Preparation and biological properties of a novel composite scaffold of nano-hydroxyapatite/chitosan/carboxymethyl cellulose for bone tissue engineering

Nowadays, bone tissue engineering, using a porous scaffold material to induce the formation of bone from the surrounding tissue or to act as a template to grow cell for bone tissue regeneration, has some distinct advantages over autografting and allografting[1], and it is a rapidly growing alternative approach to heal damaged bone tissue. However, in the realm of bone tissue engineering, it is a great challenge to develop a desirable porous scaffold material used for successful bone regeneration. Obviously, an ideal scaffold for bone tissue engineering should have highly interconnected porous structure, good mechanical property and biocompatibility[2,3]. In addition, to achieve the requirements better for bone regeneration, biomimetic matrices are usually adopted, which may provide a suitable microenvironment to promote osteoblast proliferation and osteogenesis[4]. As we know, the extracellular matrices (ECMs) of hard tissue are composed of organic and inorganic phases, the inorganic phase consisting primarily of nano-hydroxyapatite(n-HA)crystals, and the organic phase consisting mainly of type I collagen and small amount of ground substance including glycosaminoglycans (GAGs), proteoglycans and glycoproteins[5]. So n-HA/polymer composite scaffolds have been reported in succession during the process of designing the scaffold for bone tissue engineering, such as, n-HA/collagen [6], n-HA/gelatin[7], n-HA/polyamide[8,9], n-HA/poly(L-lacticacid)[10], n-HA/poly(lactide-co-glycolide)[11], which are designed according to bionic principle. However, among the selected polymers, natural biodegradable polymers are a kind of promising candidate, because they avoid a second surgical operation after new bone tissue regeneration, and they possess better biocompatibility and lower cost than synthetic polymers.Chitosan(CS), a deacetylated derivative of chitin, is a biodegradable and biocompatible cationic natural polymer, and CS-based materials can accelerate bone formation because