Morphology, Deformation, and Micromechanical Behavior of Electrospun Nano-hydroxyapatite Blended Biohybrid Scaffolds

For bone tissue engineering, nano-hydroxyapatite (nano-HAp) is a widely used bioceramic filler in polymer fibrous scaffolds that changes the morphology and micromechanical behavior of fibers. In this study, different volume fraction percentages of nano-HAp and vitamin D3 (VD3) are incorporated into electrospun polymer blend fibrous scaffolds comprising polycaprolactone (PCL), poly-L-lactic acid (PLLA), and gelatin (GEL). Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and uniaxial tensile testing are used to characterize the chemical, morphological, and micromechanical properties of the scaffolds. The FTIR analysis showed the presence of functional groups of fillers and polymers and their molecular interactions in the fibers. In the microscopic analysis, the fillers are found to affect the fiber morphology (including diameter, phase separation, and texture) and the response of the fibers under tensile deformation. The addition of 3% by volume of filler suspension results in maximum diameter of 4.34 µm, and the addition of 6%–12% filler leads to an increase in tensile strength from 0.7 to 5.6 MPa and strain at break from 2% to 37% for the composite fibers compared to neat fibers. The crazing behavior of the fiber is more noticeable at a low filler content (0%), whereas thin-layer yielding becomes predominant at a higher filler content (12%). Thus, the study shows that scaffold fibers undergo brittle-to-ductile transitions as the filler percentage in the polymer blend increases from 0% to 12%. It has been further found that morphogens used as growth factors can be easily released from hydroxyapatite after adsorption.