Biodegradable polymeric scaffolds face a growing use in tissue engineering. However, changes in material properties during degradation can impact drastically the scaffold durability and therefore the efficiency of tissue reconstruction. Few studies focus on approaches allowing the prediction of the scaffold lifetime, while there is a need for strategies using accelerated testing protocols and versatile tools to easily investigate on the material degradation rate. In the present study, we investigated the thermally-accelerated ageing and lifetime prediction in culture medium of cross-linked poly(ester-urethane-urea) (PEUU) scaffolds .
Elastomeric cross-linked poly(ester-urethane-urea) (PEUU) scaffolds have been developed through an emulsion technique allowing to produce highly interconnected porous structure . Thermally-accelerated ageing was performed in cell culture medium at different temperatures: 37°C, 55°C, 75°C and 90°C. The degradation process was followed by gravimetry, swelling measurements, compression tests and Fourier-Transform infrared spectroscopy (FTIR). Compressive set measurements were also used as an indicator of the scaffold lifetime at 90°C.
The study revealed that the PEUU scaffold degradation was associated with the hydrolytic instability of ester groups. As expected, the scaffold chemical composition variation over degradation was temperature dependant since the absorbance intensity associated to the ester stretching vibrations decreased with rising incubation time and temperature. Therefore, FTIR spectroscopy was used as a quantitative indicator of the hydrolysis content. The dependence of ester group cleavage on time of incubation was determined for each degradation temperature by regression analysis and Arrhenius type extrapolation was used to estimate the activation energy of the hydrolytic degradation reaction (80.84 kJ mol−1).
In the present study, the compressive set was selected as the failure criterion from the point of view of the scaffold functionality. For elastomeric material, the compressive set should not equal or exceed a value of 25%. Since the compressive set measurements set the scaffold lifetime at 90°C around 11.6 days of incubation in the degradation medium, the scaffold lifetime at 37°C was estimated to 1131 days (3.1 years) using an acceleration factor f equal to 97.5 as derived from the activation energy value.
It is well known that it is difficult to correlate in vitro degradation with in vivo expectation since in vivo conditions are more complex and lead to variation of the scaffold lifetime. However, the approach developed in this study could be a convenient way to simply and straightforwardly screen the durability of scaffolds when performing experimental design aiming to tailor scaffold lifetime.
1. Langueh, C. et al., Polym. Deg. Stab. 183, 109454 (2021).
2. Changotade, S. et al., Stem Cells Int. Article ID 283796 (2015).
The authors thank the Ministère de l’Enseignement Supérieur, de la Recherche et de l’Innovation for the MENRT scholarship granted to Credson Langueh."