GSH and CES2 dual-responsive biosensor for dual-signal electron spin resonance (ESR) sensing and free radical-enhanced triple-mode therapy of hepatocellular carcinoma

The abnormally high expression of glutathione (GSH) in hepatocellular carcinoma (HCC) cells significantly contributes to chemotherapy resistance by neutralizing reactive oxygen species (ROS). To address this problem, we developed a nanocomposite probe (micelle@PDA@MnO 2 NPs) which was composed of free radical-labeled micelles as the core, polydopamine (PDA) as the inner shell and MnO 2 nanosheets as the outer shell. In the HCC microenvironment, the over-expressed GSH triggered the decomposition of the MnO 2 shell, releasing Mn 2+ ions, and subsequently, the acidic condition and over-expressed carboxylesterase 2 (CES2) worked together to mediate the controlled release of nitroxide free radicals (i.e., TEMPONE) from the micelle core. With the help of dual-signal electron spin resonance (ESR) detection, it was found that much more free radicals and Mn 2+ were released in hepatoma cells than in normal liver cells, rendering the proposed nanotherapeutic platform specific to HCC and a good candidate for free radical therapy and chemodynamic therapy (CDT). Moreover, the therapy featured an intelligent self-amplified property: the abundant GSH in the tumor microenvironment rapidly activated the decomposition of the nanocomposite and triggered the release of free radical TEMPONE and Mn 2+ , and TEMPONE and Mn 2+ further amplified the oxidative stress to induce tumor apoptosis via ROS generation and GSH depletion. Finally, in combination with three therapy modes (Mn 2+ -mediated CDT, the oxidative stress enhancement effect of TEMPONE, and PDA-based photothermal therapy), significant therapeutic effects including facilitation of HepG2 cell apoptosis and inhibition of tumor growth in the HCC mouse model were achieved.