An innovative non-pump gravity-driven dynamic microfluidic chip improves mouse embryo development

OBJECTIVE: Various microfluidic techniques are currently used in assisted reproductive technology. In this study, we designed an innovative nonpump microfluidic culture platform to enhance in vitro embryo culture. We evaluated its feasibility and compared its performance with that of traditional microdrop culture systems. MATERIALS AND METHODS: We developed microfluidic chips through a series of procedures, including fabrication of an SU-8 master mold, casting of polydimethylsiloxane (PDMS) on the mold, and integration of the microfluidic device. Mouse embryos were randomly assigned to three groups: (1) a traditional static drop group, (2) static microfluidic controls, and (3) a dynamic microfluid chip group. A gravity platform with a 15° tilt angle was used to drive the culture medium through the microchannels. The cytotoxicity of the chip materials was examined using the MTT assay, and embryo development was compared among the groups. RESULTS: MTT assay results confirmed the nontoxicity of the PDMS chip materials. The proportions of two-cell embryos that developed to the 4-8-cell, morula, and early blastocyst stages were comparable among the three groups. By contrast, embryos cultured in the dynamic microfluidic chip exhibited higher rates of development to the expanding and hatching blastocyst stages. Specifically, the percentages of embryos reaching the 4-8-cell, morula, early blastocyst, expanding blastocyst, and hatching blastocyst stages were 92.4%, 85.4%, 71.2%, 52.5%, and 45.7%, respectively, in the traditional static drop group; 93.5%, 84.5%, 69.2%, 52.2%, and 45.7%, respectively, in the static microfluidic group; and 93.8%, 86.5%, 74.5%, 67.2%, and 60.4% in the dynamic microfluidic group, respectively. CONCLUSION: The combined microfluidic and nonpump tilting culture system provides dynamic stimulation and automatic waste removal, which are not achievable with traditional static culture systems. The use of gravity instead of a motor-driven system enhances convenience and feasibility, improving the quality of in vitro embryo culture.