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Project Background

You are in danger, it isn't a joke. With the progress of science and technology, human beings are making more and more troubles for themselves. Electromagnetic radiation produced by common electronic devices such as mobile phones and computers, a large number of reagents and waste gas from industrial development and even some diagnosis and treatment equipment such as MRI and CT can cause damage to our DNA[1], cause gene mutation, and even cause genetic diseases.

Current detection methods are mostly based on analytical chemistry and biology, detecting the products and intermediates of DNA damage[2][3]. Although these methods have high sensitivity and accuracy, such passive detection methods cannot reflect the response of living cells to DNA damage reagent, and cannot identify and evaluate the DNA damage capacity of unknown compounds.

Microorganisms are widely used in scientific research because they can reproduce rapidly, be operated easily and live stably. Microbial sensor is a detection method that uses the live microorganisms as sensitive materials, adds the analyte to the immobilized microorganism, and finally uses the enzyme system or metabolic system in the microorganism to identify and determine the corresponding substrate[4]. The interactions between microorganisms and target compounds can be detected by a variety of analytical techniques using appropriate transducers and the measured signal is correlated with the concentration of the measured substance[5][6].

Fig.1 Principles of genetically engineered microbial sensors[8]

We use engineering bacteria to build our microbial sensors. Based on the principle that certain chemicals or radiation can cause DNA damage and then initiating the SOS response, we screened expression vectors, SOS response-inducible promoters and reporter genes to construct engineered bacteria, through the promoter’s response to certain chemicals to control the expression of reporter genes[7]. We want to identify whether the chemicals being detected can damage DNA and describe the degree of DNA damage from the chemicals.

In this project, we designed and processed a microfluidic chip with a hybrid channel and a ratchet structure. The mixed channel can produce different concentrations of the sample to be tested for simultaneous detection. The spinous process can guide E. coli to grow and divide stably in the chip chamber without entering the channel and affecting the detection process. In addition, the design of the chip can concentrate the parallel test and the control test on one chip, which speeds up the inspection process and reduces the complexity and operation of the test.

In our project, we also built a hardware platform. We designed our own fluorescent detection system based on smartphones with mini programs, which is simple in structure, simple to operate, low cost, and can detect chips anytime, anywhere. Users take pictures of the detection area through their smartphones and use mini programs to collect and process the graphics, and obtain fluorescence expression, so as to quantify and visualize DNA damage detection.

Tips

Under normal physiological conditions, intracellular reactive oxygen species (ROS) levels are maintained within a certain range and play an important physiological function. Exogenous or pathological factors may lead to the imbalance of the REDOX state of the body, thereby causing the accumulation of ROS. ROS mainly includes superoxide anion (02 '-), hydroxyl radical (OH ·) and hydrogen peroxide (H202) and so on. ROS has the strong oxidizing and it can attack DNA, protein (including enzymes), sugar, lipid and other important biological macromolecules, hinder the full play of normal physiological function, and cause cell oxidative damage which lead to many diseases.

  • [1] Henle ES, Linn S. Formation, prevention, and repair of DNA damage by iron/hydrogen peroxide[J]. J Biol Chem,1997. 272:19095–19098.
  • [2] Poirier M C, Yuspa S H, Weinstein I B, Blobstein S. Detection of Carcinogen DNA-Adducts by Radioimmunoassay[J]. Nature, 1977, 270:186-188.
  • [3] Ostling O, Johanson K J. Microelectrophoretic study of radiation-induced DNA damages in individual mammalian cells[J]. Biochemical and Biophysical Research Communications, 1984, 123(1):291-8.
  • [4] Gs W R G. Biosensors for real-time in vivo measurements [J]. Biosensors and Bioelectronics, 2005, 20(12): 2388-2403.
  • [5] D'souza S F. Microbial biosensors [J]. Biosensors & Bioelectronics, 2001, 16(6): 337-353.
  • [6] Byfield M P, Abuknesha R A. Biochemical aspects of biosensors [J]. Biosensors & Bioelectronics, 1994, 9(4-5): 373. [4] Lei Y, Chen.
  • [7] Yagur-Kroll S, Amiel E, Rosen R, et al. Detection of 2,4-dinitrotoluene and 2,4,6-trinitrotoluene by an Escherichia coli bioreporter: performance enhancement by directed evolution [J]. Applied Microbiology & Biotechnology, 2015, 99(17): 7177- 7188.
  • [8] Islam S K, Weathers B, Terry S C, et al . Genetically-engineered whole-cell bioreporters on integrated circuits for very low-level chemical sensing [C]. European Solid-State Device Research Conference, 2005: 351-354. [12] Ravikumar S, Ganesh.