Design Guidelines for Cationic Pillar[n]arenes that Prevent Biofilm Formation by Gram-Positive Pathogens.

Dana Kaizerman-Kane,Maya Hadar,Micha Fridman,Roymon Joseph,Dana Logviniuk,Yossi Zafrani,Yoram Cohen

doi:10.1021/acsinfecdis.0c00662

Dana Kaizerman-Kane, Maya Hadar + Show 5 more

Open Access

https://doi.org/10.1021/acsinfecdis.0c00662

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Abstract

Bacterial biofilms are a major threat to human health, causing persistent infections that lead to millions of fatalities worldwide every year. Biofilms also cause billions of dollars of damage annually by interfering with industrial processes. Recently, cationic pillararenes were found to be potent inhibitors of biofilm formation in Gram-positive bacteria. To identify the structural features of pillararenes that result in antibiofilm activity, we evaluated the activity of 16 cationic pillar[5]arene derivatives including that of the first cationic water-soluble pillar[5]arene-based rotaxane. Twelve of the derivatives were potent inhibitors of biofilm formation by Gram-positive pathogens. Structure activity analyses of our pillararene derivatives indicated that positively charged head groups are critical for the observed antibiofilm activity. Although certain changes in the lipophilicity of the substituents on the positively charged head groups are tolerated, dramatic elevation in the hydrophobicity of the substituents or an increase in steric bulk on these positive charges abolishes the antibiofilm activity. An increase in the overall positive charge from 10 to 20 did not affect the activity significantly, but pillararenes with 5 positive charges and 5 long alkyl chains had reduced activity. Surprisingly, the cavity of the pillar[n]arene is not essential for the observed activity, although the macrocyclic structure of the pillar[n]arene core, which facilitates the clustering of the positive charges, appears important. Interestingly, the compounds found to be efficient inhibitors of biofilm formation were nonhemolytic at concentrations that are ∼100-fold of their MBIC50 (the minimal concentration of a compound at which at least 50% inhibition of biofilm formation was observed compared to untreated cells). The structure–activity relationship guidelines established here pave the way for a rational design of potent cationic pillar[n]arene-based antibiofilm agents.

Highlights

To explore the effect of different structural characteristics of the cationic pillararenes on their antibiofilm activity, we designed and synthesized the cationic pillar[5,6]arene derivatives presented in Scheme 1
To evaluate the ability of our cationic pillararenes to inhibit the formation of biofilm, we focused on two clinically important biofilm forming Grampositive pathogens: methicillin-resistant S. aureus (ATCC 33592) and E. faecalis (ATCC 29212).[50−53] We evaluated the entire dose response for all our compounds using the crystal violet protocol[46,47,54] from which the MBIC50, i.e., the minimal concentration of a compound at which at least 50% inhibition of biofilm formation was observed compared to untreated cells, was computed
We identified the structural determinants that affect the efficacy of cationic pillar[n]arenes in inhibiting biofilm formation by two important Gram-positive pathogens

Summary

Introduction

We found that cationic pillar[n]arenes (n = 5, 6) are potent inhibitors of biofilm formation of clinically important Gram-positive pathogens (Figure 1).[46,47] Interestingly, bearing several QACs, these cationic pillar[n]arenes show no effect on bacterial cell viability and cause no damage to red blood cells (RBCs) and no acute toxicity to human cells in culture at concentrations that are orders of magnitude higher than their antibiofilm active concentrations.[46,47] To explore the effect of different structural characteristics of the cationic pillararenes on their antibiofilm activity, we designed and synthesized the cationic pillar[5,6]arene derivatives presented in Scheme 1.

Results

Conclusion