Fluorophenylalanine-Containing Dipeptides with Antibiofilm Activity Against Pseudomonas aeruginosa Discovered Through a Collaborative Undergraduate Research and Educational Program

Discovery of new antibiotic candidates is driven by urgent global health needs and evolving resistance to current treatments. In pursuit of novel peptide-based antibiotics, more than 100 dipeptides containing fluorinated phenylalanine (F-Phe) residues were synthesized by undergraduate researchers at eight institutions and evaluated against Pseudomonas aeruginosa (P. aeruginosa) in a primary biofilm formation assay. Inclusion of multistep synthesis experiments in curricular laboratory courses at different institutions prompted the prioritization of robust and adaptable procedures that were effective at generating large compound sets for study. Several dipeptides were identified that inhibited biofilm formation at concentrations of 1 μg/mL or less. Further study of two of them, (S,S)-4-F-Phe-Ala and (S,S)-3,4-diF-Phe-Ala, revealed two distinct biological profiles. Inhibition of biofilm formation by (S,S)-4-F-Phe-Ala was directly associated with growth inhibition. In contrast, (S,S)-3,4-diF-Phe-Ala did not significantly inhibit bacterial growth at concentrations up to 100 μg/mL. Mammalian cell lines treated with either dipeptide at much higher concentrations remained viable, demonstrating selective toxicity for P. aeruginosa. Taken together, these data indicate that dipeptides comprising F-Phe are promising leads for the discovery of new antibiofilm therapeutics.