USE OF POLYPHOSPHAZENES FOR SKELETAL TISSUE REGENERATION

The hydrolytically unstable polyphosphazenes, poly [(imidazolyl) (meth ylphenoxy) phosphazenes] and poly [ethyl glycinato) (methylphenoxy) ph osphazenes], were studied as potential polymeric supports for cells in tissue regeneration. For bone repair, their specific function would b e to support osteoblast growth, forming a bone-polymer matrix. MC3T3-E 1 cells (an osteogenic cell line) were seeded onto polymer matrices an d cell adhesion and growth as well as polymer degradation were examine d. Both imidazolyl- and ethyl glycinato-substituted polyphosphazenes s upported the growth of MC3T3-E1 cells. An increase in the content of t he imidazolyl side group resulted in a reduction in cell attachment an d growth on the polymer surface and an increase in the rate of degrada tion of the polymer. In contrast, substitution with the ethyl glycinat o group favored increased cell adhesion and growth and also an increas e in the rate of degradation of the polymers. Thus, the polyphosphazen es represent a system whereby cell growth and degradation can be modul ated by varying the nature of the hydrolytically unstable side chain. This in vitro evaluation suggests that the polyphosphazenes may be sui table candidate biomaterials for the construction of a cell-polymer ma trix for tissue regeneration.