Co-culture Microdevice with Oxygen Gradient for Tumor Microenvironment Model and Metastasis Imaging

Tumor hypoxia is a major therapeutic problem since it decreases radiation effects and leads to metastasis. Oxygen is delivered to tumor tissue via abnormal and dysfunctional microvessels, which forms heterogeneity of tissue oxygenation in the tumor. Mimicking the oxygen gradient for cellular experiments in vitro is important to clarify the mechanisms involved in tumor biology, but the only method to produce hypoxic conditions at a constant level is using gas-controlled incubators, because there is currently no technique for creating an oxygen gradient using culture dishes. We designed a polydimethylsiloxane (PDMS) microfluidic device integrated with microchannels for cell cultures that enables visualization of cellular distribution under a microscope and co-culture to determine interactions between cancer and other cells. Phosphorescence-based partial oxygen measurements quantified the oxygen gradient, which can be controlled by the gas pressure between the inlet and outlet of the device. A monoculture of endothelial cells with an oxygen gradient in the device showed an increase in cell death in the hypoxic area. In addition, Lewis lung carcinoma cells co-cultured with endothelial cells showed gradient-dependent migration through a membrane pore filter, indicating that the interaction between tumor and endothelial cells under hypoxia is crucial in metastasis. The results suggest that the developed microdevice can be used to study the mechanisms of tumor metastasis under hypoxic conditions.