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Ferroptosis, a promising mechanism of killing cancer cells, has become a research hotspot in cancer therapy. Besides, advantages of polymeric nanomaterials in improving anticancer efficacy and reducing side effect are widely accepted. In this work, based on the property of polypodamine to chelate metal ions, ultrasmall poly­(ethylene glycol)-modified polydopamine nanoparticles, (UPDA-PEG)@Fe2+/3+ nanoparticles, a novel ferroptosis agent, was rationally designed by chelating iron ions on ultrasmall polydopamine nanoparticles modified by PEG. This treatment led to a bigger specific surface area, which could support more reactive sites to chelate large number of iron ions, which is beneficial for exploring the detailed mechanism of ferroptosis-induced tumor cell death by iron ions. Also, the pH-dependent release of iron ions can reach approximately 70% at pH 5.0, providing the advantage of application in tumor microenvironment. The in vitro tests showed that the as-prepared NPs exhibit an effective anticancer effect on tumor cells including 4T1 and U87MG cells, yet ferric ions show a stronger ability of killing cancer cells than ferrous ions. Differences between ferrous ions and ferric ions in the ferroptosis pathway were monitored by the change of marker, including reactive oxygen species (ROS), glutathione peroxidase 4, and lipid peroxide (LPO), as well as the promoter and inhibitor of ferroptosis pathway. UPDA-PEG@Fe2+ nanoparticles induce ferroptosis that depends more on ROS; however, a more LPO-dependent ferroptosis is induced by UPDA-PEG@Fe3+ nanoparticles. Additionally, the in vivo studies using tumor-bearing Balb/c mice demonstrated that the as-prepared NPs could significantly inhibit tumor progression. UPDA-PEG@Fe2+/3+ nanoparticles reported herein represent the nanoparticles related to iron ions for chemotherapy against cancer through the ferroptosis pathway.

High-performance energy storage materials are of essential importance in advanced electronics and pulsed power systems, and the polymer dielectrics have been considered as a promising energy storage material, because of its higher dielectric strength and more excellent flexibility compared with that of inorganic ceramic dielectrics. However, the energy storage capability of pristine polymer has been limited by its low intrinsic dielectric permittivity and ordinary ferroelectric performance. Herein, this work demonstrates a favorable method to achieve a sandwich-structured poly(vinylidene fluoride) (PVDF)-based composite by the electrospinning, solution casting, thermal quenching, and hot-pressing process. This innovative method combines with the 0.5Ba(Zr 0.2 Ti 0.8 )O 3 -0.5(Ba 0.7 Ca 0.3 )TiO 3 nanofibers (BZT-BCT NFs), which possesses good ferroelectric hysteresis, and the hybrid particles of hexagonal boron nitride nanosheets (BNNSs) coated by ferroferric oxide (Fe 3 O 4 @BNNSs), which hold high breakdown strength (E b ). It is worth mentioning that the Fe 3 O 4 particles disperse well on the surface of BNNSs to form the dipoles with the BNNSs at the interfacial region, resulting in an enhancement of the electric displacement and the dielectric permittivity of the composite. Furthermore, the influence of the volume fraction of filler particles on the electrical performance of composite was systematically investigated. Notably, the enhanced performance in terms of electric displacement (D), E b , and discharged energy density (U e ) was achieved in the sandwiched BZT-BCT NFs-PVDF/Fe 3 O 4 @BNNSs-PVDF/BZT-BCT NFs-PVDF composite. The U e of ∼8.9 J/cm 3 was achieved at 350 kV/mm, which was 740% higher than the U e of biaxially oriented polypropylene (BOPP, U e ≈ 1.2 J/cm 3 at 640 kV/mm). Of particular note is that the hybrids Fe 3 O 4 @BNNSs play a critical role to enhance the D and E b and suppress the remnant displacement (D r ) of sandwiched composite. This contribution proposes an efficient and scalable method to prepare polymer-based dielectric composite for the demanded applications.

We report enhancement of the dielectric permittivity of poly(vinylidene fluoride) (PVDF) generated by depositing magnetic iron oxide (Fe3O4) nanoparticles on the surface of barium titanate (BT) to fabricate BT–Fe3O4/PVDF composites. This process introduced an external magnetic field and the influences of external magnetic field on dielectric properties of composites were investigated systematically. The composites subjected to magnetic field treatment for 30 min at 60 °C exhibited the largest dielectric permittivity (385 at 100 Hz) when the BT–Fe3O4 concentration is approximately 33 vol.%. The BT–Fe3O4 suppressed the formation of a conducting path in the composite and induced low dielectric loss (0.3) and low conductivity (4.12 × 10−9 S/cm) in the composite. Series-parallel model suggested that the enhanced dielectric permittivity of BT–Fe3O4/PVDF composites should arise from the ultrahigh permittivity of BT–Fe3O4 hybrid particles. However, the experimental results of the BT–Fe3O4/PVDF composites treated by magnetic field agree with percolation theory, which indicates that the enhanced dielectric properties of the BT–Fe3O4/PVDF composites originate from the interfacial polarization induced by the external magnetic field. This work provides a simple and effective way for preparing nanocomposites with enhanced dielectric properties for use in the electronics industry.

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