Microwave-Assisted Rapid Synthesis of Ultralong Hydroxyapatite Nanowires Using Glycerophosphate and Their Ordered Assembly into Flexible Macroscopic Fibers

Abstract

Hydroxyapatite (HAP) nanowires are promising biomaterials due to their biocompatibility and compositional/structural similarity to bone and dental tissues, yet conventional synthesi¬s methods yield brittle, low-aspect-ratio structures limiting flexibility and functionality. Herein, we report a rapid, environmentally friendly microwave-assisted hydrothermal synthesis of flexible ultralong HAP nanowires (UHAPNWs) using β-glycerophosphate as an organic phosphorus source and calcium oleate precursor. Optimizing parameters such as Ca/P molar ratio, hydrothermal temperature, and reaction time, we achieved UHAPNWs with lengths of several hundred micrometers and aspect ratios exceeding 10,000. These nanowires self-assemble into ordered bundles along the longitudinal direction and can be further fabricated into flexible macroscopic fibers via the injection assembly. The resulting fibers exhibit superior mineralization capability in simulated body fluid, indicating potential for applications in bone regeneration and dental enamel repair. This method offers a versatile platform for developing functional HAP-based nanostructured biomaterials with enhanced flexibility and bioactivity.