Background
Current sperm preparation methods used in assisted reproductive technologies (ART) bypass the natural selection barriers of the female reproductive tract. Conventional approaches rely on limited selection criteria and do not replicate the complex, multistep physiological processes involved in natural sperm selection. This study aimed to develop a functionalised surface on a polydimethylsiloxane (PDMS) microfluidic platform that biomimics key sperm selection mechanisms of the female reproductive tract.
Methods
Five biomimetic PDMS microchannel architectures were fabricated, comprising three straight-channel designs (P1–P3) with varying channel depths and chamber heights, and two curved-channel designs (P4–P5) with different radii of curvature to generate distinct hydrodynamic resistance profiles. Microchannel surfaces were coated with plasma-polymerised polyoxazoline and functionalised with covalently immobilised gold nanoparticles and anti-phosphatidylserine antibodies to facilitate selective removal of apoptotic spermatozoa. Progesterone was incorporated near the outlet to promote chemotactic migration of functionally competent sperm. Following 60 min processing, sperm quality (n=4–6 samples/design) was evaluated by recovery rate, progressive motility, Annexin V staining, and DNA fragmentation analysis using halosperm® and TUNEL assays. Statistical analysis was performed using one-way ANOVA followed by Tukey's t-test.
Results
Microchannel geometry significantly influenced sperm selection efficiency. The curved P4 design produced the highest-quality sperm population, reducing DNA fragmentation to 0.7 ± 0.4% (P<0.05), compared with P5 (1.4 ± 0.8%), P1 (2.3 ± 1.1%), P2 (3.8 ± 2.8%), and P3 (8.0 ± 3.4%). Annexin V-positive spermatozoa were significantly reduced following P4 selection (2.7 ± 1.4%) compared with other microchannel designs and swim-up selection (11.1 ± 3.5%, P<0.05).
Conclusion
A surface-engineered PDMS microfluidic platform incorporating biomimetic microchannels successfully integrated key sperm selection mechanisms of the female reproductive tract, including immune-mediated clearance, progesterone-guided chemotaxis, and migration against hydrodynamic resistance. This platform enriched spermatozoa with enhanced motility, reduced apoptosis, and DNA fragmentation, indicating its potential as an advanced sperm preparation strategy for ART.