Preparation and use of thermosensitive polymers.

Restoration of organ structure and function, utilizing tissue engineering technologies, often requires the use of a temporary porous scaffold. The function of the scaffold is to direct the growth of cells migrating from the surrounding tissue (tissue conduction), or of cells seeded within the porous structure of the scaffold. The scaffold must therefore provide a suitable substrate for cell attachment, differentiated function, and, in certain cases, cell proliferation (1-3). These critical requirements may be met by the choice of an appropriate material from which to construct the scaffold, although the suitability of the scaffold may also be affected by the processing technique. There are many biocompatible materials that could potentially be used to construct scaffolds, however, a biodegradable material is normally desirable, since the role of the scaffold is usually only a temporary one. Many natural and synthetic biodegradable polymers, such as collagen, poly(α-hydroxyesters), and poly(anhydrides), have been widely and successfully used as scaffolding materials because of their versatility and ease of processing. Many researchers have used poly(α-hydroxyesters) as starting materials from which to fabricate scaffolds, using a wide variety of processing techniques. These polymers have proven successful as temporary substrates for a number of cell types, allowing cell attachment, proliferation, and maintenance of differentiated function (10). Poly(α-hydroxyesters) such as the polyoxamers are a family of more than 30 different nontoxic, nonionic surface active agents. These compounds are made at elevated temperature and pressure by the sequential additi on of propylene oxide and then ethylene oxide to neutralize the salt that is generally retained in the final product.