Evaluation of cobalt silver core shell as a novel photoactive candidate for Biomphalaria alexandrina snails and Schistosoma mansoni larvae

Schistosomiasis remains a major global public health concern, necessitating the development of novel and potent vector-control strategies to interrupt the parasite's transmission cycle. In this study, novel Cobalt-Silver (Co@Ag) core-shell nanoparticles were successfully synthesized via a facile chemical reduction method, utilizing hydrogen gas generated from the controlled hydrolysis of sodium borohydride to reduce silver nitrate. The successful formation of the core-shell nanostructures was visually confirmed by a characteristic dark yellowish coloration, while UV-Vis spectroscopy revealed a sharp surface plasmon resonance (SPR) absorption peak at ~410 nm. The synthesized bimetallic nanoparticles exhibited remarkable colloidal stability in aqueous media, remaining stable for several months without aggregation. Transmission electron microscopy (TEM) confirmed the well-defined core-shell morphology, and dynamic light scattering (DLS) demonstrated an average particle size of approximately 170 nm. Furthermore, Fourier-transform infrared (FTIR) spectroscopy verified the presence of surface-stabilizing functional groups, identifying characteristic stretching vibrations for O–H, C–H, C–N, and N–H bonds. These stable Co@Ag core-shell nanoparticles present significant potential for various catalytic and biomedical applications. This study evaluates the molluscicidal, endocrinological, biochemical, and ultrastructural effects of cobalt-silver core/shell bimetallic nanoparticles against the snail intermediate host Biomphalaria alexandrina and Schistosoma mansoni larval stages. Toxicity assays revealed a significant concentration-dependent molluscicidal activity with an LC 90 value of 134.48 ppm. Exposure to sub-lethal concentrations (LC 10 and LC 25) under combined dark incubation (6 h) and light exposure (3 h) induced marked physiological disruptions in snail homogenized tissues. Specifically, 17β-estradiol, total estrogen, and testosterone levels exhibited significant reductions (p < 0.001), whereas progesterone levels increased significantly (p < 0.001 to p < 0.01). Concurrently, a substantial, concentration-dependent elevation in nitrogen oxide levels (p < 0.001) indicated pronounced oxidative stress. Furthermore, scanning electron microscopy (SEM) demonstrated severe, time- and concentration-dependent morphological alterations in S. mansoni miracidia and cercariae following short-term exposure (10 min dark, 30 min light), characterized by surface wrinkling, blebbing, tegumental swelling, and catastrophic structural degradation. These findings highlight the potent multi-targeted efficacy of cobalt-silver core/shell nanoparticles as promising agents for schistosomiasis vector and parasite control.