PROJECT

Biosensor

Biosensors are analytical tools that incorporate biomolecules to a transducer to create a surface that allows the qualitative and/or quantitative measurement of a specific analyte. This tool comprises: (i) bioreceptor which corresponds to the biological element (proteins, enzymes, antibodies, nucleic acids etc.); (ii) a transducer component responsible for converting the biological signal into a measurable signal, and (iii) a detector, wherein the microprocessor signals from the transducer are amplified and analyzed. In this project, selected biosensors using electrochemical transducers, as well as our bioreceptor molecules of specific nucleic acids were chosen. For our system, we build printed electrodes modified with conductive nanocomposite. These electrodes contain immobilized DNA specific to recognize microRNA 155 molecules. This microRNA is found in the blood of patients diagnosed with breast cancer. Because of the specificity of nucleic acids, the molecules in question will hybridize when placed in contact with their target (Principle of hybridization). The electrochemical system is capable to recognize, the difference of the electrode with immobilized DNA, hybridized with DNA target through the amount of electrical current generated.

Subsequently building the Bot and ColiAlert, we work on building an electrochemical biosensor for detection of breast cancer, the BreastSensor. In the figures below, you can see the results in the construction of BreastSensor. In Figure 1 there is shown a schematic of how an electrochemical biosensor works. Figure 2 shows the results of current generated only in the read BreastSensor (Standart) where it is possible to obtain almost 17nA current. The BreastSensor after hybridization, wherein the low current average 3 nA to complementary target. Also analyzes of the non-complementary target, which shows the results obtained similar to current BreastSensor. Figure 3, shows a curve of target concentration ranging from 1 x10-6 to 1 x 10-11 molar.

Figure 4 shows the concentration curve with the target and standard deviation trend line. Through the graph of Figure 3 was used to calculate detection limit of the system constructed. Where the detection limit is equal to three times the standard deviation of the result of a concentration divided by the slope. Through this calculation, it was possible to obtain the value of the detection limit of 9.90 pM.

Finally,figure 5. shows the test conducted with samples from patients with breast cancer. Samples were collected of Barão de Lucena Hospital of Pernambuco of women already diagnosed with cancer. Blood samples were stored in RNA later solution and passed through the RNA extraction process. The extracted samples were placed to hybridize with BreastSensor. Negative samples have an approximate result to 17 nA similar to BreastSensor. Already positive samples showed current around 4 nA, proving that BreastSensor is able to recognize the presence of the specific target.

FIGURA 1 COM O DESIGN