Surface functionalization of porous Titanium scaffold for bone tissue engineering

Abstract

Event Abstract Back to Event Surface functionalization of porous Titanium scaffold for bone tissue engineering Bingjun Zhang1, Zhiwei Han1 and Jie Weng1 1 Southwest Jiaotong University, Key Laboratory of Advanced Technologies of Materials,School of Materials Science and Engineering, China Introduction: Bone tissue engineering materials has been rapidly developed in recent years as an alternative to autografts and allografts. Considerable efforts have been carried out to enhance the properties of tissue engineering architectures via surface engineering and surface functionalization for providing an extracellular matrix mimicking environment for better cell adhesion and tissue in-growth[1]. In this work, in view of excellent function of polydopamine (PDA)[2]-[4] and favourable biocompatibility and mechanical properties of Titanium (Ti), we seek to design a functional bone graft substitute based Ti in a biocompatible, cell-friendly scaffold mimicking the bone morphology would greatly enhance bone regeneration engineering. Materials and Methods: In this study, the Ti powder was used for preparing highly interconnected porous scaffolds by porogen–leaching methods, of which adopting sugar spheres (400-600μm) as pore-forming agent. Subsequently, we introduced a mussel-inspired, biomimetic technique based on a PDA ad-layer developed from oxidative polymerization of dopamine to surface modification of tissue engineering scaffolds and substrates. In virtue of the characteristic of PDA coatings, adhesion peptides (GRGDS) were simply immobilized on the titanium surfaces for efficient and reliable manipulation of bone marrow mesenchymal stem cells (BMSCs) differentiation and proliferation. The surface properties, mechanical properties, and cell adhesion and proliferation properties of the functionalized porous Ti metal scaffold were investigated systematically. Results and Discussion: In the current study, porous Ti metal scaffold had a highly open porous structure (pores size: 500μm; through holes size: 100μm, approximately) and good mechanical strength (26.33MPa). With the use of the biomimetic mineralization method, the nano-net structure calcium phosphate was formed on the surface of sintered scaffolds after immersed in SBF for 7d, indicating that the porous Ti scaffold possessed positive biological compatibility. The nano-net bone-like apatite was very similar to composition of human bone mineral, which be able to shorten the time of bone fusion and improve the biocompatibility and biological activity of Ti scaffolds. When the PDA-coating technique was applied to three-dimensional Ti scaffold, PDA coatings facilitated highly efficient, simple immobilization of GRGDS onto Ti substrates. As confirmed by quantitative alamar blue assay and alkaline phosphatase assay, after 3 days of cultubation, the effect of promoting cell proliferation had been presented on the treated Ti scaffold. It was observed that the number of BMSCs was higher than pure Ti scaffold. And statistical analysis showed that PDA–GRGDS modified Ti scaffold had significant difference compared with untreated Ti, which indicated that PDA-GRGDS introduced on the surface of implanted materials intrinsically facilitated cell adhesion and proliferation. The ALP activity of BMSCs, by 14 days, cultured on treated Ti, was significantly higher than that of pure Ti (p < 0.05).That means the early cell adhesion had play a crucial role in promoting osteogenetic activity of cells. In summary, the GRGDS conjugation greatly enhanced not only the adhesion but also mineralization of osteoblasts or BMSCs compared with untreated scaffolds, while calcium phosphate mineralized layers deposition facilitated cellular osteodifferentiation. Therefore, this kind of biocompatible scaffolds provided an optimal microenvironment for cell proliferation, migration, and differentiation, and guidance for cellular in-growth from host tissue. Conclusions: This functionalized layer formed by PDA-mediated surface modification on porous titanium scaffold promoted BMSCs adhesion and improved osteogenic differentiation and mineralization. In conclusion, this kind of bioactive Ti scaffold with such mechanical strength as that of woven bone should be a promising bone graft in clinical applications. This research was supported by grants from National Basic Research Program of China (973 Program, 2012CB933600), National Natural Science Foundation of China (51172188) and Science & Technology Pillar Project of Sichuan (2010FZ0048)