Self-regulation side effects

With the advance of pharmaceutical science, it has been recognized that constant release is not the only way to maximize drug effectiveness and minimize side effects and that the assumptions used for constant release rate sometimes fail due to physiological conditions. From this perspective, zero-order dmg release is not acceptable in all cases and externally modulated or self-regulating dmg delivery systems have been developed as novel approaches to deliver dmgs as required. To realize such dmg delivery systems, it is important to constmct a system where the dmg itself senses environmental stimuli and responds appropriately to control the dmg release. For this purpose, the phase transition polymers have been intensively exploited as a candidate material during last decade [21]. 

The size or MW is self-regulated by the termination reaction and the inherent side reactions. Externally, MW can be also adjusted by the reaction conditions. An increase of temperature causes faster AIBN decomposition, resulting in a lower MW because more chains are created on the contrary, higher pressure increases the propagation and inhibits the termination resulting in higher MW. The increase of the AIBN concentration has a similar effect to that of the increase of temperature. 

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