An investigation into the combination of low frequency ultrasound and liposomes on skin permeability

Antigen application onto skin that has been pre-treated with low frequency ultrasound leads to immunisation, and it was hypothesised that immunisation could be enhanced if antigens were entrapped within liposomes, the latter being known vaccine adjuvants. However, it has been suggested that liposomes can repair skin damage, which could limit antigen permeation and transcutaneous immunisation. The aim of the present work was therefore to investigate the influence of liposome application on subsequent: (i) in vitro antigen permeation through, and (ii) in vivo barrier properties of, ultrasound-treated skin. Sonication was conducted using either phosphate buffered saline (PBS) or an aqueous solution of sodium dodecyl sulphate (SDS) as the coupling medium, and rats were used as the animal models. Liposome application to sonicated skin reduced antigen penetration and transepidermal water loss (TEWL, used as an indication of skin integrity) when the skin had been sonicated using PBS coupling medium. The influence of liposome was evident within 5 min of its application, and smaller liposomes were more effective at repairing skin disruption caused by sonication. Such skin repair did not, however, take place when the skin had been sonicated in the presence of SDS (which caused greater skin disruption), and changes in in vitro antigen permeation and in vivo TEWL were negligible. Skin repair by liposomes seems to depend on the extent of the disruption caused by ultrasound application.