The American public has been bombarded by commercials touting the positive effects of antioxidants and negative effects of oxidative free radicals of which the interplay is controlled by the reduction/oxidation (redox) state of the cell. A cellÍs redox state has been historically difficult to determine due to a lack of analytical tools capable of operating in real time without altering the cell. We propose to develop an array of nanosensors capable of selectively and quantitatively responding to reactive oxygen species in real time finally shedding light on the cellÍs true redox state. We will then use these nanosensors to investigate an important biological problem: cancer cell metabolism. æIt is the hypothesis of our collaborators at the Beth Israel Deaconess Medical Center that the chemical fluctuations in cancer cells display a lower degree of mathematical complexity than do normal cells. The redox nanosensors developed will be tested to determine if it is possible to use a mathematical nonlinear complexity ñread-outî technique to detect differences between cancerous and normal cells. If successful, this approach can be developed as a novel diagnostic tool to discriminate between tumorigenic and non-tumorigenic cells potentially leading to new screening tools for cancer therapy agents in development.