Synthesis of zwitterionic conductive copolymer nanosuspensions for ammonia-sensing sweat sensors

In recent years, non-invasive monitoring of biomarkers has become more important for prevention and early treatment of diseases. Sweat is a promising fluid for continuous detection of various analytes, being an easy-to-collect medium and containing electrolytes, proteins, and compounds such as ammonia. Ammonia is a byproduct of protein metabolism, and an excess of it can be an indicator of liver dysfunction, such as cirrhosis, liver cancer, or encephalopathy, so its monitoring is essential for health. Electrochemical wearable sensors are an optimal approach to monitor biomarkers in real time because of their ability to provide continuous data on physiological status using conductive electrodes and selective detection techniques. In addition, they are flexible and fit tightly to the skin, making measurements accurate. The purpose of this thesis is to develop and characterize conductive copolymer nanosuspensions using zwitterionic polymers that control protein adhesion on the substrate, reducing nonspecific binding and improving electrode conductivity, ensuring accurate and reliable ammonia detection. The nanosuspensions will be the basis for the production of conductive and flexible electrodes. The first part deals with the choice of metal substrate for the electrode, which fell on silver for its high conductivity and chemical stability. Next, by RAFT polymerization, Sulfobetaine Methacrylate (SBMA) was synthesized in various lengths. Different nanosuspension formulations were then obtained by integrating pSBMA with polypyrrole (PPy) and Polystyrene Sulfonate (PSS). Finally, to assess the specificity of ammonia materials, amperometric detection tests were conducted on SPCE sensors, first in water and then in simulated sweat solutions. The flexible silver electrode was also tested, showing the potential of the developed formulations and the need for further optimisation to improve sensitivity. In conclusion, the results obtained suggests that the nanosuspensions developed represent a promising basis for electrochemical sensing sensors, paving the way for future developments for ammonia monitoring in sweat.