The role of diazacrown ether in the enhancement of the biological activity of silver nanoparticles

Abstract

The nanostructuring of hydroxyl-substituted diazacrown-ether (DC) by silver nanoparticles was obtained by green synthesis method in order to increase the antibacterial activity of silver nanoparticles. The synthesized DC, nanoparticles, and nanosupramolecular complex (Ag@DC) were studied by TEM, powder-XRD, and NMR, IR, and UV spectroscopy methods. The Ag@DC nanostructures were uniform and their sizes ranged from 8 to 18 nm. IR and UV spectra revealed the noncovalent formation of the nanosupramolecular complex. The antibacterial activities of the prepared active agents were investigated on gram-positive and gram-negative bacteria by twofold microdilution method. Ultrastructural study by TEM was performed on \textit{E. coli} BDU12 after treatment with Ag@DC. The results showed the improvement of the antibacterial action of Ag@DC compared to silver nanoparticles (E. coli BDU12 - 32 times, A. baumannii BDU32 - 16 times, K. pneumoniae BDU44 and P. aeruginosa BDU49 - 4 times, S. aureus BDU23 - 512 times). Chelating by DC significantly improved the antibacterial effects of the silver nanoparticles on gram-positive and gram-negative bacteria due to the ionophoric behavior of the crown ethers.