15 research outputs found
Smart Composite Reagent Composed of Double-Stranded DNA-Templated Copper Nanoparticle and SYBR Green I for Hydrogen Peroxide Related Biosensing
On
the basis of an interesting experimental phenomenon, a novel
and smart composite reagent consisting of double-stranded DNA-templated
copper nanoparticles (dsDNAāCuNPs) and DNA intercalator (SYBR
Green I) was developed and exploited for hydrogen peroxide (H<sub>2</sub>O<sub>2</sub>) detection as well as oxidase-based biosensing.
The study found that, within the composite reagent, the small molecule
SYBR Green I was easily adsorbed on the surfaces of CuNPs, instead
of intercalating into the dsDNA. So the composite reagent only exhibited
the red fluorescence generated from dsDNAāCuNPs. However, when
the solution of H<sub>2</sub>O<sub>2</sub> was added into the composite
reagent, the CuNPs were deconstructed and their fluorescence was quenched;
meanwhile, the inhibition of SYBR Green I binding with dsDNA was eliminated.
As a result, the mixed solution of the composite reagent with H<sub>2</sub>O<sub>2</sub> exhibited green fluorescence generated from
the intercalation of SYBR Green I into dsDNA. Since H<sub>2</sub>O<sub>2</sub> is an important molecule and involved in various research
fields, this developed composite reagent could be employed for many
applications in biological analysis. As a proof-of-application demonstration,
the sensitive detection of glucose was conducted. Moreover, the method
was also extended to the detection of other biomolecules, such as
cholesterol and horseradish peroxidase, which indicated the broad
applications of the proposed sensing strategy in biomedical analysis
Multifunctional Dumbbell-Shaped DNA-Templated Selective Formation of Fluorescent Silver Nanoclusters or Copper Nanoparticles for Sensitive Detection of Biomolecules
In
this work, a multifunctional template for selective formation of fluorescent
silver nanoclusters (AgNCs) or copper nanoparticles (CuNPs) is put
forward. This dumbbell-shaped (DS) DNA template is made up of two
cytosine hairpin loops and an adenineāthymine-rich double-helical
stem which is closed by the loops. The cytosine loops act as specific
regions for the growth of AgNCs, and the double-helical stem serves
as template for the CuNPs formation. By carefully investigating the
sequence and length of DS DNA, we present the optimal design of the
template. Benefiting from the smart design and facile synthesis, a
simple, label-free, and ultrasensitive fluorescence strategy for adenosine
triphosphate (ATP) detection is proposed. Through the systematic comparison,
it is found that the strategy based on CuNPs formation is more sensitive
for ATP assay than that based on AgNCs synthesis, and the detection
limitation was found to be 81 pM. Whatās more, the CuNPs formation-based
method is successfully applied in the detection of ATP in human serum
as well as the determination of cellular ATP. In addition to small
target molecule, the sensing strategy was also extended to the detection
of biomacromolecule (DNA), which illustrates the generality of this
biosensor
One-Pot Synthesis of DNA-CdTe:Zn<sup>2+</sup> Nanocrystals Using Na<sub>2</sub>TeO<sub>3</sub> as the Te source
DNA-functionalized quantum dots (QDs)
are powerful tools for biosensing and bioimaging applications. Facile
labeling methods with good fluorescence properties are desirable for
the development of DNA-functionalized QDs. In this article, we describe
a novel and simple approach that leads to the synthesis of DNA-functionalized
CdTe:Zn<sup>2+</sup> QDs in one step. It is the first time that DNA-functionalized
QDs have been prepared using sodium tellurite as the tellurium source
by a hydrothermal method. This approach will greatly reduce the synthesis
time (only about 1 h) and simplify the synthesis process as well as
reduce the complexity of the required experimental techniques. The
as-prepared QDs exhibit high quantum yield, small size, and low toxicity.
UVāvis spectra and FTIR characterization proved that the abundance
of DNA on the surface of the QDs increased with the increase in the
concentration of the feed DNA. Most importantly, these QDs functionalized
with DNA have great potential to bind specifically to DNA, protein,
and cell surface receptors
Multipedal DNA Walker Biosensors Based on Catalyzed Hairpin Assembly and Isothermal Strand-Displacement Polymerase Reaction for the Chemiluminescent Detection of Proteins
In this study, two
kinds of sensitive biosensors based on a multipedal
DNA walker along a three-dimensional DNA functional magnet particles
track for the chemiluminescent detection of streptavidin (SA) are
constructed and compared. In the presence of SA, a multipedal DNA
walker was constructed by a biotin-modified catalyst as a result of
the terminal protection to avoid being digested by exonuclease I.
Then, through a toehold-mediated strand exchange, a ālegā
of a multipedal DNA walker interacted with a toehold of a catalyzed
hairpin assembly (CHA)-H1 coupled with magnetic microparticles (MMPs)
and opened its hairpin structure. The newly open stem in CHA-H1 was
hybridized with a toehold of biotin-labeled H2. Via the strand displacement
process, H2 displaced one ālegā of a multipedal DNA
walker, and the other ālegā continued to interact with
the neighboring H1 to initiate the next cycle. In order to solve the
high background caused by the hybridization between CHA-H1 and H2
without a CHA-catalyst, the other model was designed. The principle
of the other model (isothermal strand-displacement polymerase reaction
(ISDPR)-DNA walker) was similar to that of the above one. After the
terminal protection of SA, a ālegā of a multipedal DNA
walker was triggered to open the hairpin of the ISDPR-H1 conjugated
with MMPs. Then, the biotin-modified primer hybridized with the newly
exposed DNA segment, triggering the polymerization reaction with the
assistance of dNTPs/polymerase. As for the extension of the primer,
the ālegā of a multipedal DNA walker was displaced so
that the other ālegā could trigger the proximal H1 to
go onto the next cycle. Due to its lower background and stronger signal,
a multipedal DNA walker based on an ISDPR had a lower limit of detection
for SA. The limit of detection for SA was 6.5 pM, and for expanding
the application of the method, the detections of the folate receptor
and thrombin were explored. In addition, these DNA walker methods
were applied in complex samples successfully
Rox-DNA Functionalized Silicon Nanodots for Ratiometric Detection of Mercury Ions in Live Cells
A ratiometric fluorescent
sensor for mercury ions (Hg<sup>2+</sup>) has been constructed via
covalent functionalization of silicon
nanodot (SiND) with Hg<sup>2+</sup>-specific 6-carboxy-X-rhodamine
(Rox)-tagged DNA. For the Rox-DNA functionalized SiND, the red fluorescence
of Rox can be quenched by the blue-emitting SiND in the presence of
Hg<sup>2+</sup> due to structural change in DNA, which serves as the
response signal. Meawhile, the fluorescence of SiND is insensitive
to Hg<sup>2+</sup> and acts as the reference signal. The wavelength
difference in the optimal emission peak is as large as 190 nm between
SiND (422 nm) and Rox (612 nm), which can efficaciously exclude the
interference of the two emission peaks, and facilitates dual-color
visualization of Hg<sup>2+</sup> ions. The biofunctionalization of
SiND improves the acidābase stability of SiND significantly,
which is favorable for its application in the intracellular environment.
Accordingly, a sensitive, simple, precise and rapid method for tracing
Hg<sup>2+</sup> was proposed. The limit of detection and precision
of this method for Hg<sup>2+</sup> was 9.2 nM and 8.8% (50 nM, <i>n</i> = 7), respectively. The increase of Hg<sup>2+</sup> concentration
in the range of 10ā1500 nM was in accordance with linearly
increase of the <i>I</i><sub>422</sub>/<i>I</i><sub>612</sub> ratio. As for practical application, the recoveries
in spiked human urine and serum samples were in the range of 81ā107%.
Moreover, this fluorescent nanosensor was utilized to the ratiometric
detection of Hg<sup>2+</sup> in HeLa cells
Periodic Fluorescent Silver Clusters Assembled by Rolling Circle Amplification and Their Sensor Application
A simple method for preparing DNA-stabilized
Ag nanoclusters (NCs)
nanowires is presented. To fabricate the Ag NCs nanowires, we use
just two unmodified component strands and a long enzymatically produced
scaffold. These nanowires form at room temperature and have periodic
sequence units that are available for fluorescence Ag NCs assembled
which formed three-way junction (TWJ) structure. These Ag NCs nanowires
can be clearly visualized by confocal microscopy. Furthermore, due
to the high efficiency of rolling circle amplification reaction in
signal amplification, the nanowires exhibit high sensitivity for the
specific DNA detection with a wide linear range from 6 to 300 pM and
a low detection limit of 0.84 pM, which shows good performance in
the complex serum samples. Therefore, these Ag NCs nanowires might
have great potential in clinical and imaging applications in the future
Peptide-Capped Gold Nanoparticle for Colorimetric Immunoassay of Conjugated Abscisic Acid
The pentapeptide Cys-Ala-Leu-Asn-Asn (CALNN) has been
proved to
be a powerful tool to stabilize the AuNPs. These CALNN-capped AuNPs
have been used to develop various bioanalysis platforms. In this paper,
the CALNN-capped AuNPs are proved to be a robust tool for aggregation-based
colorimetric immunoassays as well. A colorimetric immunoassay strategy
based upon the antibody-induced assembly of functionalized AuNPs for
Abscisic Acid glucose ester (ABA-GE) determination has been developed.
The ABA-functionalized AuNPs aggregate in the presence of specific
antibody, accompanied by a color change of the solution. The color
change is competitively inhibited by ABA-GE. The interparticle distance
in aggregates is small due to the thin peptide layer on the AuNPs
surface, and it is determined by the āYā shape antibody
linker as well. As a result of that, an obvious color change in the
immunoassays is observed. Under the optimized conditions, a linear
response range from 5 nM to 10 Ī¼M for ABA-GE determination is
obtained, and the limit of detection (LOD) is evaluated to be 2.2
nM. This method is simple, homogeneous, and has potential for visual
detection of ABA-GE
One-Step Synthesis of Rox-DNA Functionalized CdZnTeS Quantum Dots for the Visual Detection of Hydrogen Peroxide and Blood Glucose
As the blood glucose concentration
is an important clinical parameter
of diabetes, the rapid and effective detection of blood glucose is
very significant for monitoring and managing diabetes. Here, a facile
method to prepare Rox-DNA functionalized CdZnTeS quantum dots (QDs)
was developed. The Rox-DNA functionalized CdZnTeS QDs were prepared
by a one-pot hydrothermal method through phosphorothioate DNA bound
to QDs, which were employed as a ratiometric fluorescent probe for
the rapid and sensitive detection of H<sub>2</sub>O<sub>2</sub> and
glucose. Compared with the traditional multistep construction of ratiometric
fluorescent probes, this presented approach is simpler and more effective
without chemical modification and complicated separation. The CdZnTeS
QDs with green fluorescence is specifically sensitive to H<sub>2</sub>O<sub>2</sub>, while the red fluorescence of Rox is invariable. H<sub>2</sub>O<sub>2</sub> is the product from the oxidation of glucose
catalyzed by glucose oxidase (GOx). Therefore, a facile method to
detect H<sub>2</sub>O<sub>2</sub> and glucose with a detection limit
of 0.075 Ī¼M for H<sub>2</sub>O<sub>2</sub> and 0.042 Ī¼M
for glucose was developed. In addition, this proposed probe has been
employed for the detection of glucose in human serum with a satisfactory
result. Moreover, this probe has been used for visual detection, and
the health and diabetics can be distinguished by the naked eye. Meanwhile,
this nanoprobe is also generalizable and can be extended to the detection
of many other H<sub>2</sub>O<sub>2</sub>-mediated analytes
Controlled Assembly of Gold Nanoparticles through Antibody Recognition: Study and Utilizing the Effect of Particle Size on Interparticle Distance
An assembly of gold nanoparticle
through the recognition of unmodified
antibody was developed. The use of peptide (Cys-Ala-Leu-Asn-Asn) as
ligands to stabilize and functionalize gold nanoparticles provides
technical and operational convenience. These peptide-capped particles
in different sizes are recognized by antibody and assembly to form
dimers and expanded hybrid material by controlling the conditions.
The interparticle spacing of these assemblies was well studied with
small-angle X-ray scattering measurements, and it was found that the
interparticle spacing is inversely dependent on the particle size.
This relationship of interparticle spacing and particle size is closely
related to the structure of antibody linker. Therefore, analyzing
the interparticle spacing of assemblies can reveal the equilibrium
configuration of IgG. Based on the investigation, the FabāFab
angle of IgG is obtained to be ā102Ā° and the Fab arms
are ā7.8 nm. These results provide new experimental data on
the structure of flexible IgG
Simultaneous Determination of Human Enterovirus 71 and Coxsackievirus B3 by Dual-Color Quantum Dots and Homogeneous Immunoassay
Human Enterovirus 71 (EV71) and Coxsackievirus B3 (CVB3)
have high risks for morbidity and mortality. A virus quantitation
immunoassay has been proposed by employing two colored quantum dots
(QDs), antibodies of the virus, and graphene oxide (GO). The QDs are
streptavidin-conjugated quantum dots (SA-QDs), and the antibodies
are biotinylated antibodies. Biotinylated EV71 antibody (Ab1) was
associated with 525 nm green colored SA-QDs via biotin-streptavidin
interaction forming QDs-Ab1, whereas biotinylated CVB3 antibody (Ab2)
was associated with 605 nm red colored SA-QDs via biotināstreptavidin
interaction forming QDs-Ab2. GO was an excellent quencher to the fluorescence
of both QDs-Ab1 and QDs-Ab2. The targets of EV71 and CVB3 can break
up the complex of QDs-Ab and GO, recovering the fluorescence of QDs-Ab1
and QDs-Ab2, respectively. Using these two different colored QDs-Ab
fluorescence recovery intensities upon the addition of targets EV71
and CVB3, the two enteroviruses can be simultaneously quantitatively
determined with a single excitation light. The detection limits of
EV71 and CVB3 are 0.42 and 0.39 ng mL<sup>ā1</sup> based on
3 times signal-to-noise ratio, respectively. More importantly, this
strategy can be further used as a universal method for any protein
or virus determination by changing the conjugated antibodies in disease
early diagnosis, which can provide a fast and promising clinical approach
for virus differentiation and determination. In a word, a simple,
fast, sensitive, and highly selective assay for EV71 and CVB3 has
been developed. It could be applied in clinical sample analysis with
a satisfactory result. It was notable that the sensor could not only
achieve rapid and precise quantitative determination of protein/virus
by fluorescent intensity but also could be applied in semiquantitative
protein/virus determination by digital visualization