7 research outputs found
Manipulation of <i>in Vitro</i> Angiogenesis Using Peptide-Coated Gold Nanoparticles
We demonstrate the deliberate activation or inhibition of <i>in</i> <i>vitro</i> angiogenesis using functional peptide coated gold nanoparticles. The peptides, anchored to oligo-ethylene glycol capped gold nanospheres, were designed to selectively interact with cell receptors responsible for activation or inhibition of angiogenesis. The functional particles are shown to influence significantly the extent and morphology of vascular structures, without causing toxicity. Mechanistic studies show that the nanoparticles have the ability to alter the balance between naturally secreted pro- and anti-angiogenic factors, under various biological conditions. Nanoparticle-induced control over angiogenesis opens up new directions in targeted drug delivery and therapy
Formation and Plasmonic Response of Self-Assembled Layers of Colloidal Gold Nanorods and Branched Gold Nanoparticles
The plasmonic properties of self-assembled layers of
rod- and branched-shaped
gold nanoparticles were investigated using optical techniques. Nanoparticles
were synthesized by a surfactant-guided, seed-mediated growth method.
The layers were obtained by gradual assembly of nanoparticles at the
interface between a polar and a nonpolar solvent and were transferred
to a glass slide. Polarization and angle-dependent extinction measurements
showed that the layers made of gold nanorods were governed by an effective
medium response. The response of the layers made by branched gold
particles was characterized by random light scattering. Microscopic
mapping of the spatial mode structure demonstrates a uniform optical
response of the nanoparticle layers down to a submicrometer length
scale
Formation and Plasmonic Response of Self-Assembled Layers of Colloidal Gold Nanorods and Branched Gold Nanoparticles
The plasmonic properties of self-assembled layers of
rod- and branched-shaped
gold nanoparticles were investigated using optical techniques. Nanoparticles
were synthesized by a surfactant-guided, seed-mediated growth method.
The layers were obtained by gradual assembly of nanoparticles at the
interface between a polar and a nonpolar solvent and were transferred
to a glass slide. Polarization and angle-dependent extinction measurements
showed that the layers made of gold nanorods were governed by an effective
medium response. The response of the layers made by branched gold
particles was characterized by random light scattering. Microscopic
mapping of the spatial mode structure demonstrates a uniform optical
response of the nanoparticle layers down to a submicrometer length
scale
In-Depth Analysis of Excitation Dynamics in Dye-Sensitized Upconversion Core and Core/Active Shell Nanoparticles
Upconversion nanoparticles
(UCNPs) combining both dye sensitization
and core/shell enhancement are of great interest for their ability
to boost the excitation efficiency of upconversion systems. Here,
we report and investigate a 20-fold upconversion luminescence enhancement
in dye-sensitized core/active shell UCNPs compared to that in nonsensitized
core-only UCNPs. We observe a two-component luminescence rise dynamics
in the upconversion kinetics of dye-sensitized UCNPs, distinctly different
from the one-component rise dynamics of the nonsensitized UCNPs. For
dye-sensitized UCNPs, the fast sub-microsecond component of the upconversion
luminescence rise time is attributed to the radiative pumping of Er<sup>3+</sup> ions from the dye, whereas the slow sub-millisecond component
is due to the nonradiative energy transfer from the dye predominantly
to Yb<sup>3+</sup> ions, followed by the energy migration and the
nonradiative energy transfer from Yb<sup>3+</sup> to Er<sup>3+</sup> ions. Our studies provide an insight into the interplay between
radiative and nonradiative energy transfer as well as into the role
of energy migration across the active shell of dye-sensitized core/active
shell UCNPs
Graphene Oxide-Upconversion Nanoparticle Based Optical Sensors for Targeted Detection of mRNA Biomarkers Present in Alzheimerās Disease and Prostate Cancer
The
development of new sensors for the accurate detection of biomarkers
in biological fluids is of utmost importance for the early diagnosis
of diseases. Next to advanced laboratory techniques, there is a need
for relatively simple methods which can significantly broaden the
availability of diagnostic capability. Here, we demonstrate the successful
application of a sensor platform based on graphene oxide and upconversion
nanoparticles (NPs) for the specific detection of mRNA-related oligonucleotide
markers in complex biological fluids. The combination of near-infrared
light upconversion with low-background photon counting readout enables
reliable detection of low quantities of small oligonucleotide sequences
in the femtomolar range. We demonstrate the successful detection of
analytes relevant to mRNAs present in Alzheimerās disease as
well as prostate cancer in human blood serum. The high performance
and relative simplicity of the upconversion NP-graphene sensor platform
enables new opportunities in early diagnosis based on specific detection
of oligonucleotide sequences in complex environments
Fast Assembly of Gold Nanoparticles in Large-Area 2D Nanogrids Using a One-Step, Near-Infrared Radiation-Assisted Evaporation Process
When
fabricating photonic crystals from suspensions in volatile liquids
using the horizontal deposition method, the conventional approach
is to evaporate slowly to increase the time for particles to settle
in an ordered, periodic close-packed structure. Here, we show that
the greatest ordering of 10 nm aqueous gold nanoparticles (AuNPs)
in a template of larger spherical polymer particles (mean diameter
of 338 nm) is achieved with very fast water evaporation rates obtained
with near-infrared radiative heating. Fabrication of arrays over areas
of a few cm<sup>2</sup> takes only 7 min. The assembly process requires
that the evaporation rate is fast relative to the particlesā
Brownian diffusion. Then a two-dimensional colloidal crystal forms
at the falling surface, which acts as a sieve through which the AuNPs
pass, according to our Langevin dynamics computer simulations. With
sufficiently fast evaporation rates, we create a hybrid structure
consisting of a two-dimensional AuNP nanoarray (or ānanogridā)
on top of a three-dimensional polymer opal. The process is simple,
fast, and one-step. The interplay between the optical response of
the plasmonic Au nanoarray and the microstructuring of the photonic
opal results in unusual optical spectra with two extinction peaks,
which are analyzed <i>via</i> finite-difference time-domain
method simulations. Comparison between experimental and modeling results
reveals a strong interplay of plasmonic modes and collective photonic
effects, including the formation of a high-order stopband and slow-light-enhanced
plasmonic absorption. The structures, and hence their optical signatures,
are tuned by adjusting the evaporation rate <i>via</i> the
infrared power density
Optical Mie Scattering by DNA-Assembled Three-Dimensional Gold Nanoparticle Superlattice Crystals
Programmable assemblies of gold nanoparticles engineered
with DNA
have intriguing optical properties such as Coulomb-interaction-driven
strong coupling, polaritonic response in the visible range, and ultralow
dispersion dielectric response in the infrared spectral range. In
this work, we demonstrate the optical Mie resonances of individual
microcrystals of DNAāgold nanoparticle superlattices. Broadband
hyperspectral mapping of both transmission and dark-field scattering
reveal a polarization-insensitive optical response with distinct spectral
features in the visible and near-infrared ranges. Experimental observations
are supported by numerical simulations of the microcrystals under
a resonant effective medium approximation in the regime of capacitively
coupled nanoparticles. The study identifies a universal characteristic
optical response which is defined by a band of multipolar Mie resonances,
which only weakly depend on the crystal size and light polarization.
The use of gold superlattice microcrystals as scattering materials
is of interest for fields such as complex nanophotonics, thermoplasmonics,
photocatalysis, sensing, and nonlinear optics