In vitro degradation and mechanical properties of PLA-PCL copolymer unit cell scaffolds generated by two-photon polymerization

Felfel, R.M. and Poocza, Leander and Gimeno-Fabra, Miquel and Milde, Tobias and Hildebrand, Gerhard and Ahmed, Ifty and Scotchford, Colin and Sottile, Virginie and Grant, David M. and Liefeith, Klaus (2016) In vitro degradation and mechanical properties of PLA-PCL copolymer unit cell scaffolds generated by two-photon polymerization. Biomedical Materials, 11 (1). 015011. ISSN 1748-605X

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The manufacture of 3D scaffolds with specific controlled porous architecture, defined microstructure and an adjustable degradation profile was achieved using two-photon polymerization (TPP) with a size of 2  ×  4  ×  2 mm3. Scaffolds made from poly(D,L-lactide-co-ɛ-caprolactone) copolymer with varying lactic acid (LA) and ɛ -caprolactone (CL) ratios (LC16:4, 18:2 and 9:1) were generated via ring-opening-polymerization and photoactivation. The reactivity was quantified using photo-DSC, yielding a double bond conversion ranging from 70% to 90%. The pore sizes for all LC scaffolds were see 300 μm and throat sizes varied from 152 to 177 μm. In vitro degradation was conducted at different temperatures; 37, 50 and 65 °C. Change in compressive properties immersed at 37 °C over time was also measured. Variations in thermal, degradation and mechanical properties of the LC scaffolds were related to the LA/CL ratio. Scaffold LC16:4 showed significantly lower glass transition temperature (T g) (4.8 °C) in comparison with the LC 18:2 and 9:1 (see 32 °C). Rates of mass loss for the LC16:4 scaffolds at all temperatures were significantly lower than that for LC18:2 and 9:1. The degradation activation energies for scaffold materials ranged from 82.7 to 94.9 kJ mol−1. A prediction for degradation time was applied through a correlation between long-term degradation studies at 37 °C and short-term studies at elevated temperatures (50 and 65 °C) using the half-life of mass loss (Time (M1/2)) parameter. However, the initial compressive moduli for LC18:2 and 9:1 scaffolds were 7 to 14 times higher than LC16:4 (see 0.27) which was suggested to be due to its higher CL content (20%). All scaffolds showed a gradual loss in their compressive strength and modulus over time as a result of progressive mass loss over time. The manufacturing process utilized and the scaffolds produced have potential for use in tissue engineering and regenerative medicine applications.

Item Type: Article
Additional Information: This is an author-created, un-copyedited version of an article accepted for publication in Biomedical Materials. The publisher is not responsible for any errors or missions in this version of the manuscript or any version derived from it. The Version of Record is available online at doi:10.1088/1748-6041/11/1/015011.
Keywords: scaffolds, stereo-lithography, photopolymerization, conversion, degradation, activation energy, compressive properties
Schools/Departments: University of Nottingham, UK > Faculty of Engineering
University of Nottingham, UK > Faculty of Medicine and Health Sciences > School of Medicine
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Depositing User: Eprints, Support
Date Deposited: 28 Jun 2016 09:53
Last Modified: 23 Feb 2017 04:17

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