Enzymatic degradation of starch-based thermoplastic compounds used in protheses: identification of the degradation products in solution.

Apart from favourable physico-chemical and mechanical properties, the most important requirement for a biodegradable polymer to be used in medical applications is its biocompatibility and the non-cytotoxicity of its degradation products. Their combined effect should assure the safe material degradation under controlled kinetics. The present work analyses the degradation behaviour of blends of corn starch with poly(ethylene-vinyl alcohol) copolymer (SEVA-C). The characterization included long-term degradation trials on simulated physiological solution with alpha-amylase up to 200 days. The degradation solutions were analysed by several techniques. High-performance liquid chromatography (HPLC) and colorimetric methods were used to monitor the liberation of carbohydrate as a consequence of starch hydrolysis by alpha-amylase. The hydration degree was followed by thermogravimetric analysis (TGA). Several degradation products such as carbohydrates ranging from C6 to C18 were identified. After alpha-amylase action, biodegradation was more pronounced in the first 100 days, after which the biodegradation rate decreased probably due to the structure and porosity of the material. The action of alpha-amylase solely led to the starch degradation, in contrast with other assays without enzymes where no carbohydrates were found in the degradation solutions.