title: Influence of hydroxyapatite crystallization temperature and concentration on stress transfer in wet-spun nanohydroxyapatite-chitosan composite fibres.
abstract: Hydroxyapatite possesses appropriate osteoconductivity and biocompatibility for hard-tissue replacement implants but suffers from brittleness. One approach to overcome this problem is to incorporate nanometre hydroxyapatite (nHA) into a polymer matrix, such as chitosan, to yield a hydroxyapatite-chitosan (HC) composite. Here, a novel HC composite was synthesized and its elastic properties were investigated by varying (1) nHA concentration and (2) crystallization temperature (T), where T is a parameter which influences the morphology of the crystals. Crystals of nHA were precipitated at T = 40 degrees C and 100 degrees C, blended in a chitosan matrix, and wet-spun to yield fibres of HC composites at 5, 15, 20 and 40% concentrations (mass fraction of nHA). Scanning electron microscopy and energy-dispersive x-ray spectroscopy revealed a uniform distribution of nanocrystallites within the fibre. Tensile testing revealed that HC fibres, which comprised nHA treated at T = 100 degrees C, possessed low tensile strength, sigma(0), and stiffness, E, at low nHA concentrations but high sigma(0) and E at higher concentrations, i.e. beyond a 15% mass fraction of nHA. However, with nHA treated at T = 40 degrees C, the fibres yielded high sigma(0) and E at low nHA concentrations but low sigma(0) and E at high concentrations. The results strongly implicate the underlying effect of crystallite morphology on stress transfer at different concentrations.
authors.affiliation: School of Engineering, Republic Polytechnic, Woodlands Ave 9, Singapore.
authors.forename: J Z
authors.initials: JZ
authors.lastname: Xie
authors.forename: S
authors.initials: S
authors.lastname: Hein
authors.forename: K
authors.initials: K
authors.lastname: Wang
authors.forename: K
authors.initials: K
authors.lastname: Liao
authors.forename: K L
authors.initials: KL
authors.lastname: Goh
mesh_terms: D018786:Bone Substitutes / Q000737:chemistry*; D048271:Chitosan / Q000737:chemistry*; D003460:Crystallization / Q000379:methods*; D017886:Durapatite / Q000737:chemistry*; D004548:Elasticity; D006244:Hardness; D008422:Materials Testing; D049329:Nanostructures / Q000737:chemistry* / Q000648:ultrastructure*; D010316:Particle Size; D012399:Rotation; D013314:Stress, Mechanical; D013696:Temperature; D013718:Tensile Strength; D017155:Wettability
chemical_list: D018786:Bone Substitutes; D048271:Chitosan; D017886:Durapatite