NANOTOXICITY/CELL BIOLOGY: Light absorption indicates oxidative stress in cells

Researchers at École Polytechnique Fédérale de Lausanne (EPFL; Switzerland) have developed an optical method for accurately determining the toxicity of nanomaterials. They measure the light absorbed by certain proteins to determine the concentration of oxidizing substances produced by a damaged cell. The research provides a new way to understand the mechanisms of oxidative stress.

When a cell is exposed to a toxin or pathogen, the internal equilibrium between its oxidants and antioxidants breaks: Oxidants, generally oxygen derivatives, multiply excessively and attack the cell's proteins, sugars, and membrane. This hastens cellular aging, causes certain diseases, and may even lead to cell death. Thus, the overproduction of such oxidants is a sign of cell stress.

The researchers found that cytochrome c, a protein present in the cellular membrane, would absorb less light of certain wavelengths when hydrogen peroxide was present—and developed a method for measuring the variations of light absorbed. They tested and verified their method on small, unicellular algae. They say that there have previously been no reliable methods for measuring oxidative stress continuously without damaging cells.

"The test that we propose is highly sensitive and able to indicate the concentration of oxygen derivatives in a thorough and detailed way," says Olivier Martin, director of the Nanophotonics and Metrology Laboratory (NAM) at EPFL. "Since it is based in assessing a substance released outside the cells, it is also noninvasive. Therefore, it does not destroy the living organism and can be applied over a period of several hours, making it possible to observe the evolution of the situation over time."

1. G. Suarez, C. Santschi, V. I. Slaveykova, and O. J. F. Martin, Sci. Rep., 3, 3447 (2013); doi:10.1038/srep03447.