Killing Mechanism of Stable N-Halamine Cross-Linked Polymethacrylamide Nanoparticles That Selectively Target Bacteria

Abstract

Increased resistance of bacteria to disinfection and antimicrobial treatment poses a serious public health threat worldwide. This has prompted the search for agents that can inhibit both bacterial growth and withstand harsh conditions (e.g., high organic loads). In the current study, N-halamine-derivatized cross-linked polymethacrylamide nanoparticles (NPs) were synthesized by copolymerization of the monomer methacrylamide (MAA) and the cross-linker monomer N,N-methylenebis(acrylamide) (MBAA) and were subsequently loaded with oxidative chlorine using sodium hypochlorite (NaOCl). The chlorinated NPs demonstrated remarkable stability and durability to organic reagents and to repetitive bacterial loading cycles as compared with the common disinfectant NaOCl (bleach), which was extremely labile under these conditions. The antibacterial mechanism of the cross-linked P(MAA-MBAA)-Cl NPs was found to involve generation of reactive oxygen species (ROS) only upon exposure to organic media. Importantly, ROS were not generated upon suspension in water, revealing that the mode of action is target-specific. Further, a unique and specific interaction of the chlorinated NPs with Staphylococcus aureus was discovered, whereby these microorganisms were all specifically targeted and marked for destruction. This bacterial encircling was achieved without using a targeting module (e.g., an antibody or a ligand) and represents a highly beneficial, natural property of the P(MAA-MBAA)-Cl nanostructures. Our findings provide insights into the mechanism of action of P(MAA-MBAA)-Cl NPs and demonstrate the superior efficacy of the NPs over bleach (i.e., stability, specificity, and targeting). This work underscores the potential of developing sustainable P(MAA-MBAA)-Cl NP-based devices for inhibiting bacterial colonization and growth.

Synthesis of quaternary phosphonium N-chloramine biocides for antimicrobial applications

“…1,2 It is believed that the N-chloramine exhibits its biocidal function by transferring the oxidative chlorine to bacterial cellular receptors, [2][3][4] thus resulting in a highly efficacious inactivating mode. Till now, biocides based on organic N-chloramines have been extensively applied in portable water disinfection and pathogenic bacteria inactivation in hospital and public venues, 1,2 and many focus have been directed to the development of novel organic Nchloramine compounds 1,[4][5][6] and polymeric N-chloramine antibacterial materials [7][8][9][10][11][12][13][14][15] in past decades.…”

Biofilms 2018: a Diversity of Microbes and Mechanisms

“…The technology is based on N-halamine nanoparticles, which can covalently bind to a halogen and can be recharged by reexposure to a halogen. He also presented findings on the antimicrobial activity of nanoparticles based on production of reactive oxygen species (ROS) and their ability to target bacteria (62). Finally, the ability to utilize these nanoparticles to functionalize irrigation drippers and reduce biofouling for several months was discussed.…”

A simple method to prepare superhydrophobic and regenerable antibacterial films

“…Such antimicrobial polymeric films should ideally be fabricated such that they are sterile and renewable, while not degrading the durability or reusability of the polymer [8][9][10]. N-halamines are a class of antimicrobial compounds with the advantages of high antimicrobial activity, long-term stability, good durability, easy regeneration, low toxicity and minimal environmental impact [11][12][13][14][15]. These compounds function by releasing active chlorine as N-Cl functional groups are converted to N-H [16][17][18][19].…”