Electrochemical Sensing of Uric Acid Using Glassy Carbon Modified with Multiwall Carbon Nanotubes Dispersed in Polyethylenimine

Development of Electrochemical Sensors/Biosensors to Detect Natural and Synthetic Compounds Related to Agroalimentary, Environmental and Health Systems in Argentina. A Review of the Last Decade

Electrochemical sensors and biosensors are analytical tools, which are in continuous development with the aim of generating new analytical devices which are more reliable, cheaper, faster, sensitive, selective, and robust than others. In matrices related to agroalimentary, environmental, or health systems, natural or synthetic compounds occur which fulfil specific roles; some of them (such as mycotoxins or herbicides) may possess harmful properties, and others (such as antioxidants) beneficial ones. This imposes a challenge to develop new tools and analytical methodologies for their detection and quantification. This review summarises different aspects related to the development of electrochemical sensors and biosensors carried out in Argentina in the last ten years for application in agroalimentary, environmental, and health fields. The discussion focuses on the construction and development of electroanalytical methodologies for the determination of mycotoxins, herbicides, and natural and synthetic antioxidants. Studies based on the use of different electrode materials modified with micro/nanostructures, functional groups, and biomolecules, complemented by the use of chemometric tools, are explored. Results of the latest reports from research groups in Argentina are presented. The main goals are highlighted.

Novel electrochemical sensors from poly[N-(ferrocenyl formacyl) pyrrole]@multi-walled carbon nanotubes nanocomposites for simultaneous determination of ascorbic acid, dopamine and uric acid

Novel multi-walled carbon nanotubes coated with poly[N-(ferrocenyl formacyl) pyrrole] (MWCNTs@PFFP) nanocomposites were prepared through the in situ oxidation polymerization reaction of N-(ferrocenyl formacyl) pyrrole in the presence of MWCNTs. The MWCNTs@PFFP nanocomposites were characterized by FT-IR, Raman, TGA, XRD, XPS, SEM and TEM techniques. The MWCNTs@PFFP nanocomposites were fabricated into novel electrochemical sensors for simultaneous determination of ascorbic acid (AA), dopamine (DA) and uric acid (UA). The electrochemical behavior of the MWCNTs@PFFP/GCE sensors was examined, and the parameters that influence electrochemical signals were optimized. The experimental results showed that the fabricated modified electrode sensors exhibited good sensitivity, selectivity, specificity, repeatability and a long lifetime, remaining the initial current of at least 92.5% after 15 days storage in air. The sensors possessed a linear response concentration range over 200-400 μM for AA, 2-16 μM for both DA and UA, and a limit of detection as low as 40.0, 1.1 and 7.3 × 10-1 μM for AA, DA and UA, respectively. They are expected to be used as a potential tool for the simultaneous detection of DA, AA and UA in the human body.

Electrochemical Detection for Uric Acid Based on β-Lactoglobulin-Functionalized Multiwall Carbon Nanotubes Synthesis with PtNPs Nanocomposite

In this work, a simple and highly selective electrochemical biosensor for determination of uric acid (UA) is synthesized by using β-lactoglobulin (BLG)-functionalized multiwall carbon nanotubes (MWCNTs) and a platinum nanoparticles (PtNPs) nanocomposite. Urate oxidase (UOx) can oxidize uric acid to hydrogen peroxide and allantoin, which provides a good opportunity for electrochemical detection for UA. Under the optimized conditions, the current changes by the UOx/Bull Serum Albumin (BSA)/BLG-MWCNTs-PtNPs/Glassy Carbon (GC) electrode with the electrochemical method was proportional to the concentration of UA. According to experiments, we obtained a linear response with a concentration range from 0.02 to 0.5 mM and achieved a high sensitivity of 31.131 μA mM⁻¹ and a low detection limit (0.8 μΜ). Meanwhile, nanoparticles improved the performance of the biosensor and combined with BLG not only prevented the accumulation of composite nanomaterials, but also provided immobilization of uricase through electrostatic adsorption. This improves the stability and gives the constructed electrode sensing interface superior performance in UA detection.

Facile Synthesis of Gold Nanoparticles with Alginate and Its Catalytic Activity for Reduction of 4-Nitrophenol and H₂O₂ Detection

Gold nanoparticles (AuNPs) were synthesized using a facile solvothermal method with alginate sodium as both reductant and stabilizer. Formation of AuNPs was confirmed by UV-vis spectroscopic analysis. The synthesized AuNPs showed a localized surface plasmon resonance at approximately 520-560 nm. The AuNPs were characterized using transmission electron microscopy, X-ray diffraction and dynamic light scattering. Transmission electron microscopy revealed that the AuNPs were mostly nanometer-sized spherical particles. Powder X-ray diffraction analysis proved the formation of face-centered cubic structure of Au. Catalytic reduction of 4-nitrophenol was monitored via spectrophotometry using AuNPs as catalyst, and further a non-enzymatic sensor was fabricated. The results demonstrated that AuNPs presented excellent catalytic activity and provided a sensitive response to H₂O₂ detection.