Electrostatic layer-by-layer assembly for fabricating morphology-controlled hydroxyapatite/zirconia composite with enhanced osteogenic performance

Abstract

Background

Yttria-stabilized zirconia (YSZ) represents a promising alternative to titanium for dental and orthopedic implants owing to its mechanical strength and esthetics. However, its bioinertness limits osteoconductivity. Although hydroxyapatite (HAp) coatings can enhance osteointegration, uniform deposition of morphology-controlled HAp on YSZ remains challenging to achieve, limiting implant optimization.

Objectives

This study was aimed at the uniform deposition of morphology-controlled HAp on YSZ using electrostatic layer-by-layer (LBL) assembly to improve biological performance.

Methods

Plate-like HAp was hydrothermally synthesized using dodecanedioic acid and surface-modified with poly(diallyldimethylammonium chloride) and poly(sodium 4-styrenesulfonate). YSZ discs were similarly charge-modified to enable electrostatic adsorption of HAp. Samples were evaluated using scanning electron microscopy, energy-dispersive X-ray spectroscopy, Fourier-transform infrared spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and wettability tests. Osteogenic responses were assessed using MC3T3-E1 cells through alkaline phosphatase (ALP) activity and Alizarin Red S staining.

Results

Negatively charged HAp was uniformly deposited on positively charged YSZ, forming a homogeneous coating. Characterization confirmed successful HAp deposition and improved hydrophilicity. HAp/YSZ composites enhanced osteogenic differentiation, exhibiting higher ALP activity and greater calcium deposition than YSZ.

Conclusion

LBL-mediated deposition of morphology-controlled HAp enables uniform coating and enhanced osteogenic activity on YSZ, facilitating advances in next-generation bioactive zirconia implants.