Study of shape-tunable bimodal GdPO4:Eu3+ nanoparticles and their impact on Daphnia magna

Abstract

Multimodal nanoprobes offer a promising solution to the sensitivity and specificity limitations in medical assays by combining the benefits of multiple diagnostic modalities into a single particle. GdPO₄ doped with Eu is a particularly attractive nanomaterial platform for developing such nanoprobes, as it offers tunable optical and magnetic properties through shape and composition changes. However, data on the physicochemical properties of lanthanide-based bimodal NPs with different morphologies in relation to their bioaccumulation and toxicity to aquatic organisms are limited. The aim of our study was to reproducibly synthesize Gd-based NPs with variable morphologies (rod, prism and sphere), characterize their morphological, optical, and magnetic contrast properties, determine NP localization in Daphnia magna, and evaluate toxic effects in test organisms after 24-hour exposure to different morphologies and concentrations of NPs. Our study demonstrates an aqueous hydrothermal synthesis method for producing GdPO₄:Eu³⁺ particles with different morphologies, while maintaining consistent optical properties across different forms. The data obtained from the magnetic resonance imaging (MRI) study showed a direct correlation between the NP surface area and T₁ and T₂ relaxivities. Confocal fluorescence microscopy results demonstrated that after 24-hour exposure, most nanorods and nanoprisms were concentrated from the foregut towards the midgut of the D. magna intestinal tract, whereas sub-microspheres were localized only in the foregut and the beginning of the midgut. Furthermore, D. magna mortality, heart rate (HR), and behavior were affected by NP morphology and concentration, with nanorods having the most pronounced impact. The obtained results are of significant importance for the development of multimodal imaging using high-performance eco-friendly nanoprobes, aligning with the safe and sustainable by design (SSbD) principles.