MOLECULAR ELECTROMECHANICS OF CARTILAGINOUS TISSUES AND POLYELECTROLYTE GELS

The objective of this paper is to present two case studies that highlight the importance of continuum electromechanical concepts as developed by J.R. Melcher in understanding structure/function relationships in natural and synthetic biological materials. Electromechanical phenomena are described at both the molecular and macroscopic levels in synthetic polyelectrolyte gels and in articular cartilage, a member of the connective tissue family. Both of these materials are representative of a broad class of fibrous, hydrated, electrically charged, poroelastic media. Recent studies with ionized gels have shown that applied electric fields can precisely control gel swelling and deformation, leading to applications in drug delivery, separation processes, and robotic actuators. The contributions of electrical, mechanical, and chemical processes governing the extent and kinetics of gel swelling are described. Electromechanical interactions are also critical to the normal and pathological behavior of cartilage in human joints. We have found that the electromechanical transduction properties associated with functionally important cartilage matrix molecules can be used as a means of diagnosing tissue pathology, such as that relevant to osteoarthritis.