2-Heptylcyclopropane-1-Carboxylic Acid Disperses and Inhibits Bacterial Biofilms

Abstract

Fatty-acid signaling molecules can inhibit biofilm formation, signal dispersal events, and revert dormant cells within biofilms to a metabolically active state. We synthesized 2-heptylcyclopropane-1-carboxylic acid (2CP), an analog of cis-2-decenoic acid (C2DA), which contains a cyclopropanated bond that may lock the signaling factor in an active state and prevent isomerization to its least active trans-configuration (T2DA). 2CP was compared to C2DA and T2DA for ability to disperse biofilms formed by Staphylococcus aureus and Pseudomonas aeruginosa. 2CP at 125 μg/ml dispersed approximately 100% of S. aureus cells compared to 25% for C2DA; both 2CP and C2DA had significantly less S. aureus biofilm remaining compared to T2DA, which achieved no significant dispersal. 2CP at 125 μg/ml dispersed approximately 60% of P. aeruginosa biofilms, whereas C2DA and T2DA at the same concentration dispersed 40%. When combined with antibiotics tobramycin, tetracycline, or levofloxacin, 2CP decreased the minimum concentration required for biofilm inhibition and eradication, demonstrating synergistic and additive responses for certain combinations. Furthermore, 2CP supported fibroblast viability above 80% for concentrations below 1 mg/ml. This study demonstrates that 2CP shows similar or improved efficacy in biofilm dispersion, inhibition, and eradication compared to C2DA and T2DA and thus may be promising for use in preventing infection for healthcare applications.

Keywords: 2-decenoic acid; Pseudomonas aeruginosa; Staphylococcus aureus; anti-biofilm agents; biofilm; diffusible signaling factors; dispersal.

FIGURE 1

Graph showing the percentage of (A) S. aureus and (B) P. aeruginosa biofilm remaining after 1 h of exposure to T2DA, C2DA, and 2CP. Asterisks represent significantly less biofilm remaining compared to T2DA (^∗p < 0.05, ^∗∗p < 0.01), detected by one-way ANOVA with the Holm–Sidak post-hoc test. Data represent mean ± standard deviation.

FIGURE 2

NIH-3T3 cytocompatibility assay results showing the percentage of viable cells compared to non-ethanol controls 24 h after addition of fatty acids. Asterisks represent significant differences between the other groups (^∗p < 0.05, ^∗∗p < 0.01), detected by one-way ANOVA with the Holm–Sidak post-hoc tests. Data represent mean ± standard deviation.

FIGURE 3

Graphs show 2CP (left) and C2DA (right) short term solution stability over time (4 h total, 2 h shown) and concentration dependence of DSF stability when challenged with UV and the photoinitiator Irgacure.