Abstract:
Microencapsulated bead formulation prepared by using an ionotropic
gelation method between sodium alginate and calcium chloride is a common
technique. The technique proposed by this thesis, the oil incorporating technique,
was to dissolve the drug in an oil internal phase of the emulsion prior to mixing
with sodium alginate and subsequently cross-linking with calcium chloride
solution to form calcium alginate gel beads. Benzocaine was selected to be a
model lipophilic drug. The effect of involving factors in the emulsion preparation
process (i.e., sodium alginate concentration, polyvinyl alcohol concentration, and
oil ratio) and gel bead formation process (i.e., calcium chloride concentration,
cross-linking time and cross-linking temperature of calcium chloride solution) on
the properties of the formulation were investigated. The properties of emulsion
were mainly influenced by sodium alginate concentration and oil ratio due to an
effect on the emulsion viscosity. The characteristics of the microencapsulated
beads were dependent on all factors from both processes. The release of the drug
from the bead was an immediate release, which could be due to pH-dependent
solubility of benzocaine, thin wall, and numerous pores of calcium alginate gel
polymer. The bead instability occurred according to an increase in storage time
and temperature. However, the bead stability may be improved by applying a
high level of sodium alginate concentration, polyvinyl alcohol concentration, and
oil ratio in the formulation and a low cross-linking time, cross-linking
temperature, and level of calcium chloride concentration