Microfluidic integration of nanomechanical resonators for protein analysis in serum

We describe a technique for reversibly encapsulating nanomechanical resonant sensors within microfluidic channels that are reusable and easy to fabricate. We demonstrate the feasibility and sensitivity of our microfluidic system by detecting prostate specific antigen (PSA) at 1–100 fM concentrations in serum, using a nanoparticle-based mass-labeling sandwich assay. By comparing these results to our previous data for PSA detection, we observe enhanced assay sensitivity in a significantly reduced time with the microfluidic assay. In addition, we show that a binary mixture of the proteins vascular endothelial growth factor (VEGF) and interleukin-8 (IL-8) can be detected in serum using a single microfluidic channel. This work lays the groundwork for future applications of these nanomechanical resonant devices for highly sensitive, multiplexed protein analysis using microfluidics.