High level of oxidative stress is involved in formation of incipient tumor and carcinomatous cells. Here in this contribution we have explored a facile strategy to assess the oxidative stress elicited by hydrogen peroxide (H(2)O(2)) in cells with amperometric current-time technique in vitro. An electrochemical biosensor exhibiting high sensitivity and selectivity to H(2)O(2) is fabricated by integration of graphene with gold nanoparticles and poly(toluidine blue O) films. The efflux of H(2)O(2) from several representative tumor cells and normal cells on exposure to ascorbic acid could be detected by using the graphene-based nanocomposite films. The results indicate that tumor cells release much more H(2)O(2) than do the normal cells. The novel sensor raises the possibility for clinical diagnostic application to evaluate the higher level of intracellular oxidative stress of tumor cells in comparison with normal cells.
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