Diffusion Coefficients of Surface Modified Liposomes and Thermo-sensitive Liposomes Measured by Optoelectronically Induced Transient Grating Method

Liposomal products enable new therapies through the protection and controlled release of encapsulated medicines. The diffusion coefficient of a liposome is associated with its size and surface properties, and its measurement is important in the evaluation of the product and design of new drug delivery systems. We propose a rapid and label-free diffusion sensing method using light-induced dielectrophoresis for high-throughput analysis of liposomal products. In this study, the diffusion coefficient of liposomes with a diameter of approximately 100 nm was measured by observing the mutual diffusion within a few seconds. Prior to the measurement, a parametric study of the excitation conditions was performed to achieve highly efficient manipulation of liposomes by light-induced dielectrophoresis. The validation of the proposed measurement method for liposomes was demonstrated by comparing the result of observation by the transmission electron microscope. The effect of the surface functional groups of the liposomes was quantitatively evaluated using diffusion coefficient measurements. Furthermore, the thermo-sensitive liposomes were measured to demonstrate their sensitivity to phase transition during temperature change.