5 research outputs found
Single Gold Nanoparticle-Based Colorimetric Detection of Picomolar Mercury Ion with Dark-Field Microscopy
Mercury severely damages the environment
and human health, particularly
when it accumulates in the food chain. Methods for the colorimetric
detection of Hg<sup>2+</sup> have increasingly been developed over
the past decade because of the progress in nanotechnology. However,
the limits of detection (LODs) of these methods are mostly either
comparable to or higher than the allowable maximum level (10 nM) in
drinking water set by the US Environmental Protection Agency. In this
study, we report a single Au nanoparticle (AuNP)-based colorimetric
assay for Hg<sup>2+</sup> detection in solution. AuNPs modified with
oligonucleotides were fixed on the slide. The fixed AuNPs bound to
free AuNPs in the solution in the presence of Hg<sup>2+</sup> because
of oligonucleotide hybridization. This process was accompanied by
a color change from green to yellow as observed under an optical microscope.
The ratio of changed color spots corresponded with Hg<sup>2+</sup> concentration. The LOD was determined as 1.4 pM, which may help
guard against mercury accumulation. The proposed approach was applied
to environmental samples with recoveries of 98.3 ± 7.7% and 110.0
± 8.8% for Yuquan River and industrial wastewater, respectively
Superlocalization Spectral Imaging Microscopy of a Multicolor Quantum Dot Complex
The key factor of realizing super-resolution optical
microscopy
at the single-molecule level is to separately position two adjacent
molecules. An opportunity to independently localize target molecules
is provided by the intermittency (blinking) in fluorescence of a quantum
dot (QD) under the condition that the blinking of each emitter can
be recorded and identified. Herein we develop a spectral imaging based
color nanoscopy which is capable of determining which QD is blinking
in the multicolor QD complex through tracking the first-order spectrum,
and thus, the distance at tens of nanometers between two QDs is measured.
Three complementary oligonucleotides with lengths of 15, 30, and 45
bp are constructed as calibration rulers. QD585 and QD655 are each
linked at one end. The measured average distances are in good agreement
with the calculated lengths with a precision of 6 nm, and the intracellular
dual-color QDs within a diffraction-limited spot are distinguished
Superlocalization Spectral Imaging Microscopy of a Multicolor Quantum Dot Complex
The key factor of realizing super-resolution optical
microscopy
at the single-molecule level is to separately position two adjacent
molecules. An opportunity to independently localize target molecules
is provided by the intermittency (blinking) in fluorescence of a quantum
dot (QD) under the condition that the blinking of each emitter can
be recorded and identified. Herein we develop a spectral imaging based
color nanoscopy which is capable of determining which QD is blinking
in the multicolor QD complex through tracking the first-order spectrum,
and thus, the distance at tens of nanometers between two QDs is measured.
Three complementary oligonucleotides with lengths of 15, 30, and 45
bp are constructed as calibration rulers. QD585 and QD655 are each
linked at one end. The measured average distances are in good agreement
with the calculated lengths with a precision of 6 nm, and the intracellular
dual-color QDs within a diffraction-limited spot are distinguished
Superlocalization Spectral Imaging Microscopy of a Multicolor Quantum Dot Complex
The key factor of realizing super-resolution optical
microscopy
at the single-molecule level is to separately position two adjacent
molecules. An opportunity to independently localize target molecules
is provided by the intermittency (blinking) in fluorescence of a quantum
dot (QD) under the condition that the blinking of each emitter can
be recorded and identified. Herein we develop a spectral imaging based
color nanoscopy which is capable of determining which QD is blinking
in the multicolor QD complex through tracking the first-order spectrum,
and thus, the distance at tens of nanometers between two QDs is measured.
Three complementary oligonucleotides with lengths of 15, 30, and 45
bp are constructed as calibration rulers. QD585 and QD655 are each
linked at one end. The measured average distances are in good agreement
with the calculated lengths with a precision of 6 nm, and the intracellular
dual-color QDs within a diffraction-limited spot are distinguished
Sensing Active Heparin by Counting Aggregated Quantum Dots at Single-Particle Level
Developing
highly sensitive and highly selective assays for monitoring
heparin levels in blood is required during and after surgery. In previous
studies, electrostatic interactions are exploited to recognize heparin
and changes in light signal intensity are used to sense heparin. In
the present study, we developed a quantum dot (QD) aggregation-based
detection strategy to quantify heparin. When cationic micelles and
fluorescence QDs modified with anti-thrombin III (AT III) are added
into heparin sample solution, the AT III-QDs, which specifically bind
with heparin, aggregate around the micelles. The aggregated QDs are
recorded by spectral imaging fluorescence microscopy and differentiated
from single QDs based on the asynchronous process of blue shift and
photobleaching. The ratio of aggregated QD spots to all counted QD
spots is linearly related to the amount of heparin in the range of
4.65 × 10 <sup>–4</sup> U/mL to 0.023 U/mL. The limit
of detection is 9.3 × 10 <sup>–5</sup> U/mL (∼0.1
nM), and the recovery of the spiked heparin at 0.00465 U/mL (∼5
nM) in 0.1% human plasma is acceptable