Selective partitioning of cholesterol and a model drug into liposomes of varying size

► We measured the size-selective partitioning of two solutes into liposomes. ► In small unilamellar liposomes the solute-to-lipid ratio is a function of size. ► A theoretical model calculates changes of the bending stiffness for fluid bilayers. ► In fluid liposomes cholesterol rigidifies but temoporfin softens the host membrane. ► For gel-phase liposomes, defect structures in the membranes needs to be considered.