Energy Transfer Assays Using Quantum Dot–Gold Nanoparticle Complexes: Optimizing Oligonucleotide Assay Configuration Using Monovalently Conjugated Quantum Dots

Abstract

The energy transfer between quantum dots (QDs) and gold nanoparticles (AuNPs) represents a popular transduction scheme in analytical assays that use nanomaterials. The impact of the spatial arrangement of the two types of nanoparticles on analytical performance has now been evaluated using a nucleic acid strand displacement assay. The first spatial arrangement (configuration 1) involved the assembly of a number of monovalently functionalized QD-oligonucleotide conjugates around a single central AuNP that was functionalized with complementary oligonucleotide sequences. The assembly of these complexes, and subsequent disassembly via target oligonucleotide-mediated displacement, were used to evaluate energy transfer efficiencies. Furthermore, the inner filter effect of AuNPs on the fluorescence intensity of the QD was studied. AuNPs of three different diameters (6, 13, and 30 nm) were used in these studies. Configuration 2 was based on the placement of monovalently functionalized AuNP-oligonucleotide conjugates around a single QD that was functionalized with a complementary oligonucleotide. The optimal assay configuration, established by evaluating energy transfer efficiencies and inner filter effects, was obtained by arranging at most 15 QDs around the 13 nm AuNP (configuration 1). These assays provided a 2.5-fold change in fluorescence intensity in the presence of target oligonucleotides. To obtain the same response with configuration 2 required the placement of three 6 nm AuNPs around the QD. This resulted in configuration 2 having a 5-fold lower fluorescence intensity when compared to configuration 1. The use of low-cost detection systems (digital camera) further emphasized the higher analytical performance of configuration 1. Response curves obtained using these detection systems demonstrated that configuration 1 had a 10-fold higher sensitivity when compared to configuration 2. This study provides an important framework for the development of sensitive assays using gold nanoparticles and quantum dots.

Quantum Dot-Conjugated SARS-CoV-2 Spike Pseudo-Virions Enable Tracking of Angiotensin Converting Enzyme 2 Binding and Endocytosis

“…The calculated distance with 50% energy transfer, R 0 , was 14.4 nm for FRET, which was longer than that for general organic dye acceptors (typically R 0 < 10 nm), owing to the large extinction coefficient of AuNP (ε = 1.4 × 10 7 M –1 cm –1 at 520 nm). 24 With QD 514 -AuNP, the FRET model provided the best fit to our experimental data with the specifically calculated and estimated distances, which was different from our previous study using QDs and ultrasmall AuNPs (1.5 nm) and other literature reports. 15 , 23 Here, the calculated FRET model estimated higher efficiency than other models because the extinction coefficient of 5 nm AuNPs is 2–3 orders of magnitude higher than that of 1.5 nm AuNPs.…”

“…However, we could not completely exclude the inner-screening effect of AuNPs, the electron transfer, or the electrostatic interaction as additional contributions to quenching. 23 , 24 Regardless of the fit to the models, the observed PL quenching indicated the binding between the Spike subunit and ACE2, demonstrating that QD-Spike is a viable method for the production of pseudovirions that can be monitored in real time by their emission characteristics.…”

Surface Immobilized Nucleic Acid–Transcription Factor Quantum Dots for Biosensing

“…While QDs possess many favorable optical properties, surface energy transfer is a potential concern when designing a surface immobilized QD transduction system. [ 31 ] The emission spectra of our surface probe system, Au/MCH/Cy5‐DNA/BSA + (TetR‐QD) is shown in Figure 3a. The QD emission is similar compared to the emission from its aqueous solution counterpart (Figure 3b).…”

An aptamer folding‐based sensory platform decorated with nanoparticles for simple cocaine testing

“…This Y-shaped structure of cocaine binding aptamer causes the AuNP comes to the nearness of the QD, resulting in the formation of a weak fluorescent signal because of well-known fluorescence quencher effect of AuNPs. [34][35][36] The correlation between fluorescence quenching and analyte concentration was used to obtain a calibration graph for the analysis of cocaine abuse.…”