Eco-Friendly Synthesis of Chitosan–Fatty Acid Nano Micelles and Their Differential Antibacterial Activity Against Escherichia coli and Bacillus subtilis

Chitosan-based nanoparticles were prepared using an eco-friendly chemical procedure that conjugates natural fatty acids to the backbone of chitosan. This consists of reacting two molecules in the absence of a solvent and using microwaves to promote the chemical transformation. Both conditions make the whole chemical process more eco-compatible in terms of reagents and energy consumption. The chemical structure and the self-association behavior of chitosan-fatty acid conjugates were characterized by FT-IR, NMR, and dynamic light scattering. The conjugates displayed an enhanced solubility and efficient self-assembly in aqueous solution. The antimicrobial activity of the resulting nanoparticles was evaluated against <i>Escherichia coli</i> (Gram-negative) and <i>Bacillus subtilis</i> (Gram-positive). The micelles significantly inhibited <i>E. coli</i> growth (35-60%), even at relatively low concentrations, whereas negligible activity was observed against <i>B. subtilis</i>. The antibacterial efficacy appears to arise primarily from the ability of the developed nanostructured conjugates to perturb bacterial membranes. These results support the potential of chitosan-fatty acid conjugates as sustainable nanomaterials for biomedical applications, particularly as eco-friendly antimicrobial agents. Future work will evaluate their activity against other Gram-positive pathogens and explore their use in drug delivery.