Differential toxicities of manganese ferrite nanoparticles from two synthesis methods using developing zebrafish (Danio rerio): towards a biocompatible and safe magnetic nanoparticles

Abstract

Manganese ferrite nanoparticles (MnFe2O4 NPs) have several environmental and biomedical applications. However, knowledge about their toxicity, as a function of the synthesis method, is still scarce. Thus, the current study aimed to evaluate whether the synthesis method (hydrothermal: HT NPs; coprecipitation: CP NPs) of citrate-coated MnFe2O4 NPs influences their potential toxicity in zebrafish embryos and larvae through multiple biomarker assessment. HT NPs were synthesized at high pressure and temperature, whereas CP NPs synthesis included a passivation step. Fe and Mn were detected in zebrafish chorion exposed to the higher concentration of HT and CP NPs, but they were not detected on the larvae’s body surface. The MnFe2O4 NPs did not induce mortality or inhibit hatching. HT NPs (5.0 and 10 mg L−1) and CP NPs (1.25 to 10 mg L−1) reduced the spontaneous contraction frequency in zebrafish embryos. HT NPs (5.0 and 10 mg L−1) induced tachycardia, CP NPs (2.5, 5.0, and 10 mg L−1) induced bradycardia in zebrafish embryos. Pericardial edemas were a transient effect, detected only in embryos exposed to HT NPs for 48 h. After 72 h of exposure, neither NP type induced significant morphological alterations, changes in ROS levels, effects on cell viability, or behavioral alterations. Overall, synthesis-dependent early developmental effects were observed, with no evidence of persistent post-hatching toxicity under the experimental conditions. Thus, the zebrafish is a suitable model system to compare NPs effects from different synthesis methods, contributing to the development of safer nanotechnologies.