Simple fluidic system for purifying and concentrating diagnostic biomarkers using stimuli-responsive antibody conjugates and membranes.

We report a simple fluidic system that can purify and concentrate diagnostic biomarkers through the capture and triggered release of stimuli-responsive polymer−antibody conjugates at porous membranes that are grafted with the same stimuli-responsive polymer. This technique is applied here to the capture and detection of a model streptavidin antigen and subsequently to clinical ranges of the malaria antigen Plasmodium falciparum histidine-rich protein 2 (PfHRP2) from spiked human plasma. The carboxyl end-groups of semi-telechelic poly(N-isopropylacrylamide) (pNIPAAm) synthesized by reversible addition−fragmentation chain transfer (RAFT) polymerization were modified with tetrafluorophenol to yield amine-reactive ester groups for conjugation to amine groups of anti-streptavidin and anti-PfHRP2 antibodies. Stimuli-responsive membranes were constructed from 1.2 μm pore-size, hydroxylated, nylon-6,6 filters (Loprodyne, from Pall Corporation). The surface hydroxyl groups on the filters were conjugated to a 2-eth...