The currently knowledge on toxicity of TiO2 nanoparticles in microalgae: A systematic review

Titanium dioxide (TiO₂) nanoparticles (NPs) are widely applied across various industries and research fields, raising growing concerns regarding their potential as environmental pollutants. This work presents a systematic review of the toxicity of TiO₂ NPs to microalgae, providing a critical synthesis of current findings and identifying key gaps to guide future research. The analysis reveals that numerous variables associated with growth inhibition assays—such as NPs characteristics and experimental conditions—substantially influence toxicity outcomes, complicating direct comparisons across studies. The primary mechanism underlying TiO₂ NPs toxicity is the generation of oxidative stress, mainly driven by their photocatalytic activity. Furthermore, smaller NPs and those with a higher proportion of anatase exhibit markedly greater toxicity compared to larger particles or those dominated by the rutile phase. These findings highlight the urgent need for standardized methodologies and detailed reporting of experimental protocols. Future studies should carefully consider the limitations of each analytical approach, particularly regarding potential interferences caused by NPs, and ensure that the selected methods align with the intended ecological relevance of the toxicity assessment.