Raman Spectroscopy as a Novel Method for the Characterization of Polydioxanone Medical Stents Biodegradation

Abstract

Polydioxanone (PPDX), as an FDA approved polymer in tissue engineering, is an important component of some promising medical devices, e.g., biodegradable stents. The hydrolytic degradation of polydioxanone stents plays a key role in the safety and efficacy of treatment. A new fast and convenient method to quantitatively evaluate the hydrolytic degradation of PPDX stent material was developed. PPDX esophageal stents were degraded in phosphate-buffered saline for 24 weeks. For the first time, the changes in Raman spectra during PPDX biodegradation have been investigated here. The level of PPDX hydrolytic degradation was determined from the Raman spectra by calculating the area under the 1732 cm−1 peak shoulder. Raman spectroscopy, unlike Fourier transform infrared (FT-IR) spectroscopy, is also sensitive enough to monitor the decrease in the dye content in the stents during the degradation. Observation by a scanning electron microscope showed gradually growing cracks, eventually leading to the stent disintegration. The material crystallinity was increasing during the first 16 weeks, suggesting preferential degradation of the amorphous phase. Our results show a new easy and reliable way to evaluate the progression of PPDX hydrolytic degradation. The proposed approach can be useful for further studies on the behavior of PPDX materials, and for clinical practice.

A Complex In Vitro Degradation Study on Polydioxanone Biliary Stents during a Clinically Relevant Period with the Focus on Raman Spectroscopy Validation

“…The results are summarized in Table 2 . The crystallinity increases with the degradation period, which is in good agreement with previously published works [ 56 , 61 , 62 , 63 ]. In the beginning, the increase in the proportion of the crystalline phase was small (around 2%).…”

“…No crazes or cracks were observed even after this degradation period. It is not very surprising, as in the observation reported by Loskot, et al [ 56 ], esophageal PPDX stents after 8 weeks of degradation in PBS only rarely showed tiny crazes. This slight discrepancy in the surface deterioration speed can be explained by the fact that different types of stents were analyzed in these studies.…”

“…The spectral range measured was 1550–1860 cm −1 . In this spectral region, the hydrolytic degradation of PPDX is clearly noticeable, as we described in [ 56 ]. In the mentioned study, we revealed that the shoulder of the 1732 cm −1 peak (C=O stretching vibrations in the ester carbonyl group [ 57 ]) decreases during the degradation, enabling a quantitative evaluation of the progression of PPDX hydrolytic degradation.…”

“…Raman spectroscopy is a method sensitive enough to track the changes of dye content in a biodegradable stent as it degrades. A previous study showed that during the first 16 weeks of degradation, the PPDX material crystallinity was increasing, indicating that the amorphous phase was preferentially degraded [ 56 ].…”

“…In this study, Raman spectroscopy measurements of PPDX monofilaments served as a validation of the novel method to evaluate PPDX degradation used by Loskot et al [ 56 ]. Raman measurements were supported by differential scanning calorimetry (DSC).…”