Creating an effective way to target cancer cells with drugs is challenging on multiple fronts.
For example, the drugs do not always travel deeply enough through tissues, and they can get diluted in body fluids or sidetracked and taken up by healthy organs.
To get around these issues, scientists have turned in some cases to loading pharmaceuticals into bacteria, which can effectively contain drug compounds and propel themselves.
The microbes can also be guided by a magnetic field or other mechanism to reach a specific target.
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Looking for another self-propelled cell as an alternative drug carrier to bacteria, researchers at the Leibniz Institute for Solid State and Materials Research-Dresden (IFW Dresden) in Germany turned to sperm.
The researchers packaged a common cancer drug, doxorubicin, into bovine sperm cells and outfitted them with tiny magnetic harnesses.
Using a magnetic field, a sperm-hybrid motor was guided to a lab-grown tumour of cervical cancer cells. When the harness arms pressed against the tumour, the arms opened up, releasing the sperm.
The sperm then swam into the tumour, fused its membrane with that of a cancer cell, and released the drug.
Further work is needed to ensure the system could work in animals and eventually humans, but researchers said the sperm motors have the potential to one day treat cancer and other diseases in the female reproductive tract.