Carbon Nanotube Reinforced Hydroxyapatite Nanocomposites As Bone Implants: Nanostructure, Mechanical Strength And Biocompatibility

Abstract

Purpose

Hydroxyapatite (HA) is a biologically active ceramic which promotes bone growth, but it suffers from relatively weak mechanical properties. Multi-walled carbon nanotubes (MWCNTs) have high tensile strength and a degree of stiffness that can be used to strengthen HA; potentially improving the clinical utility of the bone implant.

Methods

HA was precipitated by the wet precipitation method in the presence of pristine (p) or functionalised (f) MWCNTs, and polyvinyl alcohol (PVA) or hexadecyl trimethyl ammonium bromide (HTAB) as the surfactant. The resulting composites were characterised and the diametral tensile strength and compressive strength of the composites were measured. To determine the biocompatibility of the composites, human osteoblast cells (HOB) were proliferated in the presence of the composites for 7 days.

Results

The study revealed that both the MWCNTs and surfactants play a crucial role in the nucleation and growth of the HA. Composites made with f-MWCNTs were found to have better dispersion and better interaction with the HA particles compared to composites with p-MWCNTs. The mechanical strength was improved in all the composites compared to pure HA composites. The biocompatibility study showed minimal LDH activity in the media confirming that the composites were biocompatible. Similarly, the ALP activity confirmed that the cells grown on the composites containing HTAB were comparable to the control whereas the composites containing PVA surfactant showed significantly reduced ALP activity.

Conclusions

The study shows that the composites made of f-MWCNTs HTAB are stronger than pure HA composites and biocompatible making it a suitable material to study further.

Keywords:

• calcium phosphate
• carbon nanotubes
• osteoblast cells
• LDH assay
• alkaline phosphatase

Acknowledgments

This research was supported by Plymouth University Peninsula School of Medicine and Dentistry. We thank our colleague A. Besinis from the School of Engineering, Plymouth University who provided insight and expertise. We thank our colleagues from the Plymouth Electron Microscope Centre for their help with the Scanning and Transmission Electron Microscopy techniques. We would also like to show our gratitude to A. Atfield and L. Cooper from the School of Biological & Marine Sciences, Plymouth University for their assistance with the cell culture experiments.

Data Sharing Statement

The raw/processed data required to reproduce these findings cannot be shared at this time due to technical or time limitations.

Disclosure

The authors report no conflicts of interest in this work.