Protease sensing PEG hydrogels
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1
University of Zurich, Obstetrics, Switzerland
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2
Harvard University, School of Engineering and Applied Sciences, United States
Introduction: Extracellular matrices (ECM), especially during tissue formation and regeneration, are continuously remodeled and adapted to physiological needs. Biomimetic materials which support cell function and tissue regeneration have been designed with sites for cell adhesion, proteolytic degradation and growth factor immobilization. However, the engineering of complex reciprocal interactions between biomaterials and cells have only recently been initiated. Based on Streptavidin (Strep)-linker modules we design enzymatically cross-linked poly(ethylene glycol) PEG hydrogels[2] which independent of materials stability release growth factors in response to local proteolytic environments.
Materials and Methods: Strep-based matrix metalloproteinase (MMP) plasmin sensitive or non-degradable linker modules were recombinantly expressed and purified[1]. The degradability of Strep-linkers was determined by the addition of plasmin, MMP-1 and MMP-2. Enzymatically cross-linked poly(ethylene glycol) (PEG)-based hydrogels were formed in presence of Strep-linkers. Binding of biotinylated bone morphogenetic protein (BMP-2-biotin) to Strep-linker modified PEG hydrogels as well as their release in presence or absence of plasmin, MMP-1 and MMP-2 was determined by ELISA or western blotting. Human bone marrow derived mesenchymal stem cells (hBM-MSCs) were encapsulated hydrogels which were modified with degradable or non-degradable Strep-linkers and contained immobilized BMP-2-biotin. Osteogenic differentiation of hBM-MSCs was determined after 8 days of culture by determination of alkaline phosphatase (ALP) expression. Osteogenic differentiation was quantified by comparison with ALP expression of cells cultured in presence of increasing concentrations of BMP.
Results: The modular Strep-linkers enable the formation of hydrogels which stably immobilize BMP-2-biotin. In presence of MMP or plasmin (each 2nM) the release of BMP-2-biotin from the non-degradable linker module is slow but can be significantly amplified from MMP or plasmin sensitive linkers. Hydrogels containing non-degradable Strep-linker immobilized BMP-2-biotin moderately stimulated the osteogenic differentiation of encapsulated hBM-MSCs. In contrast, if Strep-linkers were MMP or plasmin degradable the osteogenic differentiation was strongly enhanced.
Conclusion: Our work shows that release of BMP-2 from PEG hydrogels can be reinforced in presence of significant amounts of proteolytic enzymes leading to enhanced osteogenesis. Furthermore, this system in combination with the previously established IL-4 / IL-4 reporter cells system[3] could be used to determine the concentration and distribution of proteolytic in 3D cultures.
References:
[1] Metzger S. et al. Adv. Health.Mat. 2015
[2] Ehrbar M. et al. Biomacromolecules 2007
[3] Lienemann P.S. et al. Adv. Healthc.Mater. 2013
Keywords:
enzyme,
stimuli-response,
Environmental response,
matrix-cell interaction
Conference:
10th World Biomaterials Congress, Montréal, Canada, 17 May - 22 May, 2016.
Presentation Type:
Poster
Topic:
Environmentally sensitive biomaterials
Citation:
Ehrbar
M,
Metzger
S and
Lienemann
PS
(2016). Protease sensing PEG hydrogels.
Front. Bioeng. Biotechnol.
Conference Abstract:
10th World Biomaterials Congress.
doi: 10.3389/conf.FBIOE.2016.01.00094
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Received:
27 Mar 2016;
Published Online:
30 Mar 2016.