Characteristics of the Membrane Permeability of Temperature-Sensitive Liposome

Abstract

The relationship between the temperature-sensitivity of the release of an entrapped drug from liposome as well as the type of drug or liposome is discussed. The drug release from DPPC liposome (dipalmitoylphosphatidylcholine liposome) has been confirmed to increase abruptly near its phase-transition temperature for both low-molecular-weight compouds (such as calcein) and high-molecular-weight compounds (such as dextran). The amount of temperature-sensitive calcein released from the liposomes was dependent on the method of liposome preparation: that is, the release from REV (reverse phase evaporated vesicle) was the highest; next was that from LUV (large unilamellar vesicle prepered by detergent removal method), and lowest was from SUV (small unilamellar vesicle prepared by an ultrasonication method). In order to examine the size effect of liposomes on temperature-sensitive drug release, REV was fractionated into three groups according to their average sizes and calcein release for each group was investigated. The temperature at which calcein release showed a maximum was almost the same in each of three groups; while as the average liposome size of a group was larger, the initial rate of calcein release became higher and the temperature at which calcein release began became lower. The amount of release of a entrapped drug was primarily dependent on the molecular weight of the drug, in spite of the variety of drugs investigated.

Lipid Membrane Permeability of Synthetic Redox DMPC Liposomes Investigated by Single Electrochemical Collisions

“…Taken together these results show that varying the temperature is an efficient external stimulus for weakening the membrane and observing the release events. The maximum collision frequency temperature (60 ± 5 °C) is slightly but significantly higher than those reported for the maximum membrane permeability of various phospholipid liposomes (~ 42 °C), [52][53][54] and clearly higher than the phase transition temperature of the DMPC lipid (24 °C). Assuming that the concentration of encapsulated ferrocyanide (0.5 M) is the same in each redox liposome and…”

Fast solute release from photosensitive liposomes: an alternative to ‘caged’ reagents for use in biological systems

“…The behaviour in a lipid bilayer host of azobenzene-containing lipids similar to those used in this study has been investigated by Song et al [12] who find spectroscopic evidence of aggregate formation in some circumstances. It is well known that solute release from liposomes of pure gel-phase lipids is markedly increased at the midpoint of a phase transition [13] where regions of ordered and disordered lipid coexist, and indeed this has been proposed as a method to control localised delivery of soluble drugs trapped within liposomes [14]. Millisecond release of liposome contents is unlikely to be caused by an overall transition in the membrane to the fluid, liquid crystalline state, since these transitions in pure DPPC bilayers occur on a time-scale of tens of milliseconds [15].…”

Characterization of liposomes with different intraliposomal viscosities

“…11 The viscosities of 0%, 5%, and 10% CMC solutions were 1, 40, and 460 cps, respectively, according to measurement with the viscometer. After extrusion, assuming the formation of unilamellar liposome with 380 nm of average diameter after extrusion, 1,12 the number of liposomes with 380-nm diameter from 1 mg of phosphatidylchorine is approximately 6×10 11 using eq.…”