The capping of the nanoparticles plays a vital role in their interaction with algal cells as the toxicological mechanism of polyvinylpyrrolidone-CeO₂NPs is different from uncoated CeO₂NPs.

This work describes the construction of two novel self-luminescent bioreporter strains of the cyanobacterium Nostoc sp. PCC 7120 by fusing the promoter region of the sodA and sodB genes (encoding the superoxide dismutases MnSod and FeSod, respectively) to luxCDABE from Photorhabdus luminescens aimed at detecting pollutants that generate reactive oxygen species (ROS), particularly O2-. Bioreporters were tested against methyl viologen (MV) as the inducer of superoxide anion (O2-). Both bioreporters were specific for O2- and Limits of detection (LODs) and Maximum Permissive Concentrations (MPCs) were calculated: Nostoc sp. PCC 7120 pBG2154 (sodA) had a range of detection from 400 to 1000 pM of MV and for Nostoc sp. PCC 7120 pBG2165 (sodB) the range of detection was from 500 to 1800 pM of MV after 5 h-exposure. To further validate the bioreporters, they were tested with the emerging pollutant Triclosan which induced bioluminescence in both strains. Furthermore, the bioreporters performance was tested in two real environmental samples with different water matrix complexity, spiked with MV. Both bioreporters were induced by O2- in these environmental samples. In the case of the river water sample, the amount of bioavailable MV as calculated from the bioreporters output was similar to that nominally added. For the waste water sample, the bioavailable MV concentration detected by the bioreporters was one order of magnitude lower than nominal. These differences could be due to MV complexation with organic matter and/or co-occurring organic contaminants. These results confirm their high sensitivity to O2- and their suitability to detect oxidative stress-generating pollutants in fresh-waters.

Due to their ecological relevance, low cost, and easy maintenance, cyanobacteria have been used for bioreporter development. In this study, a battery of cyanobacterial bioreporters has been used to assess the ecotoxicity of four highly used metallic nanoparticles (NPs). The toxicity of these NPs was tested using the bioreporter Nostoc CPB4337 (Anabaena CPB4337). As oxidative stress is a primary toxic mechanism of metallic NPs, cyanobacterial reactive oxygen species (ROS)-detecting bioreporters were used. Metallic NPs release metal ions, which contribute to their toxic effect and the formation of ROS, so a metal-detecting bioreporter was also used to detect the bioavailable metals. The results confirm that ROS production by NPs was due to the NPs per se and not by released free-ions, which in fact were almost undetectable. Although the metal-detecting bioreporter could not detect the dissolved metal ions, it was able to detect the metallic NPs themselves, indicating that this bioreporter may be useful to detect them in the environment. ROS production varied depending on the growth medium or environmental matrices conditions and on the NP type. This work demonstrated the different levels of ROS production by metallic NPs and the importance of nanotoxicology studies in real matrices.

Background: In adults living with HIV, non-invasive biomarkers have been described for the early identification of metabolic dysfunction-associated steatotic liver diseases (MASLD). However, this issue remains unexplored in children and young people with vertical HIV (YWVH), among whom MASLD prevalence is around 30%. Methods: To identify biomarkers associated with MASLD in YWVH under sustained viral suppression with antiretroviral therapy, we analysed plasma lipid species, plasma bile acid profile, and gut microbiome composition in a cross-sectional cohort of 10 YWVH with MASLD and 19 YWVH without clinical evidence of MASLD (control). Results: Here we show that YWVH with MASLD have significantly increased circulating levels of eight specific lipid molecules and one bile acid, ursodeoxycholic acid (UDCA). UDCA and two triglycerides (TG54:5 and TG56:7) are identified as key biomolecules with strong discriminatory potential. The regression model incorporating these markers, along with hepatic steatosis index (HSI) and triglycerides-glucose index (TyG), demonstrates the highest predictive accuracy for MASLD (AUC of 0.932). UDCA correlates positively with Blautia and Collinsella genus (p = 0.040 and p = 0.021, respectively), and negatively with Faecalibacterium (p = 0.030). Notably, principal component analysis based on bile acid levels reveals two possible subpopulations within the control group, one potentially at higher risk for MASLD. Conclusions: Combining UDCA, TG54:5 and TG56:7 with the validated HSI score provides a potential model with high specificity and sensitivity for predicting MASLD in YWVH. Moreover, early alterations in the bile acid profile may help identify YWVH at risk of developing MASLD.