A German research team have been testing an unorthodox way of delivering drugs to cancer tumours—by putting drugs inside living sperm cells.
A common problem in the fight against cancer is delivering medication to the right spots in the body. Methods such as traditional chemotherapy can be very effective in destroying cancer, but can seriously damage the rest of the body. For this reason new methods of precise drug delivery are being developed all the time: from antibodies loaded with medication to specially engineered nanoparticles, and even combinations of both.
Mariana Medina-Sánchez and her team focused on a particularly unique solution to this problem which they think may be applicable to gynaecological cancers—harnessing the natural mobility of sperm cells to do their bidding. Attaching iron-coated caps onto the sperm cells, the team were able to guide the sperm cells through magnets from outside the body, precisely controlling where they were led.
They noted that in addition to the ability of the sperm to move quickly to the right spot, living cells have a better chance of successfully delivering treatment into the tumour cells than an artificial nanostructure, as they are more compatible with the cells to which they are delivering their payload. While bacteria have also been suggested as carriers for the same reason, they are problematic since they can often provoke a hostile response from the immune system of the patient thus jeopardising the delivery.
In order to make sure the cells reach their targets, the team designed a cylindrical tube which fits snugly over the sperm heads and is equipped with a simple system of four ‘arms’ which, when they come into contact with a cell wall, eject the sperm out of the front of the tube and into the cell. These microstructures, called ‘tetrapods’, were printed and coated with a thin layer of iron which allowed them to be guided accurately by magnets from a distance.
After being fitted with the caps, the bovine sperm (chosen for its similar shape and size to human sperm) were directed towards a culture of HeLa cells (artificially grown human cells), carrying a traditional chemotherapy drug. The team found that they could control the direction of the sperm very effectively, and after 72 hours found that the drug-loaded sperm had successfully killed 87 per cent of the HeLa cells, a significant improvement over those cells which were simply left in a solution of the same drug. Interestingly, the trial with sperm cells which did not carry any drugs also killed a small number of cells through damage caused by the sperm entering the cell wall.
The team acknowledges that there are still some hurdles to overcome, such as decreasing the chance of the synthetic tetrapod disintegrating during the process, but they believe it could be used to great effect not just in efficiently treating cancer in the reproductive tract, but also in other diseases which can be treated in the same area, such as pelvic inflammatory diseases.
The method may seem bizarre, but it is proving effective because delivering a payload is precisely what sperm cells were designed to do, and it shows. They are very mobile, they completely encase and protect the drugs inside them, they are very good at working with other human cells, and they have an ability to fuse into the cell wall. If further tests prove successful, the humble sperm cell could have a remarkable new job saving lives as well as creating them.
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