Violacein (Viol) is a pigment produced by several Gram-negative bacteria with many bioactivities, such as anticancer, virucide, and antiparasitic. However, violacein is insoluble under physiological conditions preventing its potential therapeutic uses. Surface-active ionic liquids (SAILs) based on the cation 1-alkylimidazolium ([C_nHim]) with n = 10 to 16 alkyl carbon side chain lengths and acetate, bromide, methanesulfonate (S) or trifluoroacetate (F) as counterions were synthesized and screened to dissolve Viol in micellar aqueous media and for toxicological studies on the human lung carcinoma A549 cell line. Screening allowed the selection of 1.5 × 10⁻³% (w/v) [C₁₆Him]-S because it combines low cytotoxicity with 71.5% cell viability and good interaction with 95.2% of the violacein kept in micellar solution for at least 48 h. [Viol-([C₁₆Him]-S)] complex was used to develop an efficient hybrid solid lipid nanoparticle (SLN) carrier based on myristyl myristate and poloxamer 188 and tailored with folate to target cancer cells. Cellular SLN uptake was evaluated with fluorescent DiOC₁₈ on A549, HCT-116, and HeLa cell lines expressing or not the folate receptor. The results showed fivefold incorporation of Viol nanoparticles in HCT-116 and HeLa cell cultures, displaying a high level of folate receptor. Biophysical characterization of the hybrid solid lipid carrier containing Viol was performed by dynamic light scattering, Fourier transform infrared, X-ray diffraction and X-ray photoelectron spectroscopies, and by transmission electron and cryo-transmission microscopies.

This work shows for the first time the link between the amount of free sulfuric acid (as detected by cyclic voltammetry) and the activity of sulfonic-acid-functionalized ionic liquids (ILs) as acid catalysts for a transesterification reaction, and demonstrates that sulfonic acid groups, while are not directly involved in the catalysis, release the free acid during the reaction. Two imidazolic ILs with bisulfate as the counterion and their corresponding task-specific ILs (TSILs) that resulted from the addition of a sulfonic acid group inside the imidazolic-base structure were studied. The outstanding catalytic activity at room temperature of the TSILs 1-(4-sulfonic acid)-butyl-3-methylimidazolium bisulfate ([bsmim]HSO₄) and 1-(4-sulfonic acid)-butyl-imidazolium bisulfate ([bsHim]HSO₄) for the transesterification of p-nitrophenyl acetate with methanol was associated to the significant amounts of free sulfuric acid in equilibria with the ionic pairs. It was concluded that these TSILs function as reservoirs for releasing the free acid, which is the actual acid catalyst. In contrast, the corresponding non-sulfonic ILs supply very little amounts of free acid and consequently present low catalytic activities at room temperature, which in fact can be improved by increasing the reaction temperature up to 100 °C.

In the present work, our objective is to take advantage of the property presented by Ionic Liquids (ILs) based on 1-alkyl-3-methylimidazolium cations by having amphiphilic character when the alkyl group is a long hydrocarbon chain. These ILs can act as surfactants forming micelles in aqueous solution. In this sense, the micellar effect on a Diels-Alder reaction (DA) was analyzed taken as a reference. The reactive system studied consists of maleic anhydride and isoprene, variables such as diene:dienophile ratio and reaction temperatura among the most important were optimized. N,N-dodecylmethylimidazolium bromide was used at the critical micellar concentration (CMC) of 1 × 10⁻² M. These “new systems” microheterogeneous would allow, in addition to better solubilization of non-polar substrates, to adopt milder reaction conditions.