Understanding transport phenomena and degradation of bioresorbable medical polymers - Durability and Reliability of Medical Polymers - page 75

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Understanding transport phenomena and
degradation of bioresorbable medical
polymers

F. Rossi and G. PeRale, Politecnico di Milano, italy

Abstract: The thermodynamic processes involved in degradation and
drug release in resorbable polymeric drug loaded systems are explained
in detail. To achieve a quantitative description of the thermodynamic
movement to equilibrium in such systems presents some mathematical
difficulties and the differing approaches are considered. The importance
of irreversible thermodynamic processes is investigated by the analysis of
phenomenological and kinetic mathematical approaches. The importance of
mathematical models in investigating the transport phenomena that influence
the design parameters and properties of drug release kinetics is discussed.

Key words: biodegradable polymers; controlled drug release; mathematical
modelling; mass transport.

4.1 Introduction to transport phenomena in
irreversible processes
Transport phenomena are the subject of more than half of chemical engineering
research. all problems of determined physical quantity, such as the manner
in which mass, energy or momentum is transferred from one point to another,
are collected under this definition. (Beek et al ., 1999; Bird et al ., 2002). For
example, the study of transport phenomena in industrial processes includes
the evaluation of: (a) the fluid velocity profile along a pipeline, and (b) the
contact surface between two phases for mass or heat transport. The study of
transport phenomena began at the end of the 19th century, with the advent
of engineering applications related to thermal machines and industrial plants.
In general, the definition of transport phenomena concerns the transfer of
physical units into a system or across its boundary. its importance is well
known to the modern scientific community and its criteria are applied to
several different studies and topics. Whereas in classic thermodynamics
equilibrium systems are studied, transport phenomena are used to investigate
systems that are far from equilibrium and where gradients of quantities
such as velocity, temperature or concentrations are present. Concentration
gradients are typical of drug delivery systems (Cu and Saltzman, 2009). One

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