Continuous-flow biomolecule concentration and detection in a slanted nanofilter array.

We demonstrate continuous-flow biomolecule concentration and detection in a microfabricated slanted sieving structure, which we term a herringbone nanofilter array (HNA). The HNA structure consists of periodically-patterned deep and shallow nanoslits meeting at right angles. In addition to concentration, we can discriminate different sized analytes by mixing a fluorescent probe with the sample and measuring the extent of the concentrating effect. Using this principle, we interrogate biomolecular interactions, including protein-DNA binding, protein-protein interaction and antibody-antigen binding. The final example demonstrates a novel method to perform a homogeneous immunoassay for detecting a disease marker, human C-reactive protein (CRP), using fluorescent-labeled antibodies at clinically relevant concentrations. The signal amplification potential and continuous flow operation provide a significant advantage over other microfluidic batch separation techniques for the easy integration of this device into a common point-of-care diagnostic platform.