Model
Our biosensor is superior to traditional methods of disease detection in aquaculture in its speed and ease of use. Notably, as tests traditionally must be taken to a lab for analysis, it can be days before a result is obtained. These tests must also be ordered on a case by case basis, as no such system exists to monitor and alert to heightened pathogen concentrations as they arise. Between these inefficiencies, it can be difficult to detect and control an outbreak before it causes significant damage to the population. As our biosensor aims to improve on the speed of these traditional systems, we decided to simulate the time between pathogen detection and color change to establish its efficacy.
To do this, we made a simple model using MATLAB's ODE45 solver that simulates 2 reactions - binding of biosensor and pathogen, and color change of complex. Molar concentration of pathogen was approximated to be 0.61µM/L using the molar mass and common mass concentration of Anatoxin-A, a similar toxin to those present in Velvet Disease. Values of an FKBP-based rapamycin sensor were used for association (2600000L/mol/s) and dissociation (0.0016/s) rates (Kon and Koff) of the biosensor-pathogen reaction, as well as in determining the ideal 1:100 ratio of biosensor to pathogen. For the turn-on rate of color change, we used 1.11/hr, the value in Loh's GFP-based biosensor which our chromoprotein platform was based on.
Figure 1: Diagram of model
Upon simulation, it can be seen that color change (change from complex to complex*) plateaus around 5 hours after reaction, in line with Loh's results as expected. The maximum chromoprotein concentration is approximately 7.3µM. Compared to Loh's maximum of 2.0µM GFP, this result indicates that with the values and ratios used in the model, our biosensor will likely yield results well before 5 hours after being triggered and be easily visible to the naked eye. Therefore, the biosensor should effectively fulfill our aim of speeding up and simplifying disease detection.
Figure 2: Results of simulation, indicating visible concentration of color-changed chromoprotein in less than 5 hours and efficient usage of biosensor amount based on concentration of pathogen.
