1,721,003 research outputs found
Advances on the Use of Graphene as a Label for Electrochemical Biosensors
No full textThere has been an overwhelming interest in the use of graphene and its derivatives for electrochemical biosensors in the last decade. Although the majority of the works describe the use of these materials as platform for the immobilization of the biorecognition element, there is a significant, often unrecognized, research effort that has shown how graphene materials can also beneficially serve as signaling labels for biosensing. Owing to its intrinsic electroactivity and small size, nano-graphene oxide, for example, has been used for this purpose, where the working signal arises from the reduction of the oxygen functionalities on the material surface. In other approaches, graphene labels modified with electroactive probes were also used to promote the signal generation. This Minireview will illustrate how the unique electrochemical and structural features make graphene a very promising material for the detection of the biorecognition event. In addition, an overview will be provided, showing the plethora of options offered by graphene and its derivatives as labels for signal generation and enhancement
How 3D printing can boost advances in analytical and bioanalytical chemistry
No full text: 3D printing fabrication methods have received lately an enormous attention by the scientific community. Laboratories and research groups working on analytical chemistry applications, among others, have advantageously adopted 3D printing to fabricate a wide range of tools, from common laboratory hardware to fluidic systems, sample treatment platforms, sensing structures, and complete fully functional analytical devices. This technology is becoming more affordable over time and therefore preferred over the commonly used fabrication processes like hot embossing, soft lithography, injection molding and micromilling. However, to better exploit 3D printing fabrication methods, it is important to fully understand their benefits and limitations which are also directly associated to the properties of the materials used for printing. Costs, printing resolution, chemical and biological compatibility of the materials, design complexity, robustness of the printed object, and integration with commercially available systems represent important aspects to be weighted in relation to the intended task. In this review, a useful introductory summary of the most commonly used 3D printing systems and mechanisms is provided before the description of the most recent trends of the use of 3D printing for analytical and bioanalytical chemistry. Concluding remarks will be also given together with a brief discussion of possible future directions
The potential of electrochemistry for the detection of coronavirus-induced infections
No full textHuman coronaviruses (HCoV) are no stranger to the global environment. The etiology of previous outbreaks with reported symptoms of respiratory tract infections was attributed to different coronavirus strains, with the latest global pandemic in 2019 also belonging to the coronavirus family. Timely detection, effective therapeutics and future prevention are stake key holders in the management of coronavirus-induced infections. Apart from the gold standard clinical diagnostics, electrochemical techniques have also demonstrated their great potentials in the detection of different viruses and their correlated antibodies and antigens, showing high sensitivities and selectivities, and faster times for the analysis. This article aims to critically review the multifaceted electrochemical approaches, not only in the development of point-of-care portable devices but also as alternative detection strategies that can be coupled with traditional methods for the detection of various strains of coronaviruses.Ministry of Education (MOE)The authors gratefully acknowledge Singapore Ministry of Education (MOE), AcRF Tier 1 grant (Reference No: RG18/17) for the funding of this research
The role of surface chemistry in impedimetric aptasensing
No full textSurface chemistry is a key parameter in the choice of proper materials for electrochemical detection. It has been previously shown that the presence of oxygen containing groups (OCGs) on the surface of graphene oxide (GO) can be both effective and detrimental. This poses a question when GO materials are used as electrochemical platforms for biosensing. In this work, we study how the surface chemistry of graphene oxide nanocolloids (GONCs) affects the impedimetric biosensing of ochratoxin A (OTA), in terms of immobilization of biorecognition element and detection step. OCGs on GONCs were tuned by applying increasing reduction potentials from −0.3 V to −1.2 V, resulting in GONC platforms with decreasing amounts of oxygen functionalities. It was discovered that the sensitivity of biosensing is correlated to the residual amount of OCGs on GO surface. For a more detailed investigation, three representative materials, namely unreduced GONCs, as well as GONCs reduced at potentials of −0.8 V and −1.2 V were chosen. Results were compared in terms of calibration sensitivity, selectivity and reproducibility of the impedimetric response. GONCs reduced at −1.2 V have shown the best electroanalytical response for the impedimetric detection of OTA. These findings are anticipated to contribute to the design of novel biosensors, whereby an optimized platform is employed for the immobilization of the biorecognition element
All-in-one : electroactive nanocarbon as simultaneous platform and label for single-step biosensing
No full textWe demonstrate here that an electroactive nanocarbon material can simultaneously work as both platform and label for the detection of mycotoxins. The versatility of the material for the immobilization of biorecognition elements was combined with its ability to provide an intrinsic electrochemical signal upon reduction of the oxygen functionalities on its surface. The intensity of peak current reflects the availability of oxygen functionalities for reduction, which can be directly correlated to the specific biorecognition event. We show that the use of electroactive nanocarbon as all-in-one biosensing component enables sensitive quantification of Fumonisin B1 (FB1 ) as model mycotoxin analyte, but it can be easily implemented to develop label-free, cost-effective and fast bioanalytical devices for universal biosensing.MOE (Min. of Education, S’pore
Unravelling the Aptamer‐Analyte Interaction Dynamics through Fluorescence Quenching in Graphene Quantum Dots (GQDs) Based Homogeneous Assays
No full textGraphene quantum dots (GQDs) are used here as a biosensing platform for the recognition of the major food contaminant ochratoxin A (OTA), with a fluorescently labelled DNA aptamer (FAM OTA aptamer) functioning as the biorecognition element. The detection principle lies in the formation of noncovalent interactions between the FAM OTA aptamer and the GQD surface, and the consequent fluorescence quenching. The further change in the fluorescence signal, induced by the formation of the FAM OTA Aptamer/OTA conjugate during the detection step, could then be correlated to the presence and concentration of the target analyte. Upon tuning the concentration of GQDs, a switch in the biorecognition mechanism occurred. Specifically, while a lower GQD concentration (0.060 mg/mL) resulted in a restoration of the fluorescence intensity upon incubation with OTA, a higher GQD concentration (0.150 mg/mL) provided a further quenching of the final fluorescence intensity. Upon further calibration study, it was discovered that the latter mechanism provided a better option in terms of linearity of response, detection limit and selectivity.Nanyang Technological UniversityA. B. acknowledges Nanyang Technological University for the financial support
Electroactive Nanocarbon Can Simultaneously Work as Platform and Signal Generator for Label‐Free Immunosensing
No full textElectroactive nanocarbon can be defined as a carbon nanomaterial that contains electrochemically reducible oxygen functionalities. We show here how an electroactive nanocarbon material can work both as a platform and as a signal generator when developing an immunosensor for the detection of mycotoxins. The suitability of the material for the immobilization of the biorecognition element by the formation of multiple noncovalent interactions, and the concurrent ability to provide a significant reduction peak are combined here in a label-free, single-step immunosensor. The variation in the current intensity, owing to the reduction of the electroactive platform, is correlated to the electrochemical availability of the oxygen functionalities involved in the interaction with the biorecognition element first, and the antibody/antigen conjugate in the detection step. We demonstrated here a direct dependence between the signal generated from the electroactive nanocarbon platform and each step of the biorecognition event, which allows the selective and precise detection of the analyte under investigation
Functionalized 2D Germanene and Its Derivatives for Electrochemical Detection of Gut-Derived Metabolites in Human Serum
No full textIn this work, germanene and its derivatives (Ge-H, Ge-CH3, Ge-C3-CN) were explored as electrochemical impedimetric platforms to develop a competitive immunoassay for the direct detection of gut-derived metabolites, kynurenic acid (KA) and quinolinic acid (QA). The competition occurs between the free KA/QA standards and BSA-conjugated antigens for a fixed amount of primary antibody binding sites. This affects the electron transfer rate of the [Fe(CN)6]3−/4− redox couple and changes the charge transfer resistance (Rct) on the electrode surface. The impedimetric signal measured due to the change in Rct is then correlated to the KA and QA concentration
Molecularly Imprinted Polypyrrole-Modified Screen-Printed Electrode for Dopamine Determination
No full text: This paper introduces a quantitative method for dopamine determination. The method is based on a molecularly imprinted polypyrrole (e-MIP)-modified screen-printed electrode, with differential pulse voltammetry (DPV) as the chosen measurement technique. The dopamine molecules are efficiently entrapped in the polymeric film, creating recognition cavities. A comparison with bare and non-imprinted polypyrrole-modified electrodes clearly demonstrates the superior sensitivity, selectivity, and reproducibility of the e-MIP-based one; indeed, a sensitivity of 0.078 μA μM-1, a detection limit (LOD) of 0.8 μM, a linear range between 0.8 and 45 μM and a dynamic range of up to 350 μM are achieved. The method was successfully tested on fortified synthetic and human urine samples to underline its applicability as a screening method for biomedical tests
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