An electrospun triphasic nanofibrous scaffold for bone tissue engineering

A nanofibrous triphasic scaffold was electrospun from a mixture of polycaprolactone (PCL), type-I collagen and hydroxyapatite nanoparticles ( nano-HA) with a mixture dry weight ratio of 50/30/20, respectively. Scaffolds were characterized by evaluating fiber morphology and chemical composition, dispersion of HA particles and nanoindentation. Scanning electron microscopy revealed fibers with an average diameter of 180 +/- 50 nm, which coincides well with the collagen fiber bundle diameter characteristic of the native extracellular matrix of bone. The triphasic fibers, stained with calcein and imaged with confocal microscopy, show a uniform dispersion of apatite particles throughout their length with minor agglomeration. Scaffold fibers of triphasic (50/30/20), collagen/nano-HA (80/20), PCL/nano-HA (80/20), pure PCL and pure collagen were each pressure consolidated into non- porous pellets for evaluation by transmission electron microscopy and nanoindentation. While the majority of apatite particles are uniformly dispersed having an average size of 30 nm, agglomerated particles as large as a few microns are sparsely distributed. Nanoindentation of the pressure-consolidated scaffolds showed a range of Young's modulus ( 0.50-3.9 GPa), with increasing average modulus in the order of (PCL < PCL/nano-HA < collagen < triphasic < collagen/nano-HA). The modulus data emphasize the importance of collagen and its interaction with other components in affecting mechanical properties of osteoconductive scaffolds.