Magnetic field boosted ferroptosis-like cell death and responsive MRI using hybrid vesicles for cancer immunotherapy

We report a strategy to boost Fenton reaction triggered by an exogenous circularly polarized magnetic field (MF) to enhance ferroptosis-like cell-death mediated immune response, as well as endow a responsive MRI capability by using a hybrid core-shell vesicles (HCSVs). HCSVs are prepared by loading ascorbic acid (AA) in the core and poly(lactic-co-glycolic acid) shell incorporating iron oxide nanocubes (IONCs). MF triggers the release of AA, resulting in the increase of ferrous ions through the redox reaction between AA and IONCs. A significant tumor suppression is achieved by Fenton reaction-mediated ferroptosis-like cell-death. The oxidative stress induced by the Fenton reaction leads to the exposure of calreticulin on tumor cells, which leads to dendritic cells maturation and the infiltration of cytotoxic T lymphocytes in tumor. Furthermore, the depletion of ferric ions during treatment enables monitoring of the Fe reaction in MRI-R2* signal change. This strategy provides a perspective on ferroptosis-based immunotherapy.

N=Z*Z*P(1-P)/(A*A) was used to calculate the sample size. "Z" is the z score, "A" is the margin of error, "N" is sample size., "P" is the population proportion. To identify as effective treatment of final tumor size with 95% confidence, and a margin of error of 5%. And according to our pilot study results and previous experience, we assume a population proportion of 99.5~99.9% ("P") could be used to present the treatment efficiency. "Z" for a 95% confidence level is 1.96. We calculated N=8~2. Thus, 6 mice was used in each group.
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Mice before treatment and imaging study were randomized grouped by simple random sampling strategy. Other samples were grouped randomly by simple random sampling strategy.
All experiments were conducted in a double blinded fashion in which the researchers were blinded to group allocation.
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The cells were purchased from ATCC. No authentication was done by ourself.
All cells were tested negative for mycoplasma in routine PCR assays.

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nature research | reporting summary
April 2020

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Does the work involve any of these experiments of concern: No Yes Demonstrate how to render a vaccine ineffective Confer resistance to therapeutically useful antibiotics or antiviral agents All animal studies were performed in accordance with protocols approved by the Institutional Animal Care and Use Committee (IACUC) Office at Northwestern University.
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To analyze immune cells, tumors were minced and digested in an 8-mL mixture of 2 mg/mL collagenase type IV (LS004188; Worthington, Lakewood, NJ), 0.2 mg/mL hyaluronidase (H3506, Sigma-Aldrich, St Louis, MO), and 0.2 mg/mL DNase I (D4527, Sigma-Aldrich) in DMEM/F12 medium at 37°C for 30 min. The mixture was shaken constantly at 20 RPM. Debris was removed by filtration through a 40-"m mesh, and the red blood cells were removed with a red blood cell lysis buffer (R7757, Sigma-Aldrich). The mixture was pelleted and re-suspended in PBS supplemented with 2% fetal bovine serum for further analyses.
Data was collected using BD FACSDIVA software, and analyzed using Flow Jo.
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