Nanosized titanium dioxide is widely used by the industry, e.g., in pigments, suncreams, and food colors. Its environmental and biological effects have been investigated in the past; however, few studiesd have focused on its crystal structure-specific effects. In our experiments, the toxicity of two types of synthetic nanoparticles was examined on primary neural cultures with different cell compositions using MTT and LDH assays. Primary murine cell cultures containing only astroglia cells originated from two brain regions, as well as mixed neurons and glia cells or microglia cells exclusively, were treated with anatase (15.8 ± 1.7 nm average diameter) and rutile (46.7 ± 2.2 nm average length and 13.7 ± 0.7 nm average diameter) TiO₂ nanoparticles at varying concentrations for 24 or 48 h. Our results show that neither anatase nor rutile nanoparticles reduced viability in cell cultures containing a mixture of neurons and glial cells, independently of the applied concentration and treatment time. Rutile but not anatase form induced cell death in cortical astroglia cultures already at 24 h of treatment above 10 µg/mL, while hippocampus-derived glial cultures were much less sensitive to rutile. The rutile form also damaged microglia. These findings suggest that products containing rutile-form nano-titanium particles may pose a targeted risk to astroglia and microglial cells in the central nervous system.

The use of nanoscale materials has expanded rapidly in recent decades, with titanium dioxide (TiO₂) nanoparticles among the most widely produced. Their increasing environmental release raises concerns about ecosystem-level effects. A key mechanism of toxicity is the generation of reactive oxygen species (ROS), although these effects strongly depend on particle properties, including crystalline form, size, morphology, surface characteristics, and exposure conditions. Here, we assessed and compared the ecological impacts of anatase and rutile TiO₂ nanoparticles across prokaryotic and eukaryotic systems, including aquatic microbial communities, microbial cultures, plant bioassays (Sinapis alba, Triticum aestivum), the SOS Chromotest, and zebrafish (Danio rerio) assays. Nano-TiO₂ exposure markedly restructured freshwater microbial communities by suppressing sensitive taxa (e.g., Actinomycetota, Flavobacterium, and Limnohabitans) while enriching more tolerant genera such as Pseudomonas, Sediminibacterium, Haliscomenobacter, and Hydrogenophaga. These shifts likely reflect differences in cell-envelope structure, biofilm formation, and antioxidant capacity. The two investigated TiO₂ nanoparticle types showed distinct biological effects: rutile was associated with more pronounced microbial community shifts and bacterial cell damage, whereas anatase caused stronger responses in plant assays, particularly by impairing hypocotyl growth and plant water balance. Besides the limited acute genotoxicity revealed by the SOS Chromotest, TiO₂ nanoparticles did not significantly affect survival or final larval body length in the zebrafish embryo assay under the tested conditions; however, the hatching delay observed at the highest concentration indicated a sublethal developmental effect. Overall, our results show that TiO₂ nanoparticle toxicity cannot be generalized across biological systems and suggest that biological responses depend on the combined influence of particle characteristics and organism-specific structural and physiological traits.