39,129 research outputs found
Short-Chained Oligo(Ethylene Oxide)-Functionalized Gold Nanoparticles: Realization Of Significant Protein Resistance
Protein corona formed on nanomaterial surfaces play an important role in the bioavailability and cellular uptake of nanomaterials. Modification of surfaces with oligoethylene glycols (OEG) are a common way to improve the resistivity of nanomaterials to protein adsorption. Short-chain ethylene oxide (EO) oligomers have been shown to improve the protein resistance of planar Au surfaces. We describe the application of these EO oligomers for improved protein resistance of 30 nm spherical gold nanoparticles (AuNPs). Functionalized AuNPs were characterized using UV-Vis spectroscopy, dynamic light scattering (DLS), and zeta potential measurements. Capillary electrophoresis (CE) was used for separation and quantitation of AuNPs and AuNP-protein mixtures. Specifically, nonequilibrium capillary electrophoresis of equilibrium mixtures (NECEEM) was employed for the determination of equilibrium and rate constants for binding between citrate-stabilized AuNPs and two model proteins, lysozyme and fibrinogen. Semi-quantitative CE analysis was carried out for mixtures of EO-functionalized AuNPs and proteins, and results demonstrated a 2.5-fold to 10-fold increase in protein binding resistance to lysozyme depending on the AuNP surface functionalization and a 15-fold increase in protein binding resistance to fibrinogen for both EO oligomers examined in this study
Thermal transport at a nanoparticle-water interface: A molecular dynamics and continuum modeling study
Heat transfer between a silver nanoparticle and surrounding water has been
studied using molecular dynamics (MD) simulations. The thermal conductance
(Kapitza conductance) at the interface between a nanoparticle and surrounding
water has been calculated using four different approaches: transient
with/without temperature gradient (internal thermal resistance) in the
nanoparticle, steady-state non-equilibrium and finally equilibrium simulations.
The results of steady-state non-equilibrium and equilibrium are in agreement
but differ from the transient approach results. MD simulations results also
reveal that in the quenching process of a hot silver nanoparticle, heat
dissipates into the solvent over a length-scale of ~ 2nm and over a timescale
of less than 5ps. By introducing a continuum solid-like model and considering a
heat conduction mechanism in water, it is observed that the results of the
temperature distribution for water shells around the nanoparticle agree well
with MD results. It is also found that the local water thermal conductivity
around the nanoparticle is greater by about 50 percent than that of bulk water.
These results have important implications for understanding heat transfer
mechanisms in nanofluids systems and also for cancer photothermal therapy,
wherein an accurate local description of heat transfer in an aqueous
environment is crucial.Comment: 22 pages, 7 figures
Hydrophobic and hydrophilic au and ag nanoparticles. Breakthroughs and perspectives
This review provides a broad look on the recent investigations on the synthesis, characterization and physico-chemical properties of noble metal nanoparticles, mainly gold and silver nanoparticles, stabilized with ligands of different chemical nature. A comprehensive review of the available literature in this field may be far too large and only some selected representative examples will be reported here, together with some recent achievements from our group, that will be discussed in more detail. Many efforts in finding synthetic routes have been performed so far to achieve metal nanoparticles with well-defined size, morphology and stability in different environments, to match the large variety of applications that can be foreseen for these materials. In particular, the synthesis and stabilization of gold and silver nanoparticles together with their properties in different emerging fields of nanomedicine, optics and sensors are reviewed and briefly commented
A health concern regarding the protein corona, aggregation and disaggregation
Nanoparticle (NP)-protein complexes exhibit the correct identity of NP in
biological media. Therefore, protein-NP interactions should be closely explored
to understand and to modulate the nature of NPs in medical implementations.
This review focuses mainly on the physicochemical parameters such as dimension,
surface chemistry, the morphology of NPs and influence of medium pH on the
formation of protein corona and conformational changes of adsorbed proteins by
different kinds of methods. Also, the impact of protein corona on the colloidal
stability of NPs is discussed. Uncontrolled protein attachment on NPs may bring
unwanted impacts such as protein denaturation and aggregation. In contrast,
controlled protein adsorption by optimal concentration, size, pH and surface
modification of NPs may result in potential implementation of NPs as
therapeutic agents especially for disaggregation of amyloid fibrils. Also, the
effect of NPs-protein corona on reducing the cytotoxicity and clinical
implications such as drug delivery, cancer therapy, imaging and diagnosis will
be discussed. Validated correlative physicochemical parameters for NP-protein
corona formation frequently derived from protein corona fingerprints of NPs
which are more valid than the parameters obtained only on the base of NP
features. This review may provide useful information regarding the potency as
well as the adverse effects of NPs to predict their behavior in the in vivo
experiments.Comment: 40 pages, 20 figure
Defects Can Increase the Melting Temperature of DNA-Nanoparticle Assemblies
DNA-gold nanoparticle assemblies have shown promise as an alternative
technology to DNA microarrays for DNA detection and RNA profiling.
Understanding the effect of DNA sequences on the melting temperature of the
system is central to developing reliable detection technology. We studied the
effects of DNA base-pairing defects, such as mismatches and deletions, on the
melting temperature of DNA-nanoparticle assemblies. We found that, contrary to
the general assumption that defects lower the melting temperature of DNA, some
defects increase the melting temperature of DNA-linked nanoparticle assemblies.
The effects of mismatches and deletions were found to depend on the specific
base pair, the sequence, and the location of the defects. Our results
demonstrate that the surface-bound DNA exhibit hybridization behavior different
from that of free DNA. Such findings indicate that a detailed understanding of
DNA-nanoparticle assembly phase behavior is required for quantitative
interpretation of DNA-nanoparticle aggregation.Comment: 12 pages, 3 figure
Shaping nanoparticle fingerprints at the interface of cholesteric droplets
The ordering of nanoparticles into predetermined configurations is of
importance to the design of advanced technologies. In this work, we moderate
the surface anchoring against the bulk elasticity of liquid crystals to
dynamically shape nanoparticle assemblies at a fluid interface. By tuning the
degree of nanoparticle hydrophobicity with surfactants that alter the molecular
anchoring of liquid crystals, we pattern nanoparticles at the interface of
cholesteric liquid crystal emulsions. Adjusting the particle hydrophobicity
more finely further modifies the rigidity of assemblies. We establish that
patterns are tunable by varying both surfactant and chiral dopant
concentrations. Since particle assembly occurs at the interface with the
desired structures exposed to the surrounding phase, we demonstrate that
particles can be readily crosslinked and manipulated, forming structures that
retain their shape under external perturbations. This study establishes the
templating of nanomaterials into reconfigurable arrangements. Interfacial
assembly is tempered by elastic patterns that arise from the geometric
frustration of confined cholesterics. This work serves as a basis for creating
materials with chemical heterogeneity and with linear, periodic structures,
essential for optical and energy applications.Comment: 16 pages with 5 figures, 4 page supplementary with 5 supplementary
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