Plant-mediated synthesis: Transforming traditional Bangladeshi medicinal plants into immunomodulatory nanoparticles for enhanced shrimp immunity and pathogen control.

This study explored the potential of plant-derived immune nanoparticles for enhancing the immunity, growth, and disease resistance of Penaeus monodon against Vibrio parahaemolyticus infection in sustainable aquaculture systems. Multi-metallic immune nanoparticles were synthesized via a green route using aqueous extracts from five Bangladeshi medicinal plants - Tulsi (Ocimum sanctum), Amloki (Emblica officinalis), Dumur (Ficus racemosa), Pepe (Carica papaya), and Haritaki (Terminalia chebula). In the synthesis process, 10 mL of each plant extract was added to 100 mL of 1 mM metal nitrate solution (AgNO3, CuSO4, ZnSO4, FeCl3, and others) and maintained at a consistent 70 °C for 60 min. The reaction mixture exhibited a visible color shift from pale yellow to brown, confirming nanoparticle formation. Scanning Electron Microscopy (SEM) and Energy-Dispersive X-ray (EDX) analyses revealed spherical nanoparticles with a stable morphology and a size range of 29-84 nm. Multi-elemental profiling confirmed the presence of silver as the dominant component, with zinc, copper, iron, and trace elements supplemented by organic phytochemical capping derived from the plant extracts. Complementary characterizations using FTIR, GC-MS, ICP-OES, and XRD validated the presence of bioactive compounds such as polyphenols and flavonoids, and high crystallinity of the nanoparticles. A 42-day feeding trial was conducted with 3000 post-larval P. monodon, divided into six treatment groups comprising control and nanoparticle-supplemented diets at 0, 25, 50, and 100 μg/g feed concentrations. Each treatment was triplicated with 100 shrimp per tank (100 L) under optimal water quality conditions (temperature 28-32 °C, salinity 25-30 ppt, pH 7.8-8.3, DO > 5.0 mg/L). Growth, immunity, and survival were assessed before and after V. parahaemolyticus challenge. The results demonstrated that shrimp fed diets enriched with Dumur-derived zinc nanoparticles (DuZnNPs) achieved the highest survival rate (96 %), weight gain (24 %), and improved immune biomarkers - lysozyme (40 U/mL), bactericidal activity (80 %), phenoloxidase activity (32 U/mL), and total hemocyte count (4 × 106 cells/mL). DuZnNPs also reduced pro-inflammatory cytokines TNF-α (-56 %) and IL-1β (-52 %) while increasing anti-inflammatory IL-10 (+46 %). Immune-related genes including β-actin, PmIRF, PmVago1-5, ProPO, and Penaeidin were upregulated by 2.7-7.8-fold, whereas AmAgNPs maintained 85 % post-challenge survival compared with 30 % in the control. No toxicity symptoms or mortality increases were detected, and residual nanoparticle concentrations in rearing water remained below safety thresholds. Overall, this work confirmed that green-synthesized, multi-metallic, plant-derived nanoparticles significantly enhanced immune performance, growth, and pathogen resistance in P. monodon, providing an eco-friendly alternative to antibiotics and a practical approach for sustainable shrimp aquaculture.