QCM detection of oligonucleotide by quiescent mode and flowing mode

The processes of HS-DNA immobilization and colloidal gold amplification of DNA hybridization signals were monitored by quartz crystal microbalance (QCM) in real time. The QCM detection was carried out in three cases: (1) Quiescent mode under open conditions; (2) Quiescent mode under sealed conditions; and (3) Flowing mode under sealed conditions. It was demonstrated that the stability of the QCM detection was greatly improved with the flowing mode under sealed conditions in comparison with those under the other two conditions. An increase of the frequency shift under flowing mode was found to be 57.6% in the HS-DNA immobilization process and 91.5% in the nanogold amplification process relative to the quiescent mode. The flowing mode can improve not only the stability but also the sensitivity of QCM detection.