Team:QHFZ-China/Hardware
Through the human practices, we found the most common uric acid detection method is to go to the hospital for blood testing. Although the accuracy is high, this method requires professional equipment and operators, which make it cannot be widely promoted. At the same time, for the patients, the process of blood testing in the hospital is complex, the waiting time is very long, the price is high, and it is difficult to achieve long-term and regular monitoring of uric acid concentration. In this regard, we proposed the use of engineered E. coli to detect uric acid concentration. In order to achieve lower cost and more portability, we have designed a set of hardware by Legos to respond to the fluorescence signal emitted by bacteria in high uric acid concentration environment, and display the results to users according to the comparison between the patients’ sample and the sample with known concentration. The working principle of the hardware design is quite simple, and the optical path is as shown in the figure below (Fig. 1). Considering that the optimized uric acid detector in E. coli expressed sfGFP under the induction of high concentration of uric acid, we selected two filters adapted to sfGFP spectra, which were placed behind the light source and before the detector. Therefore, the sfGFP protein can be fully excited, and the signal can be fully sensed by the detector, retaining the signal information to the greatest extent.
Figure 1. The optical path of hardware design.
We chose modular LEGO as construction materials. It is because, on the one hand, it can reduce the material cost and facilitate the later optimization. On the other hand, the LEGO series has optical sensors and related control circuits which adapt the frame very well. Based on these materials, we tried to build the hardware. The prototype is shown in Fig. 2. We tested the efficiency of Filters, and found they could filter non-specific wavelength light effectively.
Figure 2. Display of the prototype. (A) Structure of the prototype. Holder, Sensor and two Filters are shown. (B) Light from daylight lamp filtered by the Filter 1. (C) Light from daylight lamp filtered by the Filter 1 and Filter 2. (D) Assembled hardware equipment. No light source is shown.
We wrote a running algorithm for the prototype. A schematic diagram of the algorithm is shown in Fig. 3.
Figure 3. Diagram of the hardware based on LEGO system.
Our existing design is capable of achieving two measurement processes. The first type is called absolute brightness measurement, which directly measures the fluorescence intensity and compares it with the predetermined fluorescence value. When the sample fluorescence intensity is higher than the predetermined one, the downstream warning system will be turned on, and the user will get warning about “the sample uric acid concentration was higher than the standard” through sound and images. This method is simple in sample preparation and the reference value is preset. However, due to the uncertainty of biomaterials and samples, there may be large errors. Therefore, this method is suitable for rough detection. Another method is the relative intensity comparison method. As shown in Fig. 3, the user needs to prepare two tubes of samples at the same time, one sample from the patient, and the other is a standard sample with a known concentration. After the same treatment and culture process, these two tubes are sent to the detection system for measurement. The hardware device will compare the results of the two measurement results, and will give a warning signal when the fluorescence value from the patient sample is higher than the standard sample. This method expresses higher precision than the first one.
Figure 4. Schematic diagram of our expected inspection process.
Unfortunately, in the short summer vacation, there are many problems with the prototype we built. So far, we have not actually tested the samples by the designed hardware. After that, we will complete the debug work and make it as a more standard and more reliable industrial product in the future. Moreover, considering that the detection target of this product is fluorescence, it can be widely used in various types of fluorescence detection.
