Comparative analysis of bioaccumulation and biological impacts of cadmium sulfide (CdS) bulk versus nanoparticles in the freshwater snail Helisoma duryi.

Cadmium sulfide (CdS) nanomaterials are used in photothermal therapy, drug delivery, photocatalysis, and device lasers. Due to the rise of nanotechnology, assessments of their impact on human health and ecosystems are essential. Cadmium-based nanoparticles are notable for their physicochemical properties and use in hazardous substances like pesticides. While cadmium toxicity in fish species is well-researched, little is known about how CdS nanoparticles affect other aquatic life. This study investigates the toxicological effects of CdS in bulk and nanoparticle forms on the freshwater snail Helisoma duryi, using starch as a stabilizer and various characterization techniques. Snails were exposed to different CdS concentrations to determine LC50 values, followed by a four-week sublethal exposure and a two-week recovery phase to assess biochemical, oxidative stress, and bioaccumulation responses. Results showed that CdS-NP exhibited lower toxicity than bulk CdS. CdS-NP induced significantly higher oxidative stress) Nitric oxide, Malonaldehyde), marked by reduced antioxidant markers like catalase and total antioxidant capacity (TAC). In contrast, bulk CdS caused more pronounced biochemical disruptions, increasing hepatic enzyme activities (alkaline phosphatase (ALP), alanine aminotransferase (ALT), and aspartate aminotransferase (AST)). Bioaccumulation studies indicated greater CdS retention in soft tissues, but CdS-NP showed faster clearance during recovery. This study demonstrates the extent of CdS nanoparticles' toxicity to the environment and human and animal health. These findings highlight distinct toxicological risks: CdS-NP intensifies oxidative stress, while bulk CdS leads to severe biochemical disruptions. This study demonstrates that cadmium sulfide in nanoparticles and bulk forms exerts differential toxic effects, necessitating targeted environmental monitoring and regulation.