Environmental Aspects of Oxide Nanoparticles: Probing Oxide Nanoparticle Surface Processes Under Different Environmental Conditions.

Kinetics and Thermodynamics of Protein Adsorption: A Generalized Molecular Theoretical Approach

The spontaneous protein adsorption on nanomaterial surfaces and the formation of a protein corona around nanoparticles are poorly understood physical phenomena, with high biological relevance. The complexity arises mainly due to the poor knowledge of the structural orientation of the adsorbed proteins onto the nanoparticle surface and difficulties in correlating the protein nanoparticle interaction to the protein corona in real time scale. Here, we provide quantitative insights into the kinetics, number, and binding orientation of a few common blood proteins when they interact with citrate and cetyltriethylammoniumbromide stabilized spherical gold nanoparticles with variable sizes. The kinetics of the protein adsorption was studied experimentally by monitoring the change in hydrodynamic diameter and zeta potential of the nanoparticle-protein complex. To understand the competitive binding of human serum albumin and hemoglobin, time dependent fluorescence quenching was studied using dual fluorophore tags. We have performed molecular docking of three different proteins--human serum albumin, bovine serum albumin, and hemoglobin--on different nanoparticle surfaces to elucidate the possible structural orientation of the adsorbed protein. Our data show that the growth kinetics of a protein corona is exclusively dependent on both protein structure and surface chemistry of the nanoparticles. The study quantitatively suggests that a general physical law of protein adsorption is unlikely to exist as the interaction is unique and specific for a given pair.

The relationship between Superparamagnetic Iron Oxide Nanoparticles (SPIONs) surface chemistry and their toxicological outcomes is crucial for biomedical applications, including drug delivery and imaging diagnostics. SPIONs' surface properties-such as size, shape, type of coating agents, and charge-are directly linked to their interactions with the biological environment, significantly affecting their toxicity. Surface chemistry plays a significant role in determining biocompatibility, cellular uptake, and the potential for adverse reactions. This study focuses on building a classification and prediction model based on the experimentally obtained properties and linked with the calculated molecular descriptors to describe the nature of the various coatings used for SPIONs in such a combined mode. The predictive model helps identify how specific surface modifications, including coating types and functional groups, influence toxicity responses. The results that were obtained, which correlate well with the existing literature, confirm the effects of surface chemistry on toxicity. For instance, the model accurately predicts that chitosan derivative coatings with a higher positive charge exhibit toxic potential, which aligns with previous findings. Incorporating these experimentally obtained surface features into a predictive framework enables the design of safer SPION formulations, enhancing therapeutic efficacy while managing surface chemistry's effects on toxicity.

We report an investigation of the ligand exchange at the surface of iron oxide nanoparticles in water. For this purpose we compared two strong chelating agents on the iron oxide surface containing catechol and bisphosphonate moieties. Interactions between the coating agents (catechol/bisphosphonate) and the nanoparticle’s surface were studied by FTIR and DFT calculations. Ligand exchange experiments were performed using sonication and the exchange yield was characterized by FTIR and EDX. This methodology allowed introducing bisphosphonates with various functionalities (alkyne or biotin) permitting multi-functionalization.

In the present study, UV-curable urethane acrylate was synthesized by the reaction of isophorone diisocyanate with1,4-butanediol and 2-hydroxyethyl methacrylate in the presence of dibutyltin dilaurate as a catalyst and acetone as a solvent. The structure of urethane acrylate oligomer was characterized by nuclear magnetic resonance and Fourier transform infrared spectroscopy. In order to examine the influence of inorganic phase of zirconium oxide nanoparticles on characteristics of synthesized resin, organic–inorganic nanocomposites were prepared by urethane acrylate resin and nano zirconium oxide with 1, 3, and 5 wt%. In order to improve nanoparticles dispersion, the surface of zirconium oxide nanoparticles was modified by vinyltrimethoxysilane coupling agent. The analysis of nanoparticle surface modification by Fourier transform infrared spectroscopy and scanning electron microscopy suggested a good reaction of vinyltrimethoxysilane with the surface of zirconium oxide nanoparticles. The characteristics of the prepared nanocomposites were evaluated through thermogravimetric analysis and dynamic mechanical thermal analysis. All of conducted tests represented improved thermal stability properties, storage modulus, and viscoelastic properties of urethane acrylate–zirconium oxide nanocomposites in comparison with polymeric coatings without nanoparticles.

In a series of experiments, we coated iron oxide nanoparticles, which were originally stabilized with lauric acid, with a polymer layer of Octadecyltrichlorosilane (OTS). Characterization of the different coated nanoparticles was accomplished by Static and Dynamic Light Scattering, acoustic spectroscopy, and Atomic Force Microscopy. In various experiments, we systematically investigated the effect of different parameters such as the OTS concentration and iron oxide content on the particle size of the coated nanoparticles. It was recognized that the size of the coated nanoparticles mainly depend on the concentration of OTS (C OTS) measured with respect to the concentration of the iron oxide particles (C mag.). Below a well-defined threshold value of C OTS /C mag, we did not observe any adsorption of OTS on the surface of iron oxide nanoparticles. The particle size of OTS-coated iron oxide nanoparticles increased rapidly at concentration ratios above the threshold concentration and reached a typical plateau value for long periods of time.

Design of iron oxide nanoparticles decorated oleic acid and bovine serum albumin for drug delivery

In situ surface functionalization of magnetic nanoparticles with hydrophilic natural amino acids

A novel, efficient DNA delivery and transfection agent has been developed by chemically attaching short chain polyethyleneimine (PEI) molecules (M.W. = 423 and 1800) to the surface of composite iron oxide nanoparticles (250 nm in diameter). These particles are not only capable of delivering DNA but also can be driven by an external magnetic field. During DNA binding experiments, a remarkably low N : P ratio of <1 was recorded. This is due to the more effective distribution of the PEI molecules across the surface of the nanoparticles in comparison to particles where PEI is attached to the surface via simple electrostatic interactions. This new attachment strategy allows the use of smaller amounts of PEI with potential reduction in toxic side-effects.

An electrophoretic deposition (EPD) method has been developed for the deposition of nanostructured zinc oxide (ZnO) and TiO 2 films. It was shown that the stabilization and charging of the nanoparticles in suspensions can be achieved using organic molecules, such as dopamine and alizarin yellow (AY) dye, which were adsorbed on the oxide nanoparticles. Fourier‐transform infrared spectroscopy investigations showed that the adsorption mechanism is based on the complexation of metal ions at the surfaces of oxide nanoparticles. Cationic dopamine additive was used for the formation of deposits by cathodic EPD. The adsorption of anionic AY on the oxide nanoparticles resulted in charge reversal and enabled the formation of anodic deposits. The method enabled the codeposition of ZnO and TiO 2 and the formation of composite films. It was shown that the deposition yield and deposit composition can be controlled by the variation of deposition time and suspension composition. The deposits were studied using X‐ray diffraction and electron microscopy. The deposition mechanism and kinetics of deposition are discussed.

The structure rearrangement of polyelectrolyte shell on the surface of a charged spherical nanoparticle is investigated by methods of statistical theory of macromolecules and molecular dynamics. A mathematical model of conformational changes of adsorbed polyelectrolyte on the surface of a spherical nanoparticle is presented, and radial dependences of the concentration of macrochain links depending on the sign and magnitude of the nanoparticle charge are obtained. Molecular dynamic modeling of polypeptides with different degrees of polyelectrolyte on the surface of a charged spherical gold nanoparticle was performed. When the absolute value of the opposite sign charge on the spherical nanoparticle increased with respect to the charge of the macrochain, the polyelectrolyte shell at the surface of the nanoparticle was dense, while a loose layer of neutral macrochain links was formed at the periphery. On the uniformly charged surface of the spherical nanoparticle, the polyelectrolyte shell gradually swelled with increase in the absolute value of the nanoparticle charge and desorbed the earlier the higher the degree of polyelectrolyticity of the macrochain was.

Ag and Au nanoparticles (NPs) were used as color indicators to determine the monomer/micelle adsorption on the NP surface. A simple methodology based on the color change of Ag/Au NPs upon interacting with surface-active molecules was developed. A contrasting color change occurred when NPs interact with the monomer/micelle. This was demonstrated by monitoring the adsorption behavior of a series of Gemini surfactants. UV-visible measurements showed a large change in the intensity and wavelength of Ag/Au NP absorbance upon the surface adsorption of the monomer/micelle of Gemini surfactants. The mechanism of surface adsorption and molecular orientation on the solid-liquid interface of NPs was determined by performing the FT-IR and XPS measurements. Results demonstrated that sharp color changes from yellow to red for Ag NPs and red to purple for Au NPs happened when the Gemini surfactant monomer/micelle adsorbs on the NP surface. This colorimeter-based methodology highlighted the applicability of Ag/Au NPs in complex media where such NPs frequently encounter surface-active molecules.

Oxygen vacancy creation and annihilation are key processes in nonstoichiometric oxides such as CeO2. The oxygen vacancy creation and annihilation rates on an oxide's surface partly govern its ability to exchange oxygen with the ambient environment, which is critical for a number of applications including energy technologies, environmental pollutant remediation, and chemical synthesis. Experimental methods to probe and correlate local oxygen vacancy reaction rates with atomic-level structural heterogeneities would provide significant information for the rational design and control of surface functionality; however, such methods have been unavailable to date. Here, we characterize picoscale fluxional behavior in cations using time-resolved in situ aberration-corrected transmission electron microscopy to locate atomic-level variations in oxygen vacancy creation and annihilation rates on oxide nanoparticle surfaces. Low coordination number sites such as steps and edges, as well as locally strained sites, exhibited the greatest number of cation displacements, implying enhanced surface oxygen vacancy activity at these sites. The approach has potential applications to a much wider class of materials and catalysis problems involving surface and interfacial transport functionalities.

Multifunctional organic molecules represent an interesting challenge for nanoparticle functionalization due to the potential for undesirable interactions between the substrate material and the variable functionalities, making it difficult to control the final orientation of the ligand. In the present study, UV-induced thiol-ene click chemistry has been utilized as a means of directed functionalization of bifunctional ligands on an iron oxide nanoparticle surface. Allyl diphosphonic acid ligand was covalently deposited on the surface of thiol-presenting iron oxide nanoparticles via the formation of a UV-induced thioether. This method of thiol-ene click chemistry offers a set of reaction conditions capable of controlling the ligand deposition and circumventing the natural affinity exhibited by the phosphonic acid moiety for the iron oxide surface. These claims are supported via a multimodal characterization platform which includes thermogravimetric analysis, X-ray photoelectron spectroscopy, and metal contact analysis and are consistent with a properly oriented, highly active ligand on the nanoparticle surface. These experiments suggest thiol-ene click chemistry as both a practical and generally applicable strategy for the directed deposition of multifunctional ligands on metal oxide nanoparticle surfaces.

Structural phase changes of the liquid water component in Alpine snow