Preparation And Properties Of 3D Printed Functional Polylactic Acid Bionic Scaffolds

Bone regeneration is very complex because it involves many fields such as molecular,cellular,biochemical and mechanical aspects.Therefore,an ideal scaffold for bone tissue engineering should have a suitable shape,porosity,biodegradablity,biocompatibility and mechanical properties to induce bone regeneration.In recent years,3D printing has attracted much attention in the biomedical field,mainly due to its ability to customize an unique architecture with specific shapes and pore structures.Polylactic acid(PLA),a typical synthetic biological material,has been widely used in the research of tissue engineering scaffold materials due to its biocompatibility,biodegradability and processability.However,there are a large number of ester groups in the molecular chain of PLLA,the high hydrophobicity is unfavourable for cell adhesion.In order to improve the hydrophilicity and cell activity of the PLA material,some modifications are needed.In this paper,the amino-modified PLLA was selected as the matrix material,and the functionalized modified PLLA bionic scaffolds were prepared by low temperature 3D printing technology.The main research works and the obtained results are as follows:(1)Using ethylenediamine as an aminolytic modifier,a modified PLLA scaffold with bionic nanofiber structure was successfully prepared by combining ammonolysis with cryogenic 3D printing technology.With the pristine PLLA scaffolds prepared by using cryogenic 3D printing and FDM technology at a high temperature serving as the control groups,it was proved that the hydrophilic properties of PLLA were improved by the introduction of free amino after ammonolysis modification.The hydrophilic surface and the bionic nanofiber structure of the scaffold promoted the cell adhesion and proliferation.Meanwhile,the introduced amino groups also increased the active sites for biomineralization and improved the osteogenic properties of the scaffold.Therefore,the prepared 3D printed modified PLLA nanofiber scaffolds have a great application potential in bone tissue engineering.(2)The functionalized black phosphorus(i.e.PDA@(BP+IBU)composite nanosheets)were mixed with the modified PLLA solution,and then the functional composite nanofiber scaffolds were prepared by cryogenic 3D printing technology.The results of XPS and EDS confirmed the successful preparation of composite scaffolds.The addition of two-dimensional black phosphorus nanocomposites further improved the properties of the modified PLLA scaffold.The excellent photothermal conversion performance of black phosphorus enabled the on-demand release of anti-inflammatory drugs from scaffolds.The good biocompatibility and osteogenic activity of black phosphorus nanosheets endowed the composite scaffolds with a stronger ability to induce bone regeneration.The enhanced osteogenic activity of the scaffolds was confirmed via Alizarin red(AR)and alkaline phosphatase(ALP)staining and ALP activity assay.(3)The silver and zinc nanoparticles were introduced onto the black phosphorus nanosheets through in situ photodeposition technology and a composite scaffold with antibacterial and osteogenic activity was obtained by cryogenic 3D printing.It was found that the prepared scaffold had a nanofiber structure which was suitable for cell adhesion and growth,and the composite scaffold had sufficient mechanical properties for use as a supporting framework for bone repair,meeting the performance requirements for bone tissue engineering scaffolds.Furthermore,the composite scaffold exhibited an excellent photothermal conversion performance under NIR irradiation and a good antibacterial activity.Thus,the as-prepared composite scaffold may hold great potential for bone tissue engineering applications.