Abstract
Electrospun selenium-containing carbonated hydroxyapatite/polycaprolactone (CHAP/PCL) core/shell nanofibers were synthesized at different contents of Rb+ as a dopant in the ceramic phase. Microstructural, morphological and mechanical properties of the nanofibers were analyzed as a function of the stoichiometric content of Rb+ ions defined by the parameter x in [RbxCa(10-0.5x)(PO4)5.8(SeO3)0.2(OH)2]/PCL (0 ≤ x ≤ 0.8). Rb+ ions were incorporated inside the CHAP crystal lattice, where they induced crystal growth in the preferred c-axis direction. They also induced internal disordering, leading to reduced crystallinity. High-resolution TEM imaging demonstrated that the fibers had the form of tubes internally filled with rod-shaped CHAP nanoparticles, whose size increased from 50 to 70 nm on average as the result of doping with Rb+. The nanoparticles without any Rb+, at x = 0, were aligned well with the fiber curvature, but this alignment diminished as the fibers became more oblique at higher contents of Rb+. The attachment of human fibroblasts on the nanofibers was slightly enhanced at higher Rb+ contents. This effect was tied to an increase in the surface roughness of the composite with the amount of Rb+ in the CHAP phase, conforming to the finding that nanoparticles accommodating more of the Rb+ dopant are prone to exhibit more surface defects due to the extension of the lattice distortions to the surface. Attributed to an increase in the amorphous character of CHAP at the higher contents of Rb+ and to the resulting degeneration of the reinforcement effect, most mechanical properties were compromised with the addition of Rb+.