Cationic surfactants from lysine: synthesis, micellization and biological evaluation

Area of Science:

• * Materials Science and Chemistry
• * Biotechnology and Biomedical Engineering

Background:

• * Development of biocompatible and biodegradable surfactants is crucial for sustainable chemical applications.
• * Amino acid-based surfactants offer potential for reduced toxicity compared to conventional synthetic surfactants.

Purpose of the Study:

• * To synthesize and characterize novel biocompatible cationic surfactants derived from the amino acid lysine.
• * To evaluate the antimicrobial activity, haemolytic activity, acute toxicity, and biodegradability of these lysine-based surfactants.

Main Methods:

• * Synthesis of lysine surfactants via acylation with natural saturated fatty acids.
• * Micellization studies using Pulsed Field Gradient Spin Echo Nuclear Magnetic Resonance (PGSE-NMR) technique.
• * Antimicrobial testing against Gram-positive and Gram-negative bacteria, haemolytic activity assays, acute toxicity tests (Daphnia magna), and biodegradability assessments.

Main Results:

• * High yields of lysine-based cationic surfactants (N(epsilon)-lauroyl, N(epsilon)-myristoyl, and N(epsilon)-palmitoyl lysine methyl esters) were successfully synthesized.
• * Surfactants exhibited moderate antimicrobial activity against Gram-positive bacteria, with Gram-negative bacteria showing resistance.
• * Significantly lower haemolytic activity compared to N(alpha)-acyl amino acid analogues and reduced acute toxicity against Daphnia magna than conventional cationic surfactants.
• * All three lysine surfactants were classified as readily biodegradable.

Conclusions:

• * Lysine-derived cationic surfactants are biocompatible, readily biodegradable, and exhibit lower toxicity profiles.
• * These surfactants present a promising, eco-friendly alternative to traditional cationic surfactants, particularly for applications requiring antimicrobial properties against Gram-positive bacteria.