The impact of quantum dot on the SPR detection improvement of molecular interactions between Rap1 interacting factor1 (Rif1) and G4

The main shortcoming of the Surface Plasmon Resonance (SPR) method is its inability to detect low molecular weight (<400 Da) and dilute samples. Moreover, the study of protein-DNA interactions using SPR is one of the most challenging one. Due to these difficulties, the enhancement of SPR signals has been less explored. According to the proposition that the Rif1 protein can be considered a biomarker in breast cancer, further investigations are needed to understand the mechanism of Rif1 and G4 interaction. For this purpose, we studied different platforms to obtain kinetic data on their interaction and to investigate the increase in the SPR signal using quantum dot (Qdot) nanoparticles. Finally, the nickel-NTA chip was used to immobilize the protein, and the streptavidin was attached to Qdot through the EDC-NHS mechanism to bind the 5′-biotinylated G4 structure that was prepared. Different concentrations of biotinylated-G4 were injected, and the enhancement in the signals was studied by injecting the streptavidin-conjugated Qdots onto the chip. Our results indicate a very low dissociation constant of 6.8 ± 0.9 nM which is in consistent with our previous studies. We could enhance the signals by approximately 6 times which is believed to be due to the high bulk density and refractive index of Qdots.