Sperm Movement Control Utilizing Surface Charged Magnetic Nanoparticles.

Oligozoospermia and asthenospermia are significant issues related to male infertility, and clinical treatments for infertility are complicated and expensive. This paper presents a sperm-magnetic controlling technology to manipulate sperm movement utilizing surface charged Fe₃O₄ magnetic nanoparticles (MNPs). Since the surface membrane of sperm is negatively charged, positively charged MNPs can be attracted to the cell membrane of sperm, but the sperm cells and the negatively charged MNPs will repel each other. Under a magnetic field, the MNPs are magnetized to navigate the sperm cells. Experimental results show that, under a magnetic field intensity of 1.48 T, the translational speed of sperm cells with positively charged MNPs was 100 μm/s, while the speed of sperm cells was 80 μm/s if negatively charged MNPs were added. The translational speed of sperm, adding either positively or negatively charged MNPs, linearly and monotonically increased as the intensity and gradient of the magnetic field elevated. Moreover, the speed of sperm movement is a quadratic function of distance of the magnet location. Positively charged MNPs can drive sperm cells faster, as they are directly attracted to sperm surfaces, which is more effective than driving the sperm by electrical repulsion using negatively charged MNPs. Consequently, this proposed approach using surface charged MNPs to control the movement of sperm cells in vitro provides a simple solution for infertility.