Dynamic compressive loading influences degradation behavior of PEG-PLA hydrogels

Biodegradable hydrogels are attractive 3D environments for cell and tissue growth. In cartilage tissue engineering, mechanical stimulation has been shown to be an important regulator in promoting cartilage development. However, the impact of mechanical loading on the gel degradation kinetics has not...

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Bibliographic Details
Published in:	Biotechnology and bioengineering Vol. 102; no. 3; pp. 948 - 959
Main Authors:	Nicodemus, G.D, Shiplet, K.A, Kaltz, S.R, Bryant, S.J
Format:	Journal Article
Language:	English
Published:	Hoboken Wiley Subscription Services, Inc., A Wiley Company 15-02-2009 Wiley Wiley Subscription Services, Inc
Subjects:	Analysis of Variance Biological and medical sciences Bioreactors Biotechnology Cell growth Chemical reactors Chemical synthesis degradable hydrogels Fundamental and applied biological sciences. Psychology Hydrogels Hydrogels - chemistry Hydrogels - metabolism Kinetics Lactates - metabolism Load mechanical loading Mechanical Phenomena poly(ethylene glycol) poly(lactic acid) Polyethylene Glycols - metabolism Polymers - metabolism Tissue engineering Tissue Engineering - methods Degradation Ethylene oxide polymer mechanical loading Lactic acid polymer degradable hydrogels poly(ethylene glycol) Dynamics Hydrogel poly(lactic acid)
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Summary:	Biodegradable hydrogels are attractive 3D environments for cell and tissue growth. In cartilage tissue engineering, mechanical stimulation has been shown to be an important regulator in promoting cartilage development. However, the impact of mechanical loading on the gel degradation kinetics has not been studied. In this study, we examined hydrolytically labile gels synthesized from poly(lactic acid)-b-poly(ethylene glycol)-b-poly-(lactic acid) dimethacrylate macromers, which have been used for cartilage tissue engineering. The gels were subject to physiological loading conditions in order to examine the effects of loading on hydrogel degradation. Initially, hydrogels were formed with two different cross-linking densities and subject to a dynamic compressive strain of 15% at 0.3, 1, or 3 Hz. Degradation behavior was assessed by mass loss, equilibrium swelling and compressive modulus as a function of degradation time. From equilibrium swelling, the pseudo-first-order reaction rate constants were determined as an indication of degradation kinetics. The application of dynamic loading significantly enhanced the degradation time for the low cross-linked gels (P < 0.01) while frequency showed no statistical differences in degradation rates or bulk erosion profiles. In the higher cross-linked gels, a 3 Hz dynamic strain significantly increased the degradation kinetics resulting in an overall faster degradation time by 6 days compared to gels subject to the 0.3 and 1 Hz loads (P < 0.0001). The bioreactor set-up also influenced overall degradation behavior where the use of impermeable versus permeable platens resulted in significantly lower degradation rate constants for both cross-linked gels (P < 0.001). The compressive modulus exponentially decreased with degradation time under dynamic loading. Together, our findings indicate that both loading regime and the bioreactor setup influence degradation and should be considered when designing and tuning a biodegradable hydrogel where mechanical stimulation is employed. Biotechnol. Bioeng. 2009; 102: 948-959.
Bibliography:	http://dx.doi.org/10.1002/bit.22105 ark:/67375/WNG-WFXFD6CX-V istex:4765347EE61D0EF7564F46B882F7AE667846410F ArticleID:BIT22105 National Institute of Dental and Craniofacial Research - No. K22DE016608 ObjectType-Article-2 SourceType-Scholarly Journals-1 ObjectType-Feature-1 content type line 23 ObjectType-Article-1 ObjectType-Feature-2
ISSN:	0006-3592 1097-0290
DOI:	10.1002/bit.22105