Synthesis And Properties Of 3D Printing NHA/SA/PCL Composite Scaffold Loaded With ALN

Objective: For bone defects caused by tumor,trauma,inflammation and other causes,the body’s self-repair ability is limited,and currently there is no ideal bone replacement material that can promote the regeneration of bone tissue defects.In this study,the porous nano-hydroxyapatite(nHA)/ sodium alginate(SA)/ polycaprolactone(PCL)composite scaffolds loaded with Alendronate(ALN)were prepared by extrusion three-dimension(3D)printing technology to simulate the structure and mechanical properties of bone tissue;The material properties,drug sustained-release ability and in vitro biological behavior of the scaffolds were investigated by various characterization methods to initially explore its application prospects as an artificial implant.Methods:(1)Different contents of nHA(they are 50wt%,60wt% and 70wt%respectively)were mixed with SA to obtain uniform printing inks.Rheological properties of each set of inks were tested to evaluate their printing feasibility;(2)The extrusion 3D printer was used to print the scaffolds according to the predetermined design,and named nHA50,nHA60 and nHA70 scaffold respectively.The PCL was then assembled on the surface of the composite scaffold by dipping method.The obtained scaffolds were named nHA50P,nHA60P and nHA70P scaffold,respectively;(3)Scanning electron microscope(SEM),Fourier transform infrared spectroscopy(FTIR)and X-ray diffraction(XRD)were used to characterize the morphology,structure and component of the scaffolds,and to detect the porosity;(4)The mechanical properties,hydrophilicity and swelling properties of all scaffolds were tested to evaluate whether they met the application requirements of tissue engineering scaffolds;(5)The ALN was loaded into the nHA60P scaffold with better performance and the nHA60 scaffold as the control group,and the FTIR detection was performed after the nHA60P-ALN and nHA60-ALN scaffold were obtained.Optical density(OD)values of the scaffolds were collected periodically for 14 days to analyze the slow-release effect of PCL coating on ALN in the scaffolds;(6)The cytotoxicity and growth promoting ability of nHA60、nHA60P and nHA60P-ALN scaffolds were detected by CCK-8 method.Results:(1)Printing inks with different nHA contents have the ability to shear thinning and have good support,which meets the requirements of extrusion 3D printing;(2)nHA50,nHA60 and nHA70 scaffolds were printed and formed according to the predetermined shape,and the PCL coatings of nHA50P,nHA60P and nHA70P scaffolds were uniformly coated on the surface.The pores of all scaffolds were regular and interconnected,showing good formability;(3)SEM results showed that the surface of all scaffolds presented uneven rough surface,and the interior was loose porous structure,which was conducive to the growth of cells.The results of FTIR and XRD showed that nHA,SA and PCL components existed in the composite scaffold and their properties did not change significantly.The porosity of the six scaffolds ranged from 86-91%,providing a large surface area for cell adhesion and growth;(4)Mechanical experiments showed that with the increase of nHA ratio,the compressive strength and modulus of nHA50,nHA60 and nHA70 uncoated scaffolds and nHA50P,nHA60P and nHA70P coated scaffolds increased first and then decreased,while the PCL coated scaffolds were higher than the uncoated scaffolds.Therefore,the nHA60P scaffold had the highest compressive strength of 16 MPa.Hydrophilic experiments showed that the contact angles of nHA50,nHA60 and nHA70 scaffolds decreased successively(P < 0.05),and the contact angles of nHA50P,nHA60P and nHA70P scaffolds were increased due to PCL coating,but they were all less than 90°,which can still be defined as hydrophilic materials.Swelling experiments showed that all the composite scaffolds reached swelling equilibrium after 12 hours,and nHA60P scaffold had the lowest swelling rate,which was conducive to maintaining good structural stability after implantation;(5)FTIR detection of nHA60-ALN and nHA60P-ALN showed that ALN was loaded successfully and no obvious change in its properties was found.Drug release experiments showed that the drug release curve of nHA60P-ALN scaffold was smoother than that of nHA60-ALN scaffold,so the PCL coating could prolong the release time of ALN and play a good role in controlling slow release;(6)Cytotoxicity tests showed that the survival rates of osteoblast in the extracting liquid of nHA60,nHA60P and nHA60P-Al N scaffold were all higher than 80%,and loading 0.5wt% of ALN in the scaffolds did not affect the activity of the cells.Subsequently,each group of scaffolds were then co-cultured with osteoblast.All three groups of scaffold materials could promote osteoblast proliferation,and nHA60P-ALN scaffolds had the best effect on cell proliferation.Conclusion: By combining nHA with SA,supplemented by excellent PCL and ALN,which promote bone cell proliferation,finally the prepared drug-carrying composite scaffold has the properties of loose and porous microstructure,excellent mechanical properties,good hydrophilicity,suitable swelling,good drug slow release and biocompatibility,which provides a new candidate material for clinical repair of bone defects and lays a solid foundation for the application of ALN in tissue engineering.