Based on the fluorescence resonance energy transfer (FRET) mechanism, fluorescent DNA probes were prepared with a novel DNA hairpin template method, with SiO2coated CdTe (CdTe/SiO2) core/shell nanoparticles used as the fluorescence energy donors and gold (Au) nanoparticles (AuNPs) as the energy acceptors. The nanostructure and energy donor/acceptor ratio in a probe were controlled with this method. The relationship between the nanostructure of the probes and FRET efficiency (quenching efficiency) were investigated. The results indicated that when the donor/acceptor ratios were 2:1, 1:1, and 1:2; the corresponding FRET efficiencies were about 33.6%, 57.5%, and 74.2%, respectively. The detection results indicated that the fluorescent recovery efficiency of the detecting system was linear when the concentration of the target DNA was about 0.0446–2.230 nmol/L. Moreover, the probes showed good sensitivity and stability in different buffer conditions with a low detection limit of about 0.106 nmol/L.Keywords:fluorescent DNA probes;CdTe/SiO2nanoparticles;Au nanoparticles;DNA hairpin template;nanostructure;quenching efficiency
Nana Sun,Yuan Ding,Zhexuan Tao,Hongjie You,Xiude Hua,Minghua Wang
An upconversion fluorescence DNA probe which consists of aptamer-conjugated magnet nanoparticles (apt-MNPs) and complementary DNA-conjugated upconversion nanoparticles (cDNA-UCNPs) was developed to detect acetamiprid. Acetamiprid can specifically conjugate with the apt-MNPs to dissociate the cDNA-UCNPs from the apt-MNPs and resulted in reduced fluorescence intensity through an external magnet. The change of fluorescence intensity (△I) is positively related to the concentration of acetamiprid, which can be applied for the quantification of acetamiprid. Under optimal conditions, a linear detection range and detection limit are 0.89–114.18 μg/L and 0.65 μg/L, respectively. The probe was successfully used to detect acetamiprid in spiked paddy water, soil, pear, apple, wheat and cucumber. Average recoveries are 78.2%–103.5% with intra-day relative standard deviations (RSDs) of 2.6%–10.9% and inter-day RSDs of 4.3%–10.2%. The amounts of acetamiprid in the authentic paddy water and pear samples detected by the DNA probe are significantly correlated with that detected by high-performance liquid chromatography (HPLC).
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