Bardhan, Soumik, et al. Journal of colloid and interface science 430 (2014): 129-139.
Challenge: The design and fabrication of antimicrobial microemulsions is complicated by the need for thermodynamic stability, control of microstructure and bioactivity, especially for microemulsions formed from a mixture of a cationic and a non-ionic surfactant. Conventional oils struggle to achieve this synergy while maintaining biological compatibility.
Solution: Isopropyl myristate (IPM) served as the polar lipophilic oil in microemulsions combining cationic CTAB and non-ionic Brij surfactants with 1-pentanol cosurfactant. IPM's unique properties enabled precise interfacial control and microenvironment engineering, allowing customization of thermodynamic behavior and antimicrobial efficacy through surfactant ratio adjustments.
Methodology: Comprehensive characterization included phase behavior studies, conductivity, dynamic light scattering (DLS), FTIR, and ¹H NMR to analyze microstructure and water states. Antimicrobial efficacy was validated against Bacillus subtilis and Escherichia coli at 303 K across formulations.
Results: IPM-based microemulsions demonstrated spontaneous formation (ΔG < 0) with unique endothermic behavior at equimolar surfactant ratios. Spectroscopic evidence was found for the presence of three different types of water within the droplets of these microemulsions. Critically, antimicrobial activity varied predictably with composition, showing direct correlation between thermodynamic stability and bacterial inhibition efficacy against both Gram-positive and Gram-negative strains.