(28e) Superparamagnetic Nanobead and Electrodeposited Magnetic Nanoporous Membrane for Immunocapture of Specific Exosomes

Extracellular vehicles (EVs) are cell-derived small membrane-bounded vesicles containing various functional cargos. Both their protein and miRNA contents are suggested to be potential cancer biomarkers. Moreover, by profiling RNA cargo inside EVs with specific surface proteins, better statistics could be obtained for tumor source, size and type. Traditional immunocapture, like precipitation, antibody functionalized columns, and functionalized microbeads, has issues of low yield due to probe saturation. Their throughputs are also limited by the long incubation time (8-48 hours) because of the long transport and reaction time. A solution facilitating the yield and throughput is to use nanomagnetic beads. The large surface area per volume gives it more binding sites. The smaller size leads to higher diffusivity and shorter incubation time (~30 minutes). However, it is hard to trap due to its superparamagnetic nature. The magnetic force on them is proportional to the gradient of field squared rather than to the field. For the commonly used small magnets with low field penetration, the attraction is only effective within one radius of the curvature of the sharp tip at the magnet.

We report an electrodeposited magnetic nanoporous membrane device for high-efficiency recovery of immunocapture nanobeads to overcome this key obstacle in nanobead immunoassay. A layer of NiFe is electroplated on a track-etched PET membrane with a gold seed layer. Magnets are put on both sides of the membrane to magnetize the membrane. By flowing the solution through the membrane, the nanobeads are brought into the region of intense magnetic fields and field gradients at the edge of the nanopore. Thus, we can achieve a high recovery rate of nanobeads and captured EVs. More than 99% of beads can be recovered from the solution with a throughput of 3mL/hr on a single device. The uncaptured EVs can go through the straight pores and be collected in the flow-through. We proved our device’s efficiency and specificity using HDL (high density lipoproteins) as a model - more than 80% of HDL is recovered, nearly doubled from the commercial kits. The high and consistent yield of our system provides quantification potential for biological studies. We further demonstrated our system’s applications in exosome capturing and profiling, EGFR-positive (Epidermal Growth Factor Receptor-positive) EVs characterization, and purification of HDL-enriched EV samples.