Bioluminescence imaging on-chip platforms for non-invasive high-content bioimaging

Incorporating non-invasive biosensing features in organ-on-chip models is of paramount importance for a wider implementation of these advanced in vitro microfluidic platforms. Optical biosensors, based on Bioluminescence Imaging (BLI), enable continuous, non-invasive, and in-situ imaging of cells, tissues or miniaturized organs without the drawbacks of conventional fluorescence imaging. Here, we report the first-of-its-kind integration and optimization of BLI in microfluidic chips, for non-invasive imaging of multiple biological readouts. The cell line HEK293T-GFP was engineered to express NanoLuc® luciferase under the control of a constitutive promoter and were cultured on-chip in 3D, in standard ECM-like hydrogels, to assess optimal cell detection conditions. Using real-time in-vitro dual-color microscopy, Bioluminescence (BL) and fluorescence (FL) were detectable using distinct imaging setups. Detection of the bioluminescent signals were observed at single cell resolution on-chip 20 min post-addition of Furimazine substrate and under perfusion. All hydrogels enabled BLI with higher signal-to-noise ratios as compared to fluorescence. For instance, agarose gels showed a ∼5-fold greater BL signal over background after injection of the substrate as compared to the FL signal. The use of BLI with microfluidic chip technologies opens up the potential for simultaneous in situ detection with continuous monitoring of multicolor cell reporters. Moreover, this can be achieved in a non-invasive manner. BL has great promise as a highly desirable biosensor for studying organ-on-chip platforms.