Large‐Area Silicon Nitride Nanosieve for Enhanced Diffusion‐Based Exosome Isolation

Abstract Nanoporous membranes have a variety of applications, one of which is the size‐selective separation of nanoparticles. In drug delivery, nanoporous membranes are becoming increasingly important for the isolation of exosomes, which are bio‐nanoparticles. However, the low pore density and thickness of commercial membranes limit their efficiency. There have been many attempts to fabricate sub‐micrometer thin membranes, but the limited surface area has restricted their practicality. In this study, large‐area silicon nitride nanosieves for enhanced diffusion‐based isolation of exosomes are presented. Notably, these nanosieves are scaled to sizes of up to 4‐inch‐wafers, a significant achievement in overcoming the fabrication challenges associated with such expansive areas. The method employs a 200 nm porous sieve (38.2% porosity) for exosome separation and a 50 nm sieve (10.7% porosity) for soluble protein removal. These 300 nm thick nanosieves outperform conventional polycarbonate membranes by being 50 times thinner, thereby increasing nanoparticle permeability. The method enables a 90% recovery rate of intact exosomes from human serum and a purity ratio of 3 × 10 7 particles/µg protein, 4.6 times higher than ultracentrifugation methods. The throughput of the method is up to 15 mL by increasing the size of the nanosieve, making it an ideal solution for large‐scale exosome production for therapeutic purposes.