Controlling lamellarity and physicochemical properties of liposomes prepared using a microfluidic device.

The function of liposomal drugs and cosmetics is not only controlled by the lipid composition/formulation, but also by the liposome size and internal structure/properties (uni- and multi-lamellae) and membrane rigid/fluidic properties. Although the preparation of liposomes using microfluidic devices offers precise size control and easy scale-up in a continuous manufacturing system, their lamellarity and physicochemical property differences have not been investigated. We therefore prepared different paclitaxel (PTX)-loaded liposomes by changing two process parameters and investigated their physicochemical properties. The liposome size and drug loading were modified by changing the initial lipid concentration and flow rate ratio (FRR) of the aqueous and ethanol phases introduced into the microfluidic channels. Small-angle X-ray scattering and transmission electron microscopy revealed that the liposomes comprised a uni- or multi-lamellar structure that could be controlled by changing the FRR and initial lipid concentration. We also found that these structural differences affected the drug release profiles. Furthermore, the dissolution kinetics of the latter half of the drug release test could be modulated by the membrane fluidity of the liposomes. These differences in the drug release rates were consistent with the results of the in vitro cell viability assay, confirming that the multilamellar liposomes showed milder activity than the PTX solution by allowing the extended release of PTX. Thus, we concluded that the preparation of liposomes using microfluidic devices allows the liposome size, DL%, and drug release profiles to be adjusted as required.