Photo-responsive Photonic Hydrogel: in-situ Manipulating and Monitoring Cell Scaffold Stiffness

Building scaffolds with heterogeneous and reconfigurable mechanical properties have been recognized as the key to recapitulate the natural extracellular microenvironments for in-vitro cell incubation systems. However, in-situ changing and tracking the mechanical change of the cell scaffolds are still challenging. In this paper we developed a novel strategy to serve this problem. We show a convenient method for tracking the hardness of cell scaffolds in a non-invasively manner via its color change. This is achieved by introducing colloidal crystal feature into a photo-reconfigurable hydrogel, which leads to a smart hydrogel scaffold with dynamically adjustable and in-situ monitorable mechanical properties. The stiffness of the hydrogel can be spatiotemporally and dynamically manipulated by light, meanwhile its changes can be in-situ recognized by analyzing the hydrogel color. This allows to real-time control and investigate the extracellular stiffness in cell incubation systems in a non-invasive fashion. In addition, the cell-matrix interactions on this smart scaffold can be easily understood owing to the simultaneously observation of cell morphology and matrix stiffness under microscope. We also show that such hydrogel could be used as user-designable microarray for cell culture applications.