Fluorescent quantum dot-based nanotool for targeted identification and evaluation of the schistosomiasis circulating cathodic antigen in tissue samples.

Schistosomiasis represents a serious public health problem, a disease for which the circulating cathodic antigen (CCA) is a relevant biomarker. Quantum dots (QDs) are advantageous fluorescent nanoparticles that can be used as specific nanoprobes. In this study, a nanotool based on QDs and anti-CCA antibodies was developed, which, in association with fluorescence microscopy, was applied to trace and evaluate the CCA profile in schistosomiasis-infected tissue samples. Kidney and liver tissues from mice at different disease phases were used as models. QDs and the conjugates were characterized by absorption and emission spectroscopies. Microscopy analyses were used to map and assess CCA accumulation in infected tissue slices in respect to non-infected control samples. The fluorescent microplate assay (FMA) and Zeta potential (ζ) analyses indicated an effective conjugation, which was corroborated by the absence of labeling in non-infected tissue slices (which lack CCA) after incubation with the nanoprobe. Infected liver and kidney tissues exhibited notable staining by the QDs-anti-CCA conjugate. The CCA accumulation increased as follows: 30 < 60 = 120 days post-infection, with 30, 60, and 120 days corresponding to the pre-patent, acute, and beginning of chronic disease phases, respectively. Therefore, this innovative approach, combining imaging acquisition with the sensitivity and specificity of the QDs-anti-CCA conjugate, demonstrated efficiency in locating and comparatively evaluating CCA deposition in biological samples, thereby opening new possibilities for schistosomiasis research.

Emerging biomedical tools for biomarkers detection and diagnostics in schistosomiasis.

Schistosomiasis is a neglected disease that strikes many people from tropical and subtropical countries where there are not satisfactory sanitation and wide access to clean water. Schistosoma spp., the causative agents of schistosomiasis, exhibit a quite complex life cycle that involves two hosts (humans and snails, respectively, the definitive and the intermediate), and five evolutive forms: cercariae (human infective form), schistosomula, adult worms, eggs, and miracidia. The techniques to diagnose schistosomiasis still have various limitations, mainly regarding low-intensity infections. Although various mechanisms associated with schistosomiasis have already been evidenced, there is still a need to fulfill the comprehension of this disease, especially to prospect for novel biomarkers to improve its diagnosis. Developing methods with more sensitivity and portability to detect the infection is valuable to reach schistosomiasis control. In this context, this review has gathered information not only on schistosomiasis biomarkers but also on emerging optical and electrochemical tools proposed in selected studies from about the last ten years. Aspects of the assays regarding the sensibility, specificity, and time needed for detecting diverse biomarkers are described. We hope this review can guide future developments in the field of schistosomiasis, contributing to improving its diagnosis and eradication.

Sensitive Zika biomarker detection assisted by quantum dot-modified electrochemical immunosensing platform.

We report the development of a new nanostructured electrochemical immunosensing platform for the detection of the Zika virus envelope protein (EP-ZIKV). For this, quantum dots (QDs) were explored in combination with screen-printed carbon electrodes (SPCEs) functionalized with a conductor polymeric film, formed from 2-(1H-pyrrol-1-yl)ethanamine (Pyam), and anti-EP DIII ZIKV antibodies. Carboxylated CdTe QDs were synthesized, characterized by optical and structural techniques, and covalently immobilized onto the SPCE/PPyam surface. Then, anti-EP ZIKV antibodies were also covalently conjugated to QDs. All stages of platform assembly were evaluated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The detection of EP-ZIKV was performed by differential pulse voltammetry (DPV). Results indicated that QDs were efficiently immobilized, and did not show oxidation, under the conditions evaluated, for at least 7 months. Anti-EP ZIKV antibodies were effectively immobilized on the PPyam/QDs surface, even after 2 months of electrode storage. The platform enabled the detection of EP-ZIKV with high sensitivity using minimal sample volumes (LOD = 0.1 ng mL-1 and LOQ = 0.4 ng mL-1). The platform was also able to detect EP-ZIKV in spiked serum samples. Moreover, the platform showed specificity, not detecting the EP-DENV 3 nor a mixture of four DENV serotypes antigens. Thus, the proposed combination favored the development of a sensitive immunosensing platform, promising for the detection of Zika in the viremic phase, which also holds potential for transposition to other arboviruses.

Quantum dots-based fluoroimmunoassay for anti-Zika virus IgG antibodies detection.

Zika virus (ZIKV) has been declared a public health emergency of international concern. ZIKV has been associated with some neurological disorders, and their long-term effects are not completely understood. The majority of the methods for ZIKV diagnosis are based on the detection of IgM antibodies, which are the first signs of immunological response. However, the detection of IgG antibodies can be an important approach for ZIKV past infection diagnosis, especially for pregnant women, helping the comprehension/treatment of this disease. There has been a growing interest in applying nanoparticles for efficient ZIKV or antibodies detection. Quantum dots (QD) are unique fluorescent semiconductor nanoparticles, highly versatile for biological applications. In the present study, we explored the special QD optical properties to develop an immunofluorescence assay for anti-ZIKV IgG antibodies detection. Anti-IgG antibodies were successfully conjugated with QDs and applied in a fluorescence sensing nanoplatform. After optimization using IgG antibodies, the conjugates were employed to detect anti-ZIKV IgG antibodies in polystyrene microplates sensitized with ZIKV envelope E protein. The nanoplatform was able to detect anti-ZIKV IgG antibodies in a concentration at least 100-fold lower than the amount expected for protein E immune response. Moreover, conjugates were able to detect the antibodies for at least 4 months. Thus, our results showed that this QDs-based fluoroimmunoplatform can be considered practical, simple and promising to detect Zika past infections and/or monitoring immune response in vaccine trials.