Self-assembled Polyurethane Capsules with Selective Antimicrobial Activity against Gram-negative E. coli

The manuscript reports two-step self-assembly and antimicrobial activity of two segmented amphiphilic polyurethanes PU-1 and PU-2, containing a primary or secondary amine group, respectively. In acidic water, intra-chain H-bonding among the urethane groups followed by hierarchical assembly resulted in formation of capsules (Dh = 120 ± 20 nm and 100 ± 17 nm for PU-1 and PU-2, respectively) with highly positive surface charge. They showed selective interaction with bacterial cell mimicking liposome over mammalian cell mimicking liposome with favorable enthalpy and entropy contribution which is attributed to the electrostatic interaction and hydrophobic effect. Antimicrobial studies with E. coli. revealed very low MIC values of 7.8 µg/ mL and 15.6 µg/ mL for PU-1 and PU-2, respectively, indicating their ability to efficiently kill Gram negative bacteria. Killing of Gram positive S. aureus was noticed only at C = 500 µg/ mL, indicating unprecedented selectivity for E. coli which was further confirmed by SEM s...