Amplified QCM-D biosensor for protein based on aptamer-functionalized gold nanoparticles.

A highly sensitive quartz crystal microbalance with dissipation monitoring (QCM-D) biosensor for protein was developed using aptamer-functionalized gold nanoparticles (Apt-GNPs) for amplification. Human α-thrombin, an important physiological protease found in blood, was chosen as the target protein. Captured by immobilized aptamers, thrombin was determined on-line using Apt-GNPs to enhance both frequency and dissipation signals. The fabricated sandwich of aptamer/thrombin/Apt-GNPs on chip surface was confirmed by atomic force microscopy (AFM). Compared to direct assay, the detection limit for thrombin was down to 0.1 nM, yielding about 2 orders of magnitude improvement in sensitivity. This aptamer-based QCM-D biosensor also showed good selectivity and repeatability in complex matrix. For the first time, the dual-signal enhancement of Apt-GNPs on QCM-D sensing was demonstrated, and such design could provide a promising detection strategy for proteins with two binding sites.