The essential oils of the different parts of Lavandula dentata L. (inflorescences and aerial part without inflorescences) collected in the city of Uberaba (minas Gerais State)were obtained by hydro distillation, and their chemical composition was determined by gas chromatography coupled to mass spectrometry and compared to the chemical composition of essential oil of Lavandula hybrida and Lavandula officinalis. It was observed that the essential oils of the studied species have varied chemical composition and are composed mainly of monoterpenes. The essential oils of L. hybrida and L. officinalis showed a higher concentration of linalool and linaline acetate, while L. dentata L. presented higher concentration of fenchone, eucalyptol and camphor. Results indicate that the essential oil composition of L. dentata L. grown in Uberaba is similar to those produced in Curitiba - PR, providing a promising perspective for the cultivation and extraction of essential oils of this species in Minas Gerais.

(1) Background: Nanocrystals (NCs)-based electrochemical sensors have been proposed for biomarkers detection, although immunosensors using ZnO NCs decorated with copper are still scarce. (2) Methods: Electrochemical immunodetection of human salivary alpha-amylase (HSA) used ZnO, CuO, and ZnO:xCu (x = 0.1, 0.4, 1.0, 4.0, and 12.0) NCs. (3) Results: Substitutional incorporation of Cu²⁺ in the crystalline structure of ZnO and formation of nanocomposite were demonstrated by characterization. Graphite electrodes were used and the electrochemical signal increased by 40% when using ZnO:1Cu and 4Cu (0.25 mg·mL⁻¹), in an immunosensor (0.372 mg·mL⁻¹ of anti-alpha-amylase and 1% of casein). Different interactions of HSA with the alpha-amylase antibody were registered when adding the NCs together, either before or after the addition of saliva (4 μL). The immunosensor changed specificity due to the interaction of copper. The ZnO:1Cu and ZnO:4Cu samples showed 50% interference in detection when used before the addition of saliva. The immunosensor showed 100% specificity and a sensitivity of 0.00196 U·mL⁻¹. (4) Conclusions: Results showed that the order of NCs addition in the sensors should be tested and evaluated to avoid misinterpretation in detection and to enable advances in the validation of the immunosensor.

The COVID-19 pandemic, caused by the SARS-CoV-2 virus, has posed a major challenge to global health. The development of fast, accurate, and accessible diagnostic methods is essential in controlling the disease and mitigating its impacts. In this context, electrochemical biosensors present themselves as promising tools for the efficient monitoring of SARS-CoV-2 infection. We have developed a highly specific biosensor for the detection of anti-SARS-CoV-2 antibodies in patient sera. The use of the RBD-S region as an antigen, although purified to minimize cross-linking, poses a specific challenge. The structural similarity between SARS-CoV-2 and other respiratory viruses, as well as the complexity of the serum matrix, hinders robust analytical strategies to ensure diagnostic accuracy. This work presents a novel immunosensor for COVID-19 diagnosis using laser-induced graphene (LIG) electrodes subjected to electrochemical reduction with graphene (named rGraphene-LIG). In the present study, we chose an initial approach focused on demonstrating the concept and evaluating the feasibility of the rGraphene-LIG sensor for SARS-CoV-2 detection. The rGraphene-LIG electrodes presented a notable current increase for the redox probe in the aqueous solution of a mixture of 5 mmol L⁻¹ potassium ferricyanide/ferrocyanide ([Fe(CN)₆]³⁻/[Fe(CN)₆]⁴⁻) in 0.1 mol L⁻¹ KCl (pH set at 7.4). As a proof of concept, the rGraphene-LIG electrode was applied for antibody determination in real samples using cyclic voltammetry, and a limit of detection (LOD) of 0.032 μg L⁻¹ was achieved. When determining antigens in commercial samples, we obtained an LOD of 560 ηg mL⁻¹ and a limit of quantification of 1677 ηg mL⁻¹. The results of the electrochemical experiments were in accordance with the surface roughness obtained from atomic force microscopy images. Based on these results, the rGraphene-LIG electrode is shown to be an excellent platform for immunoglobulin detection when present in individuals after antigenic exposure caused by SARS-CoV-2.