Development and validation of a Parallel Artificial Membrane Assay Permeation model for personal care formulations

Excised human skin is the most preferred approach for the assessment of topical formulations using
in vitro skin permeation studies. The major challenges in using excised human skin are (1) the
difficulty in sourcing the skin samples and (2) intra- and inter-specimen variability (Dick and
Scott, 1992; Schmook et al., 2001). Several alternative models have been developed for prediction
of skin permeation for chemicals. One of these models, the skin Parallel Artificial Membrane
Permeation Assay (PAMPA) model has been investigated for prediction of the skin permeation of
several molecules. The skin PAMPA membrane is essentially a filter substrate coated with synthetic
lipids arranged in 96-well plate and allows for rapid and high-throughput screening of compounds.
Recently, the UCL group has performed comparative studies for permeation in the skin PAMPA membrane
and in human tissue under finite dose conditions for caffeine, ibuprofen and niacinamide. Very good
correlations were observed for cumulative amounts of active permeated over time in the PAMPA model
compared with conventional in vitro permeation studies with animal tissue. However, it is important
to note that to date, very simple formulations e.g. single or binary solvent systems have been
investigated in the PAMPA model.