No cytotoxic silver(I) complexes as antibacterial and antibiofilm agents with BSA and DNA binding properties

A synthesis of four silver(I) complexes was conducted, and they were evaluated for their antimicrobial properties and their ability to inhibit the formation of biofilms. Additionally, their binding affinities to DNA and BSA were investigated.

The complexes, chloro[1-isopropyl-3-(3-methylbenzyl)-5,6-dimethylbenzimidazole-2-ylidene]silver(I) (2a), chloro[1-isopropyl-3-(3-chlorobenzyl)-5,6-dimethylbenzimidazole-2-ylidene]silver(I) (2b), chloro[1-methallyl-3-(3-methybenzyl)-5,6-dimethylbenzimidazole-2-ylidene]silver(I) (2c) and chloro[1-methallyl-3-(3-chlorobenzyl)-5,6-dimethylbenzimidazole-2-ylidene]silver(I) (2d) were prepared in 82-84% yields and fully characterized. The biological properties of both ligands and complexes were evaluated in vitro against S.aureus, E.faecalis, E.coli, A.baumannii, C.albicans, DNA and BSA.

The complexes 2a-d exhibited a significant inhibitory effect on diverse bacterial biofilms, with percentages ranging from 73.6% to 80.3% for S.aureus, 69.5% to 85.9% for E.faecalis, 76.9% to 88.6% for E.coli, 75.9% to 84.6% for A.baumannii and 70.1% to 82.3% for C.albicans. The most significant activities were observed with complex 2b at 8.5 µM. It was observed that silver(I) complexes exhibited more effective binding to DNA (4.92 × 10³ for 2a), while NHC precursors displayed a higher binding affinity for BSA (5.52 × 10⁴ with 1-isopropyl-3-(3-methylbenzyl)-5,6-dimethylbenzimidazole chloride). While the precursors of ligands exhibited significant toxicity at their highest MIC concentrations, the complexes demonstrated minimal toxicity.