3 research outputs found
Simple and Rapid Functionalization of Gold Nanorods with Oligonucleotides Using an mPEG-SH/Tween 20-Assisted Approach
DNA conjugated gold nanorods (AuNRs)
are widely applied for nanostructure
assembly, gene therapy, biosensing, and drug delivery. However, it
is still a great challenge to attach thiolated DNA on AuNRs, because
the positively charged AuNRs readily aggregate in the presence of
negatively charged DNA. This article reports an mPEG-SH/Tween 20-assisted
method to load thiolated DNA on AuNRs in 1 h. Tween 20 and mPEG-SH
are used to synergistically displace CTAB on the surface of AuNRs
by repeated centrifugation and resuspension, and thiolated DNA are
attached to AuNRs in the presence of 1 M NaCl, 100 mM MgCl<sub>2</sub>, or 100 mM citrate. AuNRs with different sizes and aspect ratios
can be functionalized with DNA by this method. The number of DNA loaded
on each AuNR can be easily controlled by the concentrations of mPEG-SH
and Tween 20 or the ratio between DNA and AuNR. Functionalized AuNRs
were used for nanoparticle assembly and cancer cell imaging to confirm
that DNA anchored on the surface of AuNRs retains its hybridization
and molecular recognition capability. The new method is easy, rapid,
and robust for the preparation of DNA functionalized AuNRs for a variety
of applications such as cancer therapy, drug delivery, self-assembly,
and imaging
Surface-Enhanced Raman Scattering Active Plasmonic Nanoparticles with Ultrasmall Interior Nanogap for Multiplex Quantitative Detection and Cancer Cell Imaging
Due to its large enhancement effect,
nanostructure-based surface-enhanced
Raman scattering (SERS) technology had been widely applied for bioanalysis
and cell imaging. However, most SERS nanostructures suffer from poor
signal reproducibility, which hinders the application of SERS nanostructures
in quantitative detection. We report an etching-assisted approach
to synthesize SERS-active plasmonic nanoparticles with 1 nm interior
nanogap for multiplex quantitative detection and cancer cell imaging.
Raman dyes and methoxy polyÂ(ethylene glycol) thiol (mPEG–SH)
were attached to gold nanoparticles (AuNPs) to prepare gold cores.
Next, Ag atoms were deposited on gold cores in the presence of Pluronic
F127 to form a Ag shell. HAuCl<sub>4</sub> was used to etch the Ag
shell and form an interior nanogap in Au@AgAuNPs, leading to increased
Raman intensity of dyes. SERS intensity distribution of Au@AgAuNPs
was found to be more uniform than that of aggregated AuNPs. Finally,
Au@AgAuNPs were used for multiplex quantitative detection and cancer
cell imaging. With the advantages of simple and rapid preparation
of Au@AgAuNPs with highly uniform, stable, and reproducible Raman
intensity, the method reported here will widen the applications of
SERS-active nanoparticles in diagnostics and imaging
Design and Synthesis of Target-Responsive Aptamer-Cross-linked Hydrogel for Visual Quantitative Detection of Ochratoxin A
A target-responsive aptamer-cross-linked
hydrogel was designed and synthesized for portable and visual quantitative
detection of the toxin Ochratoxin A (OTA), which occurs in food and
beverages. The hydrogel network forms by hybridization between one
designed DNA strand containing the OTA aptamer and two complementary
DNA strands grafting on linear polyacrylamide chains. Upon the introduction
of OTA, the aptamer binds with OTA, leading to the dissociation of
the hydrogel, followed by release of the preloaded gold nanoparticles
(AuNPs), which can be observed by the naked eye. To enable sensitive
visual and quantitative detection, we encapsulated Au@Pt core–shell
nanoparticles (Au@PtNPs) in the hydrogel to generate quantitative
readout in a volumetric bar-chart chip (V-Chip). In the V-Chip, Au@PtNPs
catalyzes the oxidation of H<sub>2</sub>O<sub>2</sub> to generate
O<sub>2</sub>, which induces movement of an ink bar to a concentration-dependent
distance for visual quantitative readout. Furthermore, to improve
the detection limit in complex real samples, we introduced an immunoaffinity
column (IAC) of OTA to enrich OTA from beer. After the enrichment,
as low as 1.27 nM (0.51 ppb) OTA can be detected by the V-Chip, which
satisfies the test requirement (2.0 ppb) by the European Commission.
The integration of a target-responsive hydrogel with portable enrichment
by IAC, as well as signal amplification and quantitative readout by
a simple microfluidic device, offers a new method for portable detection
of food safety hazard toxin OTA