84
phototoxic to all three bacterial species than a solution in ethanol. A neutral
porphyrin, meso-tetra(4-hydroxyphenyl)porphine (THPP), was also formulated in
this way (Wikene et al. 2015b). Two deep eutectic solvents, citric acid:sucrose 1:1
and D-glucose:DL-malic acid 1:1, were chosen for tests of phototoxicity against
Enterococcus faecalis and Staphylococcus aureus. These solutions showed much
higher antibacterial phototoxicity than a solution of meso-tetra(4-hydroxyphenyl)
porphine in phosphate-buffered saline. In a subsequent study, Wikene et al. (2017)
extended the observations to four bacterial species (Escherichia coli, Staphylococcus
epidermidis, Pseudomonas aeruginosa, Klebsiella pneumoniae) as well as a fungal
pathogen (Candida albicans). In these experiments, citric acid:sucrose 1:1 and
DL-malic acid:D-fructose:D-glucose 1:1:1 were the chosen deep eutectic solvents.
Meso-tetra(4-hydroxyphenyl)porphine in the deep eutectic solvents was much more
phototoxic toward Escherichia coli than meso-tetra(4-hydroxyphenyl)porphine in
phosphate-buffered saline. Similar results were obtained with Pseudomonas
aeruginosa and Staphylococcus epidermidis. Klebsiella pneumoniae and Candida
albicans were less sensitive.
Molecular Imprinting
A different approach was recently described by Fu et al. (Fu et al. 2019). They used
a deep eutectic solvent composed of choline chloride and acrylic acid to produce a
molecularly imprinted polymer designed to selectively extract β-lactoglobulin from
complex mixtures. The polymer was formed on a base of molybdenum disulfide
(MoS 2 ) containing some iron oxide nanoparticles (Fe 3 O 4 ) to allow the polymer to be
manipulated using an external magnetic field. The deep eutectic solvent was polymerized in the presence of the protein using ethylene glycol dimethacrylate to crosslink acrylic acid. The resulting poly(ChCl-AA deep eutectic solvent)@Fe 3 O 4 @
MoS 2 was able to selectively extract β-lactoglobulin from milk but also showed
antibiotic properties. The growth of Staphylococcus aureus, Escherichia coli, and
Bacillus subtilis was retarded in the presence of the polymeric material. However,
an inverse effect was obtained with Pseudomonas fluorescens. The growth of bacterial on biomaterials always poses a problem for their use, so these results are
encouraging.
2.3.4 Cutaneous Applications
Ionic liquids and deep eutectic solvents have great potential for topical application
to the skin because of their low toxicity and their rheological properties. Furthermore,
there is evidence that these formulations can act as promoters of absorption across
the outer layers of the skin and help to deliver active substance into and across the
skin. Early work by Stott et al. showed that forming eutectics between ibuprofen
C.-H. Nguyen et al.
phototoxic to all three bacterial species than a solution in ethanol. A neutral
porphyrin, meso-tetra(4-hydroxyphenyl)porphine (THPP), was also formulated in
this way (Wikene et al. 2015b). Two deep eutectic solvents, citric acid:sucrose 1:1
and D-glucose:DL-malic acid 1:1, were chosen for tests of phototoxicity against
Enterococcus faecalis and Staphylococcus aureus. These solutions showed much
higher antibacterial phototoxicity than a solution of meso-tetra(4-hydroxyphenyl)
porphine in phosphate-buffered saline. In a subsequent study, Wikene et al. (2017)
extended the observations to four bacterial species (Escherichia coli, Staphylococcus
epidermidis, Pseudomonas aeruginosa, Klebsiella pneumoniae) as well as a fungal
pathogen (Candida albicans). In these experiments, citric acid:sucrose 1:1 and
DL-malic acid:D-fructose:D-glucose 1:1:1 were the chosen deep eutectic solvents.
Meso-tetra(4-hydroxyphenyl)porphine in the deep eutectic solvents was much more
phototoxic toward Escherichia coli than meso-tetra(4-hydroxyphenyl)porphine in
phosphate-buffered saline. Similar results were obtained with Pseudomonas
aeruginosa and Staphylococcus epidermidis. Klebsiella pneumoniae and Candida
albicans were less sensitive.
Molecular Imprinting
A different approach was recently described by Fu et al. (Fu et al. 2019). They used
a deep eutectic solvent composed of choline chloride and acrylic acid to produce a
molecularly imprinted polymer designed to selectively extract β-lactoglobulin from
complex mixtures. The polymer was formed on a base of molybdenum disulfide
(MoS 2 ) containing some iron oxide nanoparticles (Fe 3 O 4 ) to allow the polymer to be
manipulated using an external magnetic field. The deep eutectic solvent was polymerized in the presence of the protein using ethylene glycol dimethacrylate to crosslink acrylic acid. The resulting poly(ChCl-AA deep eutectic solvent)@Fe 3 O 4 @
MoS 2 was able to selectively extract β-lactoglobulin from milk but also showed
antibiotic properties. The growth of Staphylococcus aureus, Escherichia coli, and
Bacillus subtilis was retarded in the presence of the polymeric material. However,
an inverse effect was obtained with Pseudomonas fluorescens. The growth of bacterial on biomaterials always poses a problem for their use, so these results are
encouraging.
2.3.4 Cutaneous Applications
Ionic liquids and deep eutectic solvents have great potential for topical application
to the skin because of their low toxicity and their rheological properties. Furthermore,
there is evidence that these formulations can act as promoters of absorption across
the outer layers of the skin and help to deliver active substance into and across the
skin. Early work by Stott et al. showed that forming eutectics between ibuprofen
C.-H. Nguyen et al.