Improved activity of MC3T3-E1 cells by the exciting piezoelectric BaTiO₃/TC4 using low-intensity pulsed ultrasound

Highlights

• BT piezoelectric ceramic coating was hydrothermally synthesized on the surface of TC4 titanium alloy to form BT/TC4 material.

• The BT/TC4 material under ultrasound loading could produce a microcurrent of approximately 10 μA/cm².

• The piezoelectric BT/TC4 material with LIPUS loading synergistically promoted biological activity of MC3T3-E1 cells.

• Electroactivity of BT/TC4 material stimulated by LIPUS loading promoted the intracellular Ca²⁺ influx in MC3T3-E1 cells.

Abstract

Developing bioactive materials for bone implants to enhance bone healing and bone growth has for years been the focus of clinical research. Barium titanate (BT) is an electroactive material that can generate electrical signals in response to applied mechanical forces. In this study, a BT piezoelectric ceramic coating was synthesized on the surface of a TC4 titanium alloy, forming a BT/TC4 material, and low-intensity pulsed ultrasound (LIPUS) was then applied as a mechanical stimulus. The combined effects on the biological responses of MC3T3-E1 cells were investigated. Results of scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray diffraction showed that an uniform nanospheres -shaped BT coating was formed on TC4 substrate. Piezoelectric behaviors were observed using piezoelectric force microscopy with the piezoelectric coefficient d₃₃ of 0.42 pC/N. Electrochemical measures indicated that LIPUS-stimulated BT/TC4 materials could produce a microcurrent of approximately 10 μA/cm². In vitro, the greatest osteogenesis (cell adhesion, proliferation, and osteogenic differentiation) was found in MC3T3-E1 cells when BT/TC4 was stimulated using LIPUS. Furthermore, the intracellular calcium ion concentration increased in these cells, possibly because opening of the L-type calcium ion channels was promoted and expression of the Ca_V1.2 protein was increased. Therefore, the piezoelectric BT/TC4 material with LIPUS loading synergistically promoted osteogenesis, rending it a potential treatment for early stage formation of reliable bone-implant contact.