3.6. In vitro permeation study
The parallel artificial membrane permeability assay (PAMPA)
represents a potential approach for rapid assessment of absorption
(Kansy, Senner, & Gubernator, 1998). PAMPA is based on a 96-well
microplate technology and allows reasonable throughput. It enables
fast determination of the trends in the ability of the compounds
to permeate membrane by passive diffusion and is thus
suited for screening of large libraries. The experiment was carried
out measuring the ability of curcumin to diffuse from C1 formulation
to a donor compartment through a PVDF membrane. This
microemulsion was selected because it appeared the best in terms
of encapsulation efficiency and stability. Results (Table 7) showed a
strong increasing of the amount of curcumin permeated in comparison
with a saturated aqueous solution of curcumin used as
control.
It was possible to measure a quantity of curcuminoids in the
acceptor compartment already after 6 h: the value (17.44 mg) is
about 10% of the curcuminoids present in the donor compartment
(176.10 mg) and the percentage of permeation after 24 h was
approximately of 70% (corresponding to 120.12 mg).
Conversely, free curcuminoids in PBS showed a permeation
trend more linear with a progressive increase in their amount.
Initially, the amount of permeated curcuminoids from the microemulsion
or from PBS buffer solution was similar. However, there is
a remarkable difference after 6 h, in fact the amount of curcuminoids
permeated from microemulsion is 10.000 times higher than
that from buffer solution (17.44 mg vs. 0.17 103 mg), proving
a high solubilizing capacity of microemulsion. In the case of buffer
solution the total permeated curcuminoids after 24 h resulted
1.66 mg.
Moreover, the presence of surfactants at the interface could
facilitate the absorption through the phospholipid layer, the curcumin
contained in C1 formulation has a capacity of greater
permeation compared to curcumin in aqueous solution.