Evaluation of the Growth-Inhibitory Spectrum of Three Types of Cyanoacrylate Nanoparticles on Gram-Positive and Gram-Negative Bacteria

Abstract

The development of novel effective antibacterial agents is crucial due to increasing antibiotic resistance in various bacteria. Poly (alkyl cyanoacrylate) nanoparticles (PACA-NPs) are promising novel antibacterial agents as they have shown antibacterial activity against several Gram-positive and Gram-negative bacteria. However, the antibacterial mechanism remains unclear. Here, we compared the antibacterial efficacy of ethyl cyanoacrylate nanoparticles (ECA-NPs), isobutyl cyanoacrylate NPs (ⁱBCA-NPs), and ethoxyethyl cyanoacrylate NPs (EECA-NPs) using five Gram-positive and five Gram-negative bacteria. Among these resin nanoparticles, ECA-NPs showed the highest growth inhibitory effect against all the examined bacterial species, and this effect was higher against Gram-positive bacteria than Gram-negative. While ⁱBCA-NP could inhibit the cell growth only in two Gram-positive bacteria, i.e., Bacillus subtilis and Staphylococcus aureus, it had negligible inhibitory effect against all five Gram-negative bacteria examined. Irrespective of the differences in growth inhibition induced by these three NPs, N-acetyl-L-cysteine (NAC), a well-known reactive oxygen species (ROS) scavenger, efficiently restored growth in all the bacterial strains to that similar to untreated cells. This strongly suggests that the exposure to NPs generates ROS, which mainly induces cell growth inhibition irrespective of the difference in bacterial species and cyanoacrylate NPs used.

Keywords: antibacterial agent; cyanoacrylate nanoparticle; membrane damage; reactive oxygen species; stress response.

Figure 1

Bacterial growth cultures exposed to PACA-NPs. Control (blue line), growth in LB medium containing 0.01% Tween 80. All cultures were set up and grown under the same conditions as described in Materials and Methods. The growth was shown by McFarland unit. (A), Bacillus subtilis (Gram-positive); (B), Brevibacillus agri (Gram-positive); (C), Microbacterium aurum (Gram-positive); (D), Propionibacterium acnes (Gram-positive); (E), Staphylococcus aureus (Gram-positive); (F), Escherichia coli (Gram-negative); (G), Klebsiella pneumonia (Gram-negative); (H), Pseudomonas aeruginosa (Gram-negative); (I), Salmonella typhimurium (Gram-negative); (J), Serratia marcescens (Gram-negative). The error bars represent standard deviations determined from at least three duplicates.

Figure 1

Bacterial growth cultures exposed to PACA-NPs. Control (blue line), growth in LB medium containing 0.01% Tween 80. All cultures were set up and grown under the same conditions as described in Materials and Methods. The growth was shown by McFarland unit. (A), Bacillus subtilis (Gram-positive); (B), Brevibacillus agri (Gram-positive); (C), Microbacterium aurum (Gram-positive); (D), Propionibacterium acnes (Gram-positive); (E), Staphylococcus aureus (Gram-positive); (F), Escherichia coli (Gram-negative); (G), Klebsiella pneumonia (Gram-negative); (H), Pseudomonas aeruginosa (Gram-negative); (I), Salmonella typhimurium (Gram-negative); (J), Serratia marcescens (Gram-negative). The error bars represent standard deviations determined from at least three duplicates.

Figure 2

Effect of co-incubation with N-acetyl-L-cysteine for the cell growth inhibition. ECA-NPs exposure at 100 mg/L was carried out in the LB containing various concentration of NAC. The growth was shown by McFarland unit. (A), Bacillus subtilis (Gram-positive); (B), Brevibacillus agri (Gram-positive); (C), Microbacterium aurum (Gram-positive); (D), Propionibacterium acnes (Gram-positive); (E), Staphylococcus aureus (Gram-positive); (F), Escherichia coli (Gram-negative); (G), Klebsiella pneumonia (Gram-negative); (H), Pseudomonas aeruginosa (Gram-negative); (I), Salmonella typhimurium (Gram-negative); (J), Serratia marcescens (Gram-negative). The data represent the average and standard deviation from three independent experiments.

Figure 2

Effect of co-incubation with N-acetyl-L-cysteine for the cell growth inhibition. ECA-NPs exposure at 100 mg/L was carried out in the LB containing various concentration of NAC. The growth was shown by McFarland unit. (A), Bacillus subtilis (Gram-positive); (B), Brevibacillus agri (Gram-positive); (C), Microbacterium aurum (Gram-positive); (D), Propionibacterium acnes (Gram-positive); (E), Staphylococcus aureus (Gram-positive); (F), Escherichia coli (Gram-negative); (G), Klebsiella pneumonia (Gram-negative); (H), Pseudomonas aeruginosa (Gram-negative); (I), Salmonella typhimurium (Gram-negative); (J), Serratia marcescens (Gram-negative). The data represent the average and standard deviation from three independent experiments.