Laser-patterning of micromagnets for magnetophoretic biomolecule capture

Efficient and controlled isolation and patterning of biomolecules is a vital process step within sample preparation for biomolecular analysis, and within numerous diagnostic and therapeutic applications. For exosomes, nanoscale (30–150 nm) lipid bound biomolecules, efficient isolation is challenging, due in part to the minute size and their resultant behavior within biofluids. Here, we present a method towards the rapid isolation and patterning of magnetically tagged exosomes via rationally designed micromagnets. We present a novel, scalable, and high-throughput laser-based fabrication approach that enables microscale lateral resolution (< 50 µm) without lithographic processing and is agnostic to pattern geometry. Fabrication of micromagnets allows for highly tunable device configurations, and herein we have explored their use for both open-air microwells and encapsulated within a microfluidic channel. In each case, the micromagnets act to enhance the localized gradient fields, resulting in rapid magnetophoretic separation throughout the biofluid medium. Towards micromagnet unit cell geometry optimization, we have employed computational FEA modeling, simulating ‘capture zones’ for a given micromagnet geometry. Lastly, we have demonstrated proof-of-concept immunomagnetic exosome capture and patterning within both device configurations, demonstrating the flexibility and utility of the developed fabrication technique.