Antibacterial and Antibiofilm Activity of Cationic Small Molecules with Spatial Positioning of Hydrophobicity: An in Vitro and in Vivo Evaluation

More than 80% of the bacterial infections are associated with biofilm formation. To combat infections, amphiphilic small molecules have been developed as promising antibiofilm agents. However, cytotoxicity of such molecules still remains a major problem. Herein we demonstrate a concept in which antibacterial versus cytotoxic activities of cationic small molecules are tuned by spatial positioning of hydrophobic moieties while keeping positive charges constant. Compared to the molecules with more pendent hydrophobicity from positive centers (MIC = 1–4 μg/mL and HC50 = 60–65 μg/mL), molecules with more confined hydrophobicity between two centers show similar antibacterial activity but significantly less toxicity toward human erythrocytes (MIC = 1–4 μg/mL and HC50 = 805–1242 μg/mL). Notably, the optimized molecule is shown to be nontoxic toward human cells (HEK 293) at a concentration at which it eradicates established bacterial biofilms. The molecule is also shown to eradicate preformed bacterial biofilm in vivo in a murine model of superficial skin infection.