Quantification of elastic modulus variations during zebrafish embryo development using a 3D-printed microfluidic platform

Abstract

Reliable indicators to assess embryo quality are critical for the in vitro fertilization. Increasing evidence suggests that elasticity is emerging as a potential marker to evaluate the early development of embryos. This paper introduces a 3D-printed microfluidic device to measure the elastic modulus of zebrafish embryos deformed in a circular constriction channel. Firstly, numerical simulation was performed to analyze the impact of inlet pressure, embryo size and constriction channel diameter on the maximum protrusion length of the embryo. Subsequently, the zebrafish embryos were deformed using the device to record the protrusion length which was automatically measured using U-net, before the power-law rheological model was employed to calculate the elastic modulus. Experiments showed the power-law exponent and embryo elasticity were stable as the inlet pressure was not less than 250 mbar. Embryo culturing after squeezes revealed that embryos could maintain normal development even after multiple squeezes at 150 mbar while higher pressure may be fatal. Afterward, the deformation of the yolk was found to increase elasticity by 60.4 % compared to cases where only the chorion envelope was deformed. Finally, the elasticity variation of zebrafish embryos was measured for 17 hours. It revealed that the elasticity initially increased from hour 1 to hour 7–10 and then returned to approximately the original value during culture from the cleavage to the segmentation stages. The system with the ability of precise and long-term assessment of embryo elasticity may find valuable application potentials in the mechanical evaluation and sorting of embryos.