Cells are unable to build the vasculature necessary to keep up with rapid proliferation associated with tumor formation. The distribution of nutrients throughout a tissue, as well as the removal of waste products produced by the cells in that tissue, relies on mass transport from vasculature to distal regions in the tissue. In poorly vascularized tissues, such as rapidly proliferating tumor masses, each of these gradients is highly exaggerated and can result in regions of low oxygen tension (hypoxia), nutrient starvation, and low extracellular pH. Cancer cell adaptation to these extracellular environments results in cell populations with highly aggressive phenotypes capable of evading therapies. These cancerous cells commonly adopt an invasive phenotype that enables invasion into healthy neighboring tissues, which increases the likelihood of the eventual formation of metastatic sites. To evaluate cellular invasion in tumor-like environments, a variety of in vitro platforms have been developed. In this work I highlight other assays developed and describe the development of a paper-based assay to study cellular invasion in tumor-like microenvironments. This work demonstrates the versatility of paper devices through an adaptation of the commercial Transwell assay and by designing an invasion assay that is compatible with real-time imaging of cellular movement and gradient formation. This adaptation I used, employs a single sheet of paper, which was wax-patterned to contain paper channels that fluorescently labeled cells could be cultured in. This setup not only provided a technological advance, but provided biological insight into cellular responses to gradients by showing that MDA-MB-231 cells selectively invaded regions of higher oxygen tension in hypoxic cultures. To monitor the microenvironment, I designed and fully characterized an optical pH sensing film compatible with this platform that enables continuous mapping of the pH gradients that form across the cell-containing channels. I combined this sensing film with a luminescent oxygen sensor previously developed in the lab, to generate a dual sensing optode compatible with paper-based cultures. I used this dual sensing optode to relate spatiotemporal gradients of oxygen and pH to cell invasion within tumor-like environments. I found that cell invasion differs based upon location in these gradients.