ABSTRACT
The quantitative approach to regulation of multicomponent transport in polymers and polymer blends is developed, with the scope of application to polymer systems of controlled-release drugs. The approach is based on the theory of multicomponent transport in polymers of different hydrophilic character and integrates the modeling of chemical, physical, morphological, and transport properties of polymeric materials. To govern the kinetics of the release of low molecular weight species from polymers, the methods of controlled modification of matrix are proposed, which comprise the following:
• Alteration of hydrophilic-hydrophobic balance in a polymer by controlled polymer degradation
• Controlled load of fillers and additives • Application of multilayer systems, and others The fundamental aspects of multicomponent transport in polymers are dis-
cussed with reference to eventual application of the theory into practice. The understanding of general regularities of multicomponent transport in
polymers gives an opportunity to alter its kinetics and the rate. This chapter deals with the fundamental approaches to such an alteration in the systems of controlled drug delivery. In recent years new original methods have been developed using the following approaches:
1. The synthesis of novel polymeric materials with regulated hydrophilic-hydrophobic balance
2. The alteration of this balance by the controlled modification of polymers or by use of fillers and additives
3. The use of multilayer systems
The methods used to regulate the behavior of the controlled-delivery devices are not limited by the foregoing approaches. There are numerous other methods serving many specific purposes. We should mention some of them such as magnetism-activated drug delivery, ultrasound-activated drug delivery, pHactivated drug delivery, and ion-activated drug delivery, which are not considered in this chapter. The reader can find the details of their principles in the brilliant monograph edited by Lee and Good (1) and other monographs published during last decade (2-7). Also we do not discuss here the technological aspect of the design of devices, although this problem is very important for engineers.
