Possible Beneficial Molecular Effects of Nano-Chitosan Against Manganese Genotoxicity in the Nile Tilapia (Oreochromis niloticus) Using SCoT Molecular Markers

The escalating contamination of aquatic ecosystems with heavy metals, such as manganese (Mn), poses a significant threat to aquatic life, particularly fish. Mn toxicity can induce oxidative stress and DNA damage, thereby compromising fish health and survival. The present study aimed to evaluate the potential protective effects of chitosan nanoparticles (CS NPs) against Mn-induced genotoxicity in the Nile tilapia (Oreochromis niloticus) using Start Codon Targeted (SCoT) polymorphism analysis. The experimental design included two Mn exposure concentrations (45 and 27mg/ L) combined with two levels of CS NPs supplementation (1.0 and 0.5g/ kg of feed). Water quality parameters were carefully monitored throughout the experiment. At the end of the exposure period, DNA was extracted from muscle tissue, and SCoT-PCR analysis was performed using ten different primers. The SCoT analysis revealed that Mn exposure, particularly at 45mg/ L, significantly increased DNA damage. Supplementation with CS NPs, especially at 0.5g/ kg of feed combined with 27mg/ L Mn exposure, demonstrated a notable protective effect by restoring the genetic profile to a state like that of the control group, thereby mitigating Mn-induced genotoxicity. Interestingly, treatment with CS NPs alone (0.5g/ kg of feed) also resulted in the presence or absence of bands with some primers, suggesting a potential genotoxic effect of CS NPs themselves. These findings indicate that CS NPs may have a protective role against Mn-induced genotoxicity in the Nile tilapia at lower Mn concentrations. However, the observed DNA changes following CS NPs treatment alone underscore the need for caution. Further research is required to elucidate the underlying molecular mechanisms of CS NPs’ protective effects—such as their ability to reduce oxidative stress or enhance DNA repair—and to determine the optimal and safe concentrations for mitigating heavy metal toxicity in aquatic organisms.