Synthesis, Photophysical Studies on Some Anthracene–based Ionic Liquids and their Application as Biofilm Formation Inhibitor

Abstract

Imidazolium based monocationic and dicationic ionic liquids, with an anthracene moiety covalently attached to the imidazolium ions, via a methyl spacers, have been synthesized and their photophysical and biological studies have been carried out. Photophysical investigations have revealed that the monocationic anthracene based ionic liquid, AnILBr, exhibits a higher fluorescence quantum yield and average fluorescence lifetime compared to its parent fluorophore anthracene. For dication based systems (AnIL2Br2), the photophysical data have demonstrated that the attachment of two imidazolium cations on anthracene ring, leads to even further fluorescent enhancement. The quantum yield, average lifetime, red‐shifts of absorption and emission for AnIL2Br2 are observed to be relatively higher as compared to AnILBr. This observations illustrate that the imidazolium cation influences the electronic energy distribution in the fluorophore, in such a way, that it leads to enhancement of photoluminescence. Since ionic liquids have recently been shown to demonstrate anti‐biofilm activity, the potential of AnILBr, as a biofilm formation inhibiting agent has also been explored in details. The assay has revealed that addition of AnILBr up to 4 hours significantly inhibited the biofilm formed by both the strains, and this can be utilized to enhance the effectiveness of an antibacterial drug, when used along with AnILBr.

Recent Advances in Ionic Liquids in Biomedicine

“…[ 172 ] Later, researchers began to more rigorously assess the surface interactions that made ILs such strong antimicrobial candidates. [ 173 , 174 ] Recently they have been both used alone [ 175 , 176 , 177 , 178 , 179 , 180 , 181 , 182 ] and incorporated into hybrid materials. [ 183 , 184 , 185 , 186 , 187 , 188 , 189 , 190 ] In particular, poly(ionic liquids) have recently shown excellent antibacterial properties [ 191 , 192 , 193 , 194 , 195 , 196 , 197 , 198 , 199 ] and their polymeric character has been used to manufacture antibacterial membranes.…”

“…The first, more widely accepted theory, is that the infiltration of IL into the cell membrane can cause the cell to release cytoplasmic content like potassium ions, DNA, and ribonucleic acid (RNA) leading to cell death. [ 176 , 178 , 184 , 187 , 193 ] The other proposed mechanism suggests that insertion of the positively charged molecule causes neutralization of the negative zeta potential of the cell surface. This prevents proper cell growth and causes aggregation of cells, resulting in a much slower antimicrobial effect.…”

Present and Future Perspectives on Therapeutic Options for Carbapenemase-Producing Enterobacterales Infections

“…Then, cations are absorbed into the cell layers, connecting to the cytoplasmatic membrane, and penetrating the interior of the cell [ 232 ]. ILs further lead to the coagulation of cytoplasmic constituents, causing the inhibition of crucial enzymes (i.e., AMP deaminase, acylase I, cytochrome c oxidase, glutathione reductase acetylcholinesterase, carboxylesterase, catalase), interfering with energy or self-repair processes [ 233 ], and finally causing cell death.…”

Biofilm control by ionic liquids

“…Then, cations are readily absorbed into the cell layers, connecting to the cytoplasmatic membrane, and penetrating the interior of the cell [67]. ILs further provoke the coagulation of cytoplasmic constituents causing the inhibition of crucial enzymes (i.e., acetylcholinesterase, AMP deaminase, acylase I, cytochrome c oxidase, glutathione reductase, carboxylesterase, catalase, and Taq DNA polymerase), interfering with energy or self-repair processes [68,69], and finally causing cell death [38].…”

“…From a library of quinolone-based ILs, 1-alkylquinolinium bromide salts with 12 and 14 carbons in the alkyl chain demonstrated strong antibiofilm effects against diverse bacterial pathogens [34]. Imidazolium-based monocationic and dicationic ILs with an anthracene moiety covalently attached to the imidazolium efficiently inhibited the biofilms of Gram-positive bacteria [69] Furthermore, a recent study reported the synergistic bactericidal and antibiofilm activities of 1alkyl-3-methylimidazolium ILs, with the incorporation of anions containing silver or copper, against Pseudomonas aeruginosa and Staphylococcus aureus [39].…”