Magnetic black phosphorus microbubbles for targeted tumor theranostics

Black phosphorus (BP) is attracting more and more interest for the biomedical application. The absorption in a wide spectral range and high photothermal conversion efficiency make BP suitable for photothermal therapy. However, BP alone is hard to realize the targeted therapy, which limits the precision and efficiency of the therapy. Magnetic microbubbles (MBs) are favored drug carriers because they can resist the sheer force of blood flow in a magnetic field, which improves the efficiency of MBs adhesion to the vascular wall for targeted ultrasound diagnosis and therapy. This study first optimized the magnetic MBs configurations through controlling the connecting polyethylene glycol (PEG) chain length. The magnetic MBs with PEG2000 have been chosen for targeted BP nanosheets delivery due to the better stability and magnetic responsiveness. The magnetic black phosphorus microbubbles (MBBPM) can realize the targeted tumor theranostics in vitro and in vivo. They could be applied for the targeted ultrasound imaging with an enhanced echogenicity by three times when accumulated at the target site where the magnetic field is applied. As the NIR laser irradiation was applied on the accumulated MBBPM, they dynamited and the temperature increased rapidly. It improved the cell membrane permeability, thus accelerating and enhancing a precision photothermal killing effect to the breast cancer cells, compared to BP alone.