Bioactive ZnO Decorated PVDF-Based Piezoelectric, Osteoconductive Nanofibrous Coatings for Orthopedic Implants

Surface modification of titanium-based orthopedic implants has been investigated over the last decades to promote better bone-to-implant association, osseointegration, and fracture healing. Yet, post-surgical failure of coated orthopedic implants occurs due to poor adhesive strength, fatigue failure, high wear rate of coated materials, low biocompatibility, limited osseointegration, and stress-shielding effect. Therefore, there is an unmet clinical need to develop a smart coating strategy. Herein, we have created an electrospun nanofibrous coating for Ti-implants using piezoelectric Polyvinylidene fluoride (PVDF) polymer reinforced with osteoconductive nanofiller Zinc oxide (ZnO). We have found that by varying the ZnO content from 0.5 to 2.0 wt.% in the PVDF matrix, we can modulate the electrospun coating's mechanical, thermal, physicochemical stability, and piezoelectric characteristics. Our results proved that PVDF-ZnO nanofibrous coatings exhibit almost ~3-4 fold increase in the piezoelectric d₃₃ coefficient as well as output voltage, compared to pure PVDF using Piezo-responsive Force Microscopy (PFM). Furthermore, electrically poled piezoelectric PVDF-ZnO nanofibers also demonstrated a significant increment (~5-fold) in collagen deposition, hydroxyapatite formation, and improved bio- and hemo-compatibility compared to unpoled nanofibers. Furthermore, through the in vitro experiments, we have confirmed that the piezoelectric PVDF-ZnO nanofibrous activates calcium-calmodulin mediated cellular pathway to induce cell adhesion, proliferation, and cell spreading in the osteoblast cells. Nonetheless, using the biomimetic mechanical bioreactor, we have investigated the piezoelectricity-mediated increased focal adhesion and enhanced F-actin production under the physiologically relevant (i.e., 1%) mechanical strain in bone cells. Moreover, the current study elucidates the piezoelectric-based smart, multifunctional coating strategies for developing an osteoconductive implant.