Label-free single-nucleotide polymorphism detection using a cationic tetrahedralfluorene and silica nanoparticles

We developed a simple method that is able to provide label-free sequence-specific DNA detection with single-nucleotide polymorphism (SNP) detection selectivity. This method makes use of both DNA probe immobilized silica nanoparticles and optically amplifying light harvesting molecules. The recognition is accomplished by sequence-specific hybridization between the DNA probes on the silica nanoparticles and the targets of interest. After subsequent treatment with ethidium bromide (EB), a cationic tetrahedralfluorene was added to electrostatically associate with the DNA molecules on the nanoparticle surface, leading to sensitized EB emission via fluorescence resonance energy transfer (FRET). Because of the selective response of the tetrahedralfluorene to intercalated EB, the perfectly matched DNA targets were distinctively differentiated from those with mutations. The presence of tetrahedralfluorene provides improved detection sensitivity and selectivity, as compared to the use of EB alone as a signal reporter. The demonstrated highly selective label-free detection method laid the ground work for the future development of disposable and real-time testing kits in SNP screenings.