title: Quantifying oxygen in paper-based cell cultures with luminescent thin film sensors.
abstract: Paper-based scaffolds are an attractive material for generating 3D tissue-like cultures because paper is readily available and does not require specialized equipment to pattern, cut, or use. By controlling the exchange of fresh culture medium with the paper-based scaffolds, we can engineer diffusion-dominated environments similar to those found in spheroids or solid tumors. Oxygen tension directly regulates cellular phenotype and invasiveness through hypoxia-inducible transcription factors and also has chemotactic properties. To date, gradients of oxygen generated in the paper-based cultures have relied on cellular response-based readouts. In this work, we prepared a luminescent thin film capable of quantifying oxygen tensions in apposed cell-containing paper-based scaffolds. The oxygen sensors, which are polystyrene films containing a Pd(II) tetrakis(pentafluorophenyl)porphyrin dye, are photostable, stable in culture conditions, and not cytotoxic. They have a linear response for oxygen tensions ranging from 0 to 160 mmHg O2, and a Stern-Volmer constant (K sv) of 0.239 ± 0.003 mmHg O2 (-1). We used these oxygen-sensing films to measure the spatial and temporal changes in oxygen tension for paper-based cultures containing a breast cancer line that was engineered to constitutively express a fluorescent protein. By acquiring images of the oxygen-sensing film and the fluorescently labeled cells, we were able to approximate the oxygen consumption rates of the cells in our cultures.
authors.affiliation: Department of Chemistry, Kenan and Caudill Laboratories, University of North Carolina at Chapel Hill, 125 South Road, Chapel Hill, NC, 27599-3290, USA.
authors.forename: Matthew W
authors.initials: MW
authors.lastname: Boyce
authors.affiliation: Department of Chemistry, Kenan and Caudill Laboratories, University of North Carolina at Chapel Hill, 125 South Road, Chapel Hill, NC, 27599-3290, USA.
authors.forename: Rachael M
authors.initials: RM
authors.lastname: Kenney
authors.affiliation: Department of Chemistry, Kenan and Caudill Laboratories, University of North Carolina at Chapel Hill, 125 South Road, Chapel Hill, NC, 27599-3290, USA.
authors.forename: Andrew S
authors.initials: AS
authors.lastname: Truong
authors.affiliation: Department of Chemistry, Kenan and Caudill Laboratories, University of North Carolina at Chapel Hill, 125 South Road, Chapel Hill, NC, 27599-3290, USA. mlockett@unc.edu.|Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, 450 West Drive, Chapel Hill, NC, 27599-7295, USA. mlockett@unc.edu.
authors.forename: Matthew R
authors.initials: MR
authors.lastname: Lockett
mesh_terms: D018929:Cell Culture Techniques; D049449:Luminescence; D010100:Oxygen / Q000378:metabolism*; D010209:Paper
chemical_list: D010100:Oxygen
keywords: 3D culture; Fluorescence imaging; Oxygen gradient; Oxygen sensor; Paper-based scaffold; Thin film