title: A citric acid-based hydroxyapatite composite for orthopedic implants.
abstract: We describe a novel approach to process bioceramic microparticles and poly(diol citrates) into bioceramic-elastomer composites for potential use in orthopedic surgery. The composite consists of the biodegradable elastomer poly(1,8-octanediol-citrate) (POC) and the bioceramic hydroxyapatite (HA). The objective of this work was to characterize POC-HA composites and assess the feasibility of fabricating tissue fixation devices using machining and molding techniques. The mechanical properties of POC-HA composites with HA (40, 50, 60, 65wt.%) were within the range of values reported for tissue fixation devices (for POC-HA 65wt.%, S(b)=41.4+/-3.1, E(b)=501.7+/-40.3, S(c)=74.6+/-9.0, E(c)=448.8+/-27.0, S(t)=9.7+/-2.3, E(t)=334.8+/-73.5, S(s)=27.7+/-2.4, T(s)=27.3+/-4.9, all values in MPa). At 20 weeks, the weight loss of POC-HA composites ranged between 8 and 12wt.%, with 65wt.% HA composites degrading the slowest. Exposure of POC-HA to simulated body fluid resulted in extensive mineralization in the form of calcium phosphate with Ca/P of 1.5-1.7 similar to bone. POC-HA supported osteoblast adhesion in vitro and histology results from POC-HA samples that were implanted in rabbit knees for 6 weeks suggest that the composite is biocompatible. Synthesis of POC-HA is easy and inexpensive, does not involve harsh solvents or initiators, and the mechanical properties of POC-HA with 65wt.% HA are suitable for the fabrication of potentially osteoconductive bone screws.
authors.affiliation: Biomedical Engineering Department, Northwestern University, 2145 Sheridan Road, E310 Evanston, IL 60208, USA.
authors.forename: Hongjin
authors.initials: H
authors.lastname: Qiu
authors.forename: Jian
authors.initials: J
authors.lastname: Yang
authors.forename: Pradeep
authors.initials: P
authors.lastname: Kodali
authors.forename: Jason
authors.initials: J
authors.lastname: Koh
authors.forename: Guillermo A
authors.initials: GA
authors.lastname: Ameer
mesh_terms: D000818:Animals; D001863:Bone Screws; D018786:Bone Substitutes / Q000737:chemistry* / Q000378:metabolism*; D002113:Calcification, Physiologic; D019343:Citric Acid / Q000031:analogs & derivatives* / Q000737:chemistry / Q000378:metabolism; D017886:Durapatite / Q000737:chemistry / Q000378:metabolism; D006801:Humans; D008422:Materials Testing; D009985:Orthopedics; D010006:Osteoblasts / Q000166:cytology / Q000502:physiology; D011817:Rabbits; D013314:Stress, Mechanical
chemical_list: D018786:Bone Substitutes; C515169:POC-HA composite; D019343:Citric Acid; D017886:Durapatite