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Evaluation of novel injectable hydrogels for nucleus pulposus replacement
Author(s) -
Vernengo J.,
Fussell G. W.,
Smith N. G.,
Lowman A. M.
Publication year - 2008
Publication title -
journal of biomedical materials research part b: applied biomaterials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.665
H-Index - 108
eISSN - 1552-4981
pISSN - 1552-4973
DOI - 10.1002/jbm.b.30844
Subject(s) - peg ratio , swelling , self healing hydrogels , ethylene glycol , copolymer , materials science , compressive strength , polyethylene glycol , polymer chemistry , molar , stress relaxation , dissolution , elastic modulus , monomer , composite material , chemical engineering , polymer , chemistry , creep , organic chemistry , dentistry , finance , engineering , economics , medicine
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