Synthesis of zwitterionic copolymers for the design of a wearable sensor of ammonia in sweat

Nowadays, hepatic diseases are responsible for the death of 1.3 million people every year in the world and 325 million people must live with chronical infections due to the hepatitis B and C. Apart from the viral hepatic diseases, there are other issues like Non-Alcoholic Fatty Liver Disease (NAFLD) or alcohol and drugs abuse that can lead to cirrhosis and, as a final stage, to hepatic cancer. These diseases are silent, they do not present evident symptoms, so the diagnosis and the cure are very complex and, in most cases, when the issue is discovered, it is too late and the progression is inexorable. To solve this problem, new diagnostic devices are required, that can assure continuous monitoring of the patient health status, with as little pain and discomfort as possible. The work of this Master thesis focuses on the development of a flexible sensor for the detection of anomalous ammonia values in the sweat, employing conductive copolymers as the active material, for the early detection of hepatic diseases. The development of this technology is done in three steps. The first one is the definition of the electrodes structure, with the deposition of silver through standard Tollen’s reaction, following the technology developed by GEMAT group of the Institut Quìmic de Sarrià in Barcelona, where the project is developed. The next step is the creation of the active material, a combination of zwitterionic and pH-sensitive polymers to obtain a conductive nanoparticle able to sense the difference of ammonia concentration in a medium. The polymerization mechanism for the zwitterionic part is the Raft polymerization. After the zwitterionic part is completed, the second step is the formation of a copolymer or of a nanoparticle with the pH-sensitive polypyrrole chains through covalent links. Finally, the materials are tested in two media. The first one is water and ammonia, added dropwise while the sensor is immersed, to evaluate the change of conductivity through amperometric detection in an electrochemical setup. The same evaluation is done in a more complex solution, such as a basic simulated sweat. This prototype clears the way for future optimization in terms of reproducibility, sensitivity and geometry of the final sensor.