Optimization of energy transfer between quantum dots and gold nanoparticles in head-to-head configuration for detection of fusion gene

We report simultaneous detection of the variants 3a and 3b in the oncogenic EML4-ALK fusion gene using cDNA from lung cancer patients based on energy transfer between CdSe/ZnS quantum dots (QDs) and gold nanoparticles (AuNPs). To overcome the limitations of the conventional detection methods based on energy transfer, we have applied a head-to-head configuration of QDs and AuNPs. This allowed us not only to use longer probe oligonucleotides than the conventional methods, but also to optimize interparticle distance between QDs and AuNPs for maximum sensitivity and selectivity. By functionalizing two types of QDs (i.e., green- and red-emitting QDs) and 5 nm AuNPs with probe oligonucleotides, we demonstrated that energy was selectively transferred from green-emitting QDs to AuNPs when variant 3a was present in target cDNA, or from red-emitting QDs to AuNPs with variant 3b, resulting in fluorescence quenching. Our method could successfully be used to simultaneously detect two variants of EML4-ALK fusion gene at the target DNA concentration (3.45 nM) that was lower than the previously reported limit of detection values based on energy transfer phenomenon.