Sperm‐Driven Micromotors Moving in Oviduct Fluid and Viscoelastic Media

Abstract

Biohybrid micromotors propelled by motile cells are fascinating entities for autonomous biomedical operations on the microscale. Their operation under physiological conditions, including highly viscous environments, is an essential prerequisite to be translated to in vivo settings. In this work, a sperm‐driven microswimmer, referred to as a spermbot, is demonstrated to operate in oviduct fluid in vitro. The viscoelastic properties of bovine oviduct fluid (BOF), one of the fluids that sperm cells encounter on their way to the oocyte, are first characterized using passive microrheology. This allows to design an artificial oviduct fluid to match the rheological properties of oviduct fluid for further experiments. Sperm motion is analyzed and it is confirmed that kinetic parameters match in real and artificial oviduct fluids, respectively. It is demonstrated that sperm cells can efficiently couple to magnetic microtubes and propel them forward in media of different viscosities and in BOF. The flagellar beat pattern of coupled as well as of free sperm cells is investigated, revealing an alteration on the regular flagellar beat, presenting an on–off behavior caused by the additional load of the microtube. Finally, a new microcap design is proposed to improve the overall performance of the spermbot in complex biofluids.

Medical Micro/Nanorobots in Precision Medicine

“…Furthermore, sperm have unique potential as an engine of micro/nanorobots because of its limited proliferation or secretion of toxic byproducts and the inhibition of the immune reaction due to its protein-rich surface. [219,220]…”

Engineering microrobots for targeted cancer therapies from a medical perspective

“…using materials with favourable toxicity profiles or dissolvable components, to facilitate clinical progression. Moreover, although first examples of synthetic microrobots have recently reached in vivo settings 27 , the field is still young and future work towards developing microrobots optimised for propelling in applicable biofluids and tissues are required to help extend these successes 116,123 . By combining cellular and synthetic components, almost any functionality can be envisioned in hybrid microrobots matching to the needs of the targeted cancer and its location inside the body.…”

Magnetic Actuation Methods in Bio/Soft Robotics

“…A study of motion of spermbots in bovine oviduct fluid demonstrated their ability to penetrate highly viscous fluids and how sperm adapt their beat pattern to the cargo load and surrounding media. [ 140 ] In an approach to deliver anticoagulants by spermbots, stream‐like caps where used to capture bovine sperm cells and equipped with heparin‐loaded liposomes. [ 141 ] These spermbots were introduced into a microfluidic flow chamber filled with diluted blood.…”