Superparamagnetic nanobeads offer several advantages over microbeads for immunocapture of specific molecular nanocarriers (extracellular vesicles, lipoproteins, and viruses) in a bioassay: high-yield capture, reduction in incubation time, and higher capture capacity. However, nanobeads are difficult to “pull-down” because their superparamagnetic feature requires high nanoscale magnetic field gradients in addition to high magnetic fields. Here, an electroplated track-etched membrane is shown to produce a unique superparamagnetic nano edge ring with multiple edges around each nanopore. With a uniform external magnetic field, the induced monopole and dipole of this nano edge junction combine to produce a 10x higher nanobead trapping force. A dense nanobead suspension can be filtered through the magnetic nanoporous membrane (MNM) at high throughput with a 99% bead capture rate. The capture yield of specific nanocarriers in heterogeneous media (filtered plasma and conditioned cell media) by nano-beads/MNM exceeds 80%. Quantification of RNA cargo in captured extracellular vesicles demonstrates a 60x increase in the capture rate of a specific microRNA relative to magnetic bead columns. Reproducibility, low loss, and concentration-independent capture rates are also demonstrated. This new MNM material hence significantly expands the application of nanobead immunocapture to heterogeneous physiological samples, such as plasma and saliva.