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Tissue Engineering

Tissue Engineering - Poster Session E

Poster BB4 - Development of Hard and Soft Lattice Structure Biomaterials for Tissue Engineering Applications

Saturday, October 26, 2024
10:00 AM - 11:00 AM EST
Location: Exhibit Hall E, F & G

Introduction:  Lattice structures materials are materials that have interconnected porous unit cells which are arranged periodically and regularly. Their light wight and high specific strength make them an excellent candidate for tissue engineering applications. They can be used as a scaffold material for both soft and hard tissue engineering applications. For instance, bone tissue engineering is one area where the application of lattice structure materials are emerging. One of the major reasons behind this trend can be attributed to the capability to the lattice structure materials to tune the mechanical properties that can match the mechanics of the native biological tissues. The present study aims to engineer mechanically variable lattice structure polymer materials that can be used for tissue engineering applications. More specifically, we have tuned the mechanical properties of 3D printed polylactic acid (PLA) rigid structures by using different lattice structures. We have generated soft lattice structures using alginate and demonstrated the 3D bioprinting of these soft lattice structures with fibroblast cells.

Materials and

Methods:  We created twelve different lattice structures using premade designs from the nTopology (nTop) software. Each structure was 3D printed as a 15mm cubic shape with a MakerBot. Six of the structures featured the "Gyroid" lattice infill in various thicknesses, while the other six structures used a combination of five different infills: Gyroid, Diamond, Simple Cubic, Body Centered Cubic, and Face Centered Cubic. The mechanical properties of these structures were evaluated through compression testing with a Universal Testing Machine (UTM) to measure load strength, stress, and strain.
For bioprinting, we prepared an alginate-based ink mixture, consisting of 5% alginate in 100mL of distilled water and 0.5% hydroxyapatite (HAP) in 100mL of distilled water. These solutions were mixed with a magnetic stirrer overnight. To crosslink the structures, we prepared a calcium chloride (CaClâ‚‚) solution by dissolving 1g of CaClâ‚‚ in 50mL of distilled water; each structure was soaked in this solution for 1 minute and 30 seconds.

Results, Conclusions, and Discussions: We engineered hard PLA lattice structures with varying mechanics using diamond, face-centered cubic (FCC), body-centered cubic (BCC), and gyroid designs. Compressive modulus tests revealed the following for gyroid infill structures: Simple Cubic: 15.05 GPa, BCC: 17.45 GPa, and FCC: 16.78 GPa. For diamond infill structures, the results were: Simple Cubic: 6.23 GPa, BCC: 6.35 GPa, and FCC: 3.95 GPa. The face-centered cubic lattice with diamond infill exhibited the lowest modulus, while the body-centered cubic lattice with diamond infill had the highest. Within gyroid infills, the FCC lattice had the highest modulus, and the simple gyroid infill structure had the lowest. Testing with varying lattice thicknesses (1.00mm, 1.25mm, and 1.50mm) showed that simple gyroid infill ranged from 0.267 to 2.03 GPa, while gyroid infill with octet volume lattice ranged from 1.41 to 3.14 GPa.

For soft lattice structures, we used alginate hydrogel-based 3D printing to create gyroid, square honeycomb, and square rotated honeycomb designs embedded with fibroblasts. Live-dead assays confirmed that fibroblasts remained viable across all printed structures, demonstrating the effectiveness of these lattice structures in tissue engineering.

We developed both hard and soft lattice structures with engineered mechanical properties. Mechanical testing indicated that diamond lattice infill structures are more suitable for trabecular bone tissue due to their lower modulus values, whereas gyroid infill structures are better for cortical bone tissue due to their higher modulus. Increasing lattice thickness enhanced the modulus for both simple gyroid and gyroid with octet lattices, suggesting their potential for trabecular bone applications as well. Additionally, the alginate hydrogel-based soft lattice structures preserved fibroblast viability, highlighting their potential for tissue engineering applications.

Acknowledgements (Optional):