Scientists at Plymouth University, along with colleagues at AstraZeneca, have developed a nondestructive method that can measure the concentration and consumption of oxygen in 3D models of biological cells. Using Electron Paramagnetic Resonance (EPR) oximetry, the team assessed the gradient of oxygen concentration within spheroids, 3D cell cultures typically used for testing chemical toxicity within liver and tumor models.
It had previously been suggested that the centers of spheroid cultures become devoid of oxygen, leading to cell death that may limit their use, but until now there has been no way of measuring the precise levels. Work by researcher Laura Langan and senior research fellow Nicholas Dodd, Ph.D., demonstrated smaller spheroids with a diameter of less than 120 micrometers (µm), and containing fewer than 2,500 cells, lose less than 12% of their oxygen concentration after one week, decreasing to less than 50% two weeks after their creation.
Overall, the study recommends the use of smaller spheroids to allow comparable oxygen concentrations to native tissues, with scientists believing the research provides further evidence of the appropriateness of these in vivo studies as a tool to elucidate fundamental biological processes in the spheroid systems and aid in the reduction of whole animal experiments.
The study was led by Awadhesh Jha, Ph.D., from the School of Biological Sciences, and Simon Jackson, Ph.D., from the School of Biomedical and Healthcare Sciences at Plymouth University.
“It is widely accepted that the biological activities present in spheroids more closely reflect key characteristics of the living organism, and as such may offer a more relevant alternative to in vivo exposure in biological research,” said Dr. Jackson. “EPR oximetry has provided insights into the size and cell seeding densities at which oxygen gradients play a confounding role in subsequent exposure applications and thus enable the wider use of the spheroid model to non-tumor based biological studies.”
Over the past three decades, the use of three dimensional cell culture has gained increased recognition as an important tool in biological research and pre-clinical trials over conventional organs and animal models. Spheroids are one example of these, and are typically used to assess the chemical toxicity and evaluation of environmental samples in biological and ecotoxological studies.