The properties of polyurethanes based on synthetic polyhydroxybutyrate for medical application

Polyurethanes belong to materials commonly used in many different fields of our life. Very important part of their application is using as biomaterial. But their properties have to be appropriate for contact with living organisms. Using in synthesis of polyurethanes the synthetic analog of natural polyhydroxybutyrate telechelic atactic poly[(R,S)-3-hydroxybutyrate] (a-PHB) could make them more biocompatible. The investigated polyurethanes were synthesized with aliphatic and aromatic diisocyanate. Their soft segments were built with polycaprolactone and a-PHB. The physical, mechanical, thermal properties and degradability of obtained polyurethanes were estimated. The polyurethane samples were also checked for medical application. After the extraction in hexane and sterilization their influence on blood parameters and on pathogenic microorganisms were estimated. The obtained polyurethanes were amorphous and hydrophilic but the amount of absorbed water was small and is on the same level for both materials. Sterilization of aliphatic polyurethane samples insignificantly changed the mechanical properties whereas aromatic polyurethane seemed to be more sensitive to conditions of sterilization. The results of polyurethane degradation indicated higher influence of oxidative than hydrolytic mechanism. The presence of aliphatic polyurethane decreased the growth of some pathogenic microorganisms. Both kinds of polymers did not change the parameters of whole blood. In conclusion it could be stated that aliphatic polyurethane based on atactic poly[(R,S)-3-hydroxybutyrate] displayed the properties appropriate for further investigations for medical application without the risk of generation the cancerogenic degradation products which could be formed from polyurethane obtained with aromatic diisocyanate.