Macromolecules in ordered media VIII. High-performance size-exclusion chromatography as a technique for characterizing the interaction between polyanions and cationic liposomes

Characterization of loaded liposomes by size exclusion chromatography

This review focuses on the use of conventional (SEC) and high performance (HPSEC) size exclusion chromatography for the analysis of liposomes. The suitability of both techniques is examined regarding the field of liposome applications. The potentiality of conventional SEC is strongly improved by using a HPLC system associated to gel columns with a size selectivity range allowing liposome characterization in addition to particle fractionation. Practical aspects of size exclusion chromatography are described and a methodology based on HPSEC coupled to multidetection modes for on-line analysis of liposomes via label or substance encapsulation is presented. Examples of conventional SEC and HPSEC applications are described which concern polydispersity, size and encapsulation stability, bilayer permeabilization, liposome formation and reconstitution, incorporation of amphiphilic molecules. Size exclusion chromatography is a simple and powerful technique for investigation of encapsulation, insertion/interaction of substances from small solutes (ions, surfactants, drugs, etc.) up to large molecules (proteins, peptides and nucleic acids) in liposomes.

Hydrophobically driven attachments of synthetic polymers onto surfaces of biological interest: lipid bilayers and globular proteins

This paper gives a brief overview of the consequences of associations between amphiphilic water-soluble polymers and small colloidal particles of biological interest: proteins and vesicles. Typical structures of water-soluble synthetic polymers containing hydrophobic groups are presented. The segregation between polar and apolar units in these polymers induces self-organisation in micro-domains despite the lack of specific primary structure. In the presence of other amphiphilic particles like proteins and vesicles, mixed assemblies are formed. Examples of polymer associations with vesicles or globular proteins, mainly focused on the acrylic derivatives, bring out common features in these mixtures. When the size of the polymer is of the same order of magnitude as that of the particle, adsorption of polymer chains creates a protective layer around each individual particle. Depending on the hydrophobicity of the partners, the association can stabilise the dispersion of unmodified particles or induce structural changes (membrane disruption, leakage). When small particles are added to solutions of long polymers, multimolecular complexation occurs. In this case, the size of the resulting aggregates depends on the concentrations. It goes from the size of one polymer molecule up to formally infinity as revealed by gelation. The identification of non-specific association modes between biological nanoparticles and macromolecules might be revealed by the general behaviour of these synthetic mixed systems.