Enhanced piezoelectric response of hybrid biodegradable 3D poly(3-hydroxybutyrate) scaffolds coated with hydrothermally deposited ZnO for biomedical applications

Fibrous scaffolds based on biodegradable piezoelectric poly(3-hydroxybutyrate) (PHB) polymers were fabricated via electrospinning. Hydrothermal deposition of zinc oxide (ZnO) on the surfaces of fibrous PHB scaffolds resulted in a homogeneous ZnO layer that grew conformally on the porous polymeric scaffold. X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) results confirmed the formation of a hexagonal wurtzite crystal structure of ZnO on the PHB fibres. XRD patterns, TEM and EDS analysis revealed a bimodal morphology with rod-like nanostructures that grew preferentially along the c-axis as well as nanoparticles that grew randomly. The piezoelectric charge coefficient d(33) for pristine PHB scaffolds was 2.9 +/- 0.1 pC.N-1, whereas after ZnO deposition, it substantially increased to 13.7 +/- 1.6 pC.N-1. Moreover, the output surface electrical potential of PHB scaffolds after ZnO deposition also substantially increased from 0.58 +/- 0.02 to 0.88 +/- 0.04 V, showing enhanced electromechanical coupling in the piezoelectric nanocomposites. The output surface electric potential for ZnO-coated PHB scaffolds was stable within 1200 loading cycles. In addition, the ZnO rod-like nanostructured surface improved the wettability of PHB fibrous scaffolds, demonstrating synergy between the ceramic and polymeric phases in PHB/ZnO composites. Therefore, the hybrid biodegradable piezoelectric scaffolds reported in the present study are potentially useful for biomedical applications, where both improved piezoelectric response and surface wettability are required.