abstract
Layered double hydroxides (LDHs) are innovative nanomaterials (NMs) with a typical nanoclay structure (height <40 nm) consisting of layers of metallic cations and hydroxides stabilized by anions and water molecules. Upon specific triggers, anions can exchange by others in the surrounding environment. Due to this stimuli-responsive behavior, LDHs are used as carriers of active ingredients in the industrial or pharmaceutical sectors. Available technical guidelines to evaluate the ecotoxicity of conventional substances do not account for the specificities of NMs, leading to inaccuracies and uncertainty. The present study aimed to assess two different exposure methodologies (serial dilutions of the stock dispersion vs. direct addition of NM powder to each concentration) on the ecotoxicological profile of different powder grain sizes of Zn-Al LDH-NO3 and Cu-Al LDH-NO3 (bulk, <25, 25-63, 63-125, 125-250, and >250 & mu;m) in the growth of the freshwater microalgae Raphidocelis subcapitata. Results revealed that the serial dilutions methodology was preferable for Zn-Al LDH-NO3, whereas for Cu-Al LDH-NO3 both methodologies were suitable. Thus, the serial dilutions methodology was selected to assess the ecotoxicity of different grain sizes for both LDHs. All Zn-Al LDH-NO3 grain sizes yielded similar toxicity, while Cu-Al LDH-NO3 powders with smaller grain sizes caused a higher effect on microalgae growth; thus, grain size separation might be advantageous for future applications of Cu-Al LDH-NO(3)s. Considering the differences between exposure methodologies for the Zn-Al LDH-NO3, further research involving other NMs and species must be carried out to achieve harmonization and validation for inter-laboratory comparison.
keywords
LAYERED DOUBLE HYDROXIDES; DYNAMIC LIGHT-SCATTERING; TITANIUM-DIOXIDE; TIO2 NANOPARTICLES; SILVER NANOPARTICLES; OXIDE NANOPARTICLES; GOLD NANOPARTICLES; GROWTH-INHIBITION; OXIDATIVE STRESS; PARTICLE-SIZE
subject category
Science & Technology - Other Topics; Toxicology
authors
Campos, F; Silva, PV; Soares, AMVM; Martins, R; Loureiro, S
Groups
Projects
Nano-argilas para remoção/captura de fosfatos (P) e sua reutilização como fertilizante (NATURAL)
acknowledgements
The present work was supported by the Project NANOHARMONY (Grant Agreement 885931), funded by the EU Horizon 2020. Thanks are also due to FCT/MCTES for the financial support to R. Martins, who benefits from a Researcher Grant (2021.00386.CEECIND; CEECIND/01329/2017), to CESAM (UIDP/50017/2020 & nbsp;+& nbsp;UIDB/50017/2020 & nbsp;+& nbsp;LA/P/0094/2020), and the R & D project NANOGREEN (CIRCNA/BRB/0291/2019) through national funds. Patricia V. Silva was funded by the project NATURAL (CENTRO-01-0247-FEDER-047080) through a Post-Doctoral Grant (BIPD/UI50/6103/2021).