Percutaneous immunization with 40-nm antigen-encapsulated elastic liposomes

In this study, we aimed to verify the influence of the particle diameter of elastic liposomes for transdermal delivery on immune responsiveness by evaluating the amount of antibody. Albumin from chicken egg white (OVA) solution and elastic liposomes with mean volume diameter of 40 nm and 130 nm were percutaneously administrated to mice. We prepared 40-nm elastic liposomes using mechanochemical process and 130-nm elastic liposomes using extrusion process. Subcutaneous injection of OVA was also as a positive control. Forty-nanometer elastic liposomes significantly promoted antibody production compared with the OVA solution and 130-nm elastic liposomes. Furthermore, this result was nearly equivalent to that of the subcutaneous injection of OVA solution. Besides, skin permeability study shows that coumarin-6 used as a fluorescent label encapsulated in 40-nm elastic liposomes were 2.2 times more permeated than 130-nm elastic liposomes in the skin. From the observation of confocal laser microscopy images, 40-nm elastic liposomes accumulated more in the stratum corneum and deeper follicle compared to 130-nm elastic liposomes. It has been reported that particles with a diameter of 40 nm are more captured by antigen presenting cells. Thus, we considered that the 40-nm elastic liposomes are useful for percutaneous immunization.