Due to disease, degeneration, trauma, and aging, bone loss occurs in the body. Although there have been remarkable improvements in development of functional bone scaffolds, it remains difficult to fabricate porous and biocompatible constructs in physiologically relevant sizes (cm-scale). Herein we developed biomineralized origami-inspired paper scaffolds in three-dimensions (3D). To our knowledge, this work is the first demonstration that paper can be used as a 3D construct to induce template-guided mineralization by osteoblasts.
In this work, we used the principles of origami to fabricate free-standing paper scaffolds in cm-scale. Because paper is an extremely flexible material that can easily be cut, creased, and folded to form 3D structures, the scaffolds were easily fabricated in a variety of different geometries. This feature can potentially be useful in generation of constructs for patient-specific applications especially for patients who have defects of irregular sizes and shapes. After sterilizing the constructs, they were seeded with osteoblasts in a collagen matrix. The samples were cultured up to 21 days and mineralization was evaluated using various assays including colorimetric assays, immunocytochemistry, high-resolution imaging (SEM), and micro-computed tomography (micro-CT). We also performed in vivo subcutaneous implantation experiments in a rat model.
In this project, we generated paper scaffolds in different shapes, sizes, and configurations (mm-cm scale). Due to its porous structure, paper allowed for transport of oxygen and nutrients across its thickness. Paper scaffolds supported a homogenous distribution of cells within their 3D structures. In our experiments, proliferation of osteoblasts increased until day three and then decreased. Hydroxyapatite content of the samples indicated that there was a progressive increase in the amount of hydroxyapatite in the paper scaffolds over 21 day of culture period. We used SEM to visualize the deposition of mineral clusters, and EDAX to calculate the ratio of calcium to phosphate. Our in vivo experiments demonstrated that paper scaffolds did not cause inflammation. The paper implants integrated with the existing tissue strongly and rapidly vascularized.
To sum up, we have shown that origami-inspired tissue engineering is useful for template-guided mineralization. We obtained partially mineralized scaffolds in various 3D geometries. The osteoblasts deposited calcium phosphate in these scaffolds and induced template-guided mineralization. Our approach used paper, a readily available material, as the cell culture scaffold. Paper has great potential to tackle the limitations of traditional scaffolds including cost, availability, accessibility, porosity, flexibility, and ease of fabrication. In the future, paper-based scaffolds could potentially guide and accelerate bone repair using patient specific cells.