The development of a cholesterol biosensor using a liquid crystal/aqueous interface in a SDS-included β-cyclodextrin aqueous solution

• β-CD-SDS inclusion was used for the detection of cholesterol at 5CB/aqueous interface.
• The SDS enclosed within the β-CD cavity was replaced by cholesterol.
• The released SDS from the β-CD caused homeotropic orientation of 5CB.
• The cholesterol was detected from planar-to-homeotropic transition of 5CB.
• This convenient TEM grid cell provides a new method for the selective detection of cholesterol.

Sodium dodecyl sulphate (SDS) including β-cyclodextrin (β-CD) (β-CDSDS) was used to detect cholesterol at the 4-cyano-4′-pentylbiphenyl (5CB)/aqueous interface in transmission electron microscopy (TEM) grid cells. The β-CD acts as a host for SDS (guest). The guest SDS enclosed within the β-CD cavity was replaced with cholesterol by injecting cholesterol solution into the TEM cell at concentrations greater than 3 μM. The replacement of SDS with cholesterol was confirmed by pH measurement and high performance liquid chromatography (HPLC). The SDS excluded from the β-CD altered the planar orientation of the 5CB confined within the TEM grid cell to a homeotropic orientation. This planar-to-homeotropic transition was observed using a polarized optical microscope under crossed polarizers. This convenient TEM grid cell provides a new method for the selective detection of cholesterol without immobilization of the detecting receptors (enzyme, antibody, or aptamer) or the use of sophisticated instruments.

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