Investigations of fluorescence resonance energy transfer between CdTe quantum dot donors and gold nanoparticle quenchers in DNA sensing

We used luminescent CdTe quantum dots (QDs) as energy donors and gold nanoparticles (AuNPs) as accepter in fluorescent resonance energy transfer (FRET) assays. CdTe QDs donors with 2.5 nm in size and AuNPs with 16 nm in size were synthesized, and more than 95% overlap between emission spectrum of the CdTe QDs and the absorption spectrum of AuNPs was confirmed. The synthesized donor and accepter were linked to 5' and 3' end of two designed complementary single-stranded DNA (ssDNA), respectively, sensing system was then composed by hybridizing the ssDNA into a double stranded DNA (dsDNA; i.e. CdTe-dsDNA-Au). The prepared CdTe QDs, AuNPs, and CdTedsDNA- Au were characterized by UV-vis spectra, fluorescence spectra, and electrophoresis method. Furthermore, FRET efficiency was estimated to be 74.6% for the FRET-pairs in dsDNA. The complementary single-stranded target-DNA was subjected to this sensing system to measure the fluorescence recovery. The dependence of fluorescence intensity on pH value, time, and amount of added target-DNA was investigated, respectively. The resulting data exhibited that pH 7.0 is optimum for both interaction of CdTe QDs and AuNPs and stability of DNA helix. After 12h of stand, the CdTedsDNA- Au sensing system becomes unstable. Fluorescence spectra of the sensing system showed that fluorescence recovery was enhanced with increasing addition of target-DNA in a certain range. Our data showed that an effective biosensing system was constructed base on fluorescent resonance energy transfer.

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