Bioinspired quality-based sperm sorting in a spiral microfilter-enhanced microfluidic device: enhancing DNA integrity via rheotaxis and boundary dynamics

Abstract

Male infertility, often linked to poor sperm quality, poses significant challenges for assisted reproductive technologies (ARTs), such as in vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI). Compromised sperm parameters, including low motility and high DNA fragmentation, reduce fertilization rates and hinder embryo development, negatively affecting ART outcomes. Traditional sperm separation methods, such as density gradient centrifugation (DGC) and swim-up, often cause sperm damage, including increased DNA fragmentation and reduced motility, further decreasing ART success rates. These limitations underscore the need for innovative, gentle, and efficient sperm selection techniques to enhance reproductive outcomes. This study presents a novel spiral microfluidic platform for non-invasive, label-free, quality-based sperm separation. Unlike conventional spiral channel designs, this platform leverages a specialized spiral geometry to optimize gamete behaviors, such as rheotaxis, thigmotaxis, and boundary detachment–reattachment. This design achieves superior sorting precision and maximizes the recovery of high-quality sperm, particularly from heterogeneous or low-quality semen samples. The tailored spiral channel promotes sperm migration and dynamic interaction with channel walls, enabling highly efficient quality-based sorting with minimal mechanical stress. The platform's microfilter, integrated into the spiral design, separates sperm into four quality grades across distinct zones using controlled hydrodynamic flow and channel geometry. Results demonstrate that 95% of sperm are classified into these four categories, significantly outperforming traditional methods, with the highest-quality category showing a motility increase of 54.87% versus swim-up and 34.58% versus DGC, a DNA fragmentation reduction of 74.34% versus swim-up and 84.09% versus DGC, a viability improvement of 66.50% versus swim-up and 36.41% versus DGC, and a chromatin immaturity reduction of 75.29% versus swim-up and 80.44% versus DGC. By prioritizing quality-based separation and high recovery rates, this spiral microfilter microfluidic platform revolutionizes sperm selection for ART. It significantly enhances motility, DNA integrity, and chromatin maturity, offering a promising solution for challenging semen samples and improving clinical reproductive success.