Hydrolysis studies, controlled release systems

Pofycaprolactone (PCL) has been thoroughly examined as a biodegradable medium and as a matrix in controlled drug-release systems. PCL is predominantly produced in the e-caprolactone polymerization process [32-35]. Tokiwa and Suzuki [36] studied the hydrolysis process and PCL biodegradation by fungi and showed that polycaprolactone can be broken down enzymatically. 

Due to their polar M-0 bond, nonstabilized alkoxides are very sensitive toward hydrolysis, leading to the formation of metal hydroxides (M-OH), with the concurrent release of an alcohol molecule. Hydrolysis reactions are common in the use of these compounds and they have been studied in detail for the silica system, with the effects of catalysis type (acid or base), extent of hydrolysis, and resulting oligomeric species being well documented. The goal in using these precursors for film formation is to control the extent of hydrolysis and subsequent condensation to yield short-chain (a few to a few dozen metal centers) polymeric species, referred to as oligomers. 

The phenomenon of endocytosis leads us to a second example extensive and systematic studies on endocytosis using an in vitro system (7) include the evaluation of polymers containing different peptide spacers (cf Fig. 1) which link iodotyrosine as a drug model to poly(2-hydroxypropyl-methacrylamide) (8). This study shows that by variation of peptide spacer composition the rate of intracellular drug release caused by lysosomal hydrolysis of the spacer can be controlled. 

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