A harmless-to-harmful switchable and spatiotemporally activated nano-CRISPR hierarchically amplifies ferroptosis in melanoma.

Ferroptosis therapy faces challenges due to low lipid peroxide (LPO) levels. Herein, we develop a harmless-to-harmful switchable and spatiotemporally activated nano-CRISPR system (termed ARCHER) that sequentially amplifies ferroptosis sensitivity, iron ion levels, and reactive oxygen species (ROS) to amplify ferroptosis therapy efficiency. ARCHER targets cancer cells and releases CRISPR-Cas9 and Ce6Fe(III)Cl in response to hyaluronidase and tumor acidity. CRISPR-Cas9 sustains effective suppression of LPO-reducing protein GPX4. By persistently enhancing LPO accumulation through GPX4 downregulation, ARCHER primes cancer cells for ferroptosis and sensitizes them to subsequent interventions. Upon laser irradiation under acidic conditions, Ce6Fe(III)Cl undergoes spatiotemporal activation, transforming from inert form into cytotoxic Fe(III) ions and Ce6-generated ROS. Liberated Fe(III) and ROS synergistically amplify lipid peroxidation, driving LPO accumulation to trigger ferroptosis storm in sensitized cancer cells. In vivo studies demonstrated that ARCHER achieves 60% (3/5) tumor ablation with minimal off-target effects, validating its high therapeutic efficacy in ferroptosis-driven cancer treatment.