Dataset Information

Characterization of the crosslinking kinetics of multi-arm poly(ethylene glycol) hydrogels formed via Michael-type addition.

ABSTRACT: Tunable properties of multi-arm poly(ethylene glycol) (PEG) hydrogel, crosslinked by Michael-type addition, support diverse applications in tissue engineering. Bioactive modification of PEG is achieved by incorporating integrin binding sequences, like RGD, and crosslinking with tri-functional protease sensitive crosslinking peptide (GCYKNRGCYKNRCG), which compete for the same reactive groups in PEG. This competition leads to a narrow range of conditions that support sufficient crosslinking density to provide structural control. Kinetics of hydrogel formation plays an important role in defining the conditions to form hydrogels with desired mechanical and biological properties, which have not been fully characterized. In this study, we explored how increasing PEG functionality from 4 to 8-arms and the concentration of biological moieties, ranging from 0.5 mM to 3.75 mM, affected the kinetics of hydrogel formation, storage modulus, and swelling after the hydrogels were allowed to form for 15 or 60 minutes. Next, human bone marrow stromal cells were encapsulated and cultured in these modified hydrogels to investigate the combined effect of mechano-biological properties on phenotypes of encapsulated cells. While the molar concentration of the reactive functional groups (-vinyl sulfone) was identical in the conditions comparing 4 and 8-arm PEG, the 8-arm PEG formed faster, allowed a greater degree of modification, and was superior in three-dimensional culture. The degrees of swelling and storage modulus of 8-arm PEG were less affected by the modification compared to 4-arm PEG. These findings suggest that 8-arm PEG allows a more precise control of mechanical properties that could lead to a larger spectrum of tissue engineering applications.

SUBMITTER: Kim J

PROVIDER: S-EPMC4749500 | biostudies-literature | 2016 Feb

REPOSITORIES: biostudies-literature

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Characterization of the crosslinking kinetics of multi-arm poly(ethylene glycol) hydrogels formed via Michael-type addition.

Kim Jiwon J Kong Yen P YP Niedzielski Steven M SM Singh Rahul K RK Putnam Andrew J AJ Shikanov Ariella A

Soft matter 20160111 7

Tunable properties of multi-arm poly(ethylene glycol) (PEG) hydrogel, crosslinked by Michael-type addition, support diverse applications in tissue engineering. Bioactive modification of PEG is achieved by incorporating integrin binding sequences, like RGD, and crosslinking with tri-functional protease sensitive crosslinking peptide (GCYKNRGCYKNRCG), which compete for the same reactive groups in PEG. This competition leads to a narrow range of conditions that support sufficient crosslinking densi ...[more]

PMID: 26750719

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Project description:Human mesenchymal stem cells (hMSCs) are motile cells that migrate from their native niche to wounded sites where they regulate inflammation during healing. New materials are being developed as hMSC delivery platforms to enhance wound healing. To act as an effective wound healing material, the hydrogel must degrade at the same rate as tissue regeneration, while maintaining a high cell viability. This work determines the kinetics and mechanism of cell-mediated degradation in hMSC-laden poly(ethylene glycol) (PEG) hydrogels. We use a well-established hydrogel scaffold that is composed of a backbone of four-arm star PEG functionalized with norbornene that is cross-linked with a matrix metalloproteinase (MMP) degradable peptide. This peptide sequence is cleaved by cell-secreted MMPs, which allow hMSCs to actively degrade the hydrogel during motility. Three mechanisms of degradation are characterized: hydrolytic, noncellular enzymatic and cell-mediated degradation. We use bulk rheology to characterize hydrogel material properties and quantify degradation throughout the entire reaction. Hydrolysis and noncellular enzymatic degradation are first characterized in hydrogels without hMSCs, and follow first-order and Michaelis-Menten kinetics, respectively. A high cell viability is measured in hMSC-laden hydrogels, even after shearing on the rheometer. After confirming hMSC viability, bulk rheology characterizes cell-mediated degradation. When comparing cell-mediated degradation to noncellular degradation mechanisms, cell-mediated degradation is dominated by enzymatic degradation. This indicates hydrogels with hMSCs are degraded primarily due to cell-secreted MMPs and very little network structure is lost due to hydrolysis. Modeling cell-mediated degradation provides an estimate of the initial concentration of MMPs secreted by hMSCs. By changing the concentration of hMSCs, we determine the initial MMP concentration increases with increasing hMSC concentration. This work characterizes the rate and mechanism of scaffold degradation, giving new insight into the design of these materials as implantable scaffolds.

Dataset Information

Characterization of the crosslinking kinetics of multi-arm poly(ethylene glycol) hydrogels formed via Michael-type addition.

Publications

Characterization of the crosslinking kinetics of multi-arm poly(ethylene glycol) hydrogels formed via Michael-type addition.

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