Synthesis, Surface Property and Antimicrobial Activity of Cationic Gemini Surfactants Containing Adamantane and Amide Groups

A Systematic Approach: Molecular Dynamics Study and Parametrisation of Gemini Type Cationic Surfactants

The spreading of antibiotic-resistant bacteria strains is one of the most serious problem in medicine to struggle nowadays. This triggered the development of alternative antimicrobial agents in recent years. One of such group is Gemini surfactants which are massively synthesised in various structural configurations to obtain the most effective antibacterial properties. Unfortunately, the comparison of antimicrobial effectiveness among different types of Gemini agents is unfeasible since various protocols for the determination of Minimum Inhibitory Concentration are used. In this work, we proposed alternative, computational, approach for such comparison. We designed a comprehensive database of 250 Gemini surfactants. Description of structure parameters, for instance spacer type and length, are included in the database. We parametrised modelled molecules to obtain force fields for the entire Gemini database. This was used to conduct in silico studies using the molecular dynamics to investigate the incorporation of these agents into model E. coli inner membrane system. We evaluated the effect of Gemini surfactants on structural, stress and mechanical parameters of the membrane after the agent incorporation. This enabled us to select four most likely membrane properties that could correspond to Gemini’s antimicrobial effect. Based on our results we selected several types of Gemini spacers which could demonstrate a particularly strong effect on the bacterial membranes.

Studying the silver nanoparticles influence on thermodynamic behavior and antimicrobial activities of novel amide Gemini cationic surfactants

Three novels amide Gemini cationic surfactants with various alkyl chains and their silver nanohybrid with silver nanoparticles were synthesized and a confirmation study for surfactant and their nanoparticles formation has been established using IR, ¹HNMR, TEM and UV-Vis spectroscopy. The surface-active properties of these surfactants and their nanoform were investigated through surface tension and electrical conductivity measurements and a comparative study has been established. The thermodynamic parameters of micellization and adsorption were assessed at temperatures range from 25 to 65°C. The effect of silver particles on the surface behavior of the synthesized surfactant has been discussed. The aggregation behavior of silver nanoparticles with these synthesized Gemini surfactants in water were investigated using dynamic light scattering and transmission electron microscopy. Furthermore, the antimicrobial activities of these synthesized amide Gemini surfactants and their nanostructure with silver against both Gram positive and Gram negative bacteria were also investigated.

Mesoscopic Simulations on the Aggregate Behavior of Oligomeric Adamantane Surfactants in Aqueous Solutions

Oligomeric adamantane surfactants are novel surfactants using rigid adamantane as spacer group, which can form a variety of scales and shapes of micelles and aggregates in aqueous solution. In this paper, the self-assembling aggregate behavior of N,N-dimethyl dodecyl ammonium bromide adamantine [Ad-(NC12Br)], 1,3-di(N,N-dimethyl dodecyl ammonium bromide) adamantine [Ad-(NC12Br)2] and 1,3,5-tri-(N,N-dimethyl dodecyl ammonium bromide) adamantine [Ad-(NC12Br)3] in aqueous solution is studied by mesoscopic simulations of dissipative particle dynamics (DPD). The simulation results show that the critical micelle concentrations of the three adamantane oligomeric surfactants is in the order of [Ad-(NC12Br)3] < [Ad-(NC12Br)2] < [Ad-(NC12Br)]. The three oligomeric adamantane surfactants are able to form aggregates with a variety of spatial structures, such as spherical micelles, vesicles, lamellas, reticular lamellas, column lamellas or steric reticules in response to different surfactant concentrations in the aqueous solution.

Synthesis and disinfection effect of the pyridine-4-aldoxime based salts

A set of new quaternary ammonium compounds based on pyridine-4-aldoxime was synthesized, characterized with analytical data (NMR, EA, HPLC, MS) and tested for in vitro antimicrobial activity (antibacterial, antifungal) and cytotoxicity. Quaternary pyridinium-4-aldoxime salts with length of alkyl side chain from C8 to C20 and belonging to the group of cationic surfactants were investigated in this work. An HPLC experimental protocol for characterization of mixtures of all homologues has been found. Antimicrobial evaluation found that yeast-type fungi were most sensitive towards C₁₄ and C₁₆ analogues, whereas the C₁₆ analogue was completely ineffective against filamentous fungi. Antibacterial assessment showed versatility of C₁₄ and relatively high efficacy of C₁₆ against G+ strains and C₁₄ against G− strains. Notably, none of the studied compounds exceeded the efficacy and versatility of the benzalkonium C₁₂ analogue, and benzalkonium analogues also exhibited lower cytotoxicity in the cell viability assay.