Use of zein microspheres to anchor carbon black and hemoglobin in electrochemical biosensors to detect hydrogen peroxide in cosmetic products, food and biological fluids.

Hemoglobin-containing electrochemical biosensors are useful for detecting hydrogen peroxide through oxidation of the iron ion, but high efficiency can only be reached with appropriate immobilization strategies for hemoglobin. In this work, we combined zein from corn seed with carbon black to immobilize hemoglobin, as proof of concept, and form an electroactive film that could determine hydrogen peroxide within the concentration range from 4.9 × 10-6 to 3.9 × 10-4 mo L-1, and limit of detection of 4.0 × 10-6 mol L-1, using differential pulse voltammetry. The biosensor could also detect hydrogen peroxide in commercial samples of oxygenated water, synthetic serum (physiological and glycoside) and milk. The high performance is ascribed to the large surface area and conductive nature of the porous film that had carbon black and hemoglobin anchored on zein microspheres, according to scanning and transmission electron microscopies. It is significant that a protein from renewable sources (zein) combined with a low-cost carbon material (carbon black) serves as matrix for immobilization of biomolecules.

Reactive oxygen species and other biochemical and morphological biomarkers in the gills and kidneys of the Neotropical freshwater fish, Prochilodus lineatus, exposed to titanium dioxide (TiO2) nanoparticles.

This study investigated the action of titanium dioxide nanoparticles (TiO2-NPs), on the gills and kidneys of Neotropical freshwater fish, Prochilodus lineatus, with emphasis on reactive oxygen species (ROS) production, antioxidant responses, and morphological changes. Fish were exposed to 1, 5, 10, and 50 mg L-1 nominal TiO2-NPs suspended into water for 2 or 14 days. In gills, ROS decreased and glutathione (GSH) increased after 2 days, while ROS and GSH increased and superoxide dismutase activity decreased after 14 days. In kidneys, GSH and lipoperoxidation increased after 2 days and catalase activity decreased after 14 days. Common histopathologies in gills were epithelium hyperplasia, cellular hypertrophy, proliferation of mitochondria-rich cells (MRC), and lamellar stasis; in kidneys, there were cellular and nuclear hypertrophy, focal tubule degeneration, necrosis, and melanomacrophage (MM) proliferation. Although environmentally unlikely, high-dose exposures clarified biological effects of TiO2-NPs, such as ROS formation and MRC responses in the gills, which may impair ionic balance. It was also found that MM are likely responsible for eliminating NPs in the kidney. These findings will help to regulate TiO2-NP disposal, but longer-term studies are still needed.