ROS-Responsive Micelles Loaded with Podophyllotoxin Inhibit Tumor Growth via ROS Self-Amplification and Regulation of Survivin and p21 Expression.

Podophyllotoxin (PPT) inhibits tumors such as lung cancer and breast cancer. However, it has poor water solubility and causes gastrointestinal dysfunction and bone marrow suppression, which severely limit its clinical application. Based on the differential reactive oxygen species (ROS) levels between tumor microenvironments and normal tissues, we designed and constructed a ROS-responsive micelle delivery system, successfully fabricating blank micelles (M) and PPT-loaded micelles (M@PPT). Both micelles exhibited good particle size uniformity, colloidal stability, and biosafety. The ROS responsiveness experiment revealed that, after incubating blank micelles (M) with 10 mM H2O2, the particle size increased significantly, and the size distribution broadened. High-performance liquid chromatography (HPLC) confirmed the release of cinnamaldehyde from the micelles upon H2O2 exposure. Additionally, DCFH-DA assays demonstrated that treatment with blank micelles (M) enhanced intracellular ROS levels. In vitro release studies showed that drug-loaded micelles (M@PPT) achieved 77.76% cumulative PPT release within 24 h in a buffer containing 10 mM H2O2, significantly exceeding the release observed in the H2O2-free control group. These results collectively validate the ROS-responsive disintegration of micelles and the subsequent release of cinnamaldehyde. The liberated cinnamaldehyde further amplified intracellular ROS levels, establishing a positive feedback loop that accelerated drug release. Cellular assays revealed superior tumor growth inhibition by M@PPT over free PPT, mediated through apoptosis induction, G2/M phase cell cycle arrest, downregulation of the anti-apoptotic protein Survivin, and upregulation of the p21 protein. In vivo studies further confirmed the enhanced antitumor efficacy and improved biosafety of M@PPT compared to free PPT. This ROS-responsive micellar system, by enabling tumor-targeted drug delivery and controlled release, provides a novel strategy to optimize the clinical utility of podophyllotoxin-based chemotherapeutics.