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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.

Bioactive glasses (BG) incorporating antimicrobial agents can be effectively used against microorganisms. In this work, the in vitro effectiveness of silver-doped 58S BG (BGAg) against Leishmania species was studied. BG, BGAg1, and BGAg2 belonging to the system 58SiO 2 •(36-x) CaOÁ6P 2 O 5 ÁxAg 2 O, where x=0, 1, and 2 mol.% Ag, were synthesized via sol-gel, and characterized by scanning electron (SEM) and atomic force (AFM) microscopy, thermogravimetric analyses (TGA), X-ray diffraction (XRD), Fourier-transform infrared (FTIR), and surfaceenhanced Raman (Raman-SERS) spectroscopy. Cytotoxicity was assessed in A549 lung adenocarcinoma cells. Leishmania amazonensis and Leishmania braziliensis cultures were exposed to all groups, and C57BL/6 macrophages were infected by over metacyclic form L. amazonensis under the exposure of BGAg particles. SEM and AFM images showed an irregular and network arranged surface. TGA, XRD, FTIR, and RAMAN-SERS analyses confirmed silver inclusion within BG. None of the BG and BGAg presented toxicity. BGAg2 was effective in controlling promastigote forms under 150 and 300 lg/mL concentrations of both evaluated species. On macrophage invasion assay, BGAg2 presented reduction in metacyclic forms. For 72 hours, BGAg1 (150 lg/mL), BGAg1 (300 lg/

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(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.

(1) Background: The validation of biological antigens is the study’s utmost goal in biomedical applications. We evaluated three different probes with single and multiple epitopes through electrochemical detection of specific IgG in serum for human strongyloidiasis diagnosis. (2) Methods: Screen-printed gold electrodes were used and probes consisting of two single-epitope synthetic peptides (D3 and C10) with different sequences, and a multi-epitope antigen [detergent phase (DP)—hydrophobic membrane proteins]. Human serum samples from three populations were used: Strongyloides stercoralis positive, positive for other parasitic infections and negative controls. To test the immobilization of probes onto a screen-printed gold electrode and the serum IgG detection, electrochemical analyses were carried out through differential pulse voltammetry (DPV) and the electrode surface analyses were recorded using atomic force microscopy. (3) Results: The electrochemical response in screen-printed gold electrodes of peptides D3 and C10 when using positive serum was significantly higher than that when using the DP. Our sensor improved sensitivity to detect strongyloidiasis. (4) Conclusions: Probes’ sequences are critical factors for differential electrochemical responses, and the D3 peptide presented the best electrochemical performance for strongyloidiasis detection, and may efficiently substitute whole antigen extracts from parasites for strongyloidiasis diagnosis in electrochemical immunosensors.

Abstract:The detection of Leishmania spp. through a disposable surface plasmon resonance (SPR) biochip, using mono-and polychromatic sources, is presented here. A highly specific and sensitiveconstrained synthetic peptide (LC2) derived from a mimotope of Leishmania chagasi antigen was immobilized on the sensing region using a simple protocol. ELISA-and PCR-confirmed negative and positive sera of Leishmania chagasi infected patients were used. Detection of positive IgG showed a fast response with good sensitivity and specificity for the proposed method.

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