4. Conclusion
It has been demonstrated that MET can be encapsulated in NRL
membranes, lying mostly on the membrane surface, as inferred from
energy dispersive X-ray spectroscopy. MET did not interact chemically
with the membrane, with its FTIR spectrum being preserved after
encapsulation in the NRL membrane. Likewise, its crystallographic
structure was essentially maintained as encapsulated in the amorphous
membrane. The release time of MET in in vitro tests was very
promising, for the kinetics of release was fitted with a double
exponential function with characteristic times of 3.6 and 29.9 h, with
the release of ca. 1/3 of MET in the first, fast process and the other 2/3
in the second process. Significantly, the NRL membrane properties can
be easily modified by changing experimental conditions, which may
allow the kinetics profile to be tailored.