Superparamagnetic nanobeads offer several advantages over microbeads for immunocapture of specifc molecular nanocarriers (extracellular vesicles, lipoproteins, and viruses) in a bioassay: high-yield capture, reduction in incuba-tion time and higher capture capacity. However, nanobeads are difficult to “pull down” because their superparamag-netic feature requires high nanoscale magnetic field gradients in addition to high magnetic fields. Here, electroplated track-etched membrane is shown to produce a unique superparamagnetic nanowedge ring with multiple edges around each nanopore. With a uniform external magnetic field, the induced monopole and dipole of this nanowedge junction combine to produce a 10x higher nanobead trapping force. A dense nanobead suspension can be filtered through the magnetic nanoporous membrane (MNM) at a high-throughput with 99% bead capture rate. The capture yield of specific nanocarriers in heterogeneous media (filtered plasma and conditioned cell media) by nanobeads/MNM ex-ceeds 80%. Quantification of RNA cargo in captured extracellular vesicles demonstrate 60x increase in 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 nano-bead immunocapture to heterogeneous physiological samples, such as blood and saliva, whose molecular analytes are cargoes of nanocarriers.