The release profile of ALA from 20 and 30% w/w P407 gel loaded
with ALA cubosomes, showed that 65.34% and 55.52% of the drug
were released after 8 h respectively, as illustrated in Fig. 10. The release
rate constants and correlation coefficients were calculated
after fitting the release data to square root Higuchi model and
are summarized in Table 7. 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.