Evaluation of novel injectable hydrogels for nucleus pulposus replacement

Branched copolymers composed of poly(N‐isopropylacrylamide) (PNIPAAm) and poly(ethylene glycol) (PEG) are being investigated as an in situ forming replacement for the nucleus pulposus of the intervertebral disc. A family of copolymers was synthesized by varying the molecular weight of the PEG blocks...

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Published in:Journal of biomedical materials research. Part B, Applied biomaterials Applied biomaterials, 2008-01, Vol.84B (1), p.64-69
Main Authors: Vernengo, J., Fussell, G. W., Smith, N. G., Lowman, A. M.
Format: Article
Language:English
Subjects:
Acrylamides - administration & dosage
Acrylamides - chemistry
Acrylic Resins
Biocompatible Materials - chemistry
Chemical Phenomena
Chemistry, Physical
Elasticity
Hot Temperature
hydrogel
Hydrogels - administration & dosage
Hydrogels - chemistry
Injections
Intervertebral Disc
Materials Testing
Molecular Weight
nucleus replacement
PEG
PNIPAAm
Polyethylene Glycols - analysis
Polyethylene Glycols - chemistry
Polymers - administration & dosage
Polymers - chemistry
Prostheses and Implants
Solubility
Stress, Mechanical
swelling
Water - analysis
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Summary:Branched copolymers composed of poly(N‐isopropylacrylamide) (PNIPAAm) and poly(ethylene glycol) (PEG) are being investigated as an in situ forming replacement for the nucleus pulposus of the intervertebral disc. A family of copolymers was synthesized by varying the molecular weight of the PEG blocks and molar ratio of NIPAAm monomer units to PEG branches. Gel swelling, dissolution, and compressive mechanical properties were characterized over 90 days and stress relaxation behavior over 30 days immersion in vitro. It was found that the NIPAAm to PEG molar ratio did not affect the equilibrium swelling and compressive mechanical properties. However, gel elasticity exhibited a dependency on both the PEG block molecular weight and content. The equilibrium gel water content increased and compressive modulus decreased with increasing PEG block size. While all of the branched copolymers showed significant increases in stress relaxation time constant compared to the homopolymer (p < 0.05), the high PEG content PNIPAAm‐PEG (4600 and 8000 g/mol) exhibited the maximum elasticity. Because of its high water content, requisite stiffness and high elastic response, PNIPAAm‐PEG (4600 g/mol) will be further evaluated as a candidate material for nucleus pulposus replacement. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 2008
ISSN:1552-4973
1552-4981
DOI:10.1002/jbm.b.30844