10 research outputs found
Direct Quantification of DNA Base Composition by Surface-Enhanced Raman Scattering Spectroscopy
Design
of ultrasensitive DNA sensors based on the unique physical properties
of plasmonic nanostructures has become one of the most exciting areas
in nanomedicine. However, despite the vast number of proposed applications,
the determination of the base composition in nucleic acids, a fundamental
parameter in genomic analyses and taxonomic classification, is still
restricted to time-consuming and poorly sensitive conventional methods.
Herein, we demonstrate the possibility of determining the base composition
in single- and double-stranded DNA by using a simple, low-cost, high-throughput,
and label-free surface-enhanced Raman scattering (SERS) method in
combination with cationic nanoparticles
Analysis of the SERS Spectrum by Theoretical Methodology: Evaluating a Classical Dipole Model and the Detuning of the Excitation Frequency
Surface-enhanced Raman scattering
(SERS) spectroscopy is gaining
prominence as one of the most powerful ultradetection techniques.
The SERS outcome is essentially a complicated pattern of vibrational
bands that allows multiplex analysis but, at the same time, makes
difficult the interpretation of unknown analytes or known substances
in the presence of complex unknown chemical environments. Herein,
we show two computational methods to reproduce the spectral shape
of the SERS spectra. The first, based in the modification of the classical
dipole model, reproduces with a notable similarity the experimental
spectrum excited far to the red of the localized surface plasmon resonance
(LSPR). This light and time-efficient model is of great interest to
elucidate the orientation of the target on the plasmonic surface or
even to accurately identify suspected unknown targets in real samples.
However, the experimental SERS spectrum in resonance with the LSPR
is also modeled by using a more classical CPHF approach. This method
provides also good agreement with the experiment but at the expense
of much more computational time
Fast Optical Chemical and Structural Classification of RNA
As more biological activities of
ribonucleic acids continue to
emerge, the development of efficient analytical tools for RNA identification
and characterization is necessary to acquire an in-depth understanding
of their functions and chemical properties. Herein, we demonstrate
the capacity of label-free direct surface-enhanced Raman scattering
(SERS) analysis to access highly specific structural information on
RNAs at the ultrasensitive level. This includes the recognition of
distinctive vibrational features of RNAs organized into a variety
of conformations (micro-, fully complementary duplex-, small interfering-
and short hairpin-RNAs) or characterized by subtle chemical differences
(single-base variances, nucleobase modifications and backbone composition).
This method represents a key advance in the ribonucleic acid analysis
and will have a direct impact in a wide range of different fields,
including medical diagnosis, drug design, and biotechnology, by enabling
the rapid, high-throughput, simple, and low-cost identification and
classification of structurally similar RNAs
Synthesis and Optical Properties of Homogeneous Nanoshurikens
During the last years the controlled
synthesis of Au nanoparticles
(NPs) has almost become a reality, and structures such as spheres,
cubes, rods, decahedra, or octahedra can be prepared with <i>a la carte</i> dimensions in a very homogeneous manner. However,
the fabrication of spiked particles, the most efficient plasmonic
NPs, with controllable geometric parameters remains elusive. Here
we show how to prepare highly homogeneous spiked nanoparticles composed
of a penta-twinned core and five tips. These nanoparticles, reminiscent
of ninja nanoshurikens (throwing stars), exhibit the ability to concentrate
large electromagnetic fields at the apexes of the tips upon illumination.
The apexes also present high affinity for analytes, giving rise to
an unprecedented capacity for quantitative optical ultradetection
with SERS
Universal One-Pot and Scalable Synthesis of SERS Encoded Nanoparticles
Encoded
particles are one of the most powerful approaches for multiplex
high-throughput screening. Surface-enhanced Raman scattering (SERS)
based codification can, in principle, avoid many of the intrinsic
limitations due to conventional alternatives, as it decreases the
reading time and particle size while allowing for almost unlimited
codification. Unfortunately, methods for the synthetic preparation
of these particles are tedious; often subjected to limited reproducibility
(associated with large fluctuations in the size distributions of the
polymers employed in the standard protocols); and to date, limited
to a small amount of molecules. Herein, we report a universal, one-pot,
inexpensive, and scalable synthetic protocol for the fabrication of
SERS-encoded nanoparticles. This synthetic strategy is highly reproducible,
independent of the chemical nature and size of the Raman code used
(31 different codes were tested) and scalable in the liter range without
affecting the final properties of the encoded structures. Furthermore,
the SERS efficiency of the fabricated encoded nanoparticles is superior
to that of the materials produced by conventional methods, while showing
a remarkable reproducibility from batch to batch. This encoding strategy
can easily be applied to nanoparticles of different materials and
shapes
Boosting the Quantitative Inorganic Surface-Enhanced Raman Scattering Sensing to the Limit: The Case of Nitrite/Nitrate Detection
A high-performance ionic-sensing
platform has been developed by
an interdisciplinary approach, combining the classical colorimetric
Griess reaction and new concepts of nanotechnology, such as plasmonic
coupling of nanoparticles and surface-enhanced Raman scattering (SERS)
spectroscopy. This approach exploits the advantages of combined SERS/surface-enhanced
resonant Raman Scattering (SERRS) by inducing the formation of homogeneous
hot spots and a colored complex in resonance with the laser line,
to yield detection limits for nitrite down to the subpicomolar level.
The performance of this new method was compared with the classical
Griess reaction and ionic chromatography showing detection limits
about 6 and 3 orders of magnitude lower, respectively
Directed Assembly of DNA-Functionalized Gold Nanoparticles Using PyrroleâImidazole Polyamides
Traditional methods for the construction of nanoparticle
arrays
and lattices exploit WatsonâCrick base pairing of single-stranded
DNA sequences as a proxy for self-assembly. Although this approach
has been utilized in a variety of applications in nanoassembly, diagnostics,
and biomedicine, the diversity of this recognition lexicon could be
considerably increased by developing strategies that recognize the
base-pairing landscape of double-stranded DNA (dsDNA) sequences. Herein
we describe the first report of programmed gold nanoparticle (GNP)
aggregation directed by the recognition of dsDNA sequences using pyrroleâimidazole
polyamideâGNP (PAâGNP) conjugates. We demonstrate the
reversibility and selectivity of this strategy for forming GNP aggregates
in the presence of fully matched dsDNA sequences relative to dsDNA
sequences containing one- and two-base-pair mismatches
Highly Sensitive SERS Quantification of the Oncogenic Protein câJun in Cellular Extracts
A surface-enhanced
Raman scattering (SERS)-based sensor was developed
for the detection of the oncoprotein c-Jun at nanomolar levels. c-Jun
is a member of the bZIP (basic zipper) family of dimeric transcriptional
activators, and its overexpression has been associated with carcinogenic
mechanisms in several human cancers. For our sensing purpose, we exploited
the ability of c-Jun to heterodimerize with its native protein partner,
c-Fos, and therefore designed a c-Fos peptide receptor chemically
modified to incorporate a thiophenol (TP) group at the N-terminal
site. The TP functionality anchors the c-Fos protein onto the metal
substrate and works as an effective SERS probe to sense the structural
rearrangements associated with the c-Fos/c-Jun heterodimerization
SERS Detection of Amyloid Oligomers on Metallorganic-Decorated Plasmonic Beads
Protein
misfolded proteins are among the most toxic endogenous species of
macromolecules. These chemical entities are responsible for neurodegenerative
disorders such as Alzheimerâs, Parkinsonâs, CreutzfeldtâJakobâs
and different non-neurophatic amyloidosis. Notably, these oligomers
show a combination of marked heterogeneity and low abundance in body
fluids, which have prevented a reliable detection by immunological
methods so far. Herein we exploit the selectivity of proteins to react
with metallic ions and the sensitivity of surface-enhanced Raman spectroscopy
(SERS) toward small electronic changes in coordination compounds to
design and engineer a reliable optical sensor for protein misfolded
oligomers. Our strategy relies on the functionalization of Au nanoparticle-decorated
polystyrene beads with an effective metallorganic Raman chemoreceptor,
composed by Al<sup>3+</sup> ions coordinated to 4-mercaptobenzoic
acid (MBA) with high Raman cross-section, that selectively binds aberrant
protein oligomers. The mechanical deformations of the MBA phenyl ring
upon complexation with the oligomeric species are registered in its
SERS spectrum and can be quantitatively correlated with the concentration
of the target biomolecule. The SERS platform used here appears promising
for future implementation of diagnostic tools of aberrant species
associated with protein deposition diseases, including those with
a strong social and economic impact, such as Alzheimerâs and
Parkinsonâs diseases
Effect of MetalâLiquid Interface Composition on the Adsorption of a Cyanine Dye onto Gold Nanoparticles
Synthesis of asymmetric nanoparticles, such as gold nanorods,
with
tunable optical properties providing metal structures with improved
SERS performance is playing a critical role in expanding the use of
SERS to imaging and sensing applications. However, the synthetic methods
usually require surfactants or polymers as shape-directing agents.
These chemicals normally remain firmly bound to the metal after the
synthesis, preventing the direct adsorption of a large number of potential
analytes and often hampering the chemical functionalization of the
surface unless extended, and critical for the nanoparticle stability,
postremoval steps were performed. For this reason, it is of great
importance for the full exploitation of these nanostructures to gain
a deeper insight into the dependence of the analyteâmetal interaction
to the metalâliquid interface composition. In this article,
we investigated in detail the role played by each component of the
gold nanorod (GNR) interface in the adsorption of indocyanine green
(ICG) as a probe molecule. Citrate-reduced gold nanospheres were used
as a model substrate since the negative citrate anions adsorbed onto
the metal surface can be easily displaced by those chemicals usually
involved in the GNR synthesis, allowing the GNR-like interface composition
to be progressively rebuilt and modified at will on the citrate-capped
nanoparticles. The obtained results provide a meticulous description
of the role played by each individual component of the metalâliquid
interface on the ICG interaction with the metal, illustrating how
apparently minor experimental changes can dramatically modify the
affinity and optical properties of the ICG probe adsorbed onto the
nanoparticle