A Rotating Spiral Micromotor for Noninvasive Zygote Transfer

Abstract

Embryo transfer (ET) is a decisive step in the in vitro fertilization process. In most cases, the embryo is transferred to the uterus after several days of in vitro culture. Although studies have identified the beneficial effects of ET on proper embryo development in the earlier stages, this strategy is compromised by the necessity to transfer early embryos (zygotes) back to the fallopian tube instead of the uterus, which requires a more invasive, laparoscopic procedure, termed zygote intrafallopian transfer (ZIFT). Magnetic micromotors offer the possibility to mitigate such surgical interventions, as they have the potential to transport and deliver cellular cargo such as zygotes through the uterus and fallopian tube noninvasively, actuated by an externally applied rotating magnetic field. This study presents the capture, transport, and release of bovine and murine zygotes using two types of magnetic micropropellers, helix and spiral. Although helices represent an established micromotor architecture, spirals surpass them in terms of motion performance and with their ability to reliably capture and secure the cargo during both motion and transfer between different environments. Herein, this is demonstrated with murine oocytes/zygotes as the cargo; this is the first step toward the application of noninvasive, magnetic micromotor‐assisted ZIFT.

Medical Micro/Nanorobots in Precision Medicine

“…[ 238 ] Spiral‐shaped magnetically powered micromotor were used to transport and release individual fertilized oocytes in a microfluidic chip. [ 239 ] Such examples demonstrate the potential of micro/nanorobots in assisted fertilization protocols.…”

Magnetically Driven Micro and Nanorobots

“…Moreover, magnetically driven micromotors provide an invasive way to transfer zygotes through the uterus and fallopian tube ( Figure 15 D), and magnetic microrobots with spiral shapes exhibit higher maneuverability in terms of capture and transfer of the zygotes between different physiological environments than those with helical shapes. 321 Transportation of neural progenitor cells was conducted by the corkscrew-like motion of magnetically powered soft microswimmers containing piezoelectric polymer and CoFe 2 O 4 magnetic nanoparticles under a rotating magnetic field. Subsequent neuronal differentiation of PC12 cells was induced by the acoustic stimulation due to the utilization of piezoelectric polymer as a stimuli-responsive cell electrostimulation platform ( Figure 15 E).…”

“…(D) Magnetically powered microspirals for the delivery of murine zygote. Reproduced with permission from ref ( 321 ). Copyright 2020 The Authors.…”

The Energy Conversion behind Micro-and Nanomotors

“…Later, in 2016, Medina Sanchez et al developed a new type of hybrid micromotor, which was combined with immotile live sperm cells, and can artificially motorize sperm cells under the action of an external magnetic field and have potential to assist the fertilization process [ 158 ]; In subsequent research, Medina Sanchez et al continue to expand their research on reproduction. In 2020, they proposed the concept of micromotor-assisted ZIFT (zygote intrafallopian transfer), which use magnetic micromotors to capture fertilized eggs, and are promising to assist embryo implantation and development under a rotating magnetic field [ 159 ]. The artificial flagella, on the one hand, expands the application scope and can adapt to aqueous environments with different fluidity; on the other hand, it can ensure that the moving ability remains unchanged under the action of a lower energy magnetic field.…”