Size-Controlled Ammonium-Based Homopolymers as Broad-Spectrum Antibacterials

Area of Science:

• Polymer Chemistry
• Antimicrobial Agents
• Biomaterials

Background:

• Polymers with ammonium groups exhibit natural antimicrobial properties.
• These polymers can prevent or eliminate infections caused by microorganisms.
• Developing novel antibacterial agents is crucial for combating microbial resistance.

Purpose of the Study:

• To synthesize and evaluate ammonium-containing homopolymers as antibacterial agents.
• To investigate the effect of molecular weight on polymer antimicrobial activity and toxicity.
• To elucidate the mechanism of action of these polymers against bacteria.

Main Methods:

• Homopolymers were synthesized using Reversible Addition Fragmentation Chain Transfer Polymerization (RAFT).
• Antimicrobial activity was tested against Gram-positive (M. luteus, B. subtilis) and Gram-negative bacteria (E. coli, S. typhimurium).
• Mechanisms of action were studied using dye-based assays and Scanning Electron Microscopy (SEM).

Main Results:

• Three polymers were synthesized and tested at different molecular weights (10, 20, 40 kDa).
• Poly([2-(methacryloyloxy)ethyl]trimethylammonium chloride) (40 kDa) demonstrated the highest non-Gram-specific activity (MIC 16-64 µg/mL).
• SEM revealed bacterial cell envelope disruption; the most active polymer acted bactericidally by targeting the cytoplasmic membrane.

Conclusions:

• Poly([2-(methacryloyloxy)ethyl]trimethylammonium chloride) is a potent, non-hemolytic antibacterial agent.
• This polymer's effectiveness is linked to its molecular weight and ability to disrupt bacterial membranes.
• Potential biomedical applications include surface dressings and treatments for eye infections.