Silica Nanoparticle Size Determines the Mechanisms Underlying the Inhibition of Iron Oxide Nanoparticle Uptake by Daphnia magna

Carbon quantum dots modification reduces TiO2 nanoparticle toxicity in an aquatic food chain

Carbon quantum dots (CQDs) are emerging as a promising zero-dimensional carbon nanomaterial with the potential to enhance the catalytic properties of titanium dioxide nanoparticles (TiO2 NPs). Although CQDs modification alters the physicochemical properties of TiO2 NPs, the impact on their toxicity has been rarely explored. In this study, we investigated the effects of CQDs doping on the toxicity, bioaccumulation, and trophic transfer of TiO2 NPs using a representative aquatic food chain comprising phytoplankton (Scenedesmus obliquus), zooplankton (Daphnia magna), and fish (Danio rerio). Surprisingly, we found CQDs doping significantly reduces the toxicity and bioconcentration of TiO2 NPs. Mechanistic studies indicate that CQDs doping enhances the hydrogen peroxide (H2O2) scavenging ability of CQDs/TiO2 NPs through the inherent catalase-like activity of CQDs, thereby reducing oxidative stress in organisms. Additionally, CQDs doping inhibits the conversion of photogenerated holes (h+) to hydroxyl radical (·OH) on TiO2 NPs surfaces, leading to decreased free radical release. The increased surface electronegativity of CQDs/TiO2 NPs also enhances repulsive interactions with organisms, further reducing both their toxicity and bioaccumulation. This study offers a comprehensive assessment of CQDs/TiO2 NPs toxicity in aquatic ecosystems, providing a proof-of-principle for the development and application of CQDs-related composite nanomaterials.

Size Effects of Nanoenabled Agrochemicals in Sustainable Crop Production: Advances, Challenges, and Perspectives

Nanoenabled agrochemicals mainly including nanopesticides and nanofertilizers based on nanotechnology play a crucial role in plant protection and food security. These agrochemicals exhibit high dose delivery efficiency and biological activity due to their unique nanoscale properties. However, nanoscale properties can also be a double-edged sword, posing potential risks to both humans and the environment. As nanoenabled agrochemicals become more widely used, it is essential to have an objective and comprehensive discussion of the size effects of these agrochemicals. In this paper, we reviewed the research progress on the size effects of nanoenabled agrochemicals in terms of dose delivery, biological activity, and nontarget safety. We investigated the complex factors affecting size effects and sought to draw insights from research in biomedicine, engineering, food, and other relevant fields. Based on the literatures review, it could be concluded that "the smaller the better" is not always the case. We further outlooked the development prospects of studying the size effects of nanoenabled agrochemicals, emphasizing the necessity for thorough and in-depth research while critically identifying key issues that need to be addressed. In conclusion, a proper comprehension of the size effects of nanoenabled agrochemicals bridges the gap between the scientific community and industry, bolstering the role in advancing sustainable agriculture.

Direct determination of silicon overestimates the accumulation and translocation of SiO2 nanoparticles in rice seedlings

Silica nanoparticles (SiO2 NPs) have numerous applications in agriculture, but may also pose significant risks to plants. Nevertheless, their bioaccumulation, an important determinant of their risks, was often not accurately measured due to the lack of reliable methods. In this study, the accumulation in rice seedlings of SiO2 NPs of different sizes without and with a gold nanoparticle core (Au@SiO2 NPs) was examined. Potential interference from SiO2 NP dissolution was minimized by lowering the pH of the uptake medium, which did not result in any observable adverse bioeffects. Under this condition, the direct determination of Si showed the significant accumulation of SiO2 NPs in roots and shoots and a decrease in the accumulation of SiO2 NPs in shoots with increasing particle size. However, when accumulation was monitored using Au@SiO2 NPs, SiO2 NP accumulation was significantly higher when measured by direct Si determination than by Au determination, indicating that the former overestimates the accumulation of SiO2 NPs. Consequently, unlike direct Si determination, tracking the gold nanoparticle core revealed an increase in SiO2 NP accumulation in shoots with increasing particle size. Overall, accurate determination of SiO2 NP bioaccumulation is imperative for appropriate bioapplications and reliable biosafety assessments of these particles.

An Unprecedented Metal Distribution in Silica Nanoparticles Determined by Single-Particle Inductively Coupled Plasma Mass Spectrometry

Metal-containing nanoparticles are now common in applications ranging from catalysts to biomarkers. However, little research has focused on per-particle metal content in multicomponent nanoparticles. In this work, we used single-particle inductively coupled plasma mass spectrometry (ICP-MS) to determine the per-particle metal content of silica nanoparticles doped with tris(2,2'-bipyridyl)ruthenium(II). Monodispersed silica nanoparticles with varied Ru doping levels were prepared using a water-in-oil microemulsion method. These nanoparticles were characterized using common bulk-sample methods such as absorbance spectroscopy and conventional ICP-MS, and also with single-particle ICP-MS. The results showed that averaged concentrations of metal dopant measured per-particle by single-particle ICP-MS were consistent with the bulk-sample methods over a wide range of dopant levels. However, the per-particle amount of metal varied greatly and did not adhere to the usual Gaussian distribution encountered with one-component nanoparticles, such as gold or silver. Instead, the amount of metal dopant per silica particle showed an unexpected geometric distribution regardless of the prepared doping levels. The results indicate that an unusual metal dispersal mechanism is taking place during the microemulsion synthesis, and they challenge a common assumption that doped silica nanoparticles have the same metal content as the average measured by bulk-sample methods.