Beyond Amphiphilic Balance: Changing Subunit Stereochemistry Alters the Pore-Forming Activity of Nylon-3 Polymers

Area of Science:

• Polymer Chemistry
• Biomaterials Science
• Antimicrobial Agents

Background:

• Amphiphilic nylon-3 polymers show promise as antimicrobial agents, mimicking natural peptides with high bacterial potency and low eukaryotic toxicity.
• Amphiphilic balance, a key feature, dictates polymer activity, with hydrophobicity levels crucial for efficacy and safety.

Purpose of the Study:

• To investigate if factors beyond amphiphilic balance influence the biological activity of synthetic polymers.
• To explore the role of stereochemistry in modulating the activity and toxicity profiles of nylon-3 polymers.

Main Methods:

• Synthesis of new nylon-3 polymers with stereoisomeric subunits featuring ethyl and aminomethyl side chains.
• Evaluation of antibacterial activity and eukaryotic cell membrane disruption.
• Experiments using planar lipid bilayers and synthetic liposomes to elucidate membrane interaction mechanisms.

Main Results:

• Stereochemical differences in subunits significantly altered eukaryotic cell membrane disruption, despite similar amphiphilic balance.
• Antibacterial activities were largely unaffected by subunit stereochemistry.
• Eukaryotic membrane disruption was attributed to polymer-mediated pore formation.

Conclusions:

• Factors beyond amphiphilic balance, such as subunit stereochemistry, critically influence the membrane activity of synthetic polymers.
• Distinct conformational propensities arising from stereochemistry can lead to variations in polymer chain shape and membrane interaction.
• Stereochemistry represents a crucial, previously underappreciated design parameter for optimizing antimicrobial polymer specificity and efficacy.