Conjugate Addition Reactions Combined with Free-Radical Cross-Linking for the Design of Materials for Tissue Engineering

TLDR

The study aims to produce bioactive tissue‑engineering scaffolds by photopolymerizing PEG‑diacrylamide materials in direct contact with cells. PEG‑diacrylamide was synthesized and functionalized with thiol‑containing peptides via acrylamide–thiol chemistry, then the remaining acrylamide groups were cross‑linked by photoinitiated free‑radical polymerization, allowing scaffold formation at room temperature in aqueous solution. The resulting hydrogels’ stiffness, modulated by photopolymerization conditions, dictated cell spreading, and although the PEG matrix resists protein adsorption, cells were able to deposit extracellular matrix that adhered to the gels.

Abstract

PEG-diacrylamide was synthesized and utilized to make materials for tissue engineering. Acrylamide groups readily react with thiol groups, and peptides containing a single thiol group were coupled to the PEG-diacrylamide in aqueous solution at room temperature in about 2 h. If only a portion of the acrylamide groups were targeted for reaction with peptide, sufficient amounts of PEG-diacrylamide remained to be polymerized by free-radical mechanisms via photoinitiation. The photopolymerization step can be performed in contact with cells, providing a means to produce bioactive scaffolds for tissue engineering. The photopolymerization conditions and precursor composition greatly affect the stiffness of the materials, which subsequently affected cell spreading. The kinetics and extent of cell spreading on the bioactive materials were measured and compared to cell spreading on tissue culture polystyrene. Although the PEG materials resist protein adsorption, the experiments suggest that the cells can secrete extracellular matrix that can adhere to the gels.