Effect of matrix composition and process conditions on casein-gelatin beads floating properties

Casein-gelatin beads have been prepared by emulsification extraction method and cross-linked with D,L-glyceraldehyde in an acetone water mixture 3:1 ( v/v). Casein emulsifying properties cause air bubble incorporation and the formation of large holes in the beads. The high porosity of the matrix infl uences the bead properties such as drug loading, drug release and floatatio n. These effects have been stressed by comparison with low porous beads, ar tificially prepared without cavities. The percentage of casein in the matri x increases the drug loading of both low and high porous matrices, although the loading of high porous matrices is lower than that of low porous matri ces. As a matter of fact, the drug should be more easily removed during was hing and recovery because of the higher superficial pore area of the beads. This can explain the drug release rate increase, observed in high porous m atrix, in comparison with beads without cavities. This is due to the rapid diffusion of the drug through water filled ports. The study shows that cavi ties act as an air reservoir and enable beads to float. Therefore, casein s eems to be a material suitable to the inexpensive formation of an air reser voir for floating systems. (C) 2000 Elsevier Science B.V. All rights reserv ed.