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J. Van Hoorick, A. Ovsianikov, H. Declerq, M. Cornelissen, J Van Erps, P. Dubruel, S. Van Vlierberghe:
"Additive manufacturing of 3D gelatin scaffolds: direct versus indirect printing";
Poster: 10th World Biomaterials Congress, Montreal; 2016-05-17 - 2016-05-22; in: "Book of Abstracts", (2016).

Introduction: To date, gelatin is one of the most frequently applied materials in the biomaterials field. It contains tripeptide Arg-Gly-Asp sequences which are known to interact with the cell´s integrins. In the present work, we evaluate and compare the potential of direct and indirect additive manufacturing for the development of porous gelatin scaffolds for soft tissue engineering.
Materials and Methods: Methacrylic anhydride was applied to modify gelatin type B resulting in photo-crosslinkable gelatin derivatives (gel-MOD) [1]. Physical gelation properties were assessed using DSC. Crosslinking was performed using 2 mol% Irgacure 2959 and UV-A light (365 nm). Mechanical properties of hydrogel films were monitored using rheology. The hydrogels were subjected to swelling and degradation studies [2],[3]. The direct additive manufacturing approach was performed using an in-house developed polymer processing device ( figure 1). In short, the device enables the combination of 3D printing and electrospinning of (bio)polymers into one single scaffold. Moreover, it also integrates UV-induced photopolymerization capabilities. Figure 1: In-house developed processing apparatus.
For indirect additive manufacturing, PLLA (Mw = 16 kDa) scaffolds were developed via FDM. After curing 5 and 10 w/v% gel-MOD solutions (t = 120 mins), the sacrificial scaffolds were dissolved using chloroform followed by extensive washing with acetone and water. The gelatin scaffolds were characterized using SEM, µCT, optical microscopy and texturometry. Biocompatibility tests using human foreskin fibroblast (HFF) cells were performed on both types of scaffolds (i.e. live/dead staining and histology).
Results and Discussion: DSC measurements indicated that the physical gelation of gel-MOD depends on the degree of methacrylation and the concentration. Rheology indicated that cross-linked 5 w/v% gel-MOD (97% methacrylated) exhibits sufficient mechanical properties (G´= 3600 Pa ) for the production of 3D scaffolds. As the direct additive manufacturing approach only enabled the fabrication of 10 w/v% scaffolds [4], we compared this approach with an indirect approach. It was shown that a proper design transfer was realized from PLLA scaffold to gelatin hydrogel, with the latter being self-supporting [3].
Physico-chemical testing revealed scaffold properties (mechanical, degradation, swelling) to depend on the applied gelatin concentration and the methacrylamide content. The scaffolds obtained using both approaches were suitable to support the adhesion and proliferation of HFFs. After 5 days the scaffolds (V = 5*5*5 cm3) were nearly completely covered with viable cells indicating a nice cell proliferation onto the scaffolds (see figure 2). Conclusion: Scaffold structural analysis indicated the success of the selected indirect additive manufacturing approach for the production of cell-interactive, low-density (5 w/v %) gelatin scaffolds. Furthermore, the first steps have been realized to develop combination scaffolds containing both 3D printed and electrospun polymer layers in one single 3D construct using the novel in-house developed polymer processing device.

Introduction: To date, gelatin is one of the most frequently applied materials in the biomaterials field. It contains tripeptide Arg-Gly-Asp sequences which are known to interact with the cell´s integrins. In the present work, we evaluate and compare the potential of direct and indirect additive manufacturing for the development of porous gelatin scaffolds for soft tissue engineering.
Materials and Methods: Methacrylic anhydride was applied to modify gelatin type B resulting in photo-crosslinkable gelatin derivatives (gel-MOD) [1]. Physical gelation properties were assessed using DSC. Crosslinking was performed using 2 mol% Irgacure 2959 and UV-A light (365 nm). Mechanical properties of hydrogel films were monitored using rheology. The hydrogels were subjected to swelling and degradation studies [2],[3]. The direct additive manufacturing approach was performed using an in-house developed polymer processing device ( figure 1). In short, the device enables the combination of 3D printing and electrospinning of (bio)polymers into one single scaffold. Moreover, it also integrates UV-induced photopolymerization capabilities. Figure 1: In-house developed processing apparatus.
For indirect additive manufacturing, PLLA (Mw = 16 kDa) scaffolds were developed via FDM. After curing 5 and 10 w/v% gel-MOD solutions (t = 120 mins), the sacrificial scaffolds were dissolved using chloroform followed by extensive washing with acetone and water. The gelatin scaffolds were characterized using SEM, µCT, optical microscopy and texturometry. Biocompatibility tests using human foreskin fibroblast (HFF) cells were performed on both types of scaffolds (i.e. live/dead staining and histology).
Results and Discussion: DSC measurements indicated that the physical gelation of gel-MOD depends on the degree of methacrylation and the concentration. Rheology indicated that cross-linked 5 w/v% gel-MOD (97% methacrylated) exhibits sufficient mechanical properties (G´= 3600 Pa ) for the production of 3D scaffolds. As the direct additive manufacturing approach only enabled the fabrication of 10 w/v% scaffolds [4], we compared this approach with an indirect approach. It was shown that a proper design transfer was realized from PLLA scaffold to gelatin hydrogel, with the latter being self-supporting [3].
Physico-chemical testing revealed scaffold properties (mechanical, degradation, swelling) to depend on the applied gelatin concentration and the methacrylamide content. The scaffolds obtained using both approaches were suitable to support the adhesion and proliferation of HFFs. After 5 days the scaffolds (V = 5*5*5 cm3) were nearly completely covered with viable cells indicating a nice cell proliferation onto the scaffolds (see figure 2). Conclusion: Scaffold structural analysis indicated the success of the selected indirect additive manufacturing approach for the production of cell-interactive, low-density (5 w/v %) gelatin scaffolds. Furthermore, the first steps have been realized to develop combination scaffolds containing both 3D printed and electrospun polymer layers in one single 3D construct using the novel in-house developed polymer processing device.

gelatin scaffolds, printing, gel-MOD

http://dx.doi.org/10.3389/conf.FBIOE.2016.01.00425