Interactions of ionic and non-ionic surfactants with plasma low density lipoprotein

Abstract

Abstract Surfactants might be useful in facilitating the replacement of the interior of low density lipoprotein (LDL2) (ρ = 1˙02-1˙063 g ml−1) with drug molecules. We have used photon correlation spectroscopy, supported by sedimentation velocity measurements to study the effects of surfactants on LDL2. Sodium dodecyl sulphate, cetrimide, and all non-ionic surfactants studied caused rapid increases of ca 50% in the Stokes' radius up to surfactant/LDL2 molar ratios of ca 1000:1. This was interpreted as due to partial unfolding of the LDL2 protein and intercalation of surfactant with the LDL2 surface layer. At higher concentrations, ionic surfactants and non-ionics with HLB values <14˙6 decreased the Stokes' radius due to delipidation of LDL2. These interactions are similar to those between surfactants and biological membranes, thus LDL2 might be a useful model system to study surfactant structure-activity relationships.