The correlation coefficients (R) calculated for each gel concentration were above 0.99, which indicated
that in vitro drug release profiles of ALA from P407 gel fit well with
the square root Higuchi model. From these results it can be
deduced that by increasing the P407 concentration of the gel, the
release rate of ALA was prolonged. This could be explained that
by increasing the concentration of P407, the viscosity of the gel increases
as well, making it harder for the cubosomes to diffuse out
of the gel matrix.