Novel electrochemical sensing schemes for cost-effective diagnostics and on-line monitoring of nitric oxide.

摘要

Bioanalytical method development is an essential component of biophysical and biomedical research. Reliable and affordable methods are in great demand in basic research and applied engineering as well.; This work explores novel electrochemical sensing schemes. One of them is developed to provide a solution for a problem in the field of biomedical engineering: the lack of a cost-effective routine method for detecting trace levels of heavy metals in biomedical and environmental samples. The Rotating Sample System is a unique approach to electrochemical stripping methods, designed for 20 μL sample droplets. The system is electrochemically equivalent to a large surface area rotating electrode, but it is far simpler to produce and operate: there is no need for a sample container, and neither fine moving mechanical parts nor sophisticated controls are required. The system can support universal screening for lead in young children and a convenient on-site analysis of environmental samples. Analyses of lead(II) and copper(II) in water and serum were explored. The a detection limit for lead is as low as 5 ppb and the relative standard deviation of the analysis meets the requirements by the CDC. The system can also allow for calibration free, direct determinations, under certain conditions.; The other development, a specific on-line sensor helps facilitate the quantitative understanding of the signaling pathways of the recently discovered messenger nitric oxide. A simple electrochemical sensor is proposed here consisting of a glass sealed platinum micro disc electrode coated with cellulose acetate to reduce both surface fouling by proteins and response to potential interferents. A differential amperometry protocol is optimized to improve selectivity and provide a stationary oxidation state of the platinum surface, which prevents loss in sensitivity during long-term use. We found oxidation of NO by O ₂ second order in [NO] with a rate constant of 7.3 ± 0.4 × 106 M−2S−1, in good agreement with literature data obtained by other than electrochemical methods. The sensor was tested in macrophage cultures, where the release rates of NO were found to be in the order of 20pmol/(106 cells × s) and correlated well to the nitrite content.