Correlation between Morphology, Mechanical Properties and Microdeformation Behavior of Electrospun Scaffolds Based on a Biobased Polymer Blend and Biogenic Nano-Hydroxyapatite

For the investigations, scaffolds for bone regeneration (in the form of non-woven mats) were fabricated based on a polymer blend based on polycaprolactone, poly-L-lactic acid and gelatin by electrospinning which were partly modified using vitamin D3 and reinforced with 0 - 12 % nano-hydroxyapatite (nano-HAp extracted from ostrich bones) to improve both biocompatibility and mechanical performance. Electron microscopic approaches were applied to analyse the fiber microstructure due to phase separation and the microdeformation mechanisms after testing, as well as the fiber diameter as a function of the nano-HAp fraction. From uniaxial tensile testing it has been found that incorporation of nano-HAp into the blend triggers the mechanical properties of the scaffolds to a high degree, which results in an increase in tensile strength from 0.7 MPa to 5.6 MPa and an increase in strain at break from 2 % to 37 %. The transition from the very brittle behavior of the neat blend fiber mats to the highly ductile behavior of the blend fiber mats containing 12 % nano-HAp is related to a change in the microdeformation behavior of the nano- or micro-sized fibers. Whereas at lower nano-HAp content, crazing inside the fibers is prominent, thin-layer yielding becomes dominant at higher nano-HAp content.