Figure 1 (Susan, 2003)

The intensive use of nitrite has adversely affected the environment and human health. Under rapid international globalization and industrialization, nitrite now serves as an agricultural fertilizing agent, preservative, dyeing agent, food additive, and industrial corrosion inhibitor. The intensive use of nitrite has adversely affected the environment and human health. Under rapid international globalization and industrialization, nitrite now serves as an agricultural fertilizing agent, preservative, dyeing agent, food additive, and industrial corrosion inhibitor.

Figure 2 Schematic summary showing major differences in the supply and handling of nitrite and nitrate by the adult and infant. Multiple deficiencies in the infant lead to diminished nitric oxide (NO) bioactivity in the stomach and lower circulating nitrite concentrations in the blood(Jones et. al, 2015).

However, current detection methods require sophisticated pre-treatment and instrumentation, significantly limiting usage scenarios and increasing detection costs. One way was to use the conventional wide-use direct UV spectrophotometry, which provides a rapid analytical method. This method is subject to severe interference from organic matter and ionic species. Another way was to obtain chemical approaches that specifically use ion-selective electrodes to detect the electric potential. Although the selective passage of nitrite from a solution to a membrane gives rise to a difference in potential, measuring such potential in daily life is inaccessible.

Our team is therefore motivated to develop a fast, easy-operative solution for portable nitrite determination. By researching the dissimilatory nitrite reduction pathway within E.coil, we genetically engineered BL21 to overexpress nitrite reductase NrfA. After constructing a detailed regulatory model of this enzyme, we refined the experimental condition for higher expression to improve nitrite detection efficiency in the water, food, and plasma samples. With the E. coli being coated on a paper-based biosensor, electrons produced from nitrite reduction are transferred into an electrical signal and transformed to nitrite concentration after data preprocessing. The result will be shown to every customer, accompanying an evaluation of the sample's safety. Harnessing the power of nature, we lead a step toward a more intelligent, proactive, and environmentally friendly lifestyle.

Figure 3 Our sensor

Reference

Susan Mora, (2013), Tracking Nitrogen Through the Soil to Reduce Pollution From Agriculture, https://www.discovermagazine.com/environment/tracking-nitrogen-through-the-soil-to-reduce-pollution-from-agriculture

Jones, J., Hopper, A., Power, G. et al. Dietary intake and bio-activation of nitrite and nitrate in newborn infants. Pediatr Res 77, 173–181 (2015). https://doi.org/10.1038/pr.2014.168