Nano-Bio Interaction of Rare-Earth Doped BaF2 Nanophosphors Shapes the Developmental Processes of Zebrafish
The nanoparticles with biomedical applications should be evaluated for its biocompatibility. Rare-earth doped nanoparticles with unique spectral properties are superior in-vivo optical probes over quantum dots and organic dyes; however, studies describing their nano-bio interaction are still limited. Here, we have evaluated the nano-bio interaction of green-synthesized, phase pure BaF2 nanoparticles doped with rare-earth (RE3+=Ce3+/Tb3+) ions using larval zebrafish. We found that zebrafish can tolerate wide concentration range of these nanoparticles as maximal lethality was observed at very high concentrations (more than 200 mg/L) with five days of continuous exposure. At 10 mg/L concentration, where Zn+2, Ti4+ and Ag+ nanoparticles are reported to be lethal to developing zebrafish, continuous exposure of our nanoparticles for four days produced no developmental anomalies, craniofacial defects, cardiac toxicity and behavioural abnormalities in developing zebrafish larvae. We have also found that doping of rare-earth ions has no major effect on these biomarkers. Interestingly, the function of acetylcholine esterase (AChE) and cellular metabolic activity of whole zebrafish larvae remained unchanged even during continuous exposure of these nanoparticles at 150 mg/L for four days; though, severe developmental toxicities were evident at this high concentration. Based on these results we can conclude that biocompatibility of rare-earth doped nanoparticles is concentration dependent. Not all biomarkers are sensitive towards these nanoparticles. High concentration dependent toxicity occurs through a mechanism distinct from changes in metabolic or AChE activity. The significance of these findings lies in using these nanoparticles for bioimaging applications and biomarker studies, especially during the prolonged exposures.