4.4.1. Traditional liposomes
The possibility that intact vesicles penetrate human skin was suggested in the first report on liposomes as skin drug delivery systems (Mezei and Gulasekharam, 1980, 1982).
Conceptually it was difficult to believe that large lipid vesicles could penetrate the densely packed stratum corneum in great numbers,
and many workers have tested this hypothesis. Foldvari et al. (1990) applied DPPC, CH (2:1) liposomes loaded with
an electron dense marker to guinea pigs.
Electron micrography showed the presence of intact liposomes in the dermis.
The authors proposed that liposomes carrying the drug can penetrate the epidermis.
Nano-aggregates were better than a traditional gel in the treatment of eczema but not for psoriasis (Korting et al., 1990).
It was thus concluded that vesicles can penetrate diseased skin with its ruptured SC (as in eczema) but cannot invade skin with hyperkeratosis, as in psoriasis.
Subsequently, fluormicrographic studies showed that intact small unilamellar vesicles (SUVs) of PC and CH penetrated no deeper than the SC (Lasch et al., 1991).