High-performance liquid chromatographic separation and tandem mass spectrometric identification of breakdown products associated with the biological hydrolysis of a biomedical polyurethane

Abstract

As part of ongoing investigations into the biological degradation of biomaterials, methods have been developed to isolate and chemically analyze polymer biodegradation products. The use of these methods can provide information on the biodegradation product profiles and yield concentration levels for the isolated products. The latter information is required to assess the toxicological nature of biomaterials and their related degradation products. In this study a model biomedical polyurethane was synthesized with toluene diisocyante, polyester diol and ethylene diamine, and then incubated at 37°C in a biological solution containing enzyme. The biodegradation products were isolated from the in vitro system and prepared for HPLC analysis, by using a combination of ultrafiltration, freeze drying and liquid-solid extraction. The ultrafiltration and the liquid-solid extraction effectively removed protein contamination. The separation of more than 20 degradation products, with gradient HPLC, was optimized using a photodiode array detector. The separated degradation products were identified using a tandem mass spectrometer. The model polyurethane was labeled with 14C in different segments, in order to assist in confirming the efficiency of the sample preparation and isolation methods. A detection limit of 2 ng was found. No toluene diamine - a suspected human carcinogen associated with some medical implants - could be found in the test samples. This represents a significant finding since the amount of this injected samppe actually contained a total of 28 μg of degradation products isolated from the incubation medium.