Strategies to prevent dopamine oxidation and related cytotoxicity using various antioxidants and nitrogenation.

Dopamine (DA) plays several important roles in the brain and body and has recently been used as a bioadhesive precursor for medical applications. However, DA oxidizes immediately when exposed to oxygen and rapidly polymerizes into polydopamine (PDA), leading to oxidative stress, cytotoxicity, and loss of DA functionalities. As a result, preventing rapid oxidation of DA is of paramount importance but still remains a major challenge. Here, we report several strategies to impede DA oxidation in relevant aqueous solutions (i.e., water, PBS, and cell culture media). One strategy is based on using reducing agents or antioxidants such as glutathione in its reduced state (GSH) and sodium tetraborate (commonly known as borax). Another strategy is based on nitrogenation, a method used to preserve DA in its reduced form by creating an oxygen-free environment. Our data suggest that the antioxidant properties of GSH and borax substantially decreased DA oxidation for up to 2 months. Nitrogenation or oxygen removal further prevented DA oxidation, enhancing its shelf life for longer periods of time. When tested with mammalian cells, preventing DA oxidation with GSH dramatically improved viability of 3T3 fibroblasts and T cells. These results demonstrate that the use of antioxidants, alone or in combination with nitrogenation, can help prevent DA oxidation and improve its stability for cell-based studies or for the design and development of biomaterials.