IN-VIVO DEGRADATION OF POLYURETHANES - TRANSMISSION-FTIR MICROSCOPIC CHARACTERIZATION OF POLYURETHANES SECTIONED BY CRYOMICROTOMY

A combination of cryomicrotomy and transmission Fourier transform infr ared (FTIR) microscopy was used to investigate chemical changes in uns trained sheets of Pellethane(TM) 2363-80A, Tecoflex(TM) EG80A and Biom er(R) caused by biodegradation (18 month subcutaneous ovine implant). Cryomicrotomy was used to obtain thin sections (ca. 2.5 mu m) from the surface into the bulk, parallel to the plane of the surface. FTIR mic roscopy was then used to obtain infrared absorbance spectra in the ran ge 4000-600 cm(-1). Comparisons between the infrared spectra (by spect ral subtraction) from implant surface, implant interior and non-implan ted controls were used to detect chemical changes. Scanning electron m icroscopy was used to assess microstructural changes owing to biodegra dation. Biodegradation in Biomer(R) was observed as uniform pitting an d superficial fissuring (<2.0 mu m depth) over the implant surface. Bi odegradation in Pellethane(TM) 2363-80A and Tecoflex(TM) EG 80A was ob served as severe localized embrittlement of the surface with fissures infiltrating up to 40 mu m into the bulk, The chemical changes associa ted with biodegradation were observed as localized oxidation of the so ft segment and hydrolysis of the urethane bonds joining hard and soft segments. Tecoflex(TM) EG80A was also found to be susceptible to local ized hydrolysis of the urethane bond within the aliphatic hard segment . Biomer(R) showed evidence of a significant non-specific degradation in the non-implanted wet control (37 degrees C phosphate buffered sali ne at pH 7.3) samples and in the implant bulk. (C) 1997 Elsevier Scien ce Limited.