Near-Infrared-II Light Induced Mild Hyperthermia Activate Cisplatin-Artemisinin Nanoparticle for Enhanced Chemo/Chemodynamic Therapy and Immunotherapy.

Chemodynamic therapy (CDT) is an effective cancer treatment that uses Fenton reaction to induce cancer cell death. Current clinical applications of CDT are limited by the dependency of external supply of metal ions as well as low catalytic efficiency. Here, a highly efficient metal-free CDT by using endoperoxide bridge-containing artesunate as free radical-generating substance is developed. A Pt(IV) prodrug (A-Pt) containing two artesunate molecules in the axial direction is synthesized, which can be decomposed into cisplatin and artesunate under reducing intracellular environment in tumor cells. To improve the catalytic efficiency for Fenton reaction, a near-infrared-II (NIR-II) photothermal agent IR1048 is incorporated to achieve a mild hyperthermia effect. By encapsulating the A-Pt and IR1048 with human serum albumin, A-Pt-IR NP are formulated for efficient drug delivery in 4T1 tumor-bearing mice. NIR-II light irradiation of A-Pt-IR NP treated mice show accelerated Fenton reaction. In addition, A-Pt-IR NP could also induce strong immunogenic cell death, which effectively reverses the immunosuppressive tumor microenvironment, and augments antitumor immunity. This study demonstrates that A-Pt-IR NP are potent biodegradable NIR-II active chemotherapy/CDT nanomedicine for clinical translation.

Monitoring Changes in the Oligomeric State of a Candidate Endoplasmic Reticulum (ER) Ceramide Sensor by Single-molecule Photobleaching.

Single-molecule photobleaching has emerged as a powerful non-invasive approach to extract the stoichiometry of multimeric membrane proteins in their native cellular environment. However, this method has mainly been used to determine the subunit composition of ion channels and receptors at the plasma membrane. Here, we applied single-molecule photobleaching to analyze the oligomeric state of an endoplasmic reticulum (ER) resident candidate ceramide sensor protein, SMSr/SAMD8. Co-immunoprecipitation and chemical cross-linking studies previously revealed that the N-terminal sterile alpha motif (or SAM) domain of SMSr drives self-assembly of the protein into oligomers and that SMSr oligomerization is promoted by curcumin, a drug known to perturb ER ceramide and calcium homeostasis. Application of cell spreading surface-active coating materials in combination with total internal reflection fluorescence (TIRF) microscopy allowed us to image GFP-tagged SMSr proteins as single fluorescent spots in the ER of HeLa cells in which expression of endogenous SMSr was abolished. In line with our biochemical analysis, we find that the number of bleaching steps in SMSr-GFP-positive spots displays a substantial drop after removal of the SAM domain. In contrast, treatment of cells with curcumin increased the number of bleaching steps. Our results document the first successful application of single-molecule photobleaching to resolve drug-induced and domain-dependent changes in the oligomeric state of an ER-resident membrane protein, hence establishing a complementary method to unravel the mechanism by which SMSr controls ceramide levels in the ER.