Positively Charged Compact Quantum Dot–DNA Complexes for Detection of Nucleic Acids

Abstract

Novel QD-DNA complexes are prepared by simple electrostatic interaction between pegylated amine-functionalized CdSe/ZnS quantum dots (QDs) and DNA. The cationic nature of the amine functionality on the QD surface allows for formation of an electrostatic complex with negatively charged DNA. The presence of polyethylene glycol (PEG5000) molecules on the QD leads to enhanced stability and decreased nonspecific adsorption of DNA on the QD surface. Unlike assembly of QD-DNA based on hydrogen bonding, the present QD probes tend to be more strongly stabilized during the hybridization process by increasing the overall negative charges. In addition, the DNA loading efficiency can be modulated by changing the pH of the reaction medium. The fluorescence of the QD is quenched up to 90% by complexation with 5'-TAMRA-modified oligonucleotide (TAMRA=carboxytetramethylrhodamine) through fluorescence resonance energy transfer (FRET). With the FRET pair we selected, the R(0) value was calculated to be 5.5 nm and r is about 5 nm. This quenching of QD fluorescence is then reversed on binding of unlabeled target DNA. The maximum recovery of QD fluorescence is 60%. The QD-DNA probe (5DNA/QD) exhibits selective photoluminescence (PL) recovery in the presence of target oligonucleotide with a PL ratio of 3 for complementary versus noncomplementary. The present QD-DNA probes also show the capability to detect the synthetic 100-mer oligonucleotide derived from H5N1 influenza virus when present at concentrations as low as 200 nM in the solution.

Cascaded FRET in Conjugated Polymer/Quantum Dot/Dye-Labeled DNA Complexes for DNA Hybridization Detection

“…17 Most of the reported approaches required covalent conjugation of DNA to the QD surface (e.g., by EDC/NHS coupling reaction), which often decreases the colloidal stability and/or the emission intensity of QDs. 18,19 This limitation can be overcome by the use of a sensing platform relying on the electrostatic interaction of dye-labeled DNA with the oppositely charged QD surface 20 in a similar fashion as in conducting polymer-based detection assays. 4Ϫ8 In this paper, we propose a simultaneous use of conjugated polymers and semiconductor QDs for DNA hybridization detection, which can potentially combine advantages of both light-harvesting and DNA-binding properties of water-soluble polymers with photostability, lightharvesting ability, and FRET donor property of QDs.…”

Sensitive fluorescent sensing for DNA assay

“…based biosensors. Several sensor designs based on FRET between QDs and dye-labeled biomolecules have been developed [142][143][144]. Zhou et al reported preparation and specific label-free DNA detection of a compact, functional QD-DNA conjugate [145].…”

“…Most of the reported approaches require covalent conjugation of DNA to the QD surface [e.g., by 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide-N-hydroxysuccinimide (EDC/NHS) coupling reaction], which often decrease the colloidal stability and/or the emission intensity of QDs [145]. This limitation can be overcome by the use of a sensing platform relying on the electrostatic interaction of dyelabeled DNA with the oppositely charged QD surface [144]. Peng et al demonstrated a simple DNA-sensing platform on the basis of the FRET between blue-luminescent thioglycolic acid (TGA)-capped CdTe QDs and dye-labeled ssDNA (Fig.…”

Intra/Inter‐Particle Energy Transfer of Luminescence Nanocrystals for Biomedical Applications

“…It was specifically cleavable when expose to HIV-PR and such a peptide-QD system could render the detection sensitivity of HIV-PR in the range of picomol. Lee et al also designed a positively charged compact QD-DNA complex for detection of nucleic acids [16]. The fluorescence of the QD is quenched up to 90% by complexion with 5 -carboxytetramethylrhodamine-(TAMRA-) modified oligonucleotide through FRET.…”