Shrimp lectin (Md- Lec ) conjugated copper sulfide nanoparticles enhance the elimination of aquatic pathogens in infected Nile tilapia ( Oreochromis niloticus ).

Lectins are known for their ability to bind to cell surface glycans, and are useful to develop a glycan-targeted drug delivery system. This study aimed to evaluate the capacity of pectin capped copper sulfide nanoparticles (pCuS NPs) to modulate the antibacterial activity of a lectin, Md- Lec , purified from the shrimp, Metapenaeus dobsoni . Fluorescence spectroscopy revealed that Md- Lec has the ability to form a complex with pCuS NPs. Haemagglutination assay showed that the carbohydrate binding site of the lectin was preserved even after complexing with pCuS. The minimum inhibitory concentrations (MICs) obtained for Md- Lec and pCuS NPs against the tested aquatic pathogens were 50 μg ml -1 and 12.5 μM, respectively. Interestingly, the MIC of Md- Lec -pCuS NPs complex was four fold lower than that of pCuS, which was attributed to the bacterial cell surface glycan recognization activity of Md- Lec . Zone of inhibition assay showed that the zone size was highest for the lectin conjugated nanoparticles. Mechanistic study revealed that Md- Lec -pCuS NPs affect the bacterial membrane integrity and produce a large volume of reactive oxygen species to kill the bacteria. The practical aspect of using this lectin-pCuS NPs complex was evaluated by treating bacteria infected Nile tilapia ( Oreochromis niloticus ). The bacterial load was much less in the lectin-pCus NPs complex treated fish; moreover, the fish fully recovered from the infection. It was concluded that the conjugate of antibacterial lectin and NPs is more effective than the individual components.