Effect of choline carboxylate ionic liquids on biological membranes

• As expected, all choline carboxylates are of low toxicity.
• Toxicity increases with alkyl chain length in a non-linear way.
• Short chain salts do not penetrate into membranes, whereas penetration is significant for alkyl chain lengths ≥8 at concentrations above the IC50 values.

Choline carboxylates, ChCm, with m = 2–10 and choline oleate are known as biocompatible substances, yet their influence on biological membranes is not well-known, and the effect on human skin has not previously been investigated. The short chain choline carboxylates ChCm with m = 2, 4, 6 act as hydrotropes, solubilizing hydrophobic compounds in aqueous solution, while the longer chain choline carboxylates ChCm with m = 8, 10 and oleate are able to form micelles.In the present study, the cytotoxicity of choline carboxylates was tested using HeLa and SK-MEL-28 cells. The influence of these substances on liposomes prepared from dipalmitoylphosphatidylcholine (DPPC) was also evaluated to provide insights on membrane interactions. It was observed that the choline carboxylates with a chain length of m > 8 distinctly influence the bilayer, while the shorter ones had minimal interaction with the liposomes.

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