model
Firstly, we fitted the data of copper ion concentration and the initiation intensity of copper-sensitive promoter pcutR, so that we can use equations to understand the initiation of copper ion concentration on copper-sensitive promoter.
By substituting copper ion concentration into X value, the starting intensity of promoter can be obtained.
In our working system, the copper ion concentration is converted into voltage. What we do with copper ions is the expression of riboflavin, so we made a model between riboflavin concentration and maximum voltage. There is a linear relationship between copper ion concentration and riboflavin concentration, so in our model, X is the concentration of copper ion.
Equation: Y=0. 1176X +25.087
The maximum voltage can be obtained by substituting copper ion concentration into X value.
Finally, we added the amplification system, which is also the total system of our biosensors.
We test our total system and curve fit the data, and finally get the equation: Y = 0.3199X + 259.19
We can substitute Y according to the maximum voltage measured, and get X, which is the concentration of copper ions in water, which is also our working principle.
Summary
After adding external copper ions to our MFC biosensor, our sensor generates voltage. By substituting the maximum voltage Y into the equation Y = 0.3199X + 259.19, the copper ion concentration X can be obtained, and we can detect whether the copper ion concentration in water meets the standard according to X.