If the laser
focus was shifted into deeper cell layers of the
stratum corneum, no fluorescence signal could
be detected. From all samples investigated, soybean
oil and almond oil were established to
penetrate the deepest into the stratum corneum.
While curcumin in these two oils was detectable
only in volunteers 1, 2, 3 and 6 on the skin
surface and in the lipid layers surrounding the
first layer of the corneocytes, a penetration into
the second and third corneocyte layers was
observed in the case of volunteers 4 and 5
(Figs 1a and b), which was obviously due to the
somewhat dry skin of these two volunteers.