Study on Microenvironment Acidification by Microfluidic Chip with Multilayer-paper Supported Breast Cancer Tissue

A multilayer paper embedded microfluidic chip was developed for the study of tumor microenvironment acidification. Eight layers of nitrocellulose membrane with breast cancer cells cultured on were stacked, with hydrogel filling the space between neighboring membranes. The stacked membranes were packaged in a microchip to form a 3D structure mimicking the breast cancer tissue. The paper-supported breast cancer tissue was cultured in a perfusion manner for several days at different flow rates, and then the multilayer structure was disassembled to single layers. Viability, proliferation rate and intracellular lactic acid level of breast cancer cells on different layers were detected by fluorescence microscope and automatic biochemical analyzer to analyze microenvironment acidification. The experimental results demonstrated that the degree of microenvironment acidification in the breast cancer tissue was dependent on perfusion flow rate. Higher flow rate facilitated higher cell density and consequently led to a higher level of secreted acid metabolite, and vise versa. The insufficient oxygen supply was also a crucial cause of microenvironment acidification, as the level of intracellular lactic acid increased with the diffusion distance of oxygen. It was also found that cell viability and proliferation rate decreased with increasing acidification level.