Low frequency vibrating magnetic field-triggered magnetic microspheres with a nanoflagellum-like surface for cancer therapy

The magneto-mechanical force killing cancer cells is an interesting and important strategy for cancer therapy. Novel magnetic microspheres composed of a Fe.sub.3O.sub.4 nanocore, a bovine serum albumin (BSA) matrix, and a rod-like SiO.sub.2 nanoshell, which had flagellum-like surface for force-mediated cancer therapy were developed. One such magnetic microsphere (Fe.sub.3O.sub.4/BSA/rSiO.sub.2) at a cancer cell (not leave the cell surface) under a low frequency vibrating magnetic field (VMF) could generate 6.17 pN force. Interestingly, this force could induce cancer cell to generate reactive oxygen species (ROS). The force and force-induced ROS could kill cancer cells. The cell killing efficiency of Fe.sub.3O.sub.4/BSA/rSiO.sub.2 exposed to a VMF was enhanced with increasing silica nanorod length, and the microspheres with straight nanorods exhibited stronger cell killing ability than those with curled nanorods. Fe.sub.3O.sub.4/BSA/rSiO.sub.2 triggered by a VMF could efficiently inhibit mouse tumor growth, while these microspheres without a VMF had no significant effect on the cell cycle distribution, cell viability, tumor growth, and mouse health. These microspheres with unique morphological characteristics under VMF have great potential that can provide a new platform for treating solid tumors at superficial positions whether with hypoxia regions or multidrug resistance.