Mechanical Properties and Bioactivity of Poly(Lactic Acid) Composites Containing Poly(Glycolic Acid) Fiber and Hydroxyapatite Particles.

Han-Seung Ko,Jae Young Jho,Doyoung Lee,Sangwoon Lee

doi:10.3390/nano11010249

Abstract

To enhance the mechanical strength and bioactivity of poly(lactic acid) (PLA) to the level that can be used as a material for spinal implants, poly(glycolic acid) (PGA) fibers and hydroxyapatite (HA) were introduced as fillers to PLA composites. To improve the poor interface between HA and PLA, HA was grafted by PLA to form HA-g-PLA through coupling reactions, and mixed with PLA. The size of the HA particles in the PLA matrix was observed to be reduced from several micrometers to sub-micrometer by grafting PLA onto HA. The tensile and flexural strength of PLA/HA-g-PLA composites were increased compared with those of PLA/HA, apparently due to the better dispersion of HA and stronger interfacial adhesion between the HA and PLA matrix. We also examined the effects of the length and frequency of grafted PLA chains on the tensile strength of the composites. By the addition of unidirectionally aligned PGA fibers, the flexural strength of the composites was greatly improved to a level comparable with human compact bone. In the bioactivity tests, the growth of apatite on the surface was fastest and most uniform in the PLA/PGA fiber/HA-g-PLA composite.

Highlights

Mechanical strength and bioactivity have been cited as the two most important properties that materials for spinal implants should have
Aliphatic polyesters including polycaprolactone (PCL), poly(lactic acid) (PLA), and poly(glycolic acid) (PGA) are biodegradable polymers that were considered for this application [3,4]
By introducing coupling agents into the grafting reaction, a larger amount of PLA was grafted to the HA

Summary

Introduction

Mechanical strength and bioactivity have been cited as the two most important properties that materials for spinal implants should have. Metal implants have caused the stress shielding effect, a phenomenon of low load on lower-modulus material around the implant. This has been problematic in the implants, reducing the density of the regenerated bones [1]. Since polymers could avoid the stress shielding effect due to their lower modulus than metals, the use of biodegradable polymers as implant materials has been sought [2]. While PGA exhibited good mechanical properties comparable to engineering plastics, the biodegradation rate of PGA was too high [6]. This could cause the implant to be degraded before the bone was fully regenerated. As PLA showed a decent balance between mechanical properties and biodegradation rate, many studies have employing PLA as the spinal implant material have been conducted [7,8,9,10]

Methods

Results

Conclusion