Nanoaggregates of Disulfide-Decorated TrxR Inhibitor Promote Cellular Uptake, Selective Targeting, and Antitumor Efficacy

Three self-assembled nanoaggregates (CPUL1-LA NAs, CPUL1-DA NAs, and CPUL1-AA NAs) were constructed through lipoic acid (LA), dithiodipropionic acid (DA), and adipic acid (AA) decorated TrxR inhibitor (CPUL1), respectively. Measurements of DLS, TEM, UV-vis, fluorescence, 1H NMR, ITC, and MTT assays verified disulfide-containing CPUL1-LA NAs and CPUL1-DA NAs spontaneously assembled carrier-free nano-particles in aqueous solution, which possessed high drug contents, excellent stability, improved cytotoxicity against HUH7 hepatoma cells, and potential biosafety because of low cytotoxicity against L02 normal cells. In contrast, disulfide-free CPUL1-AA NAs happened to aggregate and precipitate after 48 h, which showed distinct instability in aqueous solution. Thus, disulfide units seemed to be crucial for constructing controllable and stable nanoaggregates. While measuring the reduction of nanoaggregates by TrxR/NADPH and GSH/ GR/NADPH, cyclic disulfide of LA and linear disulfide of DA were verified to endow the nanoaggregates with targeting ability to respond specifically to TrxR over GSH. Furthermore, by tests of flow cytometry, fluorescence images, and CLSM, both CPUL1-LA NAs and CPUL1-DA NAs displayed a faster cellular uptake characteristic to be internalized by cancer cells and could generate more abundant ROS to induce cell apoptosis than that of free CPUL1, resulting in significantly improved antitumor efficacy against HUH7 cells in vitro.