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.

Essential oils of Taxandria fragrans and Melaleuca alternifolia have effective antidermatophytic activities in vitro and in vivo that are antagonised by ketoconazole and potentiated in gold nanospheres.

The investigation of the effects of three essential oils (EOs) from Taxandria fragrans (FRA), Melaleuca alternifolia (TTO) and Boswellia serrata (IF), alone and combined with ketoconazole (KTZ), and their functionalised gold nanoparticles (AuNP) against Trichophyton interdigitale both in vitro and in vivo indicated that EOs presented activity against T. interdigitale. The combination of EOs and KTZ was antagonistic. FRA, TTO, gold nanoparticles capped with T. fragrans (AuNPFRA) and gold nanoparticles capped with M. alternifolia (AuNPTTO) presented antidermatophytic activity in vivo, with the capacity to reduce fungal burden and to preserve tissue architecture; however, combination treatment with KTZ increased fungal burden and caused tissue damage. The combination of EO with KTZ exhibited antagonistic activity and was histologically harmful. In contrast, FRA, TTO, AuNPFRA and AuNPTTO are promising treatments for dermatophytosis.

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.

Hybrid systems based on gold nanostructures and porphyrins as promising photosensitizers for photodynamic therapy.

Gold nanostructures of two different shapes (spheres and rods) were synthesized to form a colloidal hybrid system with 5,10,15,20-tetrakis(N-methylpyridinium-4-yl)porphyrin tosylate salt (H2TM4PyP(OTs)4) (POR) for applications in photodynamic therapy (PDT) using light in the visible spectral range. Electron paramagnetic resonance (EPR) experiments in combination with spin trapping were used for the detection of reactive oxygen species (ROS) and evaluation of the efficiency of these novel hybrid systems as photosensitizers. It is shown that the hybrid system consisting of gold nanorods (AuNR) and porphyrin (POR) is by far more efficient than its isolated components. This enhanced efficiency is explained by a synergetic effect between the AuNR and the porphyrin, wherein a rapid energy transfer from the former to the latter produces a large amount of singlet oxygen followed by its conversion into hydroxyl radicals. The mechanism was investigated using different spin traps and different ROS inhibitors. On the other hand, spherical gold nanoparticles (AuNP) do not show this synergetic effect. The synergetic effect for gold nanorods/POR hybrid is attributed to a larger field enhancement close to the gold nanorod surface in addition to the electrostatic attraction between the components of the hybrid system.

Absorption coefficient imaging by near-field scanning optical microscopy in bacteria.

We present a method for obtaining a position-dependent absorption coefficient from near-field scanning optical transmission microscopy. We show that the optical transmission intensity can be combined with the topography, resulting into an absorption coefficient that simplifies the analysis of different materials within a sample. The method is tested with the dye rhodamine 6G, and we show some analysis in biological samples such as bacteria KIebsiella pneumoniae and Pseudomonas aeruginosa. The calculated absorption coefficient images show important details of the bacteria, in particular for P. aeruginosa, in which membrane vesicles are clearly seen.