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Dissertation
Injectable bioadhesive hydrogels for nucleus pulposus replacement and repair of the damaged intervertebral disc
Doctor of Philosophy (Ph.D.), Drexel University
Jan 2007
DOI:
https://doi.org/10.17918/etd-1315
Abstract
Researchers have begun to realize the potential benefits of treating intervertebral disc degeneration by replacing the nucleus pulposus. One of the material classes being studied for nucleus replacement is the hydrogel, a three-dimensional, hydrated polymer network. The development of an injectable hydrogel nucleus replacement would have important clinical consequences because it could be injected non-invasively using a needle. Aqueous solutions of poly(N-isopropylacrylamide), or PNIPAAm, have a lower critical solution temperature (LCST) between room and body temperature, making it suitable for an injectable implant material. Aqueous polymer solutions could be injected as a free flowing liquid at 25°C and solidify to a gel within the body at 37°C. At physiological temperatures, PNIPAAm homopolymer gels hold little water and show poor elastic recovery. In the work, the swelling and mechanical properties of PNIPAAm gels are tailored by polymerizing NIPAAm in the presence of poly(ethylene) glycol dimethacrylate (PEGDM), thereby creating PNIPAAm-PEG branched copolymers. The effect of PEG molecular weight and NIPAAm/PEG molar ratio on the water content, stiffness, and elasticity of the hydrogels was determined. In addition, a suitable material candidate for nucleus pulposus replacement was chosen from this class of hydrogels. The copolymer formulation was optimized to minimize implant water loss following implantation into the intradiscal environment, allowing the implant to remain space filling in the nuclear cavity. Bioadhesive properties were then imparted to the hydrogel system by blending it with the amine containing polymer poly(ethylene imine) (PEI). After gelation in the disc, the implant will be crosslinked with itself and with the surrounding tissues by the injection of a dialdehyde. This approach will help secure the implant in place, reducing the risk of implant migration or extrusion. The bioadhesive material also has the potential to function as tissue adhesive for the repair of the damaged annulus fibrosis.
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Details
- Title
- Injectable bioadhesive hydrogels for nucleus pulposus replacement and repair of the damaged intervertebral disc
- Creators
- Jennifer Vernengo - DU
- Contributors
- Anthony M. Lowman (Advisor) - Drexel University (1970-)
- Awarding Institution
- Drexel University
- Degree Awarded
- Doctor of Philosophy (Ph.D.)
- Publisher
- Drexel University; Philadelphia, Pennsylvania
- Resource Type
- Dissertation
- Language
- English
- Academic Unit
- Chemical (and Biological) Engineering [Historical]; College of Engineering (1970-2026); Drexel University
- Other Identifier
- 1315; 991014632726604721