Efficacy of Terminalia catappa-AgNP nanocomposite towards Saprolegnia parasitica infection in angelfish (Pterophyllum scalare) eggs

A nanocomposite based on silver nanoparticles (AgNPs) and extract of Terminalia catappa was developed, characterized, and evaluated in in vitro and in vivo conditions against Saprolegnia parasitica infection. The nanocomposite contained spheroidal silver-nanoparticles (1-55 nm) and presented active compounds as gallic acid, ellagic acid, and alpha and 13 punicalagin. The nanoparticles remained stable for one year after its production. A synergistic effect was observed between AgNPs and extract under in vitro and in vivo conditions against different stages of fungal development. In an in vitro assay, the nanocomposite showed fungistatic and fungicide effects to the fungal mycelium in solid and liquid media, respectively, through an increase in the contact surface. In an in vivo bioassay, the lowest concentration of nanocomposite (T1 = 45.75 mu g.L-1 AgNPs +62.5 mu g.L-1 T. catappa extract) demonstrated similar efficiency as the positive control (methylene blue) in preventing zoospore infectivity in eggs of angelfish (Pterophyllum scalare). The fungal zoospores were more sensitive to the nanocomposite than fungal mycelia. Our results exhibited the use of a nanocomposite containing AgNPs and T. catappa aqueous extract could reduce the required effective concentrations of AgNPs against saprolegniosis in fish eggs, thus, it may as an alternative to improve fish larval survival at the hatchery stage.

Automated summary

A nanocomposite based on silver nanoparticles and extract of Terminalia catappa showed synergistic antifungal effects in vitro and in vivo conditions, with stable spheroidal silver nanoparticles and active compounds such as gallic acid and ellagic acid. The nanocomposite demonstrated fungistatic and fungicide effects against fungal mycelium, especially in preventing zoospore infectivity in fish eggs, suggesting its potential as an alternative treatment for saprolegniosis in fish farming.