Ligand concentration determines antiviral efficacy of silica multivalent nanoparticles.

We have learned from the recent COVID-19 pandemic that the emergence of a new virus can quickly become a global health burden and kill millions of lives. Antiviral drugs are essential in our fight against viral diseases, but most of them are virus-specific and are prone to viral mutations. We have developed broad-spectrum antivirals based on multivalent nanoparticles grafted with ligands that mimic the target of viral attachment ligands (VALs).

Monovalent ion-mediated charge-charge interactions drive aggregation of surface-functionalized gold nanoparticles.

Monolayer-protected metal nanoparticles (NPs) are not only promising materials with a wide range of potential industrial and biological applications, but they are also a powerful tool to investigate the behaviour of matter at nanoscopic scales, including the stability of dispersions and colloidal systems. This stability is dependent on a delicate balance between attractive and repulsive interactions that occur in the solution, and it is described in quantitative terms by the classic Derjaguin-Landau-Vewey-Overbeek (DLVO) theory, that posits that aggregation between NPs is driven by van der Waals interactions and opposed by electrostatic interactions. To investigate the limits of this theory at the nanoscale, where the continuum assumptions required by the DLVO theory break down, here we investigate NP dimerization by computing the Potential of Mean Force (PMF) of this process using fully atomistic MD simulations.

Chemical sensing with Au and Ag nanoparticles.

Noble metal nanoparticles (NPs) are ideal scaffolds for the fabrication of sensing devices because of their high surface-to-volume ratio combined with their unique optical and electrical properties which are extremely sensitive to changes in the environment. Such characteristics guarantee high sensitivity in sensing processes. Metal NPs can be decorated with ad hoc molecular building blocks which can act as receptors of specific analytes.

Multi-sulfonated ligands on gold nanoparticles as virucidal antiviral for Dengue virus.

Dengue virus (DENV) causes 390 million infections per year. Infections can be asymptomatic or range from mild fever to severe haemorrhagic fever and shock syndrome. Currently, no effective antivirals or safe universal vaccine is available.

Reproducibility warning: The curious case of polyethylene glycol 6000 and spheroid cell culture.

Reproducibility of results is essential for a well-designed and conducted experiment. Several reasons may originate failure in reproducing data, such as selective reporting, low statistical power, or poor analysis. In this study, we used PEG6000 samples from different distributors and tested their capability inducing spheroid formation upon surface coating.

Stable Ultraconcentrated and Ultradilute Colloids of CsPbX (X = Cl, Br) Nanocrystals Using Natural Lecithin as a Capping Ligand.

Attaining thermodynamic stability of colloids in a broad range of concentrations has long been a major thrust in the field of colloidal ligand-capped semiconductor nanocrystals (NCs). This challenge is particularly pressing for the novel NCs of cesium lead halide perovskites (CsPbX; X = Cl, Br) owing to their highly dynamic and labile surfaces. Herein, we demonstrate that soy lecithin, a mass-produced natural phospholipid, serves as a tightly binding surface-capping ligand suited for a high-reaction yield synthesis of CsPbX NCs (6-10 nm) and allowing for long-term retention of the colloidal and structural integrity of CsPbX NCs in a broad range of concentrations-from a few ng/mL to >400 mg/mL (inorganic core mass).

Bimodal atomic force microscopy for the characterization of thiolated self-assembled monolayers.

Surface coatings are becoming an integral part of materials. In recent years, molecular coatings have found larger acceptance and uses. Among them, self-assembled monolayers (SAMs) are attractive due to their inherent versatility, manufacturability, and scale up ease.

Quantitative 3D determination of self-assembled structures on nanoparticles using small angle neutron scattering.

The ligand shell (LS) determines a number of nanoparticles' properties. Nanoparticles' cores can be accurately characterized; yet the structure of the LS, when composed of mixture of molecules, can be described only qualitatively (e.g.

Novel Sensing Strategies Based on Monolayer Protected Gold Nanoparticles for the Detection of Metal Ions and Small Molecules.

Monolayer protected gold nanoparticles (AuNPs) have a huge potential for the development of innovative sensing systems for the detection of metal ions and small molecules. The organic ligand shell, primarily utilized to stabilize the gold core, can be rationally designed to promote selective interactions with a desired analyte. In addition, the outstanding physical and optical properties of AuNPs can be exploited to obtain analytically useful signals upon analyte binding.

Evolution of the Ligand Shell Morphology during Ligand Exchange Reactions on Gold Nanoparticles.

Ligand exchange reactions are used to achieve nanoparticles coated with a mixture of ligand molecules. Currently, nothing is known on the evolution of the morphology of the ligand shell during the reaction. Here, we use a recently developed method (based on MALDI-TOF) to follow the evolution of the ligand shell composition and morphology during the reaction.

Response to "Critical Assessment of the Evidence for Striped Nanoparticles".

Stirling et al., (10.1371/journal.

Comparative STM studies of mixed ligand monolayers on gold nanoparticles in air and in 1-phenyloctane.

Scanning tunnelling microscopy (STM) studies have found stripe-like domains on gold nanoparticles (NPs) coated with certain binary mixtures of ligand molecules. The majority of these NPs' properties have been investigated for particles in solvents. Yet, most STM studies are for NPs in a dry state.

Quantitative analysis of scanning tunneling microscopy images of mixed-ligand-functionalized nanoparticles.

Ligand-protected gold nanoparticles exhibit large local curvatures, features rapidly varying over small scales, and chemical heterogeneity. Their imaging by scanning tunneling microscopy (STM) can, in principle, provide direct information on the architecture of their ligand shell, yet STM images require laborious analysis and are challenging to interpret. Here, we report a straightforward, robust, and rigorous method for the quantitative analysis of the multiscale features contained in STM images of samples consisting of functionalized Au nanoparticles deposited onto Au/mica.

High-resolution scanning tunneling microscopy characterization of mixed monolayer protected gold nanoparticles.

Gold nanoparticles protected by a binary mixture of thiolate molecules have a ligand shell that can spontaneously separate into nanoscale domains. Complex morphologies arise in such ligand shells, including striped, patchy, and Janus domains. Characterization of these morphologies remains a challenge.

The Role of Frozen Spins in the Exchange Anisotropy of Core-Shell Fe@Fe(3)O(4) Nanoparticles.

Core-shell Fe@Fe(3)O(4) nanoparticles exhibit substantial exchange bias at low temperatures, mediated by unidirectionally aligned moments at the core-shell interface. These spins are frozen into magnetic alignment with field cooling, and are depinned in a temperature-dependent manner. The population of such frozen spins has a direct impact on both coercivity (H(C)) and the exchange-bias field (H(E)), which are modulated by external physical parameters such as the strength of the applied cooling field and the cycling history of magnetic field sweeps (training effect).

Plasmon-resonant nanoparticles and nanostars with magnetic cores: synthesis and magnetomotive imaging.

Plasmon-resonant gold nanostars (NSTs) with magnetic cores were synthesized by a multistep sequence from superparamagnetic Fe3O4 nanoparticles (NPs) and evaluated as optical contrast agents under magnetomotive (MM) imaging conditions. Core-shell Fe3O4@Au NPs were prepared in nonpolar organic solvents with nanometer control over shell thickness and with good epitaxy to the Fe3O4 surface. Anisotropic growth was performed in micellar solutions of cetyltrimethylammonium bromide (CTAB) under mildly reducing conditions, resulting in NSTs with physical features similar to those produced from colloidal gold seeds.

Gyromagnetic imaging: dynamic optical contrast using gold nanostars with magnetic cores.

Plasmon-resonant nanoparticles with optical scattering in the near-infrared (NIR) are valuable contrast agents for biophotonic imaging and may be detected at the single-particle limit against a dark background, but their contrast is often limited in environments with high noise. Here we consider gyromagnetic imaging as a dynamic mode of optical contrast, using gold nanostars with superparamagnetic cores. The nanostars exhibit polarization-sensitive NIR scattering and can produce a frequency-modulated signal in response to a rotating magnetic field gradient.

Attachment of nanoparticles to the AFM tips for direct measurements of interaction between a single nanoparticle and surfaces.

Here we report a universal method of attachment/functionalization of tips for atomic force microscope (AFM) with nanoparticles. The particles of interest are glued to the AFM tip with epoxy. While the gluing of micron size particles with epoxy has been known, attachment of nanoparticles was a problem.

AFM study of forces between silica, silicon nitride and polyurethane pads.

Interaction of silica and silicon nitride with polyurethane surfaces is rather poorly studied despite being of great interest for modern semiconductor industry, e.g., for chemical-mechanical planarization (CMP) processes.