Abstract:An advanced site-specific conjugation strategy for the preparation of quantum dot-based antibody probes applicable in various immunoassays from fluorescence to electrochemical biosensors is described.
“…The fluorescence quenching of QD is known to be result of photoinduced electron transfer from an exited QD to a proximal molecule with an intermediate in energy to the valence and conduction band edge states 27 . The fluorescence quenching upon the conjugation of QDs with other biomolecules such as antibody and antigen has been reported in the literature 28 , 29 . Figure 1 ( a ) UV absorbance and ( b ) PL emission spectra of QDs/SA and QDs/SA-Ab at the ratio of QDs/SA:Ab, 1:3.…”
A highly sensitive immunosensor using streptavidin-conjugated quantum dots (QDs/SA) was developed to detect dengue biomarker of non-structural protein 1 (NS1) at very low concentration, so that it can probe dengue infection even in the early stage. The QDs/SA were first bound to biotinylated NS1 antibody (Ab) and the QDs/SA-Ab conjugates were then used to detect the NS1 antigen (Ag) in the Ag concentration range of 1 pM to 120 nM. The formation of QDs/SA-Ab and QDs/SA-Ab-Ag conjugates was confirmed by the measurements of field emission scanning electron microscopy (FF-SEM), field emission transmission electron microscopy (FE-TEM), dynamic light scattering (DLS), and zeta-potential. Fluorescence emission spectra of QDs/SA-Ab-Ag conjugates showed that the magnitude of fluorescence quenching was linearly proportional to the NS1 Ag concentration and it nicely followed the Stern–Volmer (SV) equation in phosphate buffer solution. However, in human plasma serum solution, the fluorescence quenching behavior was negatively deviated from the SV equation presumably due to interference by the serum component biomolecules, and it was well explained by the Lehrer equation. These results suggest that the current approach is promising because it is highly sensitive, fast, simple, and convenient, and thus it has a potential of application for point-of-care.
“…The fluorescence quenching of QD is known to be result of photoinduced electron transfer from an exited QD to a proximal molecule with an intermediate in energy to the valence and conduction band edge states 27 . The fluorescence quenching upon the conjugation of QDs with other biomolecules such as antibody and antigen has been reported in the literature 28 , 29 . Figure 1 ( a ) UV absorbance and ( b ) PL emission spectra of QDs/SA and QDs/SA-Ab at the ratio of QDs/SA:Ab, 1:3.…”
A highly sensitive immunosensor using streptavidin-conjugated quantum dots (QDs/SA) was developed to detect dengue biomarker of non-structural protein 1 (NS1) at very low concentration, so that it can probe dengue infection even in the early stage. The QDs/SA were first bound to biotinylated NS1 antibody (Ab) and the QDs/SA-Ab conjugates were then used to detect the NS1 antigen (Ag) in the Ag concentration range of 1 pM to 120 nM. The formation of QDs/SA-Ab and QDs/SA-Ab-Ag conjugates was confirmed by the measurements of field emission scanning electron microscopy (FF-SEM), field emission transmission electron microscopy (FE-TEM), dynamic light scattering (DLS), and zeta-potential. Fluorescence emission spectra of QDs/SA-Ab-Ag conjugates showed that the magnitude of fluorescence quenching was linearly proportional to the NS1 Ag concentration and it nicely followed the Stern–Volmer (SV) equation in phosphate buffer solution. However, in human plasma serum solution, the fluorescence quenching behavior was negatively deviated from the SV equation presumably due to interference by the serum component biomolecules, and it was well explained by the Lehrer equation. These results suggest that the current approach is promising because it is highly sensitive, fast, simple, and convenient, and thus it has a potential of application for point-of-care.
“…The same protocol might be applied for Qdots with carboxyl groups on their surface [34]. Additionally, chemical linkers (glutaraldehyde, N, N'-carbonyldiimidazole) can also be applied for covalent antibody immobilization on Qdots [35].…”
Section: Methods Used For the Modification Of Mnps And Qdots By Antib...mentioning
confidence: 99%
“…It is easy to lose an antibody during the conjugation procedure. Additionally, a limited amount of Qdots per 1 M of IgG was mentioned as one of the disadvantages of this method [34].…”
Section: Methods Used For the Modification Of Mnps And Qdots By Antib...mentioning
With the increasing importance of healthcare and clinical diagnosis, as well as the growing demand for highly sensitive analytical instruments, immunosensors have received considerable attention. In this review, electrochemical immunosensor signal amplification strategies using metal nanoparticles (MNPs) and quantum dots (Qdots) as tags are overviewed, focusing on recent developments in the ultrasensitive detection of biomarkers. MNPs and Qdots can be used separately or in combination with other nanostructures, while performing the function of nanocarriers, electroactive labels, or catalysts. Thus, different functions of MNPs and Qdots as well as recent advances in electrochemical signal amplification are discussed. Additionally, the methods most often used for antibody immobilization on nanoparticles, immunoassay formats, and electrochemical methods for indirect biomarker detection are overviewed.
“…143−145 As opposed to using an enzyme label, fluorescent QDs are conjugated to detection antibodies to form a QD-ELISA system. A number of QD-ELISAs have been reported, in which QD−antibody conjugation was achieved via streptavidin− biotin interaction, 146 EDC chemistry, 147 trans-cyclooctene− tetrazine chemistry, 148 or a heterobifunctional linker (e.g., sulfo-SMCC). 149 Herrera et al developed a sandwich QD-ELISA for the detection of soluble cytokine tumor necrosis factor-α (TNF-α) for concentrations as low as 60 aM (1 fg/ mL).…”
Section: ■ Nanoparticles As Signal Transducersmentioning
Enzyme-linked immunosorbent assay (ELISA) is a technique
designed
for the detection and quantification of (bio)molecules in a liquid
sample. It is a powerful tool in clinical diagnostics, food safety,
and environmental monitoring. However, the main limitation of conventional
ELISA is its low sensitivity, which cannot meet the demand of analyte
analysis in complex (biological) samples. Several successful approaches
capitalizing on the unique physical and chemical properties of nanoparticles
to improve the performance of traditional ELISA have been reported.
In this review, we aim to demonstrate diverse strategies designed
to date that use metal and metal oxide nanoparticles to overcome challenges
associated with ELISA sensitivity and stability. In particular, we
discuss metal and metal oxide nanoparticles as carriers to load enzymes
and antibodies for signal amplification, as enzyme mimics to replace
the natural enzyme label, and as signal transducers to provide fluorescence
or luminescence signals as an alternative output.
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