Exploiting the role of TEMPO as radical scavenger

2,2,6,6-tetramethylpiperidin-1-oxyl, commonly known as TEMPO, is one of the most popular nitroxyl radicals. TEMPO radical and its derivatives are stable, so they have many applications: they are extensively used as oxidation catalysts for organic synthesis, mediators for controlled polymerization, spin probes and magnetic resonance imaging (MRI) contrast agents, and antioxidants in biological systems. The aim of this work is to exploit this last function, the antioxidant power, together with the anti-inflammatory and cytoprotective capabilities of TEMPO radical. To do that, TEMPO grafted polymers PEI, PEG, hydrogels and nanogels have been synthetized using different methods of functionalization with the intention of obtaining a biocompatible material that could have biomedical properties. First of all, a selected library of TEMPO-derivatives bearing different functional groups have been synthetized, to permit PEG and linear and branched PEI functionalization with different grafting degree. The last step was the synthesis of TEMPO-labelled hydrogels and nanogels to be tested as antioxidant. Thanks to NMR analysis the different molecules obtained where characterized, while EPR analysis was performed on the samples to determine the effective quantity of TEMPO. Concerning nanogels instead, DLS size and zeta potential measurements gave indications on the average size of the dissolved particles in solution and on the superficial charge. Cytotoxicity tests, on two different cell lines (HeLa cells and L929 cells) were carried out on PEI, PEG and nanogels functionalized with TEMPO. Given the good performances registered, the synthesized materials result to be particularly promising for antioxidant activity, opening the way to a possible role in biomedical field.