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Abstract Study question Does sperm selection by rheotaxis and thermotaxis in In-Situ handmade microfluidics of fluidic walls optimize ICSI outcomes and workflow? Summary answer In-Situ handmade rheo/thermotaxis microfluidics of fluidic walls is as effective and more time-efficient than centrifugation density gradients to support pre-implantation embryonic development to blastocyst. What is known already Microfluidics technologies stand as the latest sperm selection methodology for ICSI. To outline their application in ART we conceived a lab-on-a-chip approach for sperm selection by In-Situ handmade microfluidics of fluidic walls (isM) in the same ICSI plate which integrates two operative zones: one to allow seminal plasma dispersion and sperm thermotaxis and another one to allow sperm rheotaxis. Our microfluidics system can be prepared with any media suitable for ICSI, disregarding centrifugation, washing, plasticware and other cells. The isM protocol proved non-inferior to centrifugation density gradients (CDG) to support embryonic development and implantation in a previous sibling-oocyte study. Study design, size, duration The present RCT was approved by our ethical committee for research with medical products (CEIm approval number 2023/394). This preliminary analysis aims to detect deviations in the pre-defined primary outcomes: Normal Fertilization Rate, Day 5/6 usable blastocyst rate per MII, and per zygote. This analysis includes data from 21 couples undergoing an ICSI treatment in our center during December 2023-January 2024. Only patients without clinical or analytical suspicion of sperm DNA fragmentation were included. Participants/materials, setting, methods Patients were randomly allocated to isM (n 9) or to CGD (n 12) groups. All participants signed an informed consent. Sperm samples were processed directly after liquefaction. For CGD, samples were prepared in 80-40% PureSperm® layers by isopycnic centrifugation followed by washing and dilution steps. The isM system was prepared by displaying three microdroplets of different volumes following a L-shape interconnection and allowing a temperature gradient of 2ºC between the first and the second microdroplet. Main results and the role of chance Sperm characteristics showed the following total mean values for the isM and CGD groups, respectively: concentration (58,2±38,0 × 106/ml and 52,7±29,1 × 106/ml) and progressive sperm concentration (16,6±17,0 × 106/ml and 16,8±13,4 × 106/ml). Women average age was 36,7±2,9 isM and 35,8±2,5 CDG. This analysis includes a total of 168 MII oocytes (n = 69 isM and n = 99 CDG), with a mean number of MII oocytes per patient of 7,4±2,1 isM and 8,3±1,9 CDG. Comparisons between the two groups showed that isM protocol optimizes ICSI outcomes by means of Normal Fertilization Rate: 88,4% vs 76,8%; p 0,05, Day 5 A/B grade blastocyst rate: 36,1 vs 31,6%; ns, Day 5/6 usable blastocyst rate per MII: 58,0% vs 44,4%; ns and Day 5/6 usable blastocyst rate per diploid zygote: 65,6% vs 57,9%; ns. The isM protocol also optimizes the IVF workflow compared to CDG, as the time to obtain sperm for ICSI after liquefaction was 26 vs 77 minutes, respectively. Limitations, reasons for caution The study aims for a total size of 50 ICSI cycles to validate statistically our data at a power of 80%. The isM protocol depends on a free hand preparation. A ready-to-use surface would benefit the operability, albeit the use of templates and the training reduces inter and intra-operator variability. Wider implications of the findings The potential benefits of the isM protocol on fertilization could be significant for patients with a limited number of available oocytes for ICSI. According to the literature, microfluidics reduce the DNA fragmentation index in the selected sperm fraction. The isM method could be especially beneficial in patients with this pathology. Trial registration number NCT number assignment pending
Buitrago et al. (Mon,) studied this question.