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The fact that liquid crystal have a gel-liquid cryatal phase
transition temperature (Tc) is well known, and it is expected
that the permeation of chemicals through the liquid crystal
embedded membrane might be controlled by a temperature change
across the Tc. Thermophysical property of cholesteryl olyel
carbonate (COC) was determined by thermal analysis and
microscopic Fourier transform infrared spectroscopy with
differential scanning calorimetry to confirm its
thermo-responsible function. Two endothermic peaks due to
phase transition were found on the DSC thermogram.Moreover,
the peakintensity of several IR spectra changed just according
with the phase transition of COC. On the other hand, the change
of band intensity in the cooling process underwent inversely to
that in heatint process. This suggests the COC has
thermo-responsible function. The COC-embedded membranes were
prepared by vaccum filtration method at different manufacturing
temperatures and the stored at different temperatures.
Salbutamol sulfate was used as a model drug across this
COC-embedded membrane. The adsorbed amount of COC
increased linearly with the oncrease of COC concentration used.
Also, the penetration rate of drug through the membtane was
controlled by the adsorbed amount of COC on the membrane. Effects
of manufacturing temperature and storage conditions on the thermal
properties and drug penetrability of COC-embedded membranes were
also examined. It is evident that both manufacturing temperature
and storage temperatures significantly affected the characteristic
of membranes. The higher manufacturing remperature or storage
temperature, the better alignment of COC in membranes, that made
the superior regularity for grug across the membranes.
In vitro permeation study for drug through hairless rat skin
with the COC-embedded membrane on the stratum corneum side were
carried out in the response to a temperature change. Carbomer gels
were used as drug reservoirs and the results showed that an on-off
switching penetration behavior of drug through the membrane in
rersponse to the temperature cycle. The possibility of applying
this functional membrane for the development of mermo-responsive
TDDS has been confirmed.
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