Researcher(s)
- Shriya Bagdi, Neuroscience, University of Delaware
Faculty Mentor(s)
- Jason Gleghorn, Biomedical Engineering, University of Delaware
Abstract
Microphysiological systems (MPS) are powerful tools to elucidate organ development. These 3D platforms recapitulate tissue function by incorporating diverse cell types and complex cellular architectures, addressing limitations of 2D in vitro models. However, MPS devices often lack spatial control of signaling molecules and drug concentrations, a key component of the tissue microenvironment. Therefore, we have developed a simple source-sink concentration gradient generator to establish patterned molecule concentrations within the platform, which can be transferred to a cell-containing organ-on-a-chip. The polydimethylsiloxane (PDMS) device was partially filled with 3% w/v agarose, bounded by plastic histology molds to create source and sink reservoirs. Fluorescein sodium salt (MW 376.27) and 70kDa Texas Red Dextran were selected as probe molecules to visualize and validate the biochemical gradient. Gradient formation at various time points over 9 days was characterized with 12.5 μg/mL 70kDa dextran in PBS as the source molecule. Gradients were quantified as the fluorescence over the source-sink connecting bridge distance. The device successfully maintained a concentration gradient at all time points. The effect of source molecule concentration on gradient formation was investigated using 5uM, 10uM, and 25uM fluorescein sodium salt in Dulbecco’s Modified Eagle Medium (DMEM). Moreover, the 25 µM fluorescein sodium salt platform was placed on a collagen gel (4 mg/mL) for gradient transfer through the hydrogel, which formed gradients to a 1 mm depth. Transfer to this depth allows these methods to be applied for morphogen gradient transfer to collagen-based organ-on-a-chip systems. This platform enables tunability of signaling molecule concentrations to inform patterned morphogen-induced stem cell and organoid differentiation, and to model drug diffusion effects on cell populations. The system is widely applicable to tissue engineering platforms: it allows for gradients to be externally sourced from the MPS, supports long-term gradient application, and uses accessible materials.