Effects of nano-TiO2 on the bioavailability and toxicity of bis(2-ethylhexyl)-2,3,4,5-tetrabromophthalate (TBPH) in developing zebrafish

Nanoparticles like nano-TiO2 are suspected to influence the bioavailability and toxicity of co-existing organic or inorganic pollutants differently in aquatic environment. Recently, bis(2-ethylhexyl)-2,3,4,5-tetrabromophthalate (TBPH), a novel brominated flame retardants (NBFRs) with potential lipid-metabolism disruptive effects, has been detected prevalently in multiple environments including where nano-TiO2 was also observed. However, their interaction in aqueous phase and modification of nano-TiO2 on biological processes and toxicity of TBPH at environmental relevant levels remain unknown. Accordingly, we exposed zebrafish embryos to TBPH (1, 10, 100 and 1000 μg/L) alone or with nano-TiO2 (100 μg/L) until 72 h post-fertilization (hpf) with emphasis on their physicochemical interactions in solutions and variations of bioavailability and toxicity regarding lipid metabolism in vivo. Zeta potential, fourier transform infrared (FTIR) spectroscopy and TEM-EDS revealed adsorption and agglomeration between TBPH and nano-TiO2 in vitro. Decreased body contents of nano-TiO2 and TBPH implied a reduction of TBPH in bioavailability. The enhanced lipid metabolism and reduced fat storage by TBPH alone were all alleviated by co-exposure to nano-TiO2. The overall results indicate that nano-TiO2 adsorbed TBPH to form size-enlarged agglomerates and led to decreased bioavailability and consequently mitigated lipid metabolism disorders in developing zebrafish embryo/larvae.