A Three-Dimensional Magnetic Tweezer System for Intraembryonic Navigation and Measurement

Abstract

Magnetic micromanipulation has the advantage of untethered control, high precision, and biocompatibility and has recently undergone great advances. The magnetic micromanipulation task to tackle in this paper is to three dimensionally navigate a 5-μm magnetic bead inside a mouse embryo and accurately apply forces to intraembryonic structures to perform mechanical measurements at multiple locations. Existing technologies are not able to achieve these navigation and measurement goals because of poor magnetic force scaling and/or lacking the capability of applying an accurately controlled force. This paper reports a three-dimensional magnetic tweezer system that enables, for the first time, intraembryonic magnetic navigation and force application. A single magnetic bead was introduced into a mouse embryo via robotic microinjection. The magnetic tweezer system accurately controlled the position of the magnetic bead via visually servoed magnetic control. By moving the magnetic bead with known forces inside the embryo, cytoplasm viscosity was measured, which is eight times the viscosity of water. For performing mechanical measurements on the cellular structures inside the mouse embryo, the system should be capable of applying forces up to 120 pN with a resolution of 4 pN. The results revealed that the middle region is significantly more deformable than the side regions of the inner cell mass.