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The design and functioning of matrix diffusion-controlled systems, where drugs are bound to polymeric carriers. Homogeneous and porous matrix systems, their release mechanisms, and performance testing methods such as ftir, sem, xrd, dsc, and in vitro release studies.
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In a matrix diffusion-controlled system, the drug is bound to a polymeric carrier in a dispersed form. For controlled release systems using non- biodegradable polymeric materials as carriers, the solubility of the drug in the system is the controlling factor for the release rate. For biodegradable polymers, the release rate is controlled both by the solubility of the drug in the system and by the rate of degradation of the polymeric carrier.
Homogeneous Matrix Systems In a homogeneous matrix system, the drug is dissolved or dispersed in a homogeneous matrix, primarily a polymer. Once the matrix system is immersed in the dissolution medium, the drug present on the surface of the matrix will dissolve in the dissolution medium. This will result in concentration differences and the drug will diffuse from the inner to the outer layers of the matrix. As a result, a depletion zone will form at the boundary of the matrix
and will increase over time. The release rate will also decrease over time as the drug must diffuse over longer distances. Porous matrix systems Porous matrix systems are a variant of homogeneous matrix systems. In this case, the drug is dissolved in a porous polymer. Once the matrix system is immersed in the dissolution medium, the pores will be filled with the dissolution medium and the drug will be dissolved in the filled pores of the matrix. In addition to the solubility and diffusion coefficient of the drug in the release medium, the shape and volume of the pores in the matrix are also important. Performance Testing of Matrix Diffusion-Control System Before the tests are performed, the drug, polymer and other substances need to be made into polymer films, which are then subjected to a series of performance characterization tests.