Improved accuracy and reproducibility of spontaneous liposome leakage measurements by the use of supported lipid bilayer-modified quartz cuvettes

Abstract

Recent studies have revealed avid interactions between liposomes and several solid materials, such as quartz, polystyrene (PS) and poly(methyl methacrylate) (PMMA), commonly found in cuvettes used for spectroscopic measurements. These interactions risk leading to detrimental changes in liposome structure and integrity that, if overlooked, may compromise the measurements. In case of leakage experiments based on probing the spontaneous release of encapsulated hydrophilic markers, the liposome-cuvette interactions may result in the recording of erroneously high degrees of leakage. In the present study we investigate the possibilities of preventing unwanted liposome-cuvette interactions through the use of quartz cuvettes passivated with supported lipid bilayers (SLBs). The results show that this strategy leads to higher reproducibility and significantly improved accuracy of the leakage measurements. The usefulness of the method is validated in comparative experiments focused on how changes in temperature and lipid phase state, as well as inclusion of poly(ethylene glycol)-conjugated lipids (PEG-lipids), affect the release of liposome encapsulated carboxyfluorescein (CF).

Keywords: Cuvettes; Liposomes; Permeability experiments; QCM-D; SLB; Sustained release.