Rheological behavior of an injectable scaffold for bone tissue engineering

Calcium phosphate ceramics are widely used as bone substitutes, because they are non-toxic, biocompatible and exhibit bioactive behavior. For minimally invasive surgery, homogenously distributing cells and molecular signals throughout the scaffold and directly injection into cavities with irregular shape, in this study the injectable scaffolds were developed. They consist of a biopolymer (hydroxypropyl methylcellulose: HPMC) as matrix and biphasic calcium phosphate (BCP) as filler. Biphasic calcium phosphate consists of nano-sized hyadroxyapatite and nano-sized β-tricalcium phosphate with plate-like morphology.The steady and dynamic rheological properties, turbidity and injectability of the injectable scaffold were investigated. Gelation temperature of HPMC is higher than physiological temperature and dependent on the hydroxylpropyl content and its distribution in HPMC. In order to lower the gelation temperature, Na2SO4 was incorporated into the HPMC solution. The results indicated that the salt decreased the cloud point and gelation temperature of HPMC solution. The shear-thinning behaviour of this system was confirmed using the rheological experiments. No significant difference was observed in the storage modulus and loss modulus with increasing in BCP content, whereas incorporation of Na2SO4 enhanced the modulus. It may be concluded that the specimens with lower BCP phase is more suitable for using as scaffold, because of higher injectability and porosity.

Keywords:

Bone tissue engineering , injectable scaffolds , Biphasic calcium phosphates , Rheological behavior