QCM, strand displacement reaction

Toehold-mediated strand displacement reaction
(SDR) is first introduced to develop a simple quartz
crystal microbalance (QCM) biosensor without an enzyme or
label at normal temperature for highly selective and sensitive
detection of single-nucleotide polymorphism (SNP) in the p53
tumor suppressor gene. A hairpin capture probe with an
external toehold is designed and immobilized on the gold
electrode surface of QCM. A successive SDR is initiated by the
target sequence hybridization with the toehold domain and
ends with the unfolding of the capture probe. Finally, the
open-loop capture probe hybridizes with the streptavidincoupled
reporter probe as an efficient mass amplifier to enhance the QCM signal. The proposed biosensor displays remarkable
specificity to target the p53 gene fragment against single-base mutant sequences (e.g., the largest discrimination factor is 63 to
C−C mismatch) and high sensitivity with the detection limit of 0.3 nM at 20 °C. As the crucial component of the fabricated
biosensor for providing the high discrimination capability, the design rationale of the capture probe is further verified by
fluorescence sensing and atomic force microscopy imaging. Additionally, a recovery of 84.1% is obtained when detecting the
target sequence in spiked HeLa cells lysate, demonstrating the feasibility of employing this biosensor in detecting SNPs in
biological samples. Q-Sense全自动八通道石英晶体微天平