Machine learning-powered electrochemical aptasensor for simultaneous monitoring of di(2-ethylhexyl) phthalate and bisphenol A in variable pH environments

Plastic waste is a pernicious environmental pollutant that threatens ecosystems and human health by releasing contaminants including di(2-ethylhexyl) phthalate (DEHP) and bisphenol A (BPA). Therefore, a machine-learning (ML)-powered electrochemical aptasensor was developed in this study for simultaneously detecting DEHP and BPA in river waters, particularly to minimize the electrochemical signal errors caused by varying pH levels. The aptasensor leverages a straightforward and effective surface modification strategy featuring gold nanoflowers to achieve low detection limits for DEHP and BPA (0.58 and 0.59 pg/mL, respectively), excellent specificity, and stability. The least-squares boosting (LSBoost) algorithm was introduced to reliably monitor the targets regardless of pH; it employs a layer that adjusts the number of multi-indexes and the parallel learning structure of an ensemble model to accurately predict concentrations by preventing overfitting and enhancing the learning effect. The ML-powered aptasensor successfully detected targets in 12 river sites with diverse pH values, exhibiting higher accuracy and reliability. To our knowledge, the platform proposed in this study is the first attempt to utilize ML for the simultaneous assessment of DEHP and BPA. This breakthrough allows for comprehensive investigations into the effects of contamination originating from diverse plastics by eliminating external interferent-caused influences.

Facile Synthesis of Platinum Nanoparticle-Embedded Reduced Graphene Oxide for the Detection of Carbendazim

In recent years, there has been a significant interest in the advancement of electrochemical sensing platforms to detect pesticides with high sensitivity and selectivity. Current research presents a novel approach utilising platinum nanoparticles (NPs) and reduced graphene oxide deposited on a glassy carbon electrode (Pt-rGO/GCE) for direct electrochemical measurement of carbendazim (CBZ). A straightforward one-step electrodeposition process was applied to prepare the Pt-rGO sensing platform. The incorporation of conductive rGO nanosheets along with distinctive structured Pt NPs significantly enhanced the effective electrode surface area and electron transfer of CBZ. Additionally, when exposed to 50 µM CBZ, Pt-rGO/GCE exhibited a higher current response compared to the bare electrode. Further investigations were performed to analyse and optimise the experimental parameters that could influence pesticide detection. Under the optimised conditions of pH 7 and 5 min of accumulation time, the Pt-rGO/GCE sensor showed a linear concentration detection range from 0.1 µM to 50 µM, with a detection limit of 3.46 nM. The fabricated sensor was successfully employed for CBZ detection in milk and tap water with 98.88% and 98.57% recovery, respectively. The fabricated sensor showed higher sensitivity and reproducibility, thus indicating the potential of this technology in the development of reliable sensors for the detection of CBZ or similar pesticides in forthcoming applications.

Exploring the synergistic effects of enzyme@lactoferrin hybrid on biomimetic immobilization: Unveiling the impact on catalytic efficiency

Metal-organic frameworks (MOFs) have gained attention as a hopeful material for enzyme immobilization due to their advantageous characteristics, for instance, high surface area and easy construction conditions. Nonetheless, the confinement effect and competing coordination often lead to partial or complete inactivation of the immobilized enzymes. In this study, we present a novel strategy, the lactoferrin-boosted one-pot embedding approach, which efficiently connects enzymes with lactoferrin (LF) hybrid Graphene Oxide (GO)//Pt Nanoparticles/MOF-74 (referred to as enzyme@LF@rGO/PtNP@MOF-74). This approach demonstrates a high embedding efficiency. By employing a hybrid of LF and GO/Pt Nanoparticles as synchronous ligands for Zn-MOF-74, we provide a suitable environment for enzyme immobilization, resulting in enhanced enzymatic activity. The lipase@LF@rGO/PtNP@MOF-74 exhibits improved stability and resistance to organic solvents and significantly enhanced in thermal stability of the lipase@LF@rGO/PtNP@MOF-74 comparing to the free enzyme. The lipase@LF@rGO/PtNP@MOF-74 displayed excellent long-term storage stability, which could protect more than 80 % of the initial activity for 8 weeks. Besides, the lipase@LF@rGO/PtNP@MOF-74 had high reusability, which showed a high degree of activity (more than 75 %) after 20 cycles. As a bio-macromolecule, lactoferrin possesses bio-affinity, creating a favorable microenvironment for enzymes and minimizing the impact of external factors on their conformation and activity during bio-macromolecule utilization.

Reduced Graphene Oxide and Gold Nanoparticles-Modified Electrochemical Aptasensor for Highly Sensitive Detection of Doxorubicin

Doxorubicin (DOX) is the most clinically important antibiotic in cancer treatment, but its severe cardiotoxicity and other side effects limit its clinical use. Therefore, monitoring DOX concentrations during therapy is essential to improve efficacy and reduce adverse effects. Here, we fabricated a sensitive electrochemical aptasensor for DOX detection. The sensor used gold wire as the working electrode and was modified with reduced graphene oxide (rGO)/gold nanoparticles (AuNPs) to improve the sensitivity. An aptamer was used as the recognition element for the DOX. The 5' end of the aptamer was modified with a thiol group, and thus immobilized to the AuNPs, and the 3' end was modified with methylene blue, which acts as the electron mediator. The combination between the aptamer and DOX would produce a binding-induced conformation, which changes the electron transfer rate, yielding a current change that correlates with the concentration of DOX. The aptasensor exhibited good linearity in the DOX concentration range of 0.3 μM to 6 μM, with a detection limit of 0.1 μM. In addition, the aptasensor was used for DOX detection in real samples and results, and showed good recovery. The proposed electrochemical aptasensor will provide a sensitive, fast, simple, and reliable new platform for detecting DOX.

Molecularly imprinted sensor based on poly-o-phenylenediamine-hydroquinone polymer for β-amyloid-42 detection

A sensitive and selective molecularly imprinted polymer (MIP) sensor was developed for the determination of amyloid-β (1-42) (Aβ₄₂). The glassy carbon electrode (GCE) was successively modified with electrochemical reduction graphene oxide (ERG) and poly(thionine-methylene blue) (PTH-MB). The MIPs were synthesized by electropolymerization with Aβ₄₂ as a template and o-phenylenediamine (o-PD) and hydroquinone (HQ) as functional monomers. Cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), chronoamperometry (CC), and differential pulse voltammetry (DPV) were used to study the preparation process of the MIP sensor. The preparation conditions of the sensor were investigated in detail. In optimal experimental conditions, the response current of the sensor was linear in the range of 0.12-10 μg mL^-1 with a detection limit of 0.018 ng mL^-1. The MIP-based sensor successfully detected Aβ₄₂ in commercial fetal bovine serum (cFBS) and artificial cerebrospinal fluid (aCSF).

The Influence of Graphene Oxide Composition on Properties of Surface-Modified Metal Electrodes

The present paper describes the effect of the concentration of two graphene oxides (with different oxygen content) in the modifier layer on the electrochemical and structural properties of noble metal disk electrodes used as working electrodes in voltammetry. The chemistry of graphene oxides was tested using EDS, FTIR, UV-Vis spectroscopy, and combustion analysis. The structural properties of the obtained modifier layers were examined by means of scanning electron and atomic force microscopy. Cyclic voltammetry was employed for comparative electrochemical studies.

Bio-inspired PtNPs/Graphene nanocomposite based electrocatalytic sensing of metabolites of dipyrone

Noble metal nanoparticles are known to electrocatalyze various redox reactions by improving the electron transfer kinetics. In the present study, we have introduced a facile bioinspired synthesis of PtNPs and their integration for the formation of PtNPs/graphene nanocomposite using Psidium guajava (guava) leaves extract. Graphene used in nanocomposite formulation was synthesized by exfoliation of graphite in water/acetone (25:75 v/v) mixture followed by mechanical shearing using ultrasonication and microwave irradiation. PtNPs/graphene nanocomposite was drop-cast onto a glassy carbon electrode (GCE, 3 mm dia). The electrocatalytic activity of PtNPs/graphene nanocomposite was tested in a three-electrode system for sensing of metabolic products of dipyrone (DIP) formed through 1 e^- and 2 e^- transfer reactions. The modified electrode exhibited almost 50% reduction in electrode resistance. The limit of detection was found to be 0.142 μM with sensitivities of 0.820 and 0.445 μA․μM^-1cm^-2 for DIP concentration below and above 100 μM, respectively, using square wave voltammetry. The signal of sensing of metabolites of DIP was almost invariant in the presence of glucose, dopamine, uric acid, and ciprofloxacin; however, the response current was decayed by 20% within the 10th cycle. The sensing of DIP spiked in treated sewage-water and running tap-water samples was ∼100% recoverable and comparable with HPLC.

Real-time monitored photocatalytic activity and electrochemical performance of an rGO/Pt nanocomposite synthesized via a green approach

Herein, we have reported the real-time photodegradation of methylene blue (MB), an organic pollutant, in the presence of sunlight at an ambient temperature using a platinum-decorated reduced graphene oxide (rGO/Pt) nanocomposite. The photocatalyst was prepared via a simple, one-pot and green approach with the simultaneous reduction of GO and Pt using aqueous honey as a reducing agent. Moreover, the honey not only simultaneously reduced Pt ions and GO but also played a key role in the growth and dispersion of Pt nanoparticles on the surface of rGO. Various rGO/Pt nanocomposites with different percentages of Pt nanoparticles loaded on rGO were obtained by tuning the concentration of the Pt source. The high percentage of Pt nanoparticles with an average size of 2.5 nm dispersed on rGO has shown excellent electrochemical performance. The photocatalytic activity of the rGO/Pt composite was enhanced by increasing the weight percent of the Pt particles on rGO, which led to the formation of a highly efficient photocatalyst. The optimized photocatalyst exhibited remarkable photocatalytic activity and degraded 98% MB in 180 minutes; thus, it can be used for industrial and environmental applications.

Electrically-Transduced Chemical Sensors Based on Two-Dimensional Nanomaterials

Electrically-transduced sensors, with their simplicity and compatibility with standard electronic technologies, produce signals that can be efficiently acquired, processed, stored, and analyzed. Two dimensional (2D) nanomaterials, including graphene, phosphorene (BP), transition metal dichalcogenides (TMDCs), and others, have proven to be attractive for the fabrication of high-performance electrically-transduced chemical sensors due to their remarkable electronic and physical properties originating from their 2D structure. This review highlights the advances in electrically-transduced chemical sensing that rely on 2D materials. The structural components of such sensors are described, and the underlying operating principles for different types of architectures are discussed. The structural features, electronic properties, and surface chemistry of 2D nanostructures that dictate their sensing performance are reviewed. Key advances in the application of 2D materials, from both a historical and analytical perspective, are summarized for four different groups of analytes: gases, volatile compounds, ions, and biomolecules. The sensing performance is discussed in the context of the molecular design, structure-property relationships, and device fabrication technology. The outlook of challenges and opportunities for 2D nanomaterials for the future development of electrically-transduced sensors is also presented.