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Small changes in polymer chemistry have a large effect on the bone–implant interface:: evaluation of a series of degradable tyrosine-derived polycarbonates in bone defects

Paper ID Volume ID Publish Year Pages File Format Full-Text
13916 974 1999 10 PDF Available
Title
Small changes in polymer chemistry have a large effect on the bone–implant interface:: evaluation of a series of degradable tyrosine-derived polycarbonates in bone defects
Abstract

In a series of homologous, tyrosine-based polycarbonates, small changes in the chemical structure of the polymer pendent chain were found to affect the bone response in a long-term (1280 d) implantation study. Identically sized pins, prepared from poly(DTE carbonate), poly(DTB carbonate), poly(DTH carbonate), and poly(DTO carbonate) were implanted transcortically in the proximal tibia and the distal femur of skeletally mature New Zealand White Rabbits. The tissue response at the bone–implant interface was characterized in terms of the absence of a fibrous capsule (direct bone apposition, indicative of a bone bonding response) or the presence of a fibrous capsule (referred to as the encapsulation response). The relative frequency of direct bone apposition versus encapsulation was recorded for each polymer throughout the entire period of the study. While all four polymers were tissue compatible, there was a correlation between the chemical structure of the pendent chain and the type of bone response observed, with poly(DTE carbonate) having the highest tendency to elicit direct bone apposition. Based on in vivo degradation data and the ability of model polymers with carboxylate groups at their surface to chelate calcium ions, it is proposed that the ability of poly(DTE carbonate) to bond to bone is caused by the facile hydrolysis of the pendent ethyl ester groups which creates calcium ion chelation sites on the polymer surface. The incorporation of calcium chelation sites into the chemical structure of an implant material appears to be a key requirement if direct bone apposition/bone bonding is desired. This study demonstrates that very subtle changes in the chemical composition of an implant material can have significant effects on the long-term tissue response in a clinically relevant model.

Keywords
Tyrosine-based polycarbonate; Biomaterial; Prosthesis–bone interface; Bone–material interactions; Degradable polymer; Poly(DTE carbonate); Structure–property relationships; Calcium ion chelation; Bone apposition; Bone bonding
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Small changes in polymer chemistry have a large effect on the bone–implant interface:: evaluation of a series of degradable tyrosine-derived polycarbonates in bone defects
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Publisher
Database: Elsevier - ScienceDirect
Journal: Biomaterials - Volume 20, Issues 23–24, December 1999, Pages 2203–2212
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Bioengineering
Get Full-Text Now
Don't Miss Today's Special Offer
Price was $35.95
You save - $31
Price after discount Only $4.95
100% Money Back Guarantee
Full-text PDF Download
Online Support
Any Questions? feel free to contact us