New Scientist spells out how we’re able to use sperm cells to carry chemotherapy drugs directly to tumors:
Haifeng Xu at the Leibniz Institute for Solid State and Materials Research in Germany and his team are experimenting with using sperm cells to take drugs to cancers in the female reproductive tract. When they loaded sperm cells with doxorubicin, a common chemo agent, and released them in a dish containing mini cervical cancer tumours, the sperm swam towards the tumours, killing 87 per cent of their cells within three days.
The team then fitted sperm with tiny four-armed magnetic harnesses that allowed them to be guided by magnets. When the sperm hit a solid tumour, the arms sprung open, releasing the sperm and allowing them to swim into the tumour.
Video at the link.