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Natural pollen grains were cleaned to remove all external and internal cytoplastic materials to produce sporopollenin exine capsules (SECs). SECs are empty microcapsules with extensive networks of ...

Two new levulinate-based protic ionic liquids (Lev PILs) have been synthesized through an easy, scalable neutralization reaction between levulinic acid (LA), which is one of the most promising renewable building blocks obtainable from cellulose, and amidine superbases (either DBU or DBN). The prepared PILs have been characterized (by means of NMR, FT-IR, TGA and viscosity measurements) and studied as potential cellulose dissolution media. These species display a dissolving ability (weightcellulose/weightPIL) comparable with the popular, and to date best performing, acetate-based PILs. In contrast with these systems, Lev PILs are composed of a larger renewable anion (levulinate vs. acetate): this allows for a reduced amount of the expensive non-renewable superbase cation component while only slightly affecting the cellulose dissolution performance. An application of the proposed Lev PILs, namely the levulination of cellulose, has also been studied. The impact of various reaction parameters (i.e. temperature, amount of anhydride, amount of co-solvent) on the reaction outcome and on the functionalization degree (up to 1.87) has been studied. γ-Valerolactone, a renewable green solvent which is in turn prepared from LA, has been found as an effective DMSO replacement when used as co-solvent for the reaction, allowing for satisfactory functionalization degrees.

Objectives Ionic liquids have shown potential for applications as antimicrobials. Their antimicrobial activity has been shown to be higher against Gram-positive than Gram-negative bacteria, suggesting a protective role for the outer membrane of Gram-negative microorganisms. Colistin is a last-resort antibiotic often used for treating infections sustained by multi-drug resistant Gram-negative bacteria. Colistin interacts with the bacterial lipopolysaccharide, thus altering the structure and increasing the permeability of the outer membrane. The aim of this study was to investigate the interaction between colistin and the ionic liquids 1-methyl-3-dodecylimidazolium bromide, 1-dodecyl-1-methylpyrrolidinium bromide, and 1-dodecyl-1-methylpiperidinium bromide against Gram-negative bacteria of clinical importance such asEscherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, and Acinetobacter baumannii. Methods The interaction between colistin and ionic liquids against Gram-negative bacteria was evaluated by the checkerboard assay. Bacterial killing assays againstP. aeruginosa were carried out to assess whether the synergistic combinations were bactericidal. Results The results of checkerboard assays showed that all three ionic liquids interacted synergistically with colistin againstK. pneumoniae, P. aeruginosa, and A. baumannii but not against Escherichia coli, which resulted more sensitive to all three ionic liquids compared to the other tested species. The synergistic combinations showed no hemolytic activity. Bacterial killing assays showed that the synergistic effect between colistin and each one of the three tested ionic liquids against P. aeruginosa was bactericidal. Conclusion Overall, the results obtained suggest that colistin and ionic liquids might be used in combination for possible applications to combat infections sustained by multi-drug resistant Gram-negative bacteria.

Sporopollenin exine capsules (SECs) are empty microcapsules that are 25 μm in diameter and have extensive networks of ∼200 nm diameter holes obtained by chemically removing all external and internal cytoplastic materials from the natural pollen grains. We have demonstrated that a phase change material (PCM) such as n-eicosane (EIS), a natural paraffin wax, can be successfully encapsulated in the SECs to produce [EIS@SEC]. The high stability and robust nature of SECs retain EIS in the microcavity even during phase transitions, enabling EIS to fully maintain its phase change property while also protecting the EIS from elevated temperatures and corrosive environments. [EIS@SEC] can, therefore, be incorporated into cellulose (CEL) composites with a synthetic process that uses the simple ionic liquid butylmethylimmidazolium chloride to produce [CEL+EIS@SEC] composites. Similar to EIS alone, EIS in the [CEL+EIS@SEC] composites melts when heated and crystallizes when cooled. The energies associated with the crystallization and melting processes enable the [CEL+EIS@SEC] composites to fully exhibit the properties expected of PCMs, i.e., heating the surroundings when they cool and absorbing energy from the surroundings when they warm. The efficiency of latent heat storage and release of [CEL+EIS@SEC] composites was estimated to be around 57% relative to pure EIS. The fact that the DSC curves of the [CEL+EIS@SEC] composites remain the same after going through the heating-melting cycle 220 times clearly indicates that SEC effectively retains EIS in its cavity and protects it from leaking and that the [CEL+EIS@SEC] composites are highly stable and reliable as a phase change material. The [CEL+EIS@SEC] composites are superior to any other available materials based on encapsulated PCM because they are not only robust, reliable, and stable and have strong mechanical properties. They are also are sustainable and biocompatible because as they are synthesized from all naturally abundant materials using a green and recyclable synthesis. These features enable the [CEL+EIS@SEC] composites to be uniquely suited as high performance materials for such uses as dressings to treat burnt wounds, smart textiles for clothing, smart building materials, and energy storage.

In order to identify most suitable ionic liquids (ILs) for potential applications in infection prevention and control, in the present study we comparatively evaluated the antimicrobial potency and hemolytic activity of 15 ILs, including 11 previously described and four newly synthesized ILs, using standard microbiological procedures against Gram-positive and Gram-negative bacteria. ILs showing the lowest minimum inhibitory concentration (MIC) were tested for their hemolytic activity. Three ILs characterized by low MIC values and low hemolytic activity, namely 1-methyl-3-dodecylimidazolium bromide, 1-dodecyl-1-methylpyrrolidinium bromide, and 1-dodecyl-1-methylpiperidinium bromide were further investigated to determine their minimum bactericidal concentration (MBC), and their ability to inhibit biofilm formation by Staphylococcus aureus or Pseudomonas aeruginosa. Killing kinetics results revealed that both Gram-positive and Gram-negative bacteria are rapidly killed after exposure to MBC of the selected ILs. Furthermore, the selected ILs efficiently inhibited biofilm formation by S. aureus or P. aeruginosa. To our knowledge, this is the first systematic study investigating the antimicrobial potential of different types of ionic liquids using standard microbiological procedures. In the overall, the selected ILs showed low hemolytic and powerful antimicrobial activity, and efficient inhibition of biofilm formation, especially against S. aureus, suggesting their possible application as anti-biofilm agents.

Novel ammonium, phosphonium and imidazolium ionic liquids (ILs) based on levulinic acid as the anion were prepared and characterized (NMR spectroscopy, FT-IR spectroscopy, TGA, and viscosity). Commercial methyl carbonate precursors were employed to access the target levulinate ILs via a quick, one-step synthetic procedure that does not require the use of halogenated solvents or produce any waste water. The ability of the levulinate ILs to dissolve cellulose was investigated in detail. Provided the right conditions are employed, these ILs display good to remarkable dissolution ability toward their parent polysaccharide. In particular, [EMIM][Lev] is able to dissolve 29 wt% cellulose at 100 °C, which increases to 38 wt% under reduced pressure. For the best performing IL, several variations of the dissolution conditions, which are known to prevent potential side reactions of the imidazolium cation, have also been tested. The ecotoxicity of the prepared ILs as well as of the previously reported protic levulinate ILs has also been assessed by means of both freshwater and seawater model organisms belonging to different steps of the trophic chain.

Selective and potent matrix metalloproteinase 12 (MMP-12) inhibitors endowed with improved hydrophilicity are highly sought for potential use in the treatment of lung and cardiovascular diseases. In the present paper, we modified the structure of a nanomolar MMP-12 inhibitor by incorporating an ionic liquid (IL) moiety to improve aqueous solubility. Four biologically active salts were obtained by linking the sulfonamide moiety of the MMP-12 inhibitor to imidazolium-, pyrrolidinium-, piperidinium-, and DABCO-based ILs. The imidazolium-based bioactive salt was tested on human recombinant MMPs and on monocyte-derived dendritic cells, showing activity similar to that of the parent compound, but improved water solubility. The imidazolium-based bioactive salt was then used to prepare electrostatically stabilized MMP inhibitor-coated gold nanoparticles (AuNPs) able to selectively bind MMP-12. These AuNPs were used to study subcellular localization of MMP-12 in monocyte-derived dendritic cells by transmission electron microscopy analysis.