Resorbable polymeric delivery systems based on physical absorption/diffusion versus chemically controlled delivery systems

J. SAN ROMÁN; A, GALLARDO; C. ELVIRA; B. VÁZQUEZ; G.A. ABRAHAM

Biodegradable Systems in Tissue Engineering and Regenerative Medicine

CRC Press

Lugar: Boca Raton, FL, USA; Año: 2005; p. 281 - 299

In this chapter we present the most important characteristics and differences between controlled delivery systems based on physico-chemical interactions of polymeric matrices with bioactive compounds and those based on the chemical control of the release mechanism as a consequence of the labile covalent link of the bioactive component to the polymer matrix. Examples of both kinds of systems with applications in drug release, based on solution/diffusion process, as well as the action of specific “polymer drugs”, are presented as a result of a cooperative work of specialists in different areas of the material science, pharmacy, medicine and biology. According to the mechanism of release of the bioactive product (drug, growth factors, hormone, etc.) the controlled release formulations can be considered as “solvent controlled”, “diffusion controlled” and “chemically controlled” systems. This classification considers that the rate of release is controlled predominantly by solvent interactions such as swelling of the polymer chains, by the diffusion of drug through a polymer matrix or a membrane, or by chemical processes such as polymer degradation, erosion or the cleavage of the bioactive compound chemically linked to the polymeric support. It is clear that these mechanisms operate simultaneously in most of the practical situations and they can not be considered separately.