Scientists made a tiny piece of the human immune peptide LL‑37 (FFRKSKEK) that only becomes a powerful antibiotic when you shine ultrasound on it for about 15 minutes. It kills more than 99% of several tough, drug‑resistant bacteria, works better than vancomycin in a goat spine infection model, and shows almost no toxicity to human cells.

The antimicrobial effect of antimicrobial peptides is typically slow; they can be rapidly biodegraded and often have non-selective toxicity and elaborate sequences. Here we report a short peptide that is activated by ultrasound, that shows high broad-spectrum antibacterial efficiency (>99%) against clinically isolated methicillin-resistant bacteria (specifically, Staphylococcus aureus, Escherichia coli, Staphylococcus epidermidis, Enterobacter cancerogenus and Pseudomonas aeruginosa) with 15 min of ultrasound irradiation, and that has negligible toxicity and low self-antibacterial activity. We selected the peptide, FFRKSKEK (a segment from the human host-defence LL-37 peptide), from a library of peptides with piezoelectric diphenylalanine (FF) sequences, low toxicity, hydrophobicity and net positive charge. We show via all-atom molecular dynamics simulations that ultrasound amplifies the membrane-penetrating ability of peptides with FF sequences and that its piezoelectric polarization generates reactive-oxygen species and disturbs bacterial electron-transport chains. In a goat model of hard-to-treat intervertebral infection, the sonosensitive peptide led to better outcomes than vancomycin. Antimicrobial peptides activated by ultrasound may offer a clinically relevant strategy for combating antibiotic-resistant infections.