Signal Enhancement in Antibody Microarrays Using Quantum Dots Nanocrystals: Application to Potential Alzheimer’s Disease Biomarker Screening

Abstract

The performance of cadmium-selenide/zincsulfide (CdSe@ZnS) quantum dots (QDs) and the fluorescent dye Alexa 647 as reporter in an assay designed to detect apolipoprotein E (ApoE) has been compared. The assay is a sandwich immunocomplex microarray that functions via excitation by visible light. ApoE was chosen for its potential as a biomarker for Alzheimer's disease. The two versions of the microarray (QD or Alexa 647) were assessed under the same experimental conditions and then compared to a conventional enzyme-linked immunosorbent assay (ELISA) targeting ApoE. The QDs proved to be highly effective reporters in the microarrays, although their performance strongly varied in function of the excitation wavelength. At 633 nm, the QD microarray gave a limit of detection (LOD) of ∼247 pg mL −1 ; however, at an excitation wavelength of 532 nm, it provided a LOD of ∼62 pg mL −1 , five times more sensitive than that of the Alexa microarray (∼307 pg mL −1 ) and seven times more than that of the ELISA (∼470 pg mL −1 ). Finally, serial dilutions from a human serum sample were assayed with high sensitivity and acceptable precision and accuracy.

Post-Genomics Nanotechnology Is Gaining Momentum: Nanoproteomics and Applications in Life Sciences

“…QDs were also used to detect apolipoprotein E, the most important known genetic risk factor for Alzheimer disease, by designing a sandwich immunocomplex microarray assay based on cadmium-selenide/zinc-sulfide (CdSe@ZnS) quantum dots. The assay provided a low detection limit of 62 pg mL -1 , seven times more than that of the ELISA (470 pg mL -1 ) when tested under the same conditions (Morales-Narváez et al, 2012).…”

On‐the‐Spot Immobilization of Quantum Dots, Graphene Oxide, and Proteins via Hydrophobins

“…[ 7 ] The glass slides were masked using a multiwell microarray cassette to separate the surface in 24 chambers (see Figure S1 in the Supporting Information). In each chamber, a block of up to 550 micrometric drops can be dispensed.…”

“…[ 79 ] To evaluate protein adsorption and biofunctionality, two proteins, the fl uorescent Alexa555-BSA conjugate (A555B) and anti-immunoglobulin (IgG) antibodies (αIgG) dissolved in aqueous buffer, were micropatterned in microarray format as previously described, [ 7 ] and, upon adsorption onto the Vmh2 substrate, washed with detergent solutions to test the binding stability. Morphology of immobilized A555B protein spots, signal to background, and coeffi cient of variation (CV) of fl uorescence intensity were evaluated (see Figure 3 A).…”

“…Their optical properties have been reported to be advantageous when compared with those of conventional organic dyes for biomedical applications. [4][5][6][7] For instance, QDs bear sizedependent emission, from UV to mid-IR region, [ 8 ] broad excitation wavelength, large Stokes' shift, symmetric and narrow emission spectra, high brightness, and they do not display photobleaching phenomenon. [ 9 ] As a consequence, QDs provide versatile tools for optical or electrical multiplexing (detection of multiple signals, spectrally, spatially, or temporally resolved), [ 6,[10][11][12] long-term and single molecule imaging, [ 13,14 ] and offer novel approaches in biotechnology, [ 15 ] based on bar-coding, [ 16 ] chemical noses, [ 17 ] logic-gate operations, and optical switches [ 18 ] among others.…”

“…Functionality of proteins on Vmh2 layer is shown using an immunoassay in a microarray format. [ 7 ] 2. Results and Discussion…”