Controlled release and gradient formation of human glial-cell derived neurotrophic factor from heparinated poly(ethylene glycol) microsphere-based scaffolds

Jacob L. Roam, Peter K. Nguyen, Donald L. Elbert

Research output: Contribution to journalArticlepeer-review

28 Scopus citations

Abstract

Introduction of spatial patterning of proteins, while retaining activity and releasability, is critical for the field of regenerative medicine. Reversible binding to heparin, which many biological molecules exhibit, is one potential pathway to achieve this goal. We have covalently bound heparin to poly(ethylene glycol) (PEG) microspheres to create useful spatial patterns of glial-cell derived human neurotrophic factor (GDNF) in scaffolds to promote peripheral nerve regeneration. Labeled GDNF was incubated with heparinated microspheres that were subsequently centrifuged into cylindrical scaffolds in distinct layers containing different concentrations of GDNF. The GDNF was then allowed to diffuse out of the scaffold, and release was tracked via fluorescent scanning confocal microscopy. The measured release profile was compared to predicted Fickian models. Solutions of reaction-diffusion equations suggested the concentrations of GDNF in each discrete layer that would result in a nearly linear concentration gradient over much of the length of the scaffold. The agreement between the predicted and measured GDNF concentration gradients was high. Multilayer scaffolds with different amounts of heparin and GDNF and different crosslinking densities allow the design of a wide variety of gradients and release kinetics. Additionally, fabrication is much simpler and more robust than typical gradient-forming systems due to the low viscosity of the microsphere solutions compared to gelating solutions, which can easily result in premature gelation or the trapping of air bubbles with a nerve guidance conduit. The microsphere-based method provides a framework for producing specific growth factor gradients in conduits designed to enhance nerve regeneration.

Original languageEnglish (US)
Pages (from-to)6473-6481
Number of pages9
JournalBiomaterials
Volume35
Issue number24
DOIs
StatePublished - Aug 2014

All Science Journal Classification (ASJC) codes

  • Bioengineering
  • Ceramics and Composites
  • Biophysics
  • Biomaterials
  • Mechanics of Materials

Keywords

  • GDNF
  • Gradient
  • Heparin
  • Hydrogel
  • Microsphere
  • Release

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