Hydroxyapatite–Carbon Nanotube Composites for Biomedical Applications: A Review

Abstract

Hydroxyapatite (HA) has been used in clinical bone graft procedures for more than 25 years. However, its poor tensile strength and fracture toughness compared with bone make it unsuitable for major load‐bearing devices. Carbon nanotubes (CNTs), with their high aspect ratio and excellent mechanical properties, have the potential to strengthen and toughen HA without offsetting its bioactivity, thus opening up a wider range of possible clinical uses for the material. This review discusses techniques for synthesizing and processing HA–CNT composites, as well as barriers that still remain to their successful development for clinical application.

Calcium orthophosphate-based biocomposites and hybrid biomaterials

“…Another research group performed compression tests on bulk HA/nanotubes biocomposites and found an increase in strength over single-phase HA [246]. However, the highest compressive strength they achieved for any material was only 102 MPa, which is similar to that of cortical bone but much lower than the typical values for dense HA [874]. More complex formulations, such as poly-L-lysine/HA/carbon nanotube hybrid nanocomposites, have also been developed [884].…”

“…Carbon nanotubes with their small dimensions, a highaspect-ratio (length-to-diameter) as well as the exceptional mechanical properties, including extreme flexibility and strength, significant resistance to bending, high resilience and the ability to reverse any buckling of the tube, have the excellent potential to accomplish necessary mechanical properties [874]. Recent studies have even suggested that they may possess some bioactivity [875][876][877][878].…”

“…Additionally, non-functionalized carbon nanotubes tend to agglomerate and form bundles; besides, they are soluble in neither water nor organic solvents. Chemical functionalization allows carbon nanotubes to be dispersed more easily, which can improve interfacial bonding with calcium orthophosphates [247,874].…”

“…The magnitude of the interfacial bond between the phases determines how well a weak matrix transmits stress to the strong fibers. However, while a bond between the matrix and reinforcement must exist for the purpose of stress transfer, it should not be so strong that it prevents toughening mechanisms, such as debonding and fiber pullout [874].…”

Biomedical Materials for Regenerating Bone Tissue Utilizing Marine Invertebrate

“…, (White et al, 2007). , 75% , Kim et al, 2003;Trinkunaite-Felsen et al, 2014), (Ma et al, 2003 in vitro in vivo (Parizi et al, 2013;Zhang et al, 2011).…”