Binding induced strand displacement amplification for homogeneous protein assay.

An ultrasensitive and homogenous strategy for protein assay was established based upon binding-induced strand displacement amplification (BI-SDA). Binding-Induced DNA strand-displacement occurred between Apt-T•signal DNA and Apt-C, and release of signal DNA upon addition of platelet-derived growth factor (PDGF BB). The released signal DNA further hybridized with multifunctional hairpin DNA probe and induced the strand-displacement amplification in the presence of Klenow Fragment (exo-) and dNTPs. The BI-SDA product contain G-quaruplex DNA, which could be recognized and reported by the fluorescence of fluorochrome N-methyl porphyrin propionic acid IX (NMM). The fluorescence intensity was proportional to the concentration of PDGF-BB over the range of 1.0×10-11mol/L -2.0×10-9mol/L, with a detection limit of 3.6pmol/L. This proposed strategy showed good selectivity and practicality, and might be applied to other proteins in the future.