Hybrid Composites of Phosphate Glass Fibre/Nano-Hydroxyapatite/Polylactide: Effects of Nano-Hydroxyapatite on Mechanical Properties and Degradation Behaviour

Lizhe He,Chenkai Zhu,Xiaoling Liu,Jiahao Wu

doi:10.4236/msce.2018.611002

Abstract

Hydroxyapatite/polylactide (HA/PLA) composites have been intensively investigated for their potential as biodegradable fixation devices to heal bone fractures. However, most of these composites failed to achieve a bone-mimicking level of mechanical properties, which is an essential demand of the targeted application. In this study, the nano-hydroxyapatite/polylactide composites were used as the matrix and continuous phosphate glass fibres (PGF) served as the major reinforcement to obtain the nano-HA/PGF/PLA hybrid composites. While the PGF volume fraction remained constant (25%), the nano-HA content (in weight) varied from 0% to 20%. As nano-HA loading increased, the flexural modulus of the composites increased from 8.70 ± 0.35 GPa to 14.97 ± 1.30 GPa, and the flexural strengths were enhanced from 236.31 ± 10.83 MPa to 310.55 ± 22.88 MPa. However, it is found that the degradation rates are higher with more nano-HA loaded. Enhanced water absorption ability, as well as increased voids in the composites is possible reasons for the accelerated degradation of composites with higher nano-HA loading. The hybrid composites possess mechanical properties that are superior to most of the HA/PLA composites in previous research while maintaining the biodegradability. With a proper loading of nano-HA in composites of 10 weight percent, the composites are also found with improved mechanical properties without catastrophic degradation. The composites developed in this study have great potential as biodegradable bone fixation device with enhanced load-bearing ability as confirmed and superior bioactivity as anticipated.

Highlights

Stabilization of fractured sites is essential in the healing process of bone fractures
As weight fraction of nano-HA in matrices increased from 0% to 20%, a gradual increase of average flexural strengths from 236.31 ± 10.83 MPa to 310.55 ± 22.88 MPa was observed
Comparing to the control group, the relative increment of flexural strengths are approximately 9%, 11%, 19% and 31% as nano-HA loading increased by every 5%, respectively

Summary

Introduction

Stabilization of fractured sites is essential in the healing process of bone fractures. The most common practice nowadays is implantation of internal fixation devices, such as fixation plates and screws, to limit the strain of fractured bone segments for endochondral osteogenesis [1]. Many problems arise with the use of metallic implants. The mismatching of mechanical stiffness between metals and human cortical bone might lead to stress shielding of the new bones, resulting in osteoporosis of regrown bones and risks of secondary bone fractures [4]. It is considered that to eliminate the problems mentioned above, the novel materials shall possess bone-mimicking mechanical properties so that the implant is just stiff enough for the load-bearing activities in daily life without triggering the stress-shielding. The implant should be fully resorbed/degraded in the human body after the healing process is done

Methods

Results

Discussion

Conclusion