Label-free electrochemical DNA biosensor for zika virus identification.

Seventy years after its discovery, the zika virus emerged in Brazil and spread rapidly throughout the Americas, bringing unusual complications such as microcephaly. The World Health Organization classifies zika as the most harmful viral disease today and considers the development of new diagnostic methods for zika and related diseases, such as dengue, urgent. Although there are tests to identify both infections, current diagnostic methods are slow, nonspecific, and costly. This study describes an impedimetric electrochemical DNA biosensor for label-free detection of zika virus. Disposable electrodes were fabricated by thermal evaporation on polyethylene terephthalate substrates covered with a nanometric gold layer manufactured in three-contact configurations. The disposable, evaporated electrodes were morphologically characterized by atomic force microscopy and scanning electron microscopy. The electrode surface was characterized by electroanalytical techniques. Genetic sequences of primers and complementary capture probes were designed based on analysis of the zika and dengue virus genomes. The biosensor used a three-contact electrode to identify DNA sequences in a drop of sample, and for detection of zika virus sequences, it allowed for direct reading of the hybridization event without labeling on disposable electrodes and with a 1.5 h response time. In this system, impedance measurements indicated a limit of detection of 25.0 ±â€¯1.7 nM. The developed biosensors showed selectivity for zika in the synthetic DNA assays, and therefore, are promising for clinical analysis.

A novel drug delivery of 5-fluorouracil device based on TiO2/ZnS nanotubes.

The structural and electronic properties of titanium oxide nanotubes (TiO2) have attracted considerable attention for the development of therapeutic devices and imaging probes for nanomedicine. However, the fluorescence response of TiO2 has typically been within ultraviolet spectrum. In this study, the surface modification of TiO2 nanotubes with ZnS quantum dots was found to produce a red shift in the ultra violet emission band. The TiO2 nanotubes used in this work were obtained by sol-gel template synthesis. The ZnS quantum dots were deposited onto TiO2 nanotube surface by a micelle-template inducing reaction. The structure and morphology of the resulting hybrid TiO2/ZnS nanotubes were investigated by scanning electron microscopy, transmission electron microscopy and X-ray diffraction techniques. According to the results of fluorescence spectroscopy, pure TiO2 nanotubes exhibited a high emission at 380nm (3.26eV), whereas TiO2/ZnS exhibited an emission at 410nm (3.02eV). The TiO2/ZnS nanotubes demonstrated good bio-imaging ability on sycamore cultured plant cells. The biocompatibility against mammalian cells (Chinese Hamster Ovarian Cells-CHO) suggesting that TiO2/ZnS may also have suitable optical properties for use as biological markers in diagnostic medicine. The drug release characteristic of TiO2/ZnS nanotubes was explored using 5-fluorouracil (5-FU), an anticancer drug used in photodynamic therapy. The results show that the TiO2/ZnS nanotubes are a promising candidate for anticancer drug delivery systems.