# Evaluating the Molecular Basis of Nanocalcium-Induced Health Regulation in Zebra Fish (Danio rerio)

## TL;DR

This study shows that low doses of calcium oxide nanoparticles improve zebra fish health without causing harm, while higher doses are damaging.

## Contribution

The study introduces a safe nanoparticle dosage for zebra fish that enhances health and provides insights into molecular interactions.

## Key findings

- A 0.8 mg/kg CaO-NP dose improved survival and weight gain without toxicity.
- Higher doses caused liver and intestinal damage in zebra fish.
- Molecular docking showed strong NP interactions with proteins in the NRF-2 pathway.

## Abstract

The present study aimed to evaluate the impact of varying dietary concentrations of calcium oxide nanoparticles (CaO-NPs) on important health regulators in Zebra fish (Danio rerio) using integrative physiological, histopathological, and computational approaches. The co-precipitation method was used to synthesize NPs and characterization was performed through DLS, XRD, FESEM, EDX, and FTIR depicting spherical-shaped CaO-NPs with a hydrodynamic diameter of 91.2 nm. Adult Danio rerio were administered with three different feed regimes enriched with 2.4 (T1), 1.6 (T2), and 0.8 (T3) mg CaO-NPs/kg for 30 days. Growth, survival, NP accumulation, and histological assessments, and bioinformatic studies, were performed to understand interactions of NPs with fish metabolic proteins. The T3 group demonstrated the highest survival (75%) and weight gain (+39.31%), and exhibited the lowest accumulation of CaO-NPs in the brain (0.133 mg/L), liver (0.642 mg/L), and intestine (0.773 mg/L) with no evident histological alterations, whereas T1 group exhibited major liver and intestinal damage. Molecular docking targeting the NRF-2 oxidative stress pathway revealed strong binding affinities of NPs with catalase (−3.7), keap1a (−3.5), keap1b (−3.3), and mafk (−2.4), highlighting potential modulation of redox homeostasis. Hence, a 0.8mg CaO-NPs/kg feed dose is recommended to promote potential health benefits in Danio rerio, which can be further applicable to commercial aquaculture for enhanced fish health while minimizing toxicity.