We used Arduino UNO with a light frequency converter to detect the light intensity of GFP, and a color detector to distinguish the color of the test paper.
First, we set the light frequency converter(TSL235R) to measure the light intensity of GFP emitted from our CSP and Lactic acid detectors.
Secondly, we created a standard curve by using a measuring instrument in our laboratory to detect the light intensity emitted from known concentrations of CSP and Lactic acid precisely.
Finally, we compared the light intensity detected by our device with the standard curve to determine the concentration of CSP or Lactic acid in the sample.
For the detection of the fluorescence emitted by the bacteria after it combines with the targets, a monochromatic light(485nm) was set to excite the fluorescent protein. An optical sensor(TSL235R), two lens and a longpass filter(510nm) were placed to filter the unwanted light and focus the rest onto the optical sensor to detect its fluorescence intensity.
The monochromatic light
The GFP we were using was GFPmut3. Picture A shows the excitation maxima of GFPmut3 is 501nm, and picture B shows the emission maxima is 511nm.
The purple line is the 510nm filter what we use, but it’s starting point is not 510nm exactly. So we chose the 485nm light to avoid unwanted light detection.
The following curve is the fluorescein concentration corresponded to the frequency of the converter, so we know the lowest limit of our converter for detecting the fluorescein concentration is 6.25uM.
The next curve is the fluorescein concentration corresponded to the fluorescence in order to check whether two curves have similar positive correlation.
We chose a test paper with a range from pH 5.0 to pH 8.0. For example, when the color of the test paper changes from red to green, the pH value changes from 5 to 8. Color detection is used to to detect the test paper and register the RGB value. The RGB value allows us to measure the pH value.
Five values (two for the fluorescence intensity, three for the RGB values) we received will be transmitted from Arduino to the APP by our Bluetooth, HC-06.
For the fluorescence intensity, we hope we can detect the larger range of the fluorescence intensity by the circuit we designed so that the accuracy can be improved.
For the pH level, we hope we can plot the suitable curve or update our App to know the precise pH value in the future.