Advanced Artificial Extracellular Matrices Using Amphiphilic Nanogel-Cross-Linked Thin Films To Anchor Adhesion Proteins and Cytokines

A novel type of nanogel-cross-linked (NanoClik) film composed of acryloyl-modified cholesterol-bearing pullulan nanogels with pentaerythritol tetra(mercaptoethyl)polyoxyethylene as a cross-linker is created through the Michael addition coupled with solvent evaporation. Tensile testing and atomic force microscopy show that the elastic property of the NanoClik films can be controlled by changing the cross-linker concentration. The NanoClik films strongly absorb proteins after simple immersion in solutions of functional proteins, including the hormone insulin, cytokine bone morphogenetic protein-2 (BMP-2), and vitronectin. The amphiphilic nanogels in the films induce this absorption by acting as anchoring and loading proteins. Mouse embryo fibroblast cells adhere to and proliferate on the NanoClik films anchoring vitronectin, while NanoClik films loaded with BMP-2 strongly increase the differentiation of human mesenchymal stem cells into osteoblasts. These results suggest that the NanoClik films act as a novel artificial extracellular matrix that enables the reservation of various biological proteins to the nanogels.