Construction And Biological Evaluation Of Dual Sustained-Release Drugs Scaffolds

Porous scaffolds play an important role in bone tissue engineering,it not only provide growth templates for the cell proliferation,adhesion and extracellular matrix deposition,but also can guide the tissue regeneration and vascularization.However,its biological effect is limited if simply use of biological material itself composition and structure factors to regulate cell behavior and tissue regeneration.At present,the combination of drugs that promote bone growth with porous scaffolds is an ideal way to accelerate bone tissue growth.However,it is not effective to accelerate the healing of bone tissue by simply immersing the scaffolds in the drug solution,which can lead to the rapid release of the drug,the short release time and the high local drug concentration.Studies have shown that the combination of drug delivery system with scaffolds to construct drug sustained-release scaffolds could promote the growth of osteoblasts and accelerate the repair of bone tissue by providing long-term and stable release of drugs.However,the current research was almost focus on a single drug release system incorporating into scaffold,which just providing single drug effect in bone tissue repair process and it could not satisfy complex clinical need.Therefore,porous scaffolds combined with multiple drug delivery systems to provide various effects are suggested to be a new direction to coordinately control bone tissue regeneration.In this study,porous hydroxyapatite scaffolds(HAs)with excellent connectivity were prepared via the template-leaching method.Salvianolic acid B-loaded chitosan(Sal B-CS)microspheres and dexamethasone-loaded poly(lactide-co-glycolide)(dex-PLGA)microspheres was prepared by chemical cross-linking and double emulsion/solvent evaporation method,respectively.The dual microspheres based on Sal B-CS and dex-PLGA were immobilized on the porous surface of HA scaffolds pre-coated with alginate through electrostatic interaction process by step-by-step adsorption method,and then freeze-dried to obtain dual sustained-release drugs scaffolds(al-HAs/Sal B-CS/dex-PLGA scaffolds).In this paper,the mechanical properties of al-HAs/Sal B-CS/dex-PLGA scaffolds and their effects on cell growth were studied.the main results are as follows:(1)Both the Sal B-CS and dex-PLGA microspheres possessed an excellent spherical shape and smooth surface.The diameter of the Sal B-CS and dex-PLGA microspheres was 27,7 μm,respectively.(2)Sal B-CS and dex-PLGA microspheres were successfully immobilized on porous HA scaffolds coated with sodium alginate,and Sal B-CS microspheres were uniformly and stably distributed on the surface of the scaffold,the dex-PLGA microspheres were surrounded by Sal B-CS microspheres.(3)The scaffolds with a depth-diameter aspect ratio of 3:2 were prepared for mechanical experiments.The compressive strength and porosity of several different scaffolds were measured,the results showed that the compressive strength of the HAs was enhanced from 1.06 MPa to 1.55 MPa as a result of alginate penetrating into the micro-pores on the scaffold surface.Additionally,the porosity of the microsphere-immobilized scaffolds was decreased slightly because of the microspheres occupying the macro-pore spaces,but the porosity of all the scaffolds was higher than 70%,which matched the clinical requirements of bone regeneration.(4)In vitro release kinetics results showed that the initial drug release of al-HAs/Sal B-CS/dex-PLGA scaffolds was lower than that of Sal B-CS and dex-PLGA microspheres.The pH in the incubation of the al-HAs/Sal B-CS/dex-PLGA scaffolds medium remained unchanged at the same time within 30 days.(5)The extraction assay for cytotoxicity test showed that the scaffolds were cytotoxic and had good biocompatibility.Osteoblasts cultured on several porous scaffolds found that a large number of osteoblasts attached to the scaffolds surface.Osteoblast proliferation assay showed that al-HAs/Sal B-CS/dex-PLGA scaffolds were more favorable for osteoblast growth than HA scaffolds.The al-HAs/Sal B-CS/dex-PLGA scaffolds were down-regulated the expression of IL-6.ALP expression experiments showed that al-HAs/Sal B-CS/dex-PLGA scaffolds could promote the differentiation of BMSCs into osteoblasts.