Nail as a part of the body offers not only a protective
function, but is also a barrier for drugs intended for nail
diseases’ treatment. Despite of the need of human nails
for studying ungual drug preparation, unfortunately,
their availability is somehow limited. Bovine hoof is up
to now an accepted model for human nail but
significant differences between them have been
reported [1]. These differences could be related to
hooves’ ability in retaining more water and thus making
them more permeable, although human nail, hair and
bovine hoof are composed of similar keratin proteins
(α−form). Therefore a novel nail model made of human
hair was developed and its physical properties were
then compared with bovine hooves.
An early investigation showed that this model
resembled bovine hooves in terms of permeation and
binding of three tested marker substances, i.e. sodium
fluorescein (SF), fluorescein isothiocyanate-dextran MW
4000 (FD4) and rhodamine B (RB) [2].
Based on this finding, a further comprehensive
investigation was conducted to see the effect of three
nail penetration enhancers (PEs) with different
mechanisms (urea/ UR, thioglycolic acid/ TA and papain
from papaya latex/ PA) on both materials using SF, FD4
and RB as markers, which represented a water soluble,
a lipid soluble and a large molecule drug model,
respectively.