Fabiana Felix

Mycotoxins are low molecular-weight compounds produced by fungi genera as secondary metabolites during pre- and post-harvest storage of crops and foodstuff. Many reports show highly concerning issues ascribed to their carcinogenic, genotoxic, immunosuppressive, and teratogenic properties. Biosensors are compact analytical devices incorporating a biological or biologically-derived recognition element that might be either integrated within or intimately associated with a physicochemical transducer. The most applied bioreceptors are the enzymes (biosensors), DNA and RNA nucleic acids (genosensors), antibodies (immunosensors), aptamers (aptasensors) or living cells (microbial biosensors). The integration of nanotechnology to the biosensors field brought sensitivity and versatility for bioassays, since nanomaterials might play the role as new signal markers, surface subtracts for functionalization and fixation of biomolecules, and generation source of analytical signals. For electrochemical biosensors, nanostructures can enhance the sensitivity of electrochemical techniques by filling the gap between the converter and the biorecognition element. Metal nanoparticles are used to improve the analytical sensitivity by refining the electrical connectivity of the interface, increasing both the chemical accessibility of analytes and the sensing surface with higher amounts of bioaffinity recognition sites. Gold nanoparticles are among the most used nanostructures due to its unique electrocatalytic activity and conductivity. In turn, carbon-based nanomaterials are very appealing considering their large specific surface area and high electron transfer rates. Carbon nanotubes (CNTs) and graphene oxide materials are the most employed carbon-based materials. There is no doubt that the whole bioassay has become more versatile, robust, and dynamic with the introduction of the nanoscience, consolidating in an emerging field with current intense research. Hence, this work reviews some selected applications of electrochemical metallic and carbon-based nanobiosensors for the determination of mycotoxins in food, revisiting important fundamentals of the electrochemical bioassay.

According to the Coffee Market Report (2024) of the International Coffee Organization, the annual worldwide production of coffee increased 5.82% achieving 178 million bags between 2023 and 2024. South America is the coffee production leader accounting for 50.17% of the global production with Brazil playing a central role on it. To sustain the high quality standards under such a high demand, it is important to ensure the consumer health safety, while preserving the good flavor and aroma of coffee (terroir). Some key factors are required to allow the proper evaluation of crops and shipments using reliable parameters, which is the case of the determination of the elemental composition of coffee. Coffee organoleptic properties depend on several chemical elements of its composition, while accessing and monitoring their concentrations is challenging, since they might vary considerably according to some agronomical and climatic conditions that plantations are subjected. Yet, the analytes might not be homogeneously distributed throughout samples, demanding both refined solid sampling strategies and laborious sample preparation and pretreatment. Finally, several analytical techniques are available for researches and analysts to investigate the elemental composition of coffee samples, each one with their own advantages, limitations and particularities. Sometimes it is not a trivial task to choose a proper technique according to the aimed data. Therefore, an overview of the analysis of coffee elemental composition is herein presented, covering selected references from the last two decades. The selected works discuss the determination of elements affecting the quality of coffee in terms of terroir, toxicity, nutritional content, and geographical origin.

An electrochemical sensor modified with zeolite dealuminated with citric acid was developed for the determination of hydroxyzine in pharmaceutical products during BIA-amperometry experiments. The modified electrochemical sensor was prepared by mixing powdered graphite with zeolite treated with citric acid homogenized with hexane and mineral oil (60:20:20% w/w/w respectively). The developed sensor showed reproducible amperometric responses in a linear range of 1.0x10-6 – 2.0x10-5 mol L-1 in +1,28V (vs. Ag/AgCl). The detection limit and detection limit found were 3.10x10-7 mol L-1 e 1.04x10-6 mol L-1, respectively. The method developed by BIA-amperometry was applied for the determination of the analyte in tablets and commercial syrups and the results found agreement with the nominal values of the commercial samples.

The extraction and chemical characterization of essential oils from Syzygium aromaticum L., Origanum vulgare L., Mentha spicata L. and Eremanthus erythropappus M. is reported, as well as an evaluation of their antioxidant activity and of their major constituents eugenol, carvacrol, carvone and α-bisabolol, respectively, using colorimetric, electroanalytical and theoretical methods. Essential oils were obtained by hydrodistillation, identified by GC/MS and quantified using a GC coupled to a flame ionization detector. The colorimetric evaluation of the antioxidant activity was based on stabilization of DPPH radicals, β-carotene bleaching, deoxyribose degradation and reducing power. The electrochemical behavior was studied using cyclic voltammetry, and the dissociation enthalpy of the OH bond was theoretically estimated at the density functional theory ωB97X-D/6-31+g(d,p) level. The essential oils from S. aromaticum and O. vulgare L., and their major constituents eugenol and carvacrol, yielded antioxidant responses similar to the synthetic ascorbic acid and BHT, while eugenol and the essential oil from S. aromaticum exhibited better performance than carvacrol and the essential oil from O. vulgare L. Overall, eugenol was found to be a promising compound to replace marketed antioxidants or at least to be used in association with them.