Growth inhibition and antibiofilm potential of Ag nanoparticles coated with lectin, an arthropod immune molecule

Lectins from the haemolymph of arthropods, including crustaceans, are molecules potentially involved in the immune recognition and phagocytosis. Here, lectin was purified from the haemolymph of blue swimmer crab Portunus pelagicus, using mannose-coupled sepharose CL-4B affinity column chromatography. In SDS-PAGE analysis, lectin showed a molecular mass of approximately 155 kDa. The synthesis of lectin-coated silver nanoparticles (lectin-coated AgNPs) was confirmed by UV-Vis spectroscopy, XRD, FTIR, SEM, TEM, SAED, and EDX analysis. TEM analysis revealed that lectin-coated AgNPs were spherical in shape with size of 30-57 nm. Their antibacterial activity against human pathogenic Gram negative and Gram-positive bacteria was determined by agar well diffusion method. Lectin-coated AgNPs showed significant antimicrobial activity when compared to lectin and silver nitrate tested alone. The antibiofilm properties of lectin-coated AgNPs were also investigated on human pathogenic Gram-negative Proteus vulgaris, Pseudomonas aeruginosa and Gram-positive Enterococcus faecalis and Bacillus pumilus. Lectin-coated AgNPs showed antibiofilm activity on the bacteria as well as on Candida albicans. Lectin-coated AgNPs reduced the biofilm architecture interfering with cell adhesion and polysaccharide matrix. This was additionally confirmed by exopolysaccharide (EPS) quantification index revealing the trouble in the structural reliability of biofilm by decrease in EPS and bacterial adhesion to hydrocarbons.