Structural and Viscoelastic Properties of Layer-by-Layer Extracellular Matrix (ECM) Nanofilms and Their Interactions with Living Cells.

Modulation of living cell surfaces by chemical and biological engineering and the control of cellular functions has enormous potential for immunotherapy, transplantation, and drug delivery. However, traditional detection techniques have limitations in the identification of physical properties of viscoelastic films and interaction with living cells in real time. Here, we present the structural analysis of extracellular matrix (ECM) based nanofilms and their interaction with living cells using a quartz crystal microbalance (QCM) with dissipation (QCM-D), multiple parameter surface plasmon resonance (SPR), and flow cytometry measurements. QCM-D measurements according to the Voigt-based viscoelastic model allowed for the evaluation of the kinetic adsorption of extracellular matrix (ECM) proteins and physical parameters of viscoelastic ECM-nanofilms in a swelled state. These results reflected the characteristics of viscoelastic films as compared to Sauerbrey's equation. Moreover, we found that gelatin molecules played a crucial role as a binder to build up layered films and control their properties. Using the multiple parameter SPR approach, we confirmed the interaction between FN-G nanofilms and living cells from signal response in real time which was different from the gold substrate-protein signal. Moreover, flow cytometry analysis supported the importance of the domain interaction between the RGD sequence in FN and integrin as a driving force to form the films on cell surfaces. The use of three different analyses supported clarification of the contribution of the protein-protein interaction and viscoelastic properties of ECM films and investigation of the interaction between films and living cells. The knowledge regarding protein-protein and protein-cell interaction in real time would make a contribution to biomaterial design by using protein interactions for modulating the living cell surfaces in biomedical applications.