroquinone (TBHQ) is widely used to increase the stability of food products; however, it is considered to be a highly unsafe preservative ingredient that has caused serious damage to human health. Thus, in this paper, a novel molecularly imprinted electrochemical sensor was designed for ultrasensitive, and selective detection of TBHQ in edible oils. The sensor was based on the molecularly imprinted polymer (MIP) synthesized with multiwalled carbon nanotube (MWCNT), and gold nanoparticle (GNP), as the coating materials, o-phenylenediamine (o-PDA) as the functional monomer, and TBHQ as the template molecule. The electrochemical behavior of MIP/GNP/MWCNT/GCE was studied using several electrochemical methods, which showed a low detection limit of 5 nM. Furthermore the sensor demostrated excellent stability, selectivity, repeatability, and reproducibility. It was successfully used to detect TBHQ in edible oils, with recoveries ranging from 98.44% to 102.09% and relative standard deviations (RSDs) of less than 2.16%, indicating that TBHQ detection in actual samples is both possible and accurate.

Hybridized sulfated-carboxymethyl cellulose/MWNT nanocomposite as highly selective electrochemical probe for trace detection of arsenic in real environmental samples

A highly selective and ultra-sensitive electrochemical sensing probe was proposed by combining sulfated-carboxymethyl cellulose (CMC-S) and a functionalized-multiwalled carbon nanotube (f-MWNT) nano-composite with high conductivity and durability. The CMC-S/MWNT nanocomposite was impregnated on a glassy carbon electrode (GCE) to construct the non-enzymatic and mediator-free electrochemical sensing probe for trace detection of As(iii) ions. The fabricated CMC-S/MWNT nanocomposite was characterized by FTIR, SEM, TEM, and XPS. Under the optimized experimental conditions, the sensor exhibited the lowest detection limit of 0.024 nM, a high sensitivity (69.93 μA nM-1 cm-2) with a good linear relationship in the range of 0.2-90 nM As(iii) concentration. The sensor demonstrated strong repeatability, with the current response continuing at 84.52% after 28 days of use, in addition to good selectivity for the determination of As(iii). Additionally, with recovery ranging from 97.2% to 107.2%, the sensor demonstrated comparable sensing capability in tap water, sewage water, and mixed fruit juice. The electrochemical sensor for detecting trace levels of As(iii) in actual samples is anticipated to be produced by this effort and is expected to possess great selectivity, good stability, and sensitivity.

A review on carbon-based molecularly-imprinted polymers (CBMIP) for detection of hazardous pollutants in aqueous solutions

This article discusses the unique properties and performance of carbon-based molecularly-imprinted polymers (MIPs) for detecting hazardous pollutants in aqueous solutions. Although MIPs have several advantages such as specific recognition sites, selectivity, and stability, they suffer from a series of drawbacks, including loss of conductivity, electrocatalytic activity, and cost, which limit their use in various fields. Carbon-based MIPs, which utilize carbon electrodes, carbon nanoparticles, carbon dots, carbon nanotubes, and graphene substrates, have been the focus of research in recent years to enhance their properties and remove their weaknesses as much as possible. These carbon-based nanomaterials have excellent sensitivity and specificity for molecular identification. As a result, they have been widely used in various applications, such as assessing the environmental, biological, and food samples. This article examines the growth of carbon-based MIPs and their environmental applications.

Synthesis and characterization of a novel molecularly imprinted polymer for the controlled release of rivastigmine tartrate

To develop novel imprinted poly (methacrylic acid) nanoparticles for the controlled release of Rivastigmine Tartrate (RVS), the amalgamation of molecular imprinting techniques and polymerization of precipitates were applied in this work. By permuting different concentrations of pentaerythritol triacrylate (PETA) or trimethylolpropane triacrylate (TMPTA) as cross-linkers, ten different samples were synthesized, and their abilities assessed for RVS absorption. Among them, uniform mono-disperse nanoparticles were synthesized in an RVS/PMAA/PETA mole ratio of 1:6:12, named molecularly imprinted polymers 2 (MIP2), which showed the highest RVS absorption. Analytical procedures involving the Fourier transform infrared (FT-IR), Thermogeometric analysis (TGA), Field emission scanning electron microscopy (FE-SEM), Dynamic light scattering (DLS), and absorption/desorption porosimetry (BET) measurements were applied to characterize the morphology and physicochemical properties of the MIP2. In addition, the cytotoxicity of the MIP2 sample was measured by MTT assay on an L929 cell line. Studies pertaining to the in-vitro release of RVS from MIP2 samples showed that the prepared sample had a controlled and sustained release compared, which differed from the results obtained from the non-imprinted polymer (NIP) with the same formulization. Results obtained further reinforced the feasibility of prepared MIPs as a prime candidature for RVS drug delivery to alleviate Alzheimer's and other diseases.

Porous carbon derived from ZIF-8 modified molecularly imprinted electrochemical sensor for the detection of tert-butyl hydroquinone (TBHQ) in edible oil

In this manuscript, ZIF-8 derived nanoporous carbon material (ZC) was prepared and used as modification material to construct a molecularly imprinted electrochemical sensor for the direct detection of tert-butyl hydroquinone (TBHQ) in edible oil. Electrochemical characterizations, scanning electron microscopy and X-ray diffraction show that ZC has excellent conductivity, high electrochemical active area and stable porous framework structure. Using TBHQ as template and o-phenylenediamine as functional monomer, the sensor was constructed. Experimental parameters such as the number of polymerization cycle, polymerization speed, and pH of the measured solution, removal and rebinding time were studied. Under optimized conditions, the prepared sensor showed a wider linear range from 1.0 μmol L^-1 to 75.0 μmol L^-1 with the detection limit of 0.42 μmol L^-1 (S/N = 3). Meanwhile, the sensor also expressed good selectivity, repeatability, reproducibility, stability and successfully applied for the determination of TBHQ in real edible oil, giving satisfactory results.

Ultrasensitive detection of cytotoxic food preservative tert-butylhydroquinone using 3D cupric oxide nanoflowers embedded functionalized carbon nanotubes

Accurate detection of cytotoxic food preservative tert-butylhydroquinone (TBHQ) has significant importance in maintaining food quality and safety. TBHQ is a chronic hazard to aquatic life and its use in applications involving direct human exposure and frequent release to environment makes its quantification critical to maintain safety. Hence, we report development of a sensitive electrochemical sensor for TBHQ determination at nanomolar level in commonly used edible oils and water sample. Novel cupric oxide (CuO) decorated amine functionalized carbon nanotubes (NH₂-CNTs) were prepared for development of TBHQ sensor. 3D CuO nanoflowers and NH₂-CNTs were synthesized using hydrothermal and ultrasound-assisted method respectively. Techniques such as SEM, elemental mapping, XRD, FTIR, micro Raman, XPS, EIS, and UV-Visible spectroscopy were taken to affirm significant characterizations of synthesized materials. We have observed outstanding electrocatalytic activity towards TBHQ detection using the sonochemically prepared nanocomposite modified screen printed carbon electrode (SPCE). The proposed sensor exhibited ultra-low detection limit at 3 nM and exceptional sensitivity at 37.7 μA μM^-1 cm^-2. Furthermore, TBHQ sensor showcased outstanding anti-interference, stability, reproducibility, and repeatability. The practical feasibility of TBHQ detection was validated using real sample analysis resulting in excellent recovery in the range 95.90-104.87% and a maximum RSD of mere 2.71%.

Study on the performance of micro-flow injection preconcentration method on-line coupled to thermospray flame furnace AAS using MWCNTs wrapped with polyvinylpyridine nanocomposites as adsorbent

An adsorbent nanocomposite based on multi-walled carbon nanotubes and polyvinylpyridine is used in the development of a micro-flow injection preconcentration method coupled to TS-FF-AAS for the determination of very low levels of Cd.