Revealing the Significance of the Glycan Binding Property of Butea monosperma Seed Lectin for Enhancing the Antibiofilm Activity of Silver Nanoparticles against Uropathogenic Escherichia coli.

The incompetence of conventional antibiotics against bacteria residing in biofilms demands newer therapeutic intervention. In this study, we demonstrated that the interaction between silver nanoparticles (AgNPs) and Butea monosperma seed lectin (BMSL) forms efficient surface-functionalized AgNPs with excellent antibiofilm competency against uropathogenic Escherichia coli (UPEC). The minimum biofilm inhibitory concentration (MBIC) of AgNPs and the BMSL-AgNP conjugate (BAgNP) against UPEC was 75 and 9.37 µM, respectively. The eight-fold reduction in the MBIC of AgNPs was attributed to lectin functionalization. The chemical modification of serine amino acids affects the hemagglutination activity of BMSL but not its interaction with the AgNPs. At the same time, AgNPs surface-functionalized with modified BMSL display poor antibiofilm activity. Molecular docking studies revealed that BMSL binds to galactose with a free energy of -5.72 kcal/mol, whereas the serine residue-modified BMSL showed the lowest free energy values, suggesting incompetence for binding galactose. These results showcase that the sugar binding site of BMSL aids in the adhesion of AgNPs to the biofilm matrix and disturbs the formation of the biofilm, which was confirmed by light microscopy using crystal violet staining. At 37.5 µM, BAgNPs also have the capability to eradicate preformed biofilm. As a proof of concept, UPEC biofilm prevention and eradication were demonstrated on a urinary catheter. A scanning electron microscopy study showed that BAgNPs prevent bacterial colonization and thereby curtail biofilm growth. In addition to antibiofilm activity, BAgNPs exert antibacterial activity at 18.75 µM, which is four-fold lower than the MIC of AgNPs. A mechanistic study revealed that BAgNPs affect the integrity of the bacterial outer membrane and generate an imbalance in the antioxidant defense, which induces cell death. The results highlight that lectin functionalization can be extended to other nanoparticles and different antibiotics to enhance their efficacy against drug-resistant bacteria.

Sunlight mediated synthesis of silver nanoparticles using redox phytoprotein and their application in catalysis and colorimetric mercury sensing.

Owing to the benign nature, plant extracts mediated green synthesis of metal nanoparticles (NPs) is rapidly expanding. In this study, we demonstrated the successful green synthesis of silver nanoparticles (AgNPs) by utilizing natural sunlight and redox protein complex composed of ferredoxin-NADP(+) reductase (FNR) and ferredoxin (FD). The capping and stabilization of the AgNPs by the redox protein was confirmed by Fourier transform infrared spectroscopy. Light and redox protein is the prerequisite factor for the formation of AgNPs. The obtained result shows that the photo generated free radicals by the redox protein is responsible for the reduction of Ag(+) to Ag(0). Transmission electron microscopy revealed the formation of spherical AgNPs with size ranging from 10 to 15 nm. As-prepared AgNPs exhibit excellent catalytic activity toward the degradation of hazardous organic dyes, such as methylene blue, methyl orange and methyl red. These bio-inspired AgNPs is highly sensitive and selective in sensing hazardous mercury ions in the water at micromolar concentration. In addition, FNR/FD extract stabilized AgNPs showed good antimicrobial activity against gram positive and gram negative bacteria.