Nonenzymatic electrochemical sensor based on metal oxide, MO (M= Cu, Ni, Zn, and Fe) nanomaterials for neurotransmitters: An abridged review

Not Only Graphene Two-Dimensional Nanomaterials: Recent Trends in Electrochemical (Bio)sensing Area for Biomedical and Healthcare Applications

Two-dimensional (2D) nanomaterials (e.g., graphene) have attracted growing attention in the (bio)sensing area and, in particular, for biomedical applications because of their unique mechanical and physicochemical properties, such as their high thermal and electrical conductivity, biocompatibility, and large surface area. Graphene (G) and its derivatives represent the most common 2D nanomaterials applied to electrochemical (bio)sensors for healthcare applications. This review will pay particular attention to other 2D nanomaterials, such as transition metal dichalcogenides (TMDs), metal-organic frameworks (MOFs), covalent organic frameworks (COFs), and MXenes, applied to the electrochemical biomedical (bio)sensing area, considering the literature of the last five years (2018-2022). An overview of 2D nanostructures focusing on the synthetic approach, the integration with electrodic materials, including other nanomaterials, and with different biorecognition elements such as antibodies, nucleic acids, enzymes, and aptamers, will be provided. Next, significant examples of applications in the clinical field will be reported and discussed together with the role of nanomaterials, the type of (bio)sensor, and the adopted electrochemical technique. Finally, challenges related to future developments of these nanomaterials to design portable sensing systems will be shortly discussed.

Creation of a 3D Goethite-Spongin Composite Using an Extreme Biomimetics Approach

The structural biopolymer spongin in the form of a 3D scaffold resembles in shape and size numerous species of industrially useful marine keratosan demosponges. Due to the large-scale aquaculture of these sponges worldwide, it represents a unique renewable source of biological material, which has already been successfully applied in biomedicine and bioinspired materials science. In the present study, spongin from the demosponge Hippospongia communis was used as a microporous template for the development of a new 3D composite containing goethite [α-FeO(OH)]. For this purpose, an extreme biomimetic technique using iron powder, crystalline iodine, and fibrous spongin was applied under laboratory conditions for the first time. The product was characterized using SEM and digital light microscopy, infrared and Raman spectroscopy, XRD, thermogravimetry (TG/DTG), and confocal micro X-ray fluorescence spectroscopy (CMXRF). A potential application of the obtained goethite-spongin composite in the electrochemical sensing of dopamine (DA) in human urine samples was investigated, with satisfactory recoveries (96% to 116%) being obtained.

Spongin as a Unique 3D Template for the Development of Functional Iron-Based Composites Using Biomimetic Approach In Vitro

Marine sponges of the subclass Keratosa originated on our planet about 900 million years ago and represent evolutionarily ancient and hierarchically structured biological materials. One of them, proteinaceous spongin, is responsible for the formation of 3D structured fibrous skeletons and remains enigmatic with complex chemistry. The objective of this study was to investigate the interaction of spongin with iron ions in a marine environment due to biocorrosion, leading to the occurrence of lepidocrocite. For this purpose, a biomimetic approach for the development of a new lepidocrocite-containing 3D spongin scaffold under laboratory conditions at 24 °C using artificial seawater and iron is described for the first time. This method helps to obtain a new composite as "Iron-Spongin", which was characterized by infrared spectroscopy and thermogravimetry. Furthermore, sophisticated techniques such as X-ray fluorescence, microscope technique, and X-Ray diffraction were used to determine the structure. This research proposed a corresponding mechanism of lepidocrocite formation, which may be connected with the spongin amino acids functional groups. Moreover, the potential application of the biocomposite as an electrochemical dopamine sensor is proposed. The conducted research not only shows the mechanism or sensor properties of "Iron-spongin" but also opens the door to other applications of these multifunctional materials.

Metal Coordination-Driven Supramolecular Nanozyme as an Effective Colorimetric Biosensor for Neurotransmitters and Organophosphorus Pesticides

Analytical methods for detecting neurotransmitters (NTs) and organophosphorus (OP) pesticides with high sensitivity are vitally necessary for the rapid identification of physical, mental, and neurological illnesses, as well as to ensure food safety and safeguard ecosystems. In this work, we developed a supramolecular self-assembled system (SupraZyme) that exhibits multi-enzymatic activity. SupraZyme possesses the ability to show both oxidase and peroxidase-like activity, which has been employed for biosensing. The peroxidase-like activity was used for the detection of catecholamine NTs, epinephrine (EP), and norepinephrine (NE) with a detection limit of 6.3 µM and 1.8 µM, respectively, while the oxidase-like activity was utilized for the detection of organophosphate pesticides. The detection strategy for OP chemicals was based on the inhibition of acetylcholine esterase (AChE) activity: a key enzyme that is responsible for the hydrolysis of acetylthiocholine (ATCh). The corresponding limit of detection of paraoxon-methyl (POM) and methamidophos (MAP) was measured to be 0.48 ppb and 15.8 ppb, respectively. Overall, we report an efficient supramolecular system with multiple enzyme-like activities that provide a versatile toolbox for the construction of sensing platforms for the colorimetric point-of-care detection of both NTs and OP pesticides.

Facile and controllable synthesis of monodisperse gold nanoparticle bipyramid for electrochemical dopamine sensor

We demonstrated potential features of gold nanoparticle bipyramid (AuNB) for an electrochemical biosensor. The facile synthesis method and controllable shape and size of the AuNB are achieved through the optimization of cetyltrimethylammonium chloride (CTAC) surfactant over citric acid (CA) ratio determining the control of typically spherical Au seed size and its transition into a penta-twinned crystal structure. We observe that the optimized ratio of CTAC and CA facilitates flocculation control in which Au seeds with size as tiny as ∼14.8 nm could be attained and finally transformed into AuNB structures with an average length of ∼55 nm with high reproducibility. To improve the electrochemical sensing performance of a screen-printed carbon electrode, surface modification with AuNB via distinctive linking procedures effectively enhanced the electroactive surface area by 40%. Carried out for the detection of dopamine, a neurotransmitter frequently linked to the risk of Parkinson's, Alzheimer's, and Huntington's diseases, the AuNB decorated-carbon electrode shows outstanding electrocatalytic activity that improves sensing performance, including high sensitivity, low detection limit, wide dynamic range, high selectivity against different analytes, such as ascorbic acid, uric acid and urea, and excellent reproducibility.

Novel biomass-derived porous-graphitic carbon coated iron oxide nanocomposite as an efficient electrocatalyst for the sensitive detection of rutin (vitamin P) in food and environmental samples

Design and development of inexpensive, portable, and eco-friendly electrochemical non-enzymatic sensors with high selectivity and sensitivity is pivotal in analytical chemistry. In this regard, we have developed a highly porous graphitic-activated carbon (GAC, derived from tamarind fruit shell biomass) coated iron oxide (Fe₂O₃) nanocomposite (Fe₂O₃/GAC) for the efficient detection of rutin (vitamin p). Fe₂O₃/GAC nanocomposite was prepared using a facile green synthesis method and thoroughly characterized using SEM, XRD, and XPS techniques. As-prepared Fe₂O₃/GAC nanocomposite was deposited over a screen printed electrode (SPE) to fabricate Fe₂O₃/GAC/SPE and utilized as a non-enzymatic sensor for the electrochemical determination of rutin in food and environmental samples. The modified electrode was characterized using cyclic voltammetry and electrochemical impedance spectroscopy techniques, which witnessed the excellent conductivity of the developed sensor. The fabricated Fe₂O₃/GAC/SPE nanocomposite exhibited a set of redox peaks in the presence of rutin, corresponding to the electrochemical redox feature of rutin (rutin to 3',4'-diquinone). Further, the modified electrode displayed excellent electrocatalytic characteristics towards the oxidation of rutin, based on which a differential pulse voltammetry-based sensor was developed for rutin determination. The developed non-enzymatic sensor has shown prominent performance towards rutin detection in a wide linear range from 0.1 to 130 μM with an excellent detection limit of 0.027 μM. The enhanced electrocatalytic response could be ascribed to the synergistic effect of Fe₂O₃ and GAC on the developed probe. Moreover, the developed sensor was successfully utilized for real-time detection of rutin in various samples.

Gold-Modified Molecularly Imprinted N-Methacryloyl-(l)-phenylalanine-containing Electrodes for Electrochemical Detection of Dopamine

A molecularly imprinted polymer-based pencil graphite electrode (MIP PGE) sensor, modified with gold nanoparticles, was utilized for the detection of dopamine in the presence of other biochemical compounds using cyclic voltammetry (CV) and differential pulse voltammetry (DPV), depending on its strong electroactivity function. The pulse voltammetry methods recorded the highest response. In addition to the high oxidation rate of DA and the other biomolecule interferences available in the sample matrix used, which cause overlapping voltammograms, we aimed to differentiate them in a highly sensitive limit of detection range. The calibration curves for DA were obtained using the CV and DPV over the concentration range of 0.395–3.96 nM in 0.1 M phosphate buffer solution (PBS) at pH 7.4 with a correlation coefficient of 0.996 and a detection limit of 0.193 nM. The electrochemical technique was employed to detect DA molecules quantitatively in human blood plasma selected as real samples without applying any pre-treatment processes. MIP electrodes proved their ability to detect DA with high selectivity, even with epinephrine and norepinephrine competitor molecules and interferences, such as ascorbic acid (AA). The high level of recognition achieved by molecularly imprinted polymers (MIPs) is essential for many biological and pharmaceutical studies.

Electrochemical Peptide-Based Sensors for Foodborne Pathogens Detection

Food safety and quality control pose serious issues to food industry and public health domains, in general, with direct effects on consumers. Any physical, chemical, or biological unexpected or unidentified food constituent may exhibit harmful effects on people and animals from mild to severe reactions. According to the World Health Organization (WHO), unsafe foodstuffs are especially dangerous for infants, young children, elderly, and chronic patients. It is imperative to continuously develop new technologies to detect foodborne pathogens and contaminants in order to aid the strengthening of healthcare and economic systems. In recent years, peptide-based sensors gained much attention in the field of food research as an alternative to immuno-, apta-, or DNA-based sensors. This review presents an overview of the electrochemical biosensors using peptides as molecular bio-recognition elements published mainly in the last decade, highlighting their possible application for rapid, non-destructive, and in situ analysis of food samples. Comparison with peptide-based optical and piezoelectrical sensors in terms of analytical performance is presented. Methods of foodstuffs pretreatment are also discussed.

Metal-Oxide Based Nanomaterials: Synthesis, Characterization and Their Applications in Electrical and Electrochemical Sensors

Pure, mixed and doped metal oxides (MOX) have attracted great interest for the development of electrical and electrochemical sensors since they are cheaper, faster, easier to operate and capable of online analysis and real-time identification. This review focuses on highly sensitive chemoresistive type sensors based on doped-SnO₂, RhO, ZnO-Ca, Sm_x-CoFe_2−xO₄ semiconductors used to detect toxic gases (H₂, CO, NO₂) and volatile organic compounds (VOCs) (e.g., acetone, ethanol) in monitoring of gaseous markers in the breath of patients with specific pathologies and for environmental pollution control. Interesting results about the monitoring of biochemical substances as dopamine, epinephrine, serotonin and glucose have been also reported using electrochemical sensors based on hybrid MOX nanocomposite modified glassy carbon and screen-printed carbon electrodes. The fundamental sensing mechanisms and commercial limitations of the MOX-based electrical and electrochemical sensors are discussed providing research directions to bridge the existing gap between new sensing concepts and real-world analytical applications.