- ArtículoAcceso AbiertoHydrogen-bonding interactions and compostability of bionanocomposite films prepared from corn starch and nano-fillers with and without added Jamaica flower extract(2018)Bionanocomposite films processed by twin screw extrusion followed by thermo molding were prepared from corn starch (Zea mays) and pH-sensitive nano-clays packaged with Jamaica flower (Hibiscus sabdariffa) extract (JFE). The hydrogen (H)-bonding interactions of the materials obtained were evaluated by ATR/FTIR spectroscopy, and their influence on the physicochemical and surface properties of the materials was analyzed. The degree of biodegradability and compostability of the films was also recorded. This latter was analyzed in terms of the ecotoxicity of the films using the variations in the growth of the primary root of lettuce (Lactuca sativa) seedlings exposed to three concentrations (1, 10 and 100 μg/mL) of the powdered films as a biomarker. The addition of the JFE-containing nano-fillers strengthened the H-bonding interactions with the thermoplastic starch (TPS) matrix, and these interactions were more efficient when there were fewer steric impediments between the JFE and the TPS. Additionally, stronger H-bonding interactions produced more hydrophilic surfaces, with greater surface energy and rougher surface morphology. All the films tested were biodegradable. Our research group had previously encountered high cytotoxicity in one of the evaluated nano-clay systems, and in this study, we confirmed that this same nano-clay system produced a non-compostable material at high concentrations (100 μg/mL), as measured by its effect on lettuce seedlings. This confirms that biodegradable materials are not necessarily compostable.
- ArtículoAcceso AbiertoAre Oxidative Stress Biomarkers Sensitive to Environmental Concentrations of Chlorpyrifos Exposed to the Freshwater Crab, Zilchiopsis collastinensis (Decapoda; Trichodactylidae)?(2019)Global trends in pesticide use can increase aquatic pollution and affect resident fisheries. Crabs exposed to organophosphate pesticides, such as chlorpyrifos, may increase production of reactive oxygen species (ROS), affecting the pro-oxidant/antioxidant balance. Zichiopsis collastinensis crabs were exposed to environmentally relevant concentrations of chlorpyrifos (0.1 and 0.5 μg L− 1). Effects on the oxidative stress enzymes catalase, superoxide dismutase, glutathione S-transferases, glutathione reductase, and on thiobarbituric acid reactive substances and hydrogen peroxide concentrations were evaluated at four intervals during 96 h exposures. Exposures caused decreased GST activity and increased H2O2 levels in gills. There were modifications of GST, CAT and SOD activities in the hepatopancreas after 12 h of exposure, and an increase of H2O2 levels at every exposure interval observed. The present study proved that chlorpyrifos lead to oxidative stress in Z. collastinensis. However other enzymatic/non-enzymatic responses should be further investigated in order to be included as part of a battery of biomarkers, together with H2O2 levels, which is a parameter highly recommended to be taken into account.
- ArtículoAcceso AbiertoAn integrated biomarker response study explains more than the sum of the parts: Oxidative stress in the fish Australoheros facetus exposed to imidacloprid(2018)Integrated Biomarkers Response (IBR) index have been developed as a practical and robust tool to assess the susceptibility to pollutants using multiple biomarker responses. Neonicotinoid insecticides are nowadays one of the most sold pesticides worldwide. Nevertheless, imidacloprid (IMI) sub-lethal effects such as oxidative stress (OS) on fishes are scarcely studied. Hence, the aims of this work were: (1) to evaluate exposure- and damage biomarkers related to OS in the freshwater fish Australoheros facetus exposed to IMI and (2) to apply the IBR index to achieve a comprehensive understanding of OS in the fish. The results of the present study showed that all the biomarkers presented different responses in the three monitored tissues: liver, brain and gills. Results for an initial battery of 19 biomarkers were obtained and for the IBR index only those with significant differences have been considered. The biomarkers that had the most important weight on the IBR index were SOD activity in brain and gills, H2O2 concentration in liver, and carbonyl groups concentration in gills in fishes exposed to 100 and 1000 μg L−1 IMI. This index allowed affirming that a short term exposure to environmentally relevant concentrations of IMI (≥10 μg L−1) produces OS in A. facetus. However, a more deep understanding of some biomarkers response is necessary to improve the index and for finally apply it in field studies.
- ArtículoAcceso AbiertoStrategies for cadmium detoxification in the white shrimp Palaemon argentinus from clean and polluted field locations(2019)In this study, we investigated the metal handling capacity of non-tolerant and tolerant populations of Palaemon argentinus to cadmium (Cd), through evaluating of the main mechanisms of metal detoxification, metallothioneins (MT), and metal-rich granules (MRG), to prove that the presence of MRG in the second population is responsible for that condition. The tolerant population were exposed to 3.06 and 12.26 mg Cd$L 1, while the non-tolerant shrimp were exposed to 3.06 mg Cd$L 1. Each experiment involved the exposure during 3, 7, 10, and 15 days and, the depuration during 7, 14, 21, and 28 days, for which shrimp were transferred to clean water. The range values of MT concentrations for non-tolerant shrimp were: 12.24e23.91 mg g (w.w), while for tolerant shrimp were: 8.75e16.85 mg g (w.w); MRG levels were: 0.12e0.57 mg g (w.w) and 0.3e2.1 mg g (w.w), respectively. The results showed different strategies for Cd detoxification: the induction of MT was the main pathway in the non-tolerant population, while the formation of Cd-MRG was the main mechanism for tolerant shrimp. These differences could be related to environmental history and the health status of each population.
- ArtículoAcceso AbiertoCharacterization of biodegradable/non-compostable films made from cellulose acetate/corn starch blends processed under reactive extrusion conditions(2019)The manufacture of food packaging materials from food hydrocolloids has been widely studied during the last decades and multiple alternatives have been investigated, with research mainly focusing on improving the physicochemical and mechanical properties of the different materials. Processing food hydrocolloids by reactive extrusion (REx) for the development of food packaging has, however, been poorly studied. Four film systems were prepared from corn (Zea mays) thermoplastic starch (TPS) containing either cellulose acetate (C) or chromium octanoate (Cat - a potential food grade catalyst), or a blend of both (C + Cat). Processing was done under REx conditions using a twin-screw extruder. An exhaustive study of the resulting materials was carried out in terms of the structural, physicochemical, thermal, surface, mechanical and compostable properties related to their potential use in food packaging applications. The most hydrophobic material was the C-containing film. However, this physicochemical behavior was different on the film surface, thus suggesting molecular rearrangements within the material. The Cat-containing films were darker than the other materials. The mechanical behavior observed in the Cat-containing films was particularly interesting as it suggests that these film systems could be used as shape memory materials for food packaging applications, as long as the following mechanical conditions are not exceeded: 5.02% strain and 0.43 MPa stress. All the films tested were biodegradable. We confirmed that Cat-containing film systems produced non-compostable materials at high concentrations (1 mg/mL), as measured by its effect on lettuce seedlings. This confirms that biodegradable materials are not necessarily compostable.