Improvement on the extraction efficiency of low density lipoprotein in an ionic liquid microemulsion

Publication date: 1 April 2019

Source: Talanta, Volume 195

Author(s): Jian-Fang Cao, Wang Xu, Xu-Wei Chen, Yang Shu

Abstract

A novel microemulsion is developed at room temperature with 30 µL of sodium alginate sulfate (SAS, 0.02 mol/L), 0.005 g bis (2-ethylhexyl) succinate sulfonate (AOT) and 270 µL of 1-butyl-3-methylimidazolium hexafluorophosphate (BmimPF₆) ionic liquid as aqueous phase, surfactant and IL phase, respectively. The SAS/AOT/BmimPF₆ microemulsion significantly improves the extraction efficiency for low density lipoprotein (LDL). 96% LDL in a 300 µL of PBS is selectively extracted into a same volume of microemulsion, with respect to those of 67%, 76% and 85% by BmimPF₆, H₂O/AOT/BmimPF₆ microemulsion and sodium alginate (SA)/AOT/BmimPF₆ microemulsion. LDL in the SAS/AOT/BmimPF₆ microemulsion is distributed both in BmimPF₆ via hydrophobic interaction and in the "pools" of the microemulsion via electrostatic interaction with AOT and specific interaction between LDL with SAS. 83% of LDL in the microemulsion can be readily back extracted into an aqueous phase with 0.8% (m/v) of sodium dodecyl sulfate (SDS) as stripping reagent. For practical applications, LDL in human serum is selectively extracted with the microemulsion, as demonstrated by enzyme linked immunosorbent assay (ELISA) and sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE).

Graphical abstract

We prepare W/IL reverse microemulsion with SAS solution, AOT and BmimPF₆ as aqueous phase, surfactant and IL phase, respectively. SAS specifically interacts with LDL by carbohydrate-protein interactions. AOT exhibits electrostatic attraction to LDL at pH 5.0. BmimPF₆ extract LDL driven by hydrophobic interaction. These make LDL selectively transfer into the microemulsion.

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