Coating influence on locomotory behavior of zebrafish larvae treated with SPIONs

G.M.T. de Oliveira, L.W. Kist, T.C.B. Pereira, E.M.N. de Oliveira, C.E. Leite, R.M. Papaléo, M.R. Bogo
Pontifical Catholic University of Rio Grande do Sul,
Brazil

Keywords: contrast agents for MRI, nanotoxicity, iron oxide nanoparticles

Summary:

Superparamagnetic Iron Oxide Nanoparticles (SPIONs) have emerged as one of the most promising nanoparticle (NP) systems for biomedical applications, being the first to be approved for clinical use by the FDA. Dextran has been used as a traditional coating biomaterial in SPIONs, since dextran molecules can angle with the growing nanocrystals, protecting them from overgrowing and aggregating. Although dextran coating grants better biocompatibility and high blood circulation times to the NP, the stability of the coating-NP complex is still controversial. There is evidence that dextran is not strongly bound to iron oxide nanoparticles and could lead to detachment and aggregation, once inside the organism. Coating the NPs has great influence on their total size and their pharmacokinetic properties; therefore, it must be taken into consideration when studying nanotoxicity. In this study, zebrafish larvae were exposed to aminated crosslinked dextran coated SPIONs (CLIO-NH2) and non-coated SPIONs (NC-SPION) to evaluate toxic effects on animal behavior and the influence of surface termination of the NPs. NPs synthetized by coprecipitation were suspended on aqueous solutions at 6 different concentrations (0,1 mg/L, 1 mg/L, 5 mg/L, 10 mg/L, 50 mg/L and 100 mg/L). Zebrafish embryos were placed on 6 well plates and exposed to a different concentration of the NPs, during 7 days. Citrate buffer and water were used as vehicle control for CLIO-NH2 and negative control, respectively. Nanoparticle characterization was assessed using UV–VIS spectroscopy for Fe concentration; a Zetasizer for size distribution and zeta potential, and transmission electron microscopy (TEM) for size distribution and morphology. Behavioral analysis was conducted using ANYMaze® software (Stoelting Co., Wood Dale, IL, USA) to determine significant differences in larvae locomotory activity at 7 days post fertilization (dpf). Exposure to CLIO-NH2 at any of the concentrations tested impaired locomotor behavior to the larvae, particularly the turn angle and the distance travelled by the animal. Interestingly, the vehicle control also show a significant difference, indicating that the citrate buffer appears also to affect the larvae behavior. There is a need to further investigate the role of the citrate buffer on the toxicity associated to the NP system. NC-SPION exposure did not induced any significant behavioral change, however the uncoated nanoparticle stability in solution was poor, leading to a greater tendency of the system to aggregate and to deposit at the bottom of the plates during exposure. This may decrease nanoparticle absorption by the zebrafish gills, diminishing the actual amount of particles entering metabolism.