A comprehensive study on the degradation process of medical-grade polydioxanone at low pH

Polydioxanone (PPDX) has gained significant attention as a biocompatible and absorbable polymer used in various medical applications, such as sutures and tissue scaffolds. This research presents a thorough investigation into the degradation mechanisms of PPDX under low pH conditions, simulating physiological environments, e.g., esophagus and stomach. It mainly focuses on the dependence of the PPDX degradation rate on various ambient pH values (7.4 and below), which is a substantial knowledge for successful gastrointestinal treatment. The PPDX suture samples were degraded for up to 6 weeks and analyzed using size exclusion chromatography, differential scanning calorimetry, Raman spectroscopy, scanning electron microscopy, X-ray microtomography, and mechanical property measurements. The results show that the PPDX degradation is significantly accelerated at pH below 1.67. Correlations of the molecular weight, crystallinity, glass transition temperature, Young's modulus, shear modulus, tensile strength, and the 1733 cm⁻¹ Raman peak shoulder area (RPSA1733) indicate that the degradation mechanism does not change with increasing acidity. Measurements of tensile strength, shear modulus, and RPSA1733 were found to be the most suitable parameters for characterizing the PPDX filament's macroscopic integrity. Raman spectroscopy is of particular interest in this regard due to its rapidity and practically no requirements on the sample preparation.