Preparation And Research Of Degradable Drug-loaded Stent Base On 3D Printing Technology

Osteosarcoma（OS）,as a representative of bone malignant tumor,the mainstream therapeutic strategy currently available is surgical resection of tumor tissue supplemented by postoperative chemotherapy or radiotherapy.Although considerable progress has been made in the treatment of osteosarcoma,many adverse side effects remain unresolved after surgery.These mainly include limited distribution of chemotherapeutic drugs in the tumor,severe toxicity from high-dose chemotherapy,and removal of tumor tissue,usually leaving irregular bone defects.Therefore,there is an urgent need to develop a novel postoperative treatment that overcomes these limitations.3D printing technology has always been at the forefront of the fields of biological tissue engineering and drug delivery,in particular,it has great potential in the manufacture of personalized scaffolds.Based on the imaging data such as CT and magnetic resonance imaging（MRI）of the patient,the 3D model can be quickly and accurately established.which makes it possible to accurately print the irregular model.In addition,the drug-loaded stent fabricated by 3D printing technology has unique advantages in personalization,spatial structure,diversity of drug components,precision of drug loading,and sustainability of drug release.Therefore,we intended to use 3D printing technology to prepare a degradable anti-tumor stent to provide a new idea for the postoperative treatment of osteosarcoma.The main contents and conclusions of this study were as follows:（1）Preparation of polylactic acid/methotrexate（PLA/MTX）drug-carrying materialDissolve PLA and MTX raw materials in chloroform,and mix them evenly by means of ultrasonic stirring.The PLA/MTX drug-loaded wire（1.75 mm ±0.05 mm）containing 0.5%,1.5%and 2.5%MTX was prepared by melt extrusion from the dried uniform mixture of PLA and MTX.The physical and chemical properties of the composites were characterized by Fourier transform infrared spectroscopy,X-ray diffraction and three-point fracture mechanics.The drug loading rate,encapsulation rate and sustained-release ability of drugs in vivo and in vitro were detected by ultraviolet spectrophotometer.The results showed that melt extrusion will not affect the original chemical structure of PLA and MTX,and the drug-loaded wire prepared by this method presents a uniform yellow cylinder shape,with smooth surface without graininess,uniform color thickness and uniform distribution of MTX in PLA matrix.And a small amount of MTX will not destroy the mechanical structure of PLA itself.The analysis of drug loading rate and encapsulation rate showed that MTX was well introduced into PLA matrix,and the encapsulation rate can reach 98.1%.The drug loss of melt extrusion method was very small.In vitro and in vivo drug release ability The results of in vitro and in vivo drug release test showed that the drug release curve showed an "S"shape,which could maintain drug release in vivo and in vitro for 30 days.（2）Preparation and biological characterization of PLA/MTX porous scaffoldThe PLA/MTX porous drug-loaded scaffolds were prepared using FDM 3D printer by extruding through a nozzle（0.1 mm）and printing layer by layer at the temperature of 210℃,the layer height of 0.1mm,and the printing speed of 10.Elemental analysis and pore size analysis were performed on the printed porous scaffold using a scanning electron microscope.MG-63,MCF-7,A549,4T1 and MC3T3-E1 cells were selected to evaluate the biocompatibility and tumor inhibition rate of PLA/MTX porous drug-loaded scaffold,and Balb/c mice were selected to test the anti-tumor effect and tissue toxicity of PLA/MTX porous drug-loaded scaffold in vivo.The results showed that the PLA/MTX porous drug-loaded scaffold had a network of open macroporous structure,and the porosity could reach 29.7%.Besides,elemental analysis showed that MTX was distributed evenly on the scaffold.Through the analysis of the results of cell experiments in vitro and animal experiments in vivo,it was found that the PLA/MTX scaffold had a high anti-tumor effect.The tumor growth inhibition value（TGI）of 2.5%PLA/MTX group was 89.26%,which was higher than that of injection group（74.04%）.No significant toxicity to organs was found by H＆E tissue staining in vivo.（3）Preparation and characterization of polylactic acid/methotrexate-hydroxyapatite（PLA/MTX-HA）porous scaffoldsHydroxyapatite was synthesized by co-precipitation method.PLA/MTX-HA drug-loaded wires were prepared by the chemical mixing method and melt extrusion method in Chapter 1,and the content of HA was controlled at 10%,20%and 30%.The PLA/MTX-HA porous drug-loaded scaffolds were prepared using FDM 3D printer by extruding through a nozzle（0.1 mm）and printing layer by layer at the temperature of 210℃,the layer height of 0.1 mm,and the printing speed of 10.The synthesized hydroxyapatite was characterized by fourier transform infrared spectroscopy,X-ray diffraction,and scanning electron microscopy.The effect of the content of HA on the mechanical properties of PLA/MTX-HA scaffolds was studied by universal testing machine.MG-63 and MC3T3-E1 cells were selected to evaluate the biocompatibility and tumor inhibition rate of the PLA/MTX-HA porous drug-loaded scaffold.The results showed that the synthesized needle-like HA was uniformly dispersed in the PLA/MTX-HA scaffold,and the introduction of HA would improve the mechanical properties of the scaffold,such as compressive strength,impact strength and toughness.At the same time,HA will be released along with the degradation of PLA to neutralize the local acidity brought by the degradation of PLA,and avoid the occurrence of inflammation.Analysis of the results of cell experiments showed that the introduction of HA enhanced the osteogenic and osteogenic capability of the scaffold for bone repair,while the scaffold still maintained a high inhibition rate on osteosarcoma cells.