Bone plays a vital role in the structural support of the body, and despite the ability of clinical reconstruction, it is not possible to repair spontaneously or even with the help of drugs and surgical interventions in very large bone injuries. Currently, bone grafts are mostly used to treat large bone injuries, but these grafts face limitations due to finding suitable graft tissue and immune reactions. In these cases, the best treatment method is bone tissue engineering, the most important part of which is the design and construction of a scaffold suitable for the desired tissue. So far, different methods have been used to make bone scaffolds, but these methods face limitations due to poor reproducibility, lack of easy control over the shape, size and geometry of the pores and dimensions of the scaffold. Additive manufacturing methods have been developed in recent decades to overcome these limitations. Fused deposition modeling is one of the most common 3D printing methods that allows more control over porosity and pore size. It is also very important to choose the right materials to achieve functional 3D structures. Polylactic acid can be a good candidate as a biological material for printing bone tissue engineering scaffolds due to its biocompatibility and proper printing ability, but its low degradation rate, bioactivity, poor mechanical and cellular properties have led to the use of reinforcing particles to improve its properties. Used in this regard, the main goal of this research is to add bioactive glass nanoparticles and 2D nanostructure of MXene (titanium carbide) to polylactic acid and investigate the properties of their composite 3D printed scaffolds. For this purpose, first, the two-dimensional nanostructure of MXene was successfully obtained from its MAX phase. Bioactive glass doped with different percentages of strontium was also made by sol-gel method. After examining the results of characterization of bioactive glass nanoparticles, the sample containing 3.6 mole percent of strontium oxide was selected as the optimal sample for making composite scaffolds. To determine the optimal percentage of bioactive glass nanoparticles, 3D polylactic acid scaffolds with weight percentages of 10, 15, 20, and 25 bioactive glass were printed using the molten sediment modeling method. Considering their mechanical properties, the scaffold with 20% by weight of bioactive glass was selected as the optimal sample for adding MXene nanostructure and investigating its effect on scaffold properties. Finally, polylactic acid/bioactive glass/MXene scaffolds were printed and characterized. The results of the morphology eva‎luation of the scaffolds confirmed the presence of orthogonal and interconnected pores in the scaffolds and their optimal printing. The results of the biodegradability, biocompatibility and cell adhesion tests of the scaffolds showed that the addition of bioactive glass nanoparticles has significantly improved these properties of polylactic acid, and the presence of MXene nanostructure has not only had a detrimental effect on these properties, but has had positive effects especially on the biodegradability of the scaffolds. The addition of small amounts of MXene nanostructure could improve the mechanical properties of the scaffolds up to two times compared to the addition of bioactive glass. Also, their presence led to the improvement of hydrophilic properties and as a result, increased cell growth and proliferation. Therefore, the eva‎luations showed that the simultaneous addition of 20% by weight of bioactive glass nanoparticles and 4% by weight of MXene nanostructure to polylactic acid and 3D printing of their nanocomposite scaffold provides a scaffold with biodegradability, bioactivity, biocompatibility and mechanical properties suitable for bone tissue engineering.

فتح اله كريم زاده , شيدا لباف

محمد خدائي

مهران نحوي , نرگس جوهري