Inhalable Biomineralized Liposomes for Cyclic Ca2+-Burst-Centered Endoplasmic Reticulum Stress Enhanced Lung Cancer Ferroptosis Therapy

Lung cancer with the highest mortality poses a great threat to human health. Ferroptosis therapy has recently been raised as a promising strategy for lung cancer treatment by boosting the reactive species (ROS) production and lipid peroxidation (LPO) accumulation intracellularly. However, the insufficient intracellular ROS level and the unsatisfactory drug accumulation in lung cancer lesions hamper the efficacy of ferroptosis therapy. Here, an inhalable biomineralized liposome LDM co-loaded with dihydroartemisinin (DHA) and pH-responsive calcium phosphate (CaP) was constructed as a ferroptosis nanoinducer for achieving Ca2+-burst-centered endoplasmic reticulum (ER) stress enhanced lung cancer ferroptosis therapy. Equipped with excellent nebulization properties, about 6.80-fold higher lung lesions drug accumulation than intravenous injection made the proposed inhalable LDM an ideal nanoplatform for lung cancer treatment. The Fenton-like reaction mediated by DHA with peroxide bridge structure could contribute to intracellular ROS production and induce ferroptosis. Assisted by DHA-mediated sarco-/endoplasmic reticulum calcium ATPase (SERCA) inhibition, the initial Ca2+ burst caused by CaP shell degradation triggered the Ca2+-mediated intense ER stress and subsequently induced mitochondria dysfunction to further boost ROS accumulation, which strengthens ferroptosis. The second Ca2+ burst occurred as a result of Ca2+ influx through ferroptotic pores on cell membranes, thus sequentially constructing the lethal "Ca2+ burst-ER stress-ferroptosis" cycle. Consequently, the Ca2+-burst-centered ER stress enhanced ferroptosis process was confirmed as a cell swelling and cell membrane disruption process driven by notable intracellular ROS and LPO accumulation. The proposed LDM showed an encouraging lung retention property and extraordinary antitumor ability in an orthotropic lung tumor murine model. In conclusion, the constructed ferroptosis nanoinducer could be a potential tailored nanoplatform for nebulization-based pulmonary delivery and underscore the application of Ca2+-burst-centered ER stress enhanced lung cancer ferroptosis therapy.