Alamán-Díez, Pilar (Multiscale in Mechanical and Biological Engineering, Instituto de Investigación en Ingeniería de Aragón (I3A), University of Zaragoza)


Creating biofunctional scaffolds could potentially meet the demand for patients suffering from bone defects without having to rely on donors or autologous transplantation. 3D printing has emerged as a promising tool to fabricate scaffolds with high precision and accuracy by computer design using patient-specific anatomical data1. Among other relevant key points for 3D-printed bone scaffold selection, to achieve controlled degradation profiles is an essential feature to consider. Thus, the importance of a deep characterization of the biomaterial degradation under physiological conditions is needed2.

50:50 blend made of PCL-PLGA was created to fabricate cylindrical scaffolds by 3D printing. The blend was fabricated by dissolving PCL pellets and PLGA powders in dichloromethane, by casting and evaporating the solvent. PCL-PLGA filaments were extruded with a mechanical extruder. Cylindrical scaffolds were finally printed with a 7mm diameter, 2mm height, 400µm pore sizes. Their hydrolytic degradation under different conditions was quantified.
Static buffer medium and flow perfusion were applied to the samples inside an in-house fabricated bioreactor, which contains four main individual chambers. Perfusion tests were done inside the bioreactor thanks to a roller pump which imposed a PBS flow rate of 4 mL/min. Samples were incubated in normoxia (21% O2 and 5% CO2) for two and four weeks. Degradation under static conditions was also conducted inside the bioreactor with no flow. During both conditions, PBS in the wells was exchanged every two days and the pH was measured periodically.
Several techniques were used to characterize the degradation of the polymers by the end of the incubation period including chemical changes on the surface by x-ray photoelectron spectroscopy, polydispersity index by gel permeation chromatography, surface inspection by scanning electron microscopy, mechanical properties decrease weight loss and medium acidification over time.

In this work, we have thoroughly characterized the hydrolytic degradation of the final samples at different incubation periods, achieving different outcomes in agreement with our initial hypotheses. Results confirm a faster degradation of PCL-PLGA scaffolds when flow is forced through the samples. Besides, it was also confirmed the quicker degradation of PLGA in the blend. In addition, time is also a key factor and we obtained significant differences for both incubation times: 2 and 4 weeks.

Curabone project received funding from ITN-MSCA0 (grant No. 722535), the use of SAI and LMA (Universidad de Zaragoza), Spanish Ministry of Economy and Competitiveness through Projects DPI2017-84780-C2-1-R and PID2020-113819RB-I00 and the Government of Aragon in the form of grant awarded to PAD (Grant No. 2018-22).

1. Roseti, L. et al. Scaffolds for Bone Tissue Engineering: State of the art and new perspectives. Mater. Sci. Eng. C 78, 1246–1262 (2017).
2. Li, C. et al. Design of biodegradable, implantable devices towards clinical translation. Nat. Rev. Mater. 5, 61–81 (2020).


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