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A pH-Sensing Optode for Mapping Spatiotemporal Gradients in 3D Paper-Based Cell Cultures
journal contribution
posted on 2018-01-11, 00:00 authored by Rachael
M. Kenney, Matthew W. Boyce, Nathan A. Whitman, Brenden P. Kromhout, Matthew R. LockettPaper-based cultures
are an emerging platform for preparing 3D
tissue-like structures. Chemical gradients can be imposed upon these
cultures, generating microenvironments similar to those found in poorly
vascularized tumors. There is increasing evidence that the tumor microenvironment
is responsible for promoting drug resistance and increased invasiveness.
Acidosis, or the acidification of the extracellular space, is particularly
important in promoting these aggressive cancer phenotypes. To better
understand how cells respond to acidosis there is a need for 3D culture
platforms that not only model relevant disease states but also contain
sensors capable of quantifying small molecules in the extracellular
environment. In this work, we describe pH-sensing optodes that are
capable of generating high spatial and temporal resolution maps of
pH gradients in paper-based cultures. This sensor was fabricated by
suspending microparticles containing pH-sensitive (fluorescein) and
pH-insensitive (diphenylanthracene) dyes in a polyurethane hydrogel,
which was then coated onto a transparent film. The pH-sensing films
have a fast response time, are reversible, stable in long-term culture
environments, have minimal photobleaching, and are not cytotoxic.
These films have a pKa of 7.61 ±
0.04 and are sensitive in the pH range corresponding to normal and
tumorigenic tissues. With these optodes, we measured the spatiotemporal
evolution of pH gradients in paper-based tumor models.