Publicação
Carbon quantum dots for the monitoring and remediation of metals in aquatic environments
| Resumo: | Water is a valuable resource for ecosystems and human existence, but it has been significantly threatened by pollution. Metals generated by anthropogenic activities are considered a persistent group of contaminants that have been seriously contributing to water pollution and causing harmful effects on ecosystems, including bioaccumulation in aquatic organisms and biomagnification along the trophic chain. Over the years, various approaches have been developed to mitigate metal pollution. Recently, carbon quantum dots (CDs), carbon-based nanomaterials with diameters of less than 10 nm, have attracted a great deal of attention due to their optical properties and high biocompatibility. These properties make CDs highly relevant in various applications, such as monitoring agents and environmental remediation. CDs have functional groups that allow them to establish strong interactions with metal ions, potentially reducing their biotoxicity in aquatic ecosystems. The CDs used in this study were synthesised solvothermally using citric acid, urea and indocyanine green as molecular precursors, thus allowing them to be doped with sulphur and nitrogen. In this work, we used zebrafish embryos (Danio Rerio), a well-known model organism that is often used in toxicology, to study the ability of CDs to remediate aquatic environments contaminated with metal ions and reduce their toxicity on organisms. In this context, the following metal ions were tested: Cd ²+, Ni ²+ and Ag +. The embryos were exposed to binary combinations of CDs (0, 5 or 50 mg/L) and various concentrations of each metal in a full factorial design for the 3 metals tested. Various parameters were used to assess the toxicity of the metal ions, such as survival, hatching, swimming behaviour and cholinesterase enzyme activity. For the 3 metals tested, a reduction in toxicity was observed when the metals were combined with CDs. For example, when CD = 5 mg/L was added to the metal solutions, the LC50 value (lethal concentration for 50% of the organisms) increased 2.7 times for Cd ²+; 1.3 times for Ni ²+ and 2.3 times for Ag +. Hatch inhibition, although not as robust as survival, indicated the same trend for all three metals. The reduction in toxicity by the CDs was also visible by analyzing locomotion behaviour in the case of Cd ²+ and AchE activity in the case of Ni ²+ and Ag +. In addition, the CDs showed great potential as probes for monitoring metal concentrations in water. The results obtained showed a marked attenuation of CD fluorescence in the presence of Cd ²+ and Ni ²+, with the former having a more pronounced effect, and an increase in fluorescence in the case of Ag +. Fluorescence microscopy analyses of Danio Rerio organisms in the presence of ions and CDs corroborated the photophysical studies. Larvae exposed to CDs alone showed lower fluorescence than larvae exposed to the combination of Ag + and CDs. In contrast, larvae exposed to the combination of Ni ²+ and CDs showed a decrease in fluorescence. The results obtained during this study emphasize the high potential of CDs for the remediation of metals in the aquatic environment and simultaneously for in vivo monitoring of metal biotoxicity. |
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| Autores principais: | Amaral, João Carlos Barata Pais do |
| Assunto: | Behaviour Acetylcholinesterase Metals Bioremediation Monitoring Fluorescence Adsorption |
| Ano: | 2023 |
| País: | Portugal |
| Tipo de documento: | dissertação de mestrado |
| Tipo de acesso: | acesso aberto |
| Instituição associada: | Universidade de Aveiro |
| Idioma: | inglês |
| Origem: | RIA - Repositório Institucional da Universidade de Aveiro |
| Resumo: | Water is a valuable resource for ecosystems and human existence, but it has been significantly threatened by pollution. Metals generated by anthropogenic activities are considered a persistent group of contaminants that have been seriously contributing to water pollution and causing harmful effects on ecosystems, including bioaccumulation in aquatic organisms and biomagnification along the trophic chain. Over the years, various approaches have been developed to mitigate metal pollution. Recently, carbon quantum dots (CDs), carbon-based nanomaterials with diameters of less than 10 nm, have attracted a great deal of attention due to their optical properties and high biocompatibility. These properties make CDs highly relevant in various applications, such as monitoring agents and environmental remediation. CDs have functional groups that allow them to establish strong interactions with metal ions, potentially reducing their biotoxicity in aquatic ecosystems. The CDs used in this study were synthesised solvothermally using citric acid, urea and indocyanine green as molecular precursors, thus allowing them to be doped with sulphur and nitrogen. In this work, we used zebrafish embryos (Danio Rerio), a well-known model organism that is often used in toxicology, to study the ability of CDs to remediate aquatic environments contaminated with metal ions and reduce their toxicity on organisms. In this context, the following metal ions were tested: Cd ²+, Ni ²+ and Ag +. The embryos were exposed to binary combinations of CDs (0, 5 or 50 mg/L) and various concentrations of each metal in a full factorial design for the 3 metals tested. Various parameters were used to assess the toxicity of the metal ions, such as survival, hatching, swimming behaviour and cholinesterase enzyme activity. For the 3 metals tested, a reduction in toxicity was observed when the metals were combined with CDs. For example, when CD = 5 mg/L was added to the metal solutions, the LC50 value (lethal concentration for 50% of the organisms) increased 2.7 times for Cd ²+; 1.3 times for Ni ²+ and 2.3 times for Ag +. Hatch inhibition, although not as robust as survival, indicated the same trend for all three metals. The reduction in toxicity by the CDs was also visible by analyzing locomotion behaviour in the case of Cd ²+ and AchE activity in the case of Ni ²+ and Ag +. In addition, the CDs showed great potential as probes for monitoring metal concentrations in water. The results obtained showed a marked attenuation of CD fluorescence in the presence of Cd ²+ and Ni ²+, with the former having a more pronounced effect, and an increase in fluorescence in the case of Ag +. Fluorescence microscopy analyses of Danio Rerio organisms in the presence of ions and CDs corroborated the photophysical studies. Larvae exposed to CDs alone showed lower fluorescence than larvae exposed to the combination of Ag + and CDs. In contrast, larvae exposed to the combination of Ni ²+ and CDs showed a decrease in fluorescence. The results obtained during this study emphasize the high potential of CDs for the remediation of metals in the aquatic environment and simultaneously for in vivo monitoring of metal biotoxicity. |
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