Large bone defects due to trauma, congenital malformation, or tumor removal, are considered significant health problems worldwide. Not long ago, Bone Tissue Engineering (BTE) has been developed as a new approach to treat or repair bone defects. In BTE, 3D scaffolds (engineered biomaterials) loaded with patient's stem cells and/or biological molecules are implanted into the damaged area to stimulate the natural bone-healing processes. Recently, the 3D bioprinting technology has been introduced to create scaffolds similar to the natural bone of the patient. The long-term aim of the current project is to make 3D printed bone implants customized to the patient at an affordable cost.
The overarching objective of the “3DPRENT? project is to facilitate translation of the 3D printing technology for bone regeneration. Three-dimensional (3D) bioprinting is seen as a potential new solution to create personalized bone-like constructs. However, lack of ideal bioinks is a considerable issue in 3D bioprinting, as various requirements related to cell function and printability of the bioinks exist.
In the first phase of the project, the team at the University of Bergen (UiB) optimized the design features (geometry and pore size) of polycaprolactone scaffolds. The team at the Western Norway University of Applied Sciences (HVL) designed and 3D printed scaffolds with gyroid geometry that has different porosity and pore sizes. Different 3D printing parameters (speed, pressure, temperature) were also tested, and the scaffolds were successfully printed with high shape fidelity and accuracy. In collaboration with Fraunhofer Institute in Germany, UiB started to optimize the dynamic cell culture environment by trying different flow rates in a custom-designed laminar flow bioreactor.
Our international collaborator, the Institute of Science and Technology for Ceramics in Italy (ISTEC-CNR) prepared and characterized two types of nanohydroxyapatite (nHA) with different chemical composition and morphology. In collaboration with UiB, these nHA particles were incorporated in gelatin-based hydrogel with human bone marrow-derived mesenchymal stem cells (hBMSCs) to formulate the first bioink in the project. Different formulations of this bioink were optimized and characterized in terms of nHA concentration, printability, and viscosity. The needle-like nHA particles improved the viscosity of the bioinks. The short-and long-term effect of these nHA particles on hBASCs confirmed their cytocompatibility.
The research team at the University Politehnica of Bucharest in Romania (PUB) prepared an oxidized alginate hydrogel and functionalized it with different concentrations of nanodiamond particles (NDP). The developed alginate-NDP hydrogels were characterized in terms of chemical structure and viscosity. The partner RISE PFI in Trondheim successfully prepared biocompatible oxidized nanocellulose with versatile surface chemistry. UiB developed the second bioink in the project by mixing oxidized alginate, nanocellulose, nHA and hBMSCs. The developed bioink was also characterized in terms of printability, rheology and cell viability and functionality. The bioprinting parameters (speed, pressure, temperature) were optimized for different bioinks to assure the production of high shape fidelity and accuracy.
Tissue-specific hydrogels made from different formulations of natural polymers have been developed by the team. The developed biomaterial inks have been characterized for their material properties in terms of rheology, stability, and printability. Cytotoxicity of the materials and bioprinting process was evaluated.
Recent clinical studies performed by our group and other clinical partners in Europe, propose alternatives to conventional treatment modalities by using the concept of tissue engineering in which engineered biomaterials (scaffolds) are used to deliver mesenchymal stem cells (MSC) and/or growth factors. Although there have been some successes, bone tissue engineering needs to overcome several challenges to meet clinical and commercialization needs. Among these challenges, the limitations of scaffolding biomaterials to mimic the macro to nanoscale structures of native tissues.
Current bone scaffolds suffer from impaired cellular responses, inadequate delivery of growth factors, insufficient mechanical strength and incorrect design. The significance of the current project lies on combining nanotechnology and 3D printing technology. The synergetic impact of such integrated technologies has a potential to advance the field of bone tissue engineering by developing biomimetic multiscale multifunctional scaffolds for enhanced cell response and growth factor delivery.
In 3DPRENT, oxidized cellulose nanofibers (CNF)-based hydrogel will be functionalized with nano-hydroxyapatite (nHA) for osteoconductivity, nanodiamond particles (nDP) to deliver vascular endothelial growth factor (VEGF) and finally to bioprint mesenchymal stem cells (MSC). For mechanical stability and vascularization, hydrogel layers will be reinforced with 3D printed microchannel network of a thermoplastic polymer modified with (nHA). The bioengineered constructs will be fabricated based on computational model-informed design, cultured in a dynamic in vitro conditions and finally validated in relevant pre-clinical animal models. 3DPRENT will develop not only outstanding basic scientific knowledge but also sustainable solutions and innovations based on nanotechnology, 3D printing and stem cells thus improving health and promoting new medical technology to meet the needs of society.