13 January 2021
A new role for sperm
Published online 9 July 2020
Sperm cells are given another function within biohybrid magnetic microrobots.
Sperm cells that are no longer capable of self-propulsion could be combined with metallic nanoparticles to make magnetic microrobots that deliver drugs to diseased tissues or guide tethered micro-surgical apparatus.
The technology, called IRONSperm, is being developed by researchers in Germany and the Netherlands, with numerical modelling assistance from Anke Klingner, at the German University in Cairo, Egypt.
“It was a fascinating achievement to see dead sperm cells swimming,” says group member, Islam Khalil, at the University of Twente in the Netherlands. He believes the system could become even more useful when applied to live sperm cells, and might eventually be adapted to assist in clinical fertilization procedures.
Using bovine cells in their proof-of-concept work, the team found that dead sperm cells could be made to move again with a simple one-step self-assembly process. The attraction between opposite electric charges on the sperm cells, and on magnetic iron oxide nanoparticles, forms the nanoparticle-coated hybrids that the team describes as ‘flexible magnetic microswimmers’.
The biological cells provide a suitable medium for loading with drugs or diagnostic imaging compounds, for release where desired. The metallic coating will allow magnetic guidance and control of the flexible swimming motion through living tissues.
The ability to transport and deliver drugs was demonstrated by filling the cells with the anti-cancer drug doxorubicin, followed by tests that indicated there was potential to achieve drug release when desired.
Good biocompatibilty of the microrobots was also found on exposure to cultured human cancer cells, suggesting toxic side effects will be avoided.
The researchers acknowledge there is still much work to do to convert their innovation into a useful clinical tool.
“We are just starting to understand how this microswimmer works, and its performance in more complex scenarios needs to be investigated,” says team member, Veronika Magdanz of the Technical University of Dresden.
Mechanical engineer Eric Diller of the University of Toronto, who was not involved in the study, says, “These biohybrid magnetic microrobots are exciting. The process to make them is simpler than many other microrobot fabrication methods. I look forward to seeing their biomedical validation, notably safe and effective targeted drug delivery inside living tissue.”
Magdanz, V. et al. IRONSperm: Sperm-templated soft magnetic microrobots. Sci. Adv. 6, eaba5855 (2020).