Microfluidic sieve-detector for rapid capture and detection of single molecules

Ultrasensitive, quantitative and simple tests for proteins and nucleic acids could empower analysis and disease diagnosis, but slowness of analyte capture and detection prevent it. We introduce the microfluidic sieve-detector (MSD) based on microfluidic Brownian affinity traps (BATs). A BAT is a micro-conduit coated with capture probes under commensurate flow such that an analyte flowed through binds a probe following Brownian motion-induced wall collision. Digital sandwich assays are completed by sequentially flowing the reagents, partitioning BATs, and revealing single trapped analytes following enzymatic amplification. MSDs with arrays of half a million BATs sieved 200 microliters in just one minute, and quantified captured proteins (enzymes, IL-4, influenza nucleoprotein) and microRNA (miR-141) in four minutes, down to zeptomolar concentration. The MSD opens unprecedented analytical and diagnostic opportunities.