Hero Spermbots Could Battle Cervical Cancer

Bull sperm latch onto a mini device with four arms, then magnetically float to a tumor to deliver drugs.


When Dr. Mariana Medina Sánchez was 21 years old, her mother died of cervical cancer.

“She was just 38 years old when it happened,” Medina Sánchez told The Daily Beast. “And the therapies were very invasive. She had chemotherapy and radiation and many secondary effects in other organs in the body.”

Cervical cancer is caused by the human papillomavirus, or HPV, a sexually transmitted virus. The World Health Organization calls it “the most common viral infection of the reproductive tract.” And while a vaccine exists for the two strands of HPV that cause cervical cancer, there are nearly half a million affected with the disease every year, 270,000 of whom will die from it, according to the WHO.

Medina Sánchez, a group leader of the micro- and nanobiomedical engineering group at Leibniz Institute for Solid State and Materials Research Dresden in Germany, has been researching a new technique that could help decrease these numbers or at least help patients with cervical cancer feel better as they’re going through treatment: drug-loaded sperm robots that can swim through the female reproductive tract directly to a tumor.

Medina Sánchez, along with Haifeng Xu and their team at IFW Dresden, recently published a paper in ACS Nano about their successes with the technology.

Xu explained that the team loaded bovine (or bull) sperm, which swim similarly to how human sperm swim, with doxorubicin hydrochloride, a wide-spectrum anti-cancer drug. Then, they coupled the sperm with a tetrapod, a microdevice with four arms that’s covered in iron and can thus be controlled by a magnetic field, to direct the sperm exactly toward the tumor.

Sperm was a natural choice for this application, Xu told The Daily Beast, because “they can swim by themselves.” However, they need external guidance to get directly to a tumor, which is where the magnetic field comes in. Xu said that the magnetic field can change the direction of the spermbot in six different ways, directing the drug carrier exactly where it needs to go and with the exact amount of medication it needs to kill a tumor.

“With conventional drug delivery, it’s in contact with other fluids in the body and the drug is less effective,” Medina Sánchez said. “With this, once the sperm reaches the tumor and the cancer cell, they have the ability to fuse with the cell and the drug is delivered inside the cancer cell because both cells are fused.”

This technique could one day be applied to cancer patients with the same techniques used for artificial insemination; it can also be extended to treat other gynecological cancers, as sperm is a natural fit for the reproductive tract.

However, both Medina Sánchez and Xu admit this research is far from ready for human research or a clinical setting, as it has a number of issues to be worked out.

First of all, the micromotors are coated with an iron that could potentially be toxic to the body.

“We have to analyze the toxicity effects of what we’d finally use,” Medina Sánchez said. “[The iron is] not biodegradable, but in principle it should be possible to replace the material.”

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And then there’s the big problem of pregnancy. “There could be the possibility that you’d get pregnant,” Medina Sánchez said. “But it’d be possible to control if we applied the therapy when you’re not ovulating. Of course it’s something you cannot control completely, and that’s why we have the structures to guide them to effective tissue.”

For now, the team is working on improving the technology by increasing the drug dose and loading more doxorubicin hydrochloride into each spermbot to kill more cancerous cells in humans. “We are trying to collaborate with some doctors and we actually have some preliminary results but it’s not published yet,” Xu said.

Medina Sánchez added that a clinical application is about a decade away and acknowledged it’s still very unclear how the technology will transfer to humans. “We cannot say that this is better than existing technologies because we have done it in vitro, so we don’t know how effective it is in people,” she said.

The team said there’s also the possibility that the technology could be used beyond cervical cancer by guiding sperm for fertilization. But for now, the goal is to improve the quality of life in patients suffering from cervical or gynecological cancers.

Medina Sánchez, for one, is driven by her family history. “Although this happened a long time ago, I am still affected by that and that’s why I am trying to apply my knowledge on engineering and material science to the biomedicine,” she said. The spermbot might help ensure what happened to her mother won’t happen to someone else.