Poly(L-lactide)/nano-hydroxyapatite piezoelectric scaffolds for tissue engineering

The development of bone tissue engineering, a field with significant potential, requires a biomaterial with high bioactivity. The aim of this manuscript was to fabricate a nanofibrous poly(L-lactide) (PLLA) scaffold containing nano-hydroxyapatite (nHA) to investigate PLLA/nHA composites, particularly the effect of fiber arrangement and the addition of nHA on the piezoelectric phases and piezoelectricity of PLLA samples. In this study, we evaluated the effect of nHA particles on a PLLA-based electrospun scaffold with random and aligned fiber orientations. The addition of nHA increased the surface free energy of PLLA/nHA (42.9 mN/m) compared to PLLA (33.1 mN/m) in the case of aligned fibers. WAXS results indicated that at room temperature, all the fibers are in an amorphous state indicated by a lack of diffraction peaks and amorphous halo. DSC analysis showed that all samples located in the amorphous/disordered alpha' phase crystallize intensively at temperatures just above the T_g and recrystallize on further heating, achieving significantly higher crystallinity for pure PLLA than for doped nHA, 70 % vs 40 %, respectively. Additionally, PLLA/nHA fibers show a lower heat capacity for PLLA in the amorphous state, indicating that nHA reduces the molecular mobility of PLLA. Moreover, piezoelectric constant d₃₃ was found to increase with the addition of nHA and for the aligned orientation of the fibers. In vitro tests confirmed that the addition of nHA and the aligned orientation of nanofibers increased osteoblast proliferation.