title: Combined toxicity of two crystalline phases (anatase and rutile) of Titania nanoparticles towards freshwater microalgae: Chlorella sp.
abstract: In view of the increasing usage of anatase and rutile crystalline phases of titania NPs in the consumer products, their entry into the aquatic environment may pose a serious risk to the ecosystem. In the present study, the possible toxic impact of anatase and rutile nanoparticles (individually and in binary mixture) was investigated using freshwater microalgae, Chlorella sp. at low exposure concentrations (0.25, 0.5 and 1mg/L) in freshwater medium under UV irradiation. Reduction of cell viability as well as a reduction in chlorophyll content were observed due to the presence of NPs. An antagonistic effect was noted at certain concentrations of binary mixture such as (0.25, 0.25), (0.25, 0.5), and (0.5, 0.5) mg/L, and an additive effect for the other combinations, (0.25, 1), (0.5, 0.25), (0.5, 1), (1, 0.25), (1, 0.5), and (1, 1) mg/L. The hydrodynamic size analyses in the test medium revealed that rutile NPs were more stable in lake water than the anatase and binary mixtures [at 6h, the sizes of anatase (1mg/L), rutile NPs (1mg/L), and binary mixture (1, 1mg/L) were 948.83±35.01nm, 555.74±19.93nm, and 1620.24±237.87nm, respectively]. The generation of oxidative stress was found to be strongly dependent on the crystallinity of the nanoparticles. The transmission electron microscopic images revealed damages in the nucleus and cell membrane of algal cells due to the interaction of anatase NPs, whereas rutile NPs were found to cause chloroplast and internal organelle damages. Mis-shaped chloroplasts, lack of nucleus, and starch-pyrenoid complex were noted in binary-treated cells. The findings from the current study may facilitate the environmental risk assessment of titania NPs in an aquatic ecosystem.
authors.affiliation: Centre for Nanobiotechnology, VIT University, Vellore, India.
authors.forename: V
authors.initials: V
authors.lastname: Iswarya
authors.affiliation: Centre for Nanobiotechnology, VIT University, Vellore, India.
authors.forename: M
authors.initials: M
authors.lastname: Bhuvaneshwari
authors.affiliation: Centre for Nanobiotechnology, VIT University, Vellore, India.
authors.forename: Sruthi Ann
authors.initials: SA
authors.lastname: Alex
authors.affiliation: Centre for Nanobiotechnology, VIT University, Vellore, India.
authors.forename: Siddharth
authors.initials: S
authors.lastname: Iyer
authors.affiliation: Centre for Nanobiotechnology, VIT University, Vellore, India.
authors.forename: Gouri
authors.initials: G
authors.lastname: Chaudhuri
authors.affiliation: Department of Materials Engineering, Indian Institute of Science, Bangalore, India.
authors.forename: Prathna Thanjavur
authors.initials: PT
authors.lastname: Chandrasekaran
authors.affiliation: UGC-DAE CSR, Kalpakkam Node, Kokilamedu, India.
authors.forename: Gopalkrishna M
authors.initials: GM
authors.lastname: Bhalerao
authors.affiliation: UGC-DAE CSR, Kalpakkam Node, Kokilamedu, India.
authors.forename: Sujoy
authors.initials: S
authors.lastname: Chakravarty
authors.affiliation: Department of Materials Engineering, Indian Institute of Science, Bangalore, India.
authors.forename: Ashok M
authors.initials: AM
authors.lastname: Raichur
authors.affiliation: Centre for Nanobiotechnology, VIT University, Vellore, India.
authors.forename: N
authors.initials: N
authors.lastname: Chandrasekaran
authors.affiliation: Centre for Nanobiotechnology, VIT University, Vellore, India. Electronic address: amit.mookerjea@gmail.com.
authors.forename: Amitava
authors.initials: A
authors.lastname: Mukherjee
mesh_terms: D002470:Cell Survival / Q000187:drug effects; D002708:Chlorella / Q000187:drug effects* / Q000648:ultrastructure; D002734:Chlorophyll / Q000378:metabolism; D005618:Fresh Water; D053768:Metal Nanoparticles / Q000633:toxicity*; D046529:Microscopy, Electron, Transmission; D010316:Particle Size; D014025:Titanium / Q000633:toxicity*; D014466:Ultraviolet Rays; D014874:Water Pollutants, Chemical / Q000633:toxicity
chemical_list: D014874:Water Pollutants, Chemical; D002734:Chlorophyll; C009495:titanium dioxide; D014025:Titanium
keywords: Binary mixture; Bio uptake; Crystalline phases; Titania NPs; Toxicity