52 research outputs found
Bi-directional DNA Walking Machine and Its Application in an Enzyme-Free Electrochemiluminescence Biosensor for Sensitive Detection of MicroRNAs
Herein, a dual microRNA
(miRNA) powered bi-directional DNA walking
machine with precise control was developed to fabricate an enzyme-free
biosensor on the basis of distance-based electrochemiluminescence
(ECL) energy transfer for multiple detection of miRNAs. By using miRNA-21
as the driving force, the DNA walker could move forth along the track
and generated quenching of ECL response due to the proximity between
Au nanoparticles (AuNPs) and Mn<sup>2+</sup> doped CdS nanocrystals
(CdS:Mn NCs) film as the ECL emitters, realizing ultrasensitive determination
of miRNA-21. Impressively, once miRNA-155 was introduced as the driving
force, the walker could move back along the track automatically, and
surface plasmon resonance (SPR) occurred owing to the appropriate
large separation between AuNPs and CdS:Mn NCs, achieving an ECL enhancement
and realizing ultrasensitive detection of miRNA-155. The bi-directional
movement of the DNA walker on the track led to continuous distance-based
energy transfer from CdS:Mn NCs film by AuNPs, which resulted in significant
ECL signal variation of CdS:Mn NCs for multiple detection of miRNA-21
and miRNA-155 down to 1.51 fM and 1.67 fM, respectively. Amazingly,
the elaborated biosensor provided a new chance for constructing controllable
molecular nanomachines in biosensing, disease diagnosis, and clinical
analysis
An âOffâOnâ Electrochemiluminescent Biosensor Based on DNAzyme-Assisted Target Recycling and Rolling Circle Amplifications for Ultrasensitive Detection of microRNA
In this study, an offâon switching
of a dual amplified electrochemiluminescence
(ECL) biosensor based on Pb<sup>2+</sup>-induced DNAzyme-assisted
target recycling and rolling circle amplification (RCA) was constructed
for microRNA (miRNA) detection. First, the primer probe with assistant
probe and miRNA formed Y junction which was cleaved with the addition
of Pb<sup>2+</sup> to release miRNA. Subsequently, the released miRNA
could initiate the next recycling process, leading to the generation
of numerous intermediate DNA sequences (S2). Afterward, bare glassy
carbon electrode (GCE) was immersed into HAuCl<sub>4</sub> solution
to electrodeposit a Au nanoparticle layer (depAu), followed by the
assembly of a hairpin probe (HP). Then, dopamine (DA)-modified DNA
sequence (S1) was employed to hybridize with HP, which switching off
the sensing system. This is the first work that employs DA to quench
luminol ECL signal, possessing the biosensor ultralow background signal.
Afterward, S2 produced by the target recycling process was loaded
onto the prepared electrode to displace S1 and served as an initiator
for RCA. With rational design, numerous repeated DNA sequences coupling
with hemin to form hemin/G-quadruplex were generated, which could
exhibit strongly catalytic toward H<sub>2</sub>O<sub>2</sub>, thus
amplified the ECL signal and switched the ON state of the sensing
system. The liner range for miRNA detection was from 1.0 fM to 100
pM with a low detection limit down to 0.3 fM. Moreover, with the high
sensitivity and specificity induced by the dual signal amplification,
the proposed miRNA biosensor holds great potential for analysis of
other interesting tumor markers
An Electrochemical Biosensor for Sensitive Detection of MicroRNA-155: Combining Target Recycling with Cascade Catalysis for Signal Amplification
In this work, a new electrochemical
biosensor based on catalyzed
hairpin assembly target recycling and cascade electrocatalysis (cytochrome <i>c</i> (Cyt <i>c</i>) and alcohol oxidase (AOx)) for
signal amplification was constructed for highly sensitive detection
of microRNA (miRNA). It is worth pointing out that target recycling
was achieved only based on strand displacement process without the
help of nuclease. Moreover, porous TiO<sub>2</sub> nanosphere was
synthesized, which could offer more surface area for Pt nanoparticles
(PtNPs) enwrapping and enhance the amount of immobilized DNA strand
1 (S1) and Cyt <i>c</i> accordingly. With the mimicking
sandwich-type reaction, the cascade catalysis amplification strategy
was carried out by AOx catalyzing ethanol to acetaldehyde with the
concomitant formation of high concentration of H<sub>2</sub>O<sub>2</sub>, which was further electrocatalyzed by PtNPs and Cyt <i>c</i>. This newly designed biosensor provided a sensitive detection
of miRNA-155 from 0.8 fM to 1 nM with a relatively low detection limit
of 0.35 fM
Numerical analysis of particle motion and collision of surround U-clevis in windy and sandy environment
This paper was reviewed and accepted by the APCWE-IX Programme Committee for Presentation at the 9th Asia-Pacific Conference on Wind Engineering, University of Auckland, Auckland, New Zealand, held from 3-7 December 2017
Highly Ordered and Field-Free 3D DNA Nanostructure: The Next Generation of DNA Nanomachine for Rapid Single-Step Sensing
Herein,
by directly using WatsonâCrick base pairing, a highly
ordered and field-free three-dimensional (3D) DNA nanostructure is
self-assembled by azobenzene (azo)-functionalized DNA nippers in a
few minutes, which was applied as a 3D DNA nanomachine with an improved
movement efficiency compared to traditional Au-based 3D nanomachines
due to the organized and high local concentration of nippers on homogeneous
DNA nanostructure. Once microRNA (miRNA) interacts with the 3D nanomachine,
the nippers âopenâ to hybridize with the miRNA. Impressively,
photoisomerization of the azo group induces dehybridization/hybridization
of the nippers and miRNA under irradiation at different wavelengths,
which easily solves one main technical challenge of DNA nanotechnology
and biosensing: reversible locomotion in one step within 10 min. As
a proof of concept, the described 3D machine is successfully applied
in the rapid single-step detection of a biomarker, which gives impetus
to the design of new generations of mechanical devices beyond the
traditional ones with ultimate applications in sensing analysis and
diagnostic technologies
Dual microRNAs-Fueled DNA Nanogears: A Case of Regenerated Strategy for Multiple Electrochemiluminescence Detection of microRNAs with Single Luminophore
The
determination of multiple biomarkers from cancer cells features
a considerable step toward early diagnosis of cancers. However, realizing
different biomarkers detection with single electrochemiluminescence
(ECL) luminophore and regenerating the sensing platform remain a compelling
goal. Herein, dual miRNAs-fueled DNA nanogears were designed for an
enzyme-free ECL biosensor construction to perform the multiple sensitive
detection of the microRNA (miRNA) biomarkers with single luminophore.
The nanogears were assembled on CdS quantum dots (QDs) modified sensing
surface. Using miRNA-21 as motive power, Au nanoparticles (AuNPs)-labeled
nanogears B could be activated to roll against nanogear A, increasing
the distance between AuNPs and CdS QDs. Thus, the significant ECL
enhancement of CdS QDs was obtained owing to the ECL energy transfer
between AuNPs and CdS QDs, simultaneously realizing the detection
of miRNA-21. After the incubation of miRNA-155, nanogear B revolved
against nanogear A continuously and realized the close-range of AuNPs
and CdS QDs, resulting in the quenching of ECL intensity due to the
FoÌrster energy transfer and realizing the analysis of miRNA-155.
The successive locomotion of the nanogears led to a significant ECL
increasing for analysis of miRNA-21 down to 0.16 fM and a remarkable
ECL suppression for determination of miRNA-155 down to 0.33 fM. Impressively,
the proposed biosensor was able to be regenerated along with the gears
roll against each other. In general, this enzyme-free strategy initiates
a new thought to realize the multiple ECL detection with single luminophore,
paving the way for applications of nanomachines in biosensing and
clinical diagnosis
Electrochemiluminescent Graphene Quantum Dots as a Sensing Platform: A Dual Amplification for MicroRNA Assay
Graphene quantum dots (GQDs) with
an average diameter as small
as 2.3 nm were synthesized to fabricate an electrochemiluminescence
(ECL) biosensor based on T7 exonuclease-assisted cyclic amplification
and three-dimensional (3D) DNA-mediated silver enhancement for microRNA
(miRNA) analysis. Herein, to overcome the barrier in immobilizing
GQDs, aminated 3,4,9,10-perylenetetracarboxylic acid (PTCAâNH<sub>2</sub>) was introduced to load GQDs through ÏâÏ
stacking (GQDs/PTCAâNH<sub>2</sub>), realizing the solid-state
GQDs application. Furthermore, Fe<sub>3</sub>O<sub>4</sub>âAu
coreâshell nanocomposite (Au@Fe<sub>3</sub>O<sub>4</sub>) was
adopted as a probe anchor to form a novel electrochemiluminescent
signal tag of GQDs/PTCAâNH<sub>2</sub>/Au@Fe<sub>3</sub>O<sub>4</sub>. The prepared ECL signal tag was decorated on the electrode
surface, exhibiting excellent film-forming performance, good electronic
conductivity, and favorable stability, all of which overcame the obstacle
for applying GQDs in ECL biosensing and showed a satisfactory ECL
response under the coreactant of S<sub>2</sub>O<sub>8</sub><sup>2â</sup> (peroxydisulfate). Afterward, hairpin probe modified on the electrode
was opened by helper DNA, followed by assembling target to hybridize
with the exposed stem of the helper DNA. Significantly, T7 exonuclease
was employed to digest the DNA/RNA duplex and trigger the target recycling
without asking for a specific recognition site in the target sequence,
realizing a series of RNA/DNA detections by changing the sequence
of the complementary DNA. At last, the ECL signal was further enhanced
by silver nanoparticles (AgNPs)-based 3D DNA networks. After the two
amplifications, the ECL signal of GQDs was extraordinarily increased
and the prepared biosensor achieved a high sensitivity with the detection
limit of 0.83 fM. The biosensor was also explored in real samples,
and the result was in good accordance with the performance of quantitative
real-time polymerase chain reaction (qRT-PCR). Considering the excellent
sensitivity and applicability, we believe that the proposed biosensor
is a potential candidate for nucleic acid biosensing
Detection of TUNEL-positive cells.
<p>A) Representative TUNEL staining of normal retina, injured retina 7 days after injury, and hUCBSC-transplanted retinas 7 days after surgery. TUNEL-positive cells were seen in inner nuclear layer and ganglion cell layer. Arrows indicated the TUNEL-positive cells (Brown). ONL: outer nuclear layer; INL: inner nuclear layer; GCL: ganglion cell layer. B) TUNEL-positive cells counting in retina in RGC layer at different time points in injury and hUCBSC transplanted rats. Nâ=â5. <sup>*</sup><i>p</i><0.05, <sup>**</sup><i>p</i><0.01 <i>vs</i>. 3 hrs. <sup>#</sup><i>p</i><0.05, <sup>##</sup><i>p</i><0.01 <i>vs</i>. injury group.</p
Detection of CHOP mRNA expression.
<p>A) Representative RT-PCR of CHOP expression. CHOP mRNA expression was detected 3 hrs, 12 hrs, 24 hrs, 48 hrs and 7 days post surgery in the injury (Inj) and hUCBSC transplantation (Inj+SC) groups. B) Comparison of the band-pixel values of CHOP mRNA in injury and hUCBSC transplantation rats. <sup>*</sup><i>p</i><0.001 <i>vs.</i> hUCBSC transplantation. Nâ=â5.</p
Detection of retinal ganglion cells.
<p>A) Normal eye staining. ONL: outer nuclear layer; INL: inner nuclear layer; GCL: ganglion cell layer. BâE) Staining for injured (Inj) eyes at 3-day, 1-week, 2-week, and 4-week post injury, respectively. FâI) Staining for hUCBSC transplanted (Inj+SC) eyes at 3-day, 1-week, 2-week and 4-week post surgery, respectively. J) Comparison of RGC number. <sup>*</sup><i>p</i><0.05, <sup>**</sup><i>p</i><0.001 <i>vs</i>. injury group. Nâ=â5. A scale bar measures 100 microns.</p
- âŠ