The cytoprotective messenger nitric oxide (NO) and
cytotoxic peroxynitrite (ONOO-) are the main components of oxidative
stress and can be generated by endothelial cells. A tandem of electrochemical
nanosensors (diameter 200-300 nm) were used to measure, in situ, the balance between NO and ONOO-produced by human umbilical vein endothelial cells (HUVEC’s). The amperometric
nanosensors were placed 5 ± 2 μm from the surface of the endothelial cells and
the concentration of NO and ONOO- was measured at 630 mV and -300 mV (vs
Ag/AgCl) respectively. Normal, functional, endothelial cells produced maximal 450
± 25 nmol.L-1 of NO and 180 ± 15 nmol.L-1 of ONOO- in about 3 s, after stimulation with calcium ionophore. The in situ measurements of NO and ONOO- were validated using nitric oxide synthase inhibitor L-NMMA, ONOO- scavenger Mn(III) porphyrin, and superoxide
dismutase (PEG-SOD). The ratio of NO concentration to ONOO- concentration ([NO]/[ONOO-]) was introduced for quantification of
both, the redox balance and the level of the nitroxidative stress in the
endothelium. [NO]/[ONOO-] was 2.7 ±
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