ABSTRACT
Effective delivery of DNA to direct cell behavior in a well defined three dimensional scaffold offers a superior approach in tissue engineering. In this study, we synthesized biodegradable nanostructured hydrogels with tunable physical properties for cell and gene delivery. The hydrogels were formed via Michael addition chemistry by reacting a four-arm acrylate-terminated PEG with a four-arm thiol-functionalized PEG. Nanosized micelles self-assembled from the amphiphilic PEG-b-polycarbonate diblock copolymer, having reactive end-groups, were chemically incorporated into the hydrogel networks at various contents. The use of Michael addition chemistry allows for in situ hydrogel formation under the physiological conditions. Mechanical property analysis of the hydrogels revealed a correlation between the content of micelles and the storage modulus of the hydrogels. Internal morphology of hydrogels was observed using a field emission scanning electron microscope, which showed that the number and/or size of the pores in the hydrogel increased with increasing micelle content due to reduced crosslinking degree. There exists an optimal micelle content for cell proliferation and gene transfection. MTT assays demonstrated the highest cell viability in the hydrogel with 20% micelles. The gene expression level in hMSCs in the hydrogel with 20% micelles was also significantly higher than that in the hydrogel without micelles. The enhanced cell viability and gene expression in the hydrogel with the optimized micelle content are likely attributed to the physical properties that provide a better environment for cell-matrix interactions. Therefore, incorporating micelles into the hydrogel is a good strategy to control cellular behavior in 3-D through changes in physical properties of the microenvironment.
Subject(s)
Gene Transfer Techniques , Hydrogels/chemistry , Mesenchymal Stem Cells/metabolism , Nanostructures/chemistry , Physical Phenomena , Polyethylene Glycols/chemistry , Cell Death , Cell Survival , DNA/metabolism , Elastic Modulus , Humans , Hydrogels/chemical synthesis , Luciferases/metabolism , Magnetic Resonance Spectroscopy , Mesenchymal Stem Cells/cytology , Micelles , Nanostructures/ultrastructure , Polycarboxylate Cement/chemical synthesis , Polycarboxylate Cement/chemistry , Polyethylene Glycols/chemical synthesis , Sulfones/chemical synthesis , Sulfones/chemistry , Surface-Active Agents/chemistry , TransfectionABSTRACT
Current tissue engineering approaches combine different scaffold materials with living cells to provide biological substitutes that can repair and eventually improve tissue functions. Both natural and synthetic materials have been fabricated for transplantation of stem cells and their specific differentiation into muscles, bones, and cartilages. One of the key objectives for bone regeneration therapy to be successful is to direct stem cells' proliferation and to accelerate their differentiation in a controlled manner through the use of growth factors and osteogenic inducers. Here we show that graphene provides a promising biocompatible scaffold that does not hamper the proliferation of human mesenchymal stem cells (hMSCs) and accelerates their specific differentiation into bone cells. The differentiation rate is comparable to the one achieved with common growth factors, demonstrating graphene's potential for stem cell research.