Antimicrobial resistance is a global crisis driven by a scarce pipeline of new antibiotics. A major contributor is the intrinsic resistance conferred by the bacterial envelope, highlighting the need for innovative molecules for improved therapies. In this study, TAT–ArgBD, a conjugate of the cell-penetrating TAT peptide and arginine biodynamer (ArgBD), serves in vitro as a multivalent macromolecular antibiotic and synergist. TAT–ArgBD rapidly kills 99.9% of Pseudomonas aeruginosa at 32 µg/mL within 1 h, outperforming colistin, and shows minimum inhibitory concentrations (MICs) of 2–8 µg/mL against Acinetobacter baumannii and Staphylococcus aureus. Notably, it potentiates antibiotics such as novobiocin, chloramphenicol, and imipenem, leading to lowered MICs up to 256-fold. Notably, novobiocin, typically active only against Gram-positive bacteria, showed activity against Gram-negative bacteria when combined with TAT–ArgBD. Mechanistic studies suggest TAT–ArgBD antimicrobial and synergistic actions result from preferential binding to POPG and cardiolipin. This interaction induces bacterial membrane pore formation by adopting an α-helical conformation in the presence of bacterial lipids. With a favorable in vitro safety profile, a membranolytic index > 64 and low mammalian cell toxicity at effective bactericidal concentrations, TAT–ArgBD’s potential to enhance antibiotic efficacy, as well as function as a stand-alone treatment, supports further preclinical evaluation as an antimicrobial adjuvant.
2026, 198 17 S..