Shungite Nanocarbon Research Articles

Fatty acid transfer between serum albumins and shungite carbon nanoparticles and its effect on protein aggregation and association.

The bioactivity of the natural ultrafine carbon form shungite nanocarbon (ShC) is of particular interest both for biomedical applications of such nanomaterials and their negative impact on the aquatic environmental. Here we studied the interaction of serum albumin (SA) with ShC nanoparticles in aqueous dispersion with respect to its structural-dynamic, thermodynamic, and hydrodynamic effects. Electron spin resonance (EPR) with a 5-DOXYL-stearic acid spin probe (5DSA) demonstrates that ShC can affect fatty acid (FA) binding by SA, protein conformation in the stearic FA spin probe binding region, and protein aggregation due to the partial transfer of FA to the ShC nanoparticles. The ratio of SA fractions changes in the presence of ShC in favor of the fraction that is less saturated with FA as shown by differential scanning calorimetry (DSC). The stability of interaction with ShC is significantly higher for aggregates of SA molecules that carry physiological amounts of FA, compared to aggregates of the FA-free protein, as studied by dynamic light scattering (DLS) analysis. Generally, the mixed dispersion of SA and ShC nanoparticles is more homogeneous than the SA solution alone. This is manifested both in the size of the molecular associates and in the microenvironment of the protein-bound FA. The formation of the SA-ShC interface is likely to result in a greater uniformity of the FA binding sites and a decrease in protein fractions and "hot patches" on the protein surface responsible for the supramolecular heterogeneity of the protein in solution.

Rheological properties of “Vaseline – Carbon nanoparticles” model systems under conditions of non-destructive deformations”

The paper presents experimental data on the rheological properties of “Vaseline – Carbon Nanoparticles” systems, which were obtained through oscillation tests. The nanoparticles used are multi-layered oxidized graphene (Gr), single- (SWCNTs) and multi-walled (MWCNTs) carbon nanotubes, as well as shungite nanocarbon (Sh). It was demonstrated that when carbon nanoparticles were added to the Vaseline (VM) at concentrations from 0.5 to 1.5 wt.%, the elasticity of the systems increased as compared with the pure VM, wherein the system containing 1.0 wt. % of MWCNTs was characterized by the greatest elasticity. All the studied carbon nanoparticles proved to be rheomodifiers. However, Gr, SWCNTs and MWCNTs acted essentially depending on their concentration in the vaseline system, resulting in both shortening and lengthening of the relaxation time. The natural shungite nanocarbon always led to the decrease of the relaxation time within the studied concentration range. The obtained results form an experimental basis for the development of scientific approaches to the production of lubricants operating in various friction modes

THROMBOGENICITY OF SHUNGITE CARBON NANOPARTICLES IN VITRO

When nanoparticles enter a living organism, it is very likely they will appear in the bloodstream, which raises the question of the hemocompatibility of various nanomaterials. The effect of carbon nanoparticles (shungite nanocarbon and nanodiamonds) on the human and mink blood coagulation system in vitro was studied. The time of plasma clotting triggered by recalcification was used as a test parameter for assessing the state of the internal coagulation system activation pathways. The effect of shungite nanocarbon at 3 to 6 μg/ml concentrations on the activity of the human coagulation system manifest itself in a significant decrease in the recalcification time. When carbon nanoparticles were added to the mink plasma, a significant decrease in the recalcification time was observed starting at a concentration of 6 μg/ml. The presence of nanodiamonds in the 9 μg/ml concentration significantly accelerated the formation of a human plasma clot. We suppose that hypercoagulation in the presence of shungite carbon and nanodiamonds can be associated with a faster fibrin polymerization. This may be a result of fibrin interaction with shungite carbon nanoparticles and nanodiamonds, which can thus induce platelet activation and/or aggregation. The molecular mechanism behind the revealed thrombogenicity of carbon nanoparticles is discussed.

STRUCTURAL DYNAMIC EFFECTS OF PROTEIN AND OTHER BIOLOGICALLY SIGNIFICANT MOLECULES’ INTERACTION WITH SHUNGITE NANOCARBON

Understanding of physicochemical interactions of proteins and other biologically significant molecules with shungite nanocarbon (ShC), a graphene family nanomaterial, is required to provide biosafety in various fields of its application including biomedicine. Dynamic characteristics of potential bio-nano interface, characteristics of interaction with the solvent (hydration) carry important information about the types of arising bonds and interactions, the interaction of ligand transfer among them, as well as about the properties of the corresponding bio-nano hybrid forms. The dynamic state of the interface (surface) of carbon nanoclusters in ShC dispersions and protein (bovine serum albumin, BSA) and other biologically significant molecules and ions (sucrose, urea, NaCl, HCl, NaOH) that can affect hydration have been studied using electron spin resonance (ESR) of spin probe based on stearic fatty acid (FA) molecule. A transfer of spin probe (FA) from protein to nanocarbon and vice versa in a mixed dispersion of ShC and BSA has been shown to occur depending on their concentration ratio. Nanoparticle protein corona is probably involved in the transfer. The effect has been observed at ShC concentration an order of magnitude lower than that of protein. This signifies the possibility to influence FA binding and transport by serum albumin using ShC dispersion. This effect can be regulated by additional solutes, as has been observed in the case of sucrose. Nonlinearities of Arrhenius dependences of ESR spin probe spectrum parameters in mixed ShC dispersions may indicate the phase transition as in polymer solutions.

Luminescence of ZnS:Cu particles modified by shungite nanocarbon

This paper presents a study of the luminescence properties of the commercial phosphor ZnS:Cu modified with nanoparticles of shungite carbon. It shows that even a small amount of the modifying additive causes substantial surface darkening of the phosphor and reduces the reflectance at a wavelength of 490 nm. A number of competing processes are observed: a reduction of the luminance of the electroluminescence because part of the emitted light is absorbed, and an increase of the luminance, probably because the electric field is concentrated on the phosphor particles. Besides altering the luminance, such modification alters the electroluminescence spectra. Modification by shungite-carbon nanoparticles is thus promising from the viewpoint of directed adjustment of the characteristics of commercial phosphors, and optimizing the modification conditions makes it possible to obtain luminescence whose luminance exceeds that in unmodified samples.

THERMODYNAMIC EFFECTS OF SERUM ALBUMIN INTERACTION WITH SHUNGITE NANOCARBON

The bioactivity features of shungite nanocarbon (ShC) as a new ultrafine carbon form are of particular interest from the point of view of both biomedical applications of the nanomaterial and environmental issues. Thermodynamic effects of human serum albumin (SA) interaction with ShC in water nanodispersion have been studied regarding the molecular structure and protein fraction content using differential scanning calorimetry. Deconvolution of the albumin denaturation curve on the basis of Gaussian functions was used to analyze the characteristics (temperature, enthalpy) of individual endothermic transitions of the protein. The increase of the temperature difference of individual transitions was found to be the major SA-ShC interaction effect. No overall thermal destabilization of the protein was observed, although some partial destabilization did occur. This result cannot ensue from changes in intramolecular interdomain interactions in protein molecules at intermolecular interactions with ShC since only a small part of the total protein in nanodispersion has access to nanoparticle surface. The effects observed are shown to be related to the ShC influence on the ratio of the protein fractions with different fatty acids (FA) content by affecting some part of FA at their protein binding sites and their transition to nanoparticles. Protein and nanocarbon probably compete for FA in the process, and their concentration ratio in the dispersion is of decisive importance. The significance of this sort of competition consists in the possibility to influence the transport function of serum albumin with respect to FA.

Comparative studies of optical limiting in fullerene and shungite nanocarbon aqueous dispersions

Optical limiting properties of natural carbon nanoparticles (Shungite carbon) and fullerene aggregates in aqueous dispersions were for the first time studied and juxtaposed. For the picosecond laser pulses both dispersions exhibited comparable optical limiting property, apparently due to nonlinear absorption (mainly TPA). In the domain of the nanosecond laser pulses, nonlinear scattering NLS is thought to be main optical limiting mechanism in the dispersions under study. Shungite carbon dispersion showed stronger optical limiting (being similar to CBS) in visible and IR, which we ascribe to its structure more favorable to the thermal relaxation processes responsible for the NLS mechanism.

Aggregation and stabilization of shungite carbon nanoparticles

Globular clusters of natural shungite carbon appear to be aggregates formed by nonplanar graphenes through stable aqueous dispersion. The ability of the clusters for spontaneous disaggregation in water and stabilization without surfactants was demonstrated. Due to their size and curvature, shungite graphenes contribute most substantially to stabilization of the carbon clusters in water and predetermine amphiphilicity of shungites. The condensation of aqueous shungite nanocarbon dispersion is accompanied by formation of a three-dimensional network with characteristic micro- and submesopores of <0.7–5.0 nm. The pore structure is distinguished by a changeable sorption capacity due to mobility of the graphene fragments forming the pore walls.

Effect of the conditions of structure formation on the physicochemical properties of ozonated shungites

It was investigated the influence of ozone on the physicochemical properties of shungites (type 1) (75–98% C) from Nigozero and Chebolaksha deposits (Karelia) formed by hydrothermal (Nigozero) and high-temperature (Chebolaksha) processes. Ozonation was found to affect the specific surface and the total pore volume of shungites considerably. The pore size distribution pattern depends on the volume morphology (texture) of the sample. An increase in the temperature and pressure during the structure formation of shungite (Chebolaksha) led to a shift of the maximum on the distribution pattern towards the formation of mesopores. The size distribution of pores with the dominant contents of micro- and submesopores for both shungites correlated with the basic structural nanoelements of shungite carbon. The peculiarities of the ozonation of shungite nanocarbon found previously (the non-steady state vibrational kinetics of ozonation and the absence of carbon(II) oxide among the reaction products) were confirmed.

Effect of ozone on the structure and physicochemical properties of ultradisperse diamond and shungite nanocarbon elements

A comparative study of the effect of ozonization on the physicochemical properties of naturally and synthetically generated nanocarbon materials, shungite carbon (ShC) and ultra-disperse diamond (UDD) after special treatment in the form of monodisperse single nano-diamond particulates (mdsn-D), that have a similar two-level structural pattern (hierarchical system structure) and curved graphene shells or their fragments contribute to the formation of the structure and surface properties of both ShC and mdsn-D particles, was conducted. The ozonization kinetics of ShC and mdsn-D showed their high catalytic activity during ozone decomposition. Upon ozonization, the graphene shell is removed selectively from the surface of the diamond core of mdsn-D, as shown by Fourier transform-infrared (FT-IR) spectroscopy and derivatography data. A distinctive characteristic of ShC is a substantial change in structural parameters upon ozonization: structural porosity increases and the size of coherent scatter domains decreases in the direction perpendicular to graphene layers [as shown by small-angle X-ray scattering (SAXS), transmission electron microscopy (TEM), and selected area electron diffraction (SAED) data], which agrees with adsorption experiments that showed an increase in ultramicroporosity and mesoporosity upon ozonization of ShC. The molecular probe technique was used to monitor changes in microporosity of ShC and mdsn-D.