Degradation controlled delivery systems

Degradable Controlled Release Systems Useful for Protein Delivery... 

These molecules present a challenge to the formulators designing controlled delivery systems. They can be most efficiently delivered paren-terally because they are extensively degraded in the gastrointestinal tract... 

A different approach to polyphosphazene-based drug delivery systems deals with hydrolytically unstable phosphazene substrates, able to degrade in a controlled way under physiological conditions in human body. A list of these bio-erodible substrates is reported in Table 21. 

Biodegradable polyurethanes have been proposed and studied before (9-72). The difference in our study is the inclusion of a phosphoester linkage instead of the commonly used polyester component. This seems to provide more flexibility as the side chain of the phosphate or phosphonate can be varied. For controlled drug delivery applications, drugs can be linked to this site to form a pendant delivery system. Moreover, for certain medical applications, fast degradation rate is obtainable by the introduction of these hydrolyzable phosphoester bonds. With the LDI based polyurethanes, drugs or other compounds of interest can also be coupled to the ester side chain of the lysine portion. 

Poly-j3-malate is readily degraded completely to L-malic acid under both acid and base conditions [108], and it can also be hydrolyzed by enzymes within the cell [105,106]. Recently, several bacteria were isolated which were able to utilize poly-/i-malate as sole carbon source for growth [109]. Because the polymer is biodegradable and bioadsorbable, it is of considerable interest for pharmaceutical applications, especially in controlled-release drug delivery systems [97,98]. Chemical routes to poly-/ -malate are expected to provide materials with various properties [110]. 

Dissolution, of viscose, 11 254-255 Dissolution-controlled drug delivery, degradation/ erosion-based drug delivery systems, 9 11-19 Dissolution inhibition, by... 

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