Visceral leishmaniasis is a reemerging neglected tropical disease with limitations for its diagnosis, including low concentration of antibodies in the serum of asymptomatic patients and cross-reactions. In this context, this work proposes an electrochemical immunosensor for the diagnosis of visceral leishmaniasis in a more sensitive way that is capable of avoiding cross-reaction with Chagas disease (CD). Crude Leishmania infantum antigens tested in the enzyme-linked immunosorbent assay (ELISA) were methodologically standardized to best engage to the sensor. The antibodies anti-Trypanosoma cruzi and anti-Leishmania sp. Present in serum from patients with diverse types of CD or leishmaniasis were chosen. A screen-printed carbon electrode modified with gold nanoparticles was the best platform to guarantee effective adsorption of all antigens so that the epitope of specific recognition for leishmaniasis occurred efficiently and without cross-reaction with the evaluated CD. The current peaks reduced linearly after the recognition, and still were able to notice the discrimination between different kinds of diseases (digestive, cardiac, undetermined Chagas/acute and visceral chronic leishmaniasis). Comparative analyses with ELISA were performed with the same groups, and a low specificity (44%) was verified due to cross-reactions (high number of false positives) on ELISA tests, while the proposed immunosensor presented high selectivity and specificity (100%) without any false positives or false negatives for the serum samples from isolated patients with different types of CD and visceral leishmaniasis. Furthermore, the biosensor was stable for 5 days and presented a detection limit of 200 ng mL−1.
(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.
Knowing that ticks have bioactive molecules in their saliva which modulate hemostatic and immunomodulatory activities in humans, we carried out a systematic search for biomolecules present in tick saliva with great pharmacological potential. We evaluated studies published in the last ten years. Following the recommendations of the Prisma tool, primary and secondary studies of a systematic nature were selected, with no language or country restriction. Studies that included arthropods other than ticks and studies in which the use of saliva had no pharmacological application were excluded. For searches, we used the following databases: MEDLINE®/PubMed®, Web of Science, LILACS, EMBASE, Cochrane and SCOPUS. The methodological quality was performed using the tools available in Joanna Briggs, always with two or more independent evaluators. The generated data were tabulated and summarized through qualitative narrative analysis. The methodology selected 19 articles that met the eligibility criteria. The saliva of hard ticks, found in the Americas, is more promising when used in experimental studies with human cells. The elucidation of the biomolecules was possible, with evasin and serpine being the biomolecules with the most evident pharmacological potential for anti-inflammatory action. In the selected studies, we found only experimental studies, with no pre-clinical or clinical studies, making methodological qualification difficult; in some studies, with the biomolecule Evasin and Serpin, the need for elucidation of these biomolecules in question was suggested. Thus, we found evidence that the saliva of American hard ticks is the most studied for pharmacological applications of anti-inflammatory and immunomodulatory action.
In December 2019, the new coronavirus that was named SARS-CoV-2 was identified in China. The virus spreaded quickly and in March of 2020 it was declared a pandemic by the World Health Organization. Due to the initial lack of rapid diagnoses and effective treatments, the health systems were overloaded as a consequence of the high number of infected and severe cases. The diagnostic techniques currently available have limitations, for this reason, the search for new methods with sensitive, fast, cheap and locally used techniques, such as electrochemical biosensors, has been widely explored. Given the advantages of developing electrochemical biosensors for sensitive and selective diagnosis, this systematic review aimed to search for publications on the subject and answer the following question: The diagnosis of COVID-19 performed through an electrochemical biosensor, in individuals with suspected disease is it as efficient as that performed by RT-PCR? A study protocol was developed following the PRISMA-DTA guidelines and registered with PROSPERO under the approval code CRD42021282561. Searches were carried out in six electronic databases, inclusion and exclusion criteria were applied and seventeen publications were selected for this review. Based on the data, the analyse of risk was done using QUADAS-2. The results were presented in a descriptive qualitative manner it was not possible to carry out a meta-analysis.
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