Clinical and biological efficacy of microfluidic chips for sperm selection in infertility treatment using assisted reproductive technologies

Relevance: In modern assisted reproductive technology (ART) laboratories, two primary methods are widely used to process ejaculates and isolate a fraction of morphologically normal motile sperm: density gradient centrifugation and the swim-up method. Both techniques involve high-speed centrifugation (300 g), which can negatively impact DNA integrity in male germ cells and promote the formation of reactive oxygen species, potentially reducing sperm fertilization capacity by causing DNA fragmentation. Microfluidic systems have attracted attention as a promising alternative for male germ cell selection in infertility treatment due to their ability to select sperm with enhanced reproductive potential.

Objective: To evaluate the clinical efficacy of microfluidic chips for sperm selection in ART-based infertility treatment and analyze the morpho-functional characteristics of male gametes selected using microfluidics.

Materials and methods: This study included 94 married couples undergoing ART infertility treatment, divided into two groups: the study group (n=47), in which fertilization was performed using sperm isolated on microfluidic chips, and the control group (n=47), in which standard ejaculate sample preparation was conducted using density gradient centrifugation. The clinical and embryological outcomes were assessed. In the second phase, the ejaculate from men in the study group was divided into three samples: native (unprocessed) group, study group (processed using Fertile Plus microfluidic chips, Turkey), and control group (processed by density gradient centrifugation at 300 g per the manufacturer’s protocol, PanECO, Russia). Sperm concentration (C), progressive motility (PR%), morphology (N%), and chromatin maturity (%) were also assessed. Nuclear protein analysis (for chromatin maturity/condensation) was performed using aniline blue staining (Sperm Processor; India). Statistical analysis was conducted using SPSS Statistics (USA), and the Mann–Whitney U test was used to identify group differences. Statistical significance was set at p<0.05.

Results: ART programs using microfluidic technology resulted in a statistically significant increase in the number of high-quality blastocysts on culture days 5–6. No significant differences were observed between the groups in terms of fertilization rate, clinical pregnancy rate, or early pregnancy loss (up to 12 weeks gestation). In the second phase, the biological assessment of male gametes indicated no differences in sperm concentration and motility among the groups. However, statistically significant differences were noted in the percentage of morphologically normal spermatozoa (p<0.05): native – 2 (2; 3); microfluidic chip group – 3 (3; 4); and gradient centrifugation group – 3 (3; 3). Chromatin quality in the isolated spermatozoa also differed significantly: the percentage of immature spermatozoa was 14 (8; 20) in the native sample, 3 (5.5; 12) in the microfluidic chip group, and 8 (5; 10) in the gradient group, with a normal range of ≤15%.

Conclusion: The findings from this study suggest that microfluidic chips not only enhance the selection of morphologically normal spermatozoa but also increase the proportion of male germ cells with well-packed chromatin, which is a crucial factor for sustained pregnancies achieved through ART. Moreover, sperm selection without centrifugation using solely microfluidic devices (including passive ones) may improve embryological outcomes. Further studies are required to confirm the clinical effectiveness of this approach.