CONICET | Buscador de Institutos y Recursos Humanos

The relationship between antimicrobial properties and structure of montmorillonite (MMT)containing hexadecyltrimethylammonium bromide (HDTMA-Br) and silver (Ag) was determined.HDTMA was adsorbed at the clay interlayer by a cation exchange, through the positive head of theammonium group. At higher surfactant loadings (100 and 200% cation exchange capacity (CEC); MH1and MH2 samples, respectively) the prevalence of weak adsorption (Van der Waals forces) wasobserved; whereas below the clay CEC (50%, MH0.5) strong interactions predominated (cationexchange). These different interactions impacted on antimicrobial activity, increasing bactericidalcapacity when the surfactant was more available to diffuse. For organo-montmorillonites (OMMT) andall samples with Ag, zeta potential pointed out electrical charge changes on the outer surface, respect toMMT. XPS analyses showed peaks attributed to clusters formation, silver oxidation, and Ag0 in MMTAgand MH0.5-Ag. The Ag0 peak was also present in MH1-Ag and MH2-Ag, the later showing an extrapeak associated with AgBr. HDMTA+ and Ag adsorbed on the MMT acted synergistically againstStaphylococcus aureus. This effect was less noticeable for Escherichia coli and the result was attributedto both, E. coli outer envelope which might lower the efficacy of HDMTA+ adsorbed on the MMT, anddecreasing silver proportions when the surfactant loading increased. MH1-Ag presented the bestbactericidal properties, showing synergistic effects against S. aureus, while maintaining activity againstE. coli compared to MMT-Ag. Understanding MMT-HDMTA-Ag efficacy contributes to the design ofnew antimicrobial materials for potential applications in health care.