Islet-on-a-Chip Provides an Optical Window into Cellular Metabolism and Insulin Secretion

Many labs are actively exploring beta-cell heterogeneity and how it relates to glucose-stimulated insulin secretion and type 2 diabetes. In particular beta-cells appear to exhibit significant variability in metabolic gene expression, yet it is unclear how this variability ultimately impacts islet function since beta-cells are electrically coupled to one another. Our goal is to assess the impact of beta-cell heterogeneity on islet function by combining quantitative fluorescence microscopy (e.g. genetically encoded metabolic sensors) with islet-on-a-chip microfluidic devices designed to hold individual islets stationary for imaging purposes. We hypothesize that due to electrical coupling, beta-cells non-responsive to glucose could inhibit overall individual islet secretion. Islets in our devices are held against a glass coverslip facilitating live cell imaging with controlled non-turbulent laminar flow. We are now leveraging these features to design a multiparametric islet-on-a-chip device to dynamically assay the metabolism (oxygen consumption rate) and function (insulin secretion) of individual islets. More specifically, we are placing oxygen sensitive fluorophores into microwells adjacent to each islet to measure oxygen consumption rates. We have thus far used COMSOL finite element analysis to optimize the cross-sectional area and depth of the microwells, and explored the dynamic range of multiple oxygen sensitive fluorophores. Finally, we are developing an antibody competition assay to measure insulin secretion. We have selected the optimal monoclonal antibody and determined the detection sensitivity using fluorescence anisotropy imaging. Ultimately, we aim to combine these methods with cellular metabolic imaging to determine the impact of non-responsive beta-cells in dictating islet insulin secretion.