Preparation And Properties Of Bone Scaffolds Based On Selective Laser Sintering

Treatment of critically sized bone defects,which was caused by accidental injury or disease,remains a great challenge.Artificial bone scaffolds provide a new solution for bone repair,which overcomes the disadvantages of traditional autologous bone grafts such as limited donors and allogeneic bone grafts that easily cause immune rejection.Artificial bone scaffolds not only need good biological activity to meet the needs of bone repair,but also have antibacterial properties to deal with the problem of bacterial infection in the initial stage of implantation.Among implant-related infections,80%are caused by biofilms.However,traditional antibiotics and other treatments are difficult to effectively remove biofilms,so how to effectively remove biofilms is crucial for the treatment of implant bacterial infections.In this work,CeO₂@PCN-224 nanosystem and PCN-224@CNT nanosystem was introduced into the poly-L-lactic acid（PLLA）scaffold,respectively,to achieve effective removal of biofilm and kill bacteria.Finally,Sr²⁺slow-release system was introduced into the PLLA scaffold to enhance the bioactivity.The specific work of this paper is as follows:1.The CeO₂@PCN-224 nanosystem was constructed and introduced into the PLLA scaffold.On the one hand,Ce⁴⁺in CeO₂ can hydrolyze the e DNA on the biofilm,leading to the disintegration of the biofilm;on the other hand,in the absence of biofilm protection,the ROS produced by PCN-224 under light can effectively damage the protein and genetic material of bacteria,thereby killing the bacteria.The CeO₂@PCN-224/PLLA scaffold could effectively hydrolyze the e DNA on the biofilm and remove the bacterial biofilm.At the same time,fluorescent staining and CCK-8 experiments proved that the scaffold had good biocompatibility.2.The photosensitizer PCN-224 and the photothermal material carbon nanotube（CNT）were simultaneously introduced into the PLLA scaffold to achieve combined antibacterial of photodynamic therapy（PDT）and photothermal therapy（PTT）.On the one hand,PTT could destroy the integrity of biofilm and make up for the deficiency that single PDT was difficult to destroy bacterial biofilm;on the other hand,PTT could make up for the defect that single PTT need higher temperature.In this paper,the PCN-224@CNT nanosystem was constructed and introduced into the scaffold,the photothermal performance of the scaffold was studied,and the antibacterial performance of the scaffold was evaluated.The photothermal conversion efficiency of the scaffold was 32.56%.Antibacterial experiments showed that the scaffold had excellent antibacterial ability when irradiated with light of 660 nm and 808 nm,and could effectively remove biofilm.3.The introduction of Sr²⁺into the PLLA scaffold improved its biological activity,but directly introducing Sr²⁺into the PLLA scaffold would lead to the burst release of Sr²⁺,which would cause biotoxicity to normal cells and tissues.In this work,hydroxyapatite（HA）was used as the carrier of Sr²⁺to construct a sustained-release system.On the one hand,Ca²⁺in HA can provide a large number of replacement sites for Sr²⁺.On the other hand,the ionic bonds formed between Sr²⁺and surrounding ions,Slow and controlled release of Sr²⁺can be realized.The released Sr²⁺can significantly promote cell proliferation and differentiation,showing higher cell optical density and alkaline phosphatase（ALP）activity.In addition,the mechanical properties of the PLLA scaffold were greatly improved with the addition of Sr HA.