Posted by In recent years, a significant number of publications have been devoted to studying ionic liquids as a new type of biocides with a wide range of antimicrobial activity against bacteria, fungi, algae, as well as microbial biofilms. The positively charged organic cations of ionic liquids can easily pass through the cell membranes of microorganisms and destroy them, which is also facilitated by the presence of long linear hydrocarbon substituents. Ionic liquids are of great interest as potential biocidal additives for various household and industrial materials. Since ionic liquids are very polar in nature, they are able to migrate into the environment and possibly be included in the food chain and bioaccumulate in living organisms. Thus, the practical use of ionic liquids should be preceded by an appropriate toxicological assessment.
Thus, the inclusion complexation of ionic liquid, IL, (1-dodecylpyridinium tetrafluoroborate (PyrC12-BF4) with sulfobutyl ether-β-cyclodextrin sodium salt (SBECD) has been investigated by a series of appropriate methods. Sodium salt of sulfobutyl ether β-cyclodextrin (SBECD) has significant advantages over initial -CD, such as higher water solubility, as well as much lower acute toxicity. In this connection, inclusion complexation of cationic surfactants with SBECD can be an efficient approach for obtaining new antimicrobial systems for various practical applications.
The stability constant of the complex of SBECD-IL (K = 1210 M–1) was determined by the method of Higuchi and Connors. An increase in the surface tension of solutions with different SBECD’s content was recorded by using the method of Wilhelm’s plate, which could serve as an additional evidence of the formation of inclusion complex between SBECD and IL. Analysis of the TGA results provided for the initial IL and SBECD, their mechanical mixture and the complex elaborated allows us to conclude that the “guest-host” type complexation is emerged. Differential scanning calorimetry (DSC) data also confirmed the formation of inclusion complex between SBECD and IL. While the guest molecule is incorporated into cyclodextrin cavity, its thermal properties are changed. So, the loss of physically bonded water in the complex is equal to 5% by weight, indicating the IL’s molecule being located in the SBECD’s hydrophobic cavity. The thermogram of inclusion complex demonstrates just one endothermic peak at 740 C. The complex is formed by entering the long alkyl chain of ionic liquid into the hydrophobic cavity of SBECD. The results of 1H NMR study revealed physicochemical interactions between the hydrophobic alkyl chain of PyrC12-BF4 and protons of the inner cavity of SBECD, as well as between the C-H protons of pyridinium cation and the polar SBECD groups.
Thus, complexation of long-chain pyridinium salt with sulfobutyl ether-β-cyclodextrin sodium salt can be an efficient approach for the preparation of new antimicrobial formulations with reduced toxicity.
Reference:
L. Kobrina, V.Boiko, V. Shtompel, N. Hudzenko, S. Rogalsky, M. Frasinyuk, A. Kozitskiy, S. Riabov (2024) Inclusion complex of ionic liquid 1-dodecylpyridinium tetrafluoroborate with sulfobutyl ether-β-cyclodextrin: Preparation and characterization. Journal of Molecular Structure 1309, 138137. https://doi.org/10.1016/j.molstruc.2024.138137