Sublethal toxicity of TiO2 nanoparticles to common carp (Cyprinus carpio, Linnaeus, 1758) under visible light and dark conditions

The ubiquitous presence of TiO2 nanoparticles (nTiO2) and microplastics (MPs) in marine ecosystems has raised serious concerns about their combined impact on marine biota. This study investigated the combined toxic effect of nTiO2 (1 mg/L) and NH2 and COOH surface functionalized polystyrene MPs (PSMPs) (2.5 and 10 mg/L) on Chlorella sp. All the experiments were carried out under both visible light and UV-A radiation conditions to elucidate the impact of light on the combined toxicity of these pollutants. Growth inhibition results indicated that pristine nTiO2 exhibited a more toxic effect (38%) under UV-A radiation when compared to visible light conditions (27%). However, no significant change in the growth inhibitory effects of pristine PSMPs was observed between visible light and UVA radiation conditions. The combined pollutants (nTiO2 + 10 mg/L PSMPs) under UV-A radiation exhibited more growth inhibition (nTiO2 + NH2 PSMPs 66%; nTiO2 + COOH PSMPs 50%) than under visible light conditions (nTiO2 + NH2 PSMPs 55%; TiO2 + COOH PSMPs 44%). Independent action modeling indicated that the mixture of nTiO2 with PSMPs (10 mg/L) exhibited an additive effect on the algal growth inhibition under both the light conditions. The photoactive nTiO2 promoted increased production of reactive oxygen species under UV-A exposure, resulting in cellular damage, lipid peroxidation, and impaired photosynthesis. The effects were more pronounced in case of the mixtures where PSMPs added to the oxidative stress. The toxic effects of the binary mixtures of nTiO2 and PSMPs were further confirmed through the field emission electron microscopy, revealing specific morphological abnormalities. This study provides valuable insights into the potential risks associated with the combination of nTiO2 and MPs in marine environments, considering the influence of environmentally relevant light conditions and the test medium.

Bactericidal mechanisms of Ag2O/TNBs under both dark and light conditions

This study evaluated the toxicity potential of ZnO and TiO2 nanoparticles under pre-UV-A irradiation and visible light condition on Artemia salina. The nanoparticle suspension was prepared in seawater medium and exposed under pre-UV-A (0.23mW/cm2) and visible light (0.18mW/cm2) conditions. The aggregation profiles of both nanoparticles (NPs) and dissolution of ZnO NPs under both irradiation conditions at various kinetic intervals (1, 24, 48h) were studied. The 48-h LC50 values were found to be 27.62 and 71.63mg/L for ZnO NPs and 117 and 120.9mg/L for TiO2 NPs under pre-UV-A and visible light conditions. ZnO NPs were found to be more toxic to A. salina as compared to TiO2 NPs. The enhanced toxicity was observed under pre-UV-A-irradiated ZnO NPs, signifying its phototoxicity. Accumulation of ZnO and TiO2 NPs into A. salina depends on the concentration of particles and type irradiations. Elimination of accumulated nanoparticles was also evident under both irradiation conditions. Other than ZnO NPs, the dissolved Zn2+ also had a significant effect on toxicity and accumulation in A. salina. Increased catalase (CAT) activity in A. salina indicates the generation of oxidative stress due to NP interaction. Thus, this study provides an understanding of the toxicity of photoreactive ZnO and TiO2 NPs as related to the effects of pre-UV-A and visible light irradiation.

Cytotoxicity of titania nanoparticles towards waste water isolate Exiguobacterium acetylicum under UVA, visible light and dark conditions

Remarkable bactericidal traits of a metal-ceramic composite coating elated by hierarchically structured surface.

Research on eliminating organic pollutants in water by using heterogeneous photocatalysts such as nano-TiO_2 abound. However, the question is whether metabolites, resulting from optical dispersion of environmental pollutants, are still toxic to aquatic organisms. Therefore, this study was designed to evaluate the effect of a co-exposure to paraquat and TiO_2-NPs on blood biochemical indices of common carp. Fish were exposed to 0.2 and 0.4 mg L^-1 paraquat with 0.125 mg L^-1 TiO_2-NPs for 21 days under different light conditions, including natural photoperiod (16 L 8h^-1 D) and complete darkness. No significant alterations in the Aspartate aminotransferase (AST), Alanine aminotransferase (ALT), Lactate dehydrogenase (LDH), Alkaline phosphatase (ALP) and Creatine phosphokinase (CPK), activities and total protein, albumin, globulin, glucose, cholesterol and triglyceride levels were observed in fish exposed to TiO_2-NPs and 0.2 mg L^-1 paraquat under normal lighting conditions. However, a significant change in blood biochemical indices in fish exposed to TiO2-NPs with 0.4 mg L^-1 paraquat (16 L 8h^-1 D) and in fish exposed to TiO_2-NPs and paraquat (under darkness). A significant decrease in the activity of Gamma-glutamyltransferase (GGT) and a significant increase in creatinine level were observed in all groups which were exposed to TiO_2-NPs and paraquat. The results of this study indicate that using 0.125 mg L^-1 nano-TiO2 in order to remove paraquat (0.2 mg L^-1) under lighting conditions can minimize the adverse effects of paraquat and its metabolites on blood biochemical indices of fish. So, using nano-TiO_2 (0.125 mg L^-1) to remove paraquat under lighting conditions can significantly reduce its toxic effects.

The current study deals with Cr(VI) removal by nanotitania under fluorescent light and dark conditions. The equilibrium removal capacities, 85.85 and 59.4 mg of Cr(VI) g−1 of nanoparticle were noted for nanotitania interacted under light and dark conditions, respectively, at optimized conditions (pH: 7.0, contact time: 30 min, initial Cr(VI) concentration: 20 mg l−1, nanoparticle dosage: 0.1 g l−1). Under both the conditions, the equilibrium removal data fitted well with the Langmuir isotherm model. The nanotitania followed a second-order kinetics under light condition whereas a pseudo-second-order kinetics was observed under dark condition. The surface characterization of nanotitania was carried out by zeta potential measurement and transmission electron microscope (TEM). Fourier transform infrared (FT-IR) studies carried out under light and dark conditions indicate the interaction of surface functional groups to Cr(VI). Cr(VI) removal study carried out in the Cr(VI)–Cr(III) mixture showed a decrease in Cr(VI) removal capacity with increase in Cr(III) concentration. A 92% regeneration of nanoparticle was observed indicating efficient reusability of the system. The applicability of the nanotitania in Cr(VI) contaminated water was studied by spiking Cr(VI) in natural water matrices like ground water and lake water.

Mercury (Hg) is assumed to be predominantly methylated by microorganisms in the environment. However, the mechanisms and extent of abiotic methylation are poorly appreciated. The understanding of the mechanisms leading to abiotic methylation and demethylation in the aquatic environment is of special concern since methylmercury (MeHg) biomagnifies in the food web. Bioaccumulating organisms have also been found to preserve specific Hg isotopic signatures that provide direct insight into aquatic Hg transformations. In this study we investigated the influence of chloride on the magnitude of Hg isotope fractionation during abiotic methylation of inorganic Hg (Hg(II)) using methylcobalamin as methyl donor compound. Coupling of gas chromatography with multi-collector inductively coupled plasma mass spectrometry has allowed to determine simultaneously isotopic ratios of inorganic and methyl-Hg species. Kinetic experiments demonstrated that the presence of chloride not only slowed the chemical alkylation of Hg(II) by methylcobalamin, but also decreased the extent of the methylation, which it is especially significant under visible light conditions due to the enhancement of MeHg photodecomposition. Abiotic methylation of Hg(II) by methylcobalamin in the presence of chloride caused significant Hg mass-dependent isotope fractionation (MDF) for both Hg(II) substrate (δ202Hg(II) from −0.74‰ to 2.48‰) and produced MeHg (δ202MeHg from −1.44‰ to 0.38‰) both under dark and visible light conditions. The value of this MDF under such saline conditions was higher than that previously reported (δ202MeHg from −0.73‰ to 0.09‰) in the absence of chloride and appeared mainly related to inorganic Hg speciation in solution, which is predominantly mercuric chloro-complexes (i.e. HgCl42−). Different isotopic signatures were observed for the different Hg species at the same time of reaction for either dark or visible light (450–650nm wavelengths) conditions. However, no significant mass-independent fractionation (MIF) was induced under any conditions within the analytical uncertainties (−0.17±0.31<∆201Hg<0.17±0.28‰), suggesting that photo-induced demethylation does not always involve MIF. These results also suggest that methylation by methylcobalamin can be an experimental model to study Hg isotope fractionation extent during elementary reaction of methyl transfer in biotic systems.

In this study, we investigated the possible effects of paraquat and micro-plastics on blood biochemical parameters in common carp (Cyprinus carpio). We exposed C. carpio for 21 days to sublethal concentrations of paraquat (0.2 and 0.4 mg L−1) and micro-plastics (1 and 2 mg L−1), alone or in combination. Blood biochemical analysis indicated that exposure to 0.4 mg L−1 paraquat and mixture of paraquat and micro-plastics was followed by an increase in aspartate aminotransferase (AST), alkaline phosphatase (ALP), and creatine phosphokinase (CPK) activities and glucose levels. The activity of ALP and CPK showed a significant increase in fish treated with 2 mg L−1 micro-plastics. No significant changes were observed in glucose level, AST, ALT, and LDH activities in fish exposed to micro-plastics. Exposure to paraquat and/or micro-plastics resulted in a significant decrease in total protein, globulin, cholesterol, and triglyceride levels and γ-glutamyl transferase activity. When fish were exposed to paraquat or paraquat and micro-plastics, alanine aminotransferase (ALT) and lactate dehydrogenase (LDH) activities increased significantly compared to the control group. Treating fishes with a mixture of paraquat and 2 mg L−1 micro-plastics caused a significant increase in albumin levels. However, a significant decrease in the albumin level was observed after exposure to paraquat or micro-plastics. Creatinine levels increased after exposure to paraquat and/or micro-plastics. The results indicate that increased doses of micro-plastics in water significantly increased toxic effects of paraquat in fish. Finally, these data support the hypothesis that changes in blood biochemical parameters were induced by exposure to paraquat and/or micro-plastics.

Nitrogen doped titanium dioxide as an aesthetic antimicrobial filler in dental polymers

The main drawback of conventional palm oil mill effluent (POME) treatment is that the process is time and space-consuming. Besides, the treatment produces highly polluted wastewater that pollutes the environment if discharged directly. Photocatalytic process has significant potential to degrade recalcitrant organic pollutants and has recently attracted tremendous attention. However, current approaches mainly focus on visible light condition, which is still an ineffective treatment for POME. In this study, POME was successfully degraded using graphitic carbon nitride (g-C3N4) photocatalyst synthesised by calcination. The prepared photocatalyst was characterised by ultraviolet-visible diffuse reflectance (UV-Vis DRS) spectroscopy and scanning electron microscopy (SEM). The SEM results revealed the morphology of g-C3N4 photocatalyst. g-C3N4 could act as a visible-light-driven (VLD) photocatalyst with the highest photocatalytic efficiency of 71% under visible light. The present work highlights the potential of g-C3N4 towards the degradation of POME under visible light and dark condition. The highly enhanced photocatalytic performance is attributed to g-C3N4, but it does not work well in round-the-clock photocatalysis. However, g-C3N4 can work as the band alignment to drive separate photogenerated charge carriers, leading to effective photocatalytic degradation. g-C3N4 photocatalyst may be considered as an ideal candidate for treating POME.

Neural retina from most species contains 3,4- dihydroxyphenylethylamine (dopamine) receptors coupled to stimulation of adenylate cyclase activity. It has been demonstrated that release of dopamine from its neurons and subsequent occupation of dopamine receptors is increased by light. In this study, we have shown that adenylate cyclase activity in bovine retina is highly responsive to the endogenous Ca2+-binding protein, calmodulin, and that calmodulin can increase dopamine-sensitive adenylate cyclase activity in bovine retina. We further demonstrate that both dopamine- and calmodulin-stimulated adenylate cyclase activities can be regulated by alterations in light. Bovine retinas were dissected from the eye under a low-intensity red safety light, defined as dark conditions, and incubated for 20 min in an oxygenated Krebs Henseleit buffer under either dark or light conditions. The retinas were then homogenized and adenylate cyclase activity measured in a particulate fraction washed to deplete it of endogenous Ca2+ and calmodulin. Activation of adenylate cyclase activity by calmodulin, dopamine, and the nonhydrolyzable GTP analog, guanosine-5'-(beta,gamma-imido)triphosphate ( GppNHp ), was significantly (60%) greater in particulate fractions from retinas that had been incubated under dark conditions as compared to those incubated under light conditions. Basal, Mn2+-, and GTP-stimulated adenylate cyclase activities were not altered by changes in lighting conditions. Calmodulin could increase the maximum stimulation of adenylate cyclase by dopamine in retinas incubated under either dark or light conditions, but the degree of its effect was greater in retinas incubated under light conditions.(ABSTRACT TRUNCATED AT 250 WORDS)

Chlorpyrifos, an organophosphate pesticide, is widely used to control pests in agriculture farms and orchards of fruit trees. In this study, the fish were exposed to sub-lethal concentrations of chlorpyrifos which were determined based on numerical value of 96 h LC 50 . Blood was sampled after 10, 20 and 30 days and biochemical parameters including glucose, total protein, albumin, globulin, triglyceride and cholesterol levels, and aspartate aminotransferase (AST), alanine aminotransferase (ALT), lactate dehydrogenase (LDH), creatine kinase (CK), alkaline phosphatase (ALP) and acetylcholinsetrase (AChE) activities were measured. Behavioral changes in the fish were also recorded during the experiment. Unbalanced swimming, swimming in the surface water and hyperglycemia, increased blood triglyceride, and increased levels of AST, LDH and CK activities as well as decreased levels of AChE activity were important changes that were observed in the specimens exposed to chlorpyrifos during experimental periods. The most important alterations in the blood biochemical parameters were measured in the specimens exposed to 40 µg/L chlorpyrifos on the 20 th and 30 th day of the trial. In conclusion, results of the present study indicated that exposure to sub-lethal concentrations of chlorpyrifos as low as 40 µg/L may cause biochemical and behavioral changes in Cyprinus carpio .

Biofouling is a major obstacle to the efficient extraction of uranium from seawater due to the numerous marine microorganisms in the ocean. Herein, we report a novel amidoxime (AO) crystalline cova...

Photocatalytic effect of N–TiO2 conjugated with folic acid against biofilm-forming resistant bacteria