Spin Probe Method Research Articles

Phase State of Polar Liquids in the Interplane Space of Graphite Oxide as Revealed by the Spin Probe Method

Phase State of Polar Liquids in the Interplane Space of Graphite Oxide as Revealed by the Spin Probe Method

Study of the effect of ethanol on the properties of poloxamer 338 solutions by rotational viscometry and spin probe method

The aim. Study the properties of 20 % solutions of poloxamer 338 (P338) in water and mixed solvents water-ethanol using rotational viscometry and the spin probe method at various temperatures. Materials and methods. 20 % m/m solutions of P338 in water and water – ethanol mixtures were the objects of research. The solutions were studied by rotational viscometry at various temperatures; the flow behaviour, lower yield stress (t0) and dynamic or apparent viscosity (η) were determined. Spin probes based on fatty acids, which differ in molecular structure, solubility, and radical localization, were added to the solutions. Electron paramagnetic resonance (EPR) spectra were obtained to determine their type and parameters. Results. Depending on the content, ethanol affects the rheological properties of 20 % solution of P338. The solution was demonstrated to be able to thermally induce sol → gel transition at 32 °C when ethanol content is 5 % m/m. The rheological parameters of the gel at 32 °C and 37 °C exhibit an increase (in comparison to the gel without ethanol), accompanied by a reduction in the packing density of polypropylene oxide (PPO) chains within the cores of P338 micelles. At an ethanol content of 10 % m/m, the gel formation temperature rises to 40 °C. At ethanol content of 15 % m/m and above, 20 % P338 solutions do not form gels at temperatures between 25 °C and 40 °C. The values of rotational correlation times (τ) and the order parameter (S) of fatty acid-based spin probes were observed to decrease with increasing ethanol content up to 30 % m/m; in the case of the ammonium salt of 5‑doxylstearic acid (5-DSA NH4 salt), the anisotropic EPR spectra transform, becoming a superposition of two triplets and subsequently a triplet. P338 solutions retain their ability to undergo thermally induced sol ↔ gel transitions as long as the EPR spectra of this probe exhibit anisotropy at temperatures ranging from 25 °C to 37 °C. As the concentration of ethanol in the solution increases, the solvation of the cores of P338 micelles by the dispersion medium of the solution also increases. Conclusions. It was demonstrated that ethanol, when added to the 20 % P338 solution, results in changes to the rheological properties of this solution. However, at the ethanol content of 5-10 % m/m, the ability of P338 to thermally induce sol → gel transition remains unaltered. The rheological properties of the 20 % P338 solution exhibit a correlation with the observed change in EPR spectra types for the 5-DSA NH4 salt. As the ethanol content in the solution increases, the solvation of P338 micelle cores by the dispersion medium increases, accompanied by decreased density and orderliness of the PPO chains packing in the micelle cores

Study of aqueous solutions of poloxamers by rotational viscometry and spin probe method

The aim. To study aqueous solutions of different poloxamers by spin probe method and rotational viscometry depending on the temperature and poloxamer content.
 Materials and methods. The aqueous solutions of poloxamers 188, 237, 338 and 407 were studied. The solutions were studied by rotational viscometry at different temperatures; the flow behaviour, yield stress (t0), and dynamic or apparent viscosity (η) were determined. Five spin probes differing in molecular structure, solubility, and radical localisation were introduced into the solutions. Electron paramagnetic resonance (EPR) spectra were obtained. The EPR spectra were used to determine their type and to calculate parameters.
 Results. Three factors are important for gel formation: the poloxamer type, its concentration in aqueous solution, and temperature. As the temperature of aqueous solutions of poloxamers 237, 338, and 407 increases, the rotational correlation times of fatty acid-based spin probes and the order parameters of their EPR spectra decrease. This indicates a decrease in the packing density and orderliness of the polypropylene oxide (PPO) chains in the non-polar part of the poloxamer associates, leading to an increase in the volume fraction of micelles/mesophases and promoting the formation of gels. As the temperature decreases, the opposite processes occur, leading to a gel → sol transition. At 37 °C, non-polar micelle cores could be characterised as two-dimensionally liquid and one-dimensionally solid. The rotational correlation times of the hydrophilic spin probe 4-OXO-TEMPO in 25 % aqueous solutions of poloxamers 338 and 407 are approximately constant or increasing despite an increase in the temperature. This indicates that in the polar part of the poloxamer associates, where this probe is partially localised, structural rearrangements occur with increasing temperature, which probably prevents hydrophobic hydration of the PPO chains.
 Conclusions. The rheological properties of aqueous solutions of poloxamers depend on their type, concentration, and temperature. According to the parameters of the EPR spectra of fatty acid-based spin probes, it was found that with increasing temperature, the packing density and the orderliness of the PPO chains in the non-polar part of the poloxamer associates decrease, probably leading to an increase in the volume of the micelles and causing a sol → gel transition

The possibility of diagnosing the prescription of death in the study of embalmed corpses by the method of spin probes. (Experimental study)

Is to establish the possibility of studying the vitreous body of the eye from embalmed corpses using the spin probe method to develop diagnostic criteria for the prescription of death coming. The article presents data showing the possibility of diagnosing the prescription of death coming by the method of spin probes with the examination of the vitreous body of the eye from embalmed corpses. A total of 510 spectra obtained during incubation of the 1-oxyl-4-oxo-2.2.6.6-tetramethyl-piperidin spin probe in the vitreous body were studied. Measurements of each of the 6 objects were carried out daily for 10 days after embalming. The prospects of studying the vitreous body by spin probes in embalmed corpses for the development of diagnostic criteria for the prescription of death coming up to 4 days from the moment of embalming have been established.

Study of factors affecting the in vitro release of ketoprofen from carbomers-based gels

The aim. To identify some factors affecting the in vitro release of ketoprofen from carbomer-based gels.
 Materials and methods. Carbomer-based gels containing ketoprofen as well as a Newtonian liquid without carbomer, which was the dispersion medium of the gel, were studied by rotational viscometry and spin probe method. The flow behaviour and rheological parameters were determined using the rheograms, and the rotational correlation times of the two dissolved spin probes, the molecules of which contain a carboxyl group or an amino group, were determined by EPR spectra. In vitro release tests were performed using vertical diffusion chambers using a validated method. The quantitative determination of ketoprofen in gels, liquid and receptor medium was performed by liquid chromatography, and ethanol was quantified by gas chromatography according to validated procedures. Gels with different brands of carbomers, neutralised with trolamine or trometamol, with different contents of ketoprofen and ethanol, and with pH from 6.0 to 7.0 were studied.
 Results. The sol → gel transition due to the neutralisation of the carbomer did not affect the shape and parameters of the EPR spectrum of the spin probe containing a carboxyl group in the molecule (like a carbomer and ketoprofen) in contrast to the probe with an amino group. If the substance dissolved in the gels does not interact with the carbomer, then its molecules/ions rotate rapidly in the liquid medium. This facilitates the release of a such substance from carbomer-based gels. The medicinal product Nobi Gel® gel 2.5 % and Newtonian liquid were equivalent in relation to the in vitro release parameters of ketoprofen from these objects. Сarbomer-based gels, which differed significantly in terms of rheological parameters, were also found to be equivalent in terms of ketoprofen release parameters. The in vitro release of ketoprofen was affected by its concentration and ethanol content in the gel. A change in pH from 6.0 to 7.0 practically did not affect the parameters of in vitro release of ketoprofen from gels.
 Conclusions. The formation of a carbomer-based gel did not affect the rotational correlation time of the probe, which did not interact with the carbomer. Parameters of in vitro release of ketoprofen from the gel and Newtonian liquid differed little; these parameters were also little affected by the difference in apparent viscosity of the gels. The in vitro release of ketoprofen depended on its concentration and ethanol content

Effect of the composition of emulsifiers and the dispersion medium on the properties of bases for semi-solid preparations

The aim. To study the effect of cetostearyl alcohol (CSA) on the rheological properties of bases with different dispersion media, the release of propylene glycol (PG) from them, and the ability of these bases to absorb water.
 Materials and methods. Micelles of a non-ionic surfactant and its aggregates with CSA in a mixed solvent where the structure of water prevails, mixed solvent PG – macrogol 400 (M400) and hydrophilic bases-vehicles with different dispersion media were studied. The research was carried out by the spin probe method using a probe simulating a cationic surfactant and by rotational viscometry. The microstructure of the bases was studied by optical microscopy. The in vitro release test to study the release of PG and M400 from solutions and bases was performed using vertical diffusion chambers. The content of PG and M400 in the dialysate was determined by gas chromatography according to the validated analytical procedures. The absorption of water by solutions and bases was determined by dialysis through the membrane.
 Results. CSA, which was the part of the bases together with surfactants in certain ratios, was a significant factor in increasing their rheological parameters, reducing the parameters of PG release during in vitro release tests, as well as reducing water absorption. The mechanisms of such influence are different for bases with different structures of the dispersion medium. In the bases, where the structure of water prevailed, lateral phase separation occurred in the supramolecular structures of surfactant and CSA with the formation of liquid domains of surfactant and solid domains of CSA, which contributed to the formation of coagulation structures. In the mixed non-aqueous solvent PG – M400, surfactant micelles and mixed aggregates of surfactant and CSA molecules were not formed; at 25 oC, surfactants and CSA became separate dispersed phases of suspensions, which contributed to the formation of gels. When CSA was added into an aqueous solution of poloxamer 338, PG, M400 and cationic surfactant, the flow behaviour changed, and the rheological parameters increased, which led to a decrease in the release rate and extended for PG and M400 as well as in the ability to absorb water. The rate and extent of PG release from the solution were greater compared to the M400 release.
 Conclusions. The addition of CSA in combination with surfactants into the bases for semi-solid preparations is a significant factor for modifying their rheological parameters, the kinetics of PG release from them, and water absorption during experiments in vitro. The mechanisms of such an effect are different and depend on the composition and structure of the dispersion medium of the base

Redox imaging of dextran sodium sulfate-induced colitis mice treated with nitric oxide synthase inhibitors

Ulcerative colitis (UC) is an inflammatory bowel disease of unknown cause. Redox imbalance, as characterized by excessive production of reactive oxygen species (ROS) and nitric oxide (NO), and deficient levels of endogenous antioxidants, is associated with the pathogenesis of UC. Overhauser-enhanced magnetic resonance imaging (OMRI) combined with a spin-probe method produces high-resolution images of redox imbalance in disease states. We aimed to investigate the effect of NO synthase (NOS) inhibitors on colonic ROS generation in mice with colitis induced by dextran sodium sulfate (DSS) using the OMRI/spin-probe method. Symptoms of DSS-induced colitis were ameliorated by an inducible NOS (iNOS) inhibitor, aminoguanidine (AG), but not by a non-selective NOS inhibitor, NG-Nitro-L-arginine methyl ester (L-NAME). Intracellular ROS generation, observed as the enhancement of OMRI contrast decay rates of a 3-methoxy-2,2,5,5-tetramethylpyrrolidine-1-oxyl probe in the colons of DSS-induced colitis mice, was suppressed by AG, in agreement with the results of an in vivo electron spin resonance study. AG had an inhibitory effect on ROS production at the upper colon and rectum during the initiation stage of colitis, and at the upper and lower colon during the advanced stage. Additionally, there were partial differences in the localization of iNOS protein and nitrite/nitrate levels. L-NAME treatment showed a tendency for increased ROS generation at the upper colon during the advanced stage. The OMRI/spin-probe method provides a novel tool for screening ROS inhibitory activity in vivo in DSS-induced colitis mice.

Synthesis of Vanadia-Mayenite Nanocomposites and Characterization of Their Structure, Morphology and Surface Sites

Calcium aluminates (CA) with a mayenite structure have attracted a growing interest during the last decades. The present paper reports the preparation of vanadia-mayenite composites performed via an impregnation of pure CA with ammonium vanadate solution. The properties of the prepared materials were explored by a low-temperature nitrogen adsorption/desorption technique, X-ray diffraction analysis, transmission electron microscopy, and spin probe method. As revealed, the addition of vanadium significantly affects the textural properties and the porous structure of mayenite. The blockage of micropores by vanadium species is supposed. The spin probe electron paramagnetic resonance technique based on the adsorption of 1,3,5-trinitrobenzene, phenothiazine, and diphenylamine has been applied to study the active sites on the surface of the composite samples. The results demonstrated an increase in the concentration of weak electron-acceptor sites when the vanadium loading was 10 wt%. X-ray diffraction analysis and transmission electron microscopy studies showed that the composites consist of few phases including mayenite, CaO, and calcium vanadates.

Study of the formation of micelles and their structure by the spin probe method

The aim. To study the surfactant solutions depending on the type and concentration of surfactants as well as their interaction with some excipients by spin probe method.
 Materials and methods. Solutions of ionic and nonionic surfactants containing 4 spin probes differing in molecular structure and solubility were studied. Electronic paramagnetic resonance (EPR) spectra were obtained and their type and parameters were determined. The critical micelle concentration (CMC) was determined from the surface tension isotherm, and the rheological parameters were studied by rotational viscometry.
 Results. The shape of the EPR spectra and the spectral parameters of the spin probes depended on both the surfactant concentration and the molecular structure and solubility of these spin probes. There was a concentration range in which associations with surfactants formed at surfactant concentrations below the CMC. At surfactant concentrations above the CMC and up to 1 %, the structure of the surfactant micelles did not change. In the micelles, the surfactant modelling probes rotated rapidly about the long axis of the molecule and perpendicular to it, while they were fixed in the radial direction. The rotational diffusion of probes dissolved in water was much faster. The micelle cores formed by nonionic surfactant and P338 were more viscous compared to ionic surfactants. Surfactant micelles were anisotropic in viscosity, and different segments of the alkyl chains of surfactant modelling probes had different dynamic properties. The packing of molecules in the micelles was more ordered and compacted at the level of the fifth carbon atom. The interactions between surfactant and probe and between cationic surfactant and disodium edetate were determined from the parameters of the EPR spectra. The relationship between the changes in the parameters of the EPR spectra with increasing temperature, the P338 content in the solutions, and the sol-gel transition was revealed. Solubilization of lipophilic substances by P338 solutions increased due to the interaction of propylene glycol and P338.
 Conclusions. The shape and parameters of the EPR spectra in real solutions and micellar solutions of surfactants were different and also depended on the structure and solubility of spin probes. Surfactant micelles were anisotropic in viscosity, and different segments of the alkyl chains of surfactant modelling probes had different dynamic properties. The packing of molecules in the micelles was more ordered and compacted at the level of the fifth carbon atom. The EPR spectra and/or their parameters changed due to the interaction between surfactant and probe, surfactant and other substances, or sol-gel transitions in P338 solutions

Mayenite Synthesis from Hydroxide Precursors: Structure Formation and Active Sites on Its Surface.

We studied the formation process of a mayenite structure from hydroxide precursors in different gas media. According to X-ray diffraction data, this method allows a well-crystallized mayenite (Ca12Al14O33 or C12A7) phase to be obtained at low (500–900 °C) temperatures with an insignificant impurity of CaO. It was shown that the lattice parameters for C12A7 obtained in an inert atmosphere (Ar) were lower when compared with similar samples in the air. These results can be explained by the different levels of oxygen nonstoichiometry in the resulting phase. We noted that sintering and crystallization of mayenite proceeds at lower temperatures in Ar than in the air medium. We found the presence of donor and acceptor active sites on the surface of mayenite, which was detected by the spin probe method. The specific (per unit surface) concentration of such sites (2.5 × 1016 m−2 and 1.5 × 1015 m−2 for donor and acceptor sites, respectively) is comparable to that of γ-Al2O3, which is traditionally used as catalyst support. This allows it to be used in adsorption and catalytic technologies, taking into account its high specific surface area (~30–50 m2/g at a low synthesis temperature).

Resolution and characterization of confinement- and temperature-dependent dynamics in solvent phases that surround proteins in frozen aqueous solution by using spin-probe EPR spectroscopy.

Spin probe electron paramagnetic resonance spectroscopy is applied to characterize the dynamics of concentric hydration and mesophase solvent domains that surround proteins within the ice boundary in frozen aqueous solutions. The solvent dynamics are tuned by variation of temperature (190-265K) and by the degree of ice boundary confinement, which is modulated by the volume of added cryosolvent (0-~50Å separation distance from protein surface). Goals are to: (1) characterize the protein-coupled solvent dynamics on correlation time scales of ~10-10<τ<10-7s, and spatial scales from protein surface to periphery of the surrounding solution, from the perspective of a free, small-molecule (~7Å diameter) probe, and (2) reveal properties of the solvent-protein coupling that can be correlated with protein functions, that are measureable under the same conditions. Rotational mobility of the nitroxide spin probe, TEMPOL, resolves and tracks two solvent components, the protein-associated domain (PAD; akin to hydration layer) and surrounding mesodomain, through their distinct temperature- and confinement-dependent values of τ and normalized weight. Detailed protocols are described for simulation of two-component nitroxide EPR spectra, which are categorized by line shape regime and guided by a library of template spectra and simulation parameters derived from two model soluble globular proteins. The order-disorder transition in the PAD, which is a universal feature of protein-coupled solvent dynamics, provides a well-defined, tunable property for elucidating mechanism in solvent-protein-function dynamical coupling. The low-temperature mesodomain system and EPR spin probe method are generally applicable to reveal solvent contributions to a broad range of macromolecule-mediated biological processes.

Structure and Properties of Biopolymeric Fibrous Materials Based on Polyhydroxybutyrate-Metalloporphyrin Complexes.

Ultrathin fibrous materials based on natural bacterial polymer polyhydroxybutyrate (PHB) were prepared by the electrospinning method. Using scanning electron and optical microscopy techniques the macrophysical characteristics of the fibrous layer were determined and classified. The physicomechanical characteristics of the resultant materials and their changes caused by ozonation were determined as well. Structure formation in the ultrathin polyhydroxybutyrate fibers containing low antibacterial concentrations was studied. The effect of low concentrations of zinc tetraphenylporphyrin and iron(III) chloroteteraphenylporphyrin complexes on the structure of polyhydroxybutyrate-based ultrathin fibers was elucidated. Techniques used in the study were X-ray diffraction analysis, ESR spin probe method, differential scanning calorimetry, and optical and electron scanning microscopy. It was shown that addition of the metal porphyrin complexes caused changes in the degree of crystallinity and in the crystallite size of the PHB fibers, while the proportion of dense domains in the amorphous phase of the polymer fiber increased.

Sorption of Water Vapor by Gelatin-Based Polymers: Estimation of Rate and Degree of Sorption Using the Spin-Probe Method

The spin-probe method is applied to estimate the rate and degree of sorption of water vapor by gelatin-based polymers. The rate and the sorption degree of gelatins are shown to be affected by the extent that they are crosslinked. Cross-linked gelatin swells in water vapor at 300 K for a time period that is thrice as long as the time for which native gelatin swells in the same conditions.

Study of cytotoxicity performance of carbon nanohorns by method of spin probes

The effects of as-produced and treated by HNO3(3M) carbon nanohorns on the microviscosity of rat erythrocyte membranes and the viscosity of the water-containing plasma protein matrix were investigated by the method of spin probes. Addition of nanohorns at the concentration of 100 μg/ml to a suspension of erythrocytes led to an increase in membrane microviscosity during 4 h (about 60% effect). In addition, it was shown that nanohorns also induced an increased polarity of the microenvironment for lipophilic probes in the outer layer of membrane phospholipids, as well as disorders in erythrocytes membranes. Addition of nanohorns to plasma led to a little decrease in the viscosity of water and protein matrix, apparently, due to its partial destruction, impacting especially albumin. Pristine and treated by HNO3(3M) acid nanohorns was found more cytotoxic than nanoparticles of oxidized graphene, and significantly less than carbon nanotubes, which are known to dramatically increase the microviscosity of the membranes of erythrocytes and disrupt their integrity.

Mobility of liquids intercalated into the interplane space of graphite oxide as revealed by a combination of 19F NMR, 1H NMR and EPR spin probe methods.

A combination of 19F and 1H NMR with the Carr-Purcell-Meiboom-Gill (CPMG) pulse sequence was used to examine the mobility of liquids in the interplane space of graphite oxide (GO) for the first time. The proposed approach allows for the reduction of NMR signals from immobile hydrogen-containing groups on the surface of GO and for monitoring of the molecular mobility of intercalated liquids. The mobile fractions of H2O, CH3CN and CF3CH2OH were detected inside the corresponding swollen GO samples. For H2O, the amount of mobile liquid showed a peculiar temperature dependence where a certain portion survived well below 273 K. The sensitivity of the proposed 1H NMR + CPMG procedure is also compared to the sensitivity of the EPR nitroxide spin probe method.

In Russian

The microviscosity of erythrocyte membranes is directly related to their integrity, the violation of which in the presence of foreign objects manifests itself in a sharp increase in the microviscosity index, which certainly indicates the degree of cytotoxic effect of objects in contact with cells of a living organism. Using the spin probe method, a comparative study was made of the effect of a number of carbon nanoparticles on the microviscosity of rat erythrocyte membranes. It has been found that the presence of oxidized graphene (OG) in suspension of red blood cells practically does not affect the microviscosity index of membranes. In the presence of carbon nanotubes (CNTs) of various structures during prolonged (24 h) incubation with erythrocytes, an increase in the microviscosity of erythrocyte membranes is 1.5–2 times. Oxidized multi-walled nanotubes exert the greatest effect. Hydrophobic multi-walled CNTs have a smaller effect, and single-walled nanotubes are characterized by a slight effect on the membranes. Incubation of erythrocytes with carbon nanochorns (CNCh) leads to a significant increase in the microviscosity of erythrocyte membranes by 60 % and higher; after 1 h of incubation, the polarity of the surface of the lipid layer of the membranes increases stepwise, apparently due to the destruction of the membrane and the ingress of water molecules there, as well as the disorder of phospholipids. The introduction of detonation nanodiamond (DND) nanoparticles into a suspension of erythrocytes at a concentration of 25 μg/ml produced no noticeable change in the membrane microviscosity index. An increase in the concentration of DND in suspension of red blood cells to 50 and 75 μg/ml led to a decrease in the microviscosity of erythrocyte membranes (increase in fluidity of the membranes) by 20 and 28 %, respectively. Thus, among carbon nanoparticles, nanotubes and nanochorns can exhibit cytotoxicity, which is mainly due to their structure, size, and shape.

ИЗУЧЕНИЕ МЕХАНИЗМОВ РАСШИРЕНИЯ СПЕКТРА ЦИТОТОКСИЧНОСТИ ПЕГИЛИРОВАННЫХ ЛИПОСОМАЛЬНЫХ СИСТЕМ ДОСТАВКИ ПРОТИВООПУХОЛЕВЫХ ПРЕПАРАТОВ МЕТОДОМ СПИНОВЫХ ЗОНДОВ

&#x0D; &#x0D; &#x0D; &#x0D; Pegylated liposomal anticancer drugs, in particular, doxorubicin have an expansion of the spectrum of toxicity. To study the mechanisms of influence of polyethylene glycol (PEG) on the structure of cell membranes, the sensitive biophysical method of spin probes was used. Using the spin probe method, it has been shown that in the presence of an increased prothrombin blood index, increased blood viscosity and a high density of red blood cells and other blood components, large and long fragments of PEG molecules located on the surface of pegylated liposomal delivery systems can effectively interact with the membranes of neighboring cells. The list of even these possible effects, which were determined and described by us in experiments for bovine serum albumin, liposomes, erythrocytes and skin tissue, suggests that the expansion of the spectrum of the specific toxicity of pegylated liposomes may be directly or indirectly associated with the mechanisms of action of PEG on proteins and cell membranes.&#x0D; &#x0D; &#x0D; &#x0D;

In Russian

The method of spin probes investigated the effect of various concentrations of detonation nanodiamonds (DND) 25, 50 and 75 µg/ml on the microviscosity of rat erythrocyte membranes. For this, a lipophilic spin probe based on palmetic acid was introduced into the erythrocyte membrane. The introduction of DND into a suspension of erythrocytes at a concentration of 25 μg/ml did not lead to any changes in the microviscosity of erythrocyte membranes within the experimental error. At the same time, an increase in the concentration of DND in suspension of erythrocytes to 50 and 75 µg/ml resulted in to a marked decrease in the microviscosity of erythrocyte membranes (increase in membrane fluidity) by 20 and 28 %, respectively. A noticeable decrease in the intensity of the EPR spectrum after 4 h of incubation of erythrocytes with DNA (50 µg/ml) indicates the antioxidant activity of nanodiamond — the ability to be an electron donor and restore the nitroxyl stable radical (spin probe) to hydroxylamine. Physiologically, an increase in erythrocyte membrane turnover is of great importance for the organism, since allows red blood cells to better penetrate thin or narrowed capillaries and more efficiently nourish the tissues and organs of the body with oxygen. In addition, an increase in cell membrane fluidity increases the activity of membrane enzymes, which should lead to activation of metabolic and regulatory processes in cells and in the body as a whole. Perhaps this may explain the successful use of DND in oncology, treatment of the gastrointestinal tract, etc. At the same time, an excessive increase in the fluidity of cell membranes at high concentrations of DND can lead to irreversible changes in the native structure of cell membranes.

Evaluation of Dry Eye Symptomatology at Patients with Keratoconus

The aim of this study was firstly to determine and quantify the dry eye symptomatology of patients with keratoconus, in comparison with those without this condition and secondly to evaluate the suitability of the spin probe method of electron paramagnetic resonance spectroscopy in analysis of tears secretion. As such were considered two groups of patients for evaluation: 36 cases with keratoconus (keratoconus group) and 36 cases without ocular disease (control group). Besides general ophthalmological examination we have conducted Schirmer test I, tears break-up time (BUT) and quantify the answers about dry eye symptomatology to establish ocular surface disease index (OSDI). We have included a prospective correlation of ophthalmologic parameters with parameters of the spin probes added in tear secretions collected from both groups of patients. The results show that the value of OSDI for patients with keratoconus was higher (41.07 � 23.68) than the corresponding value of the control group (14.63 � 9.27). Also, the patients with keratoconus present lower mean values for BUT and Schirmer tests comparatively with the cases from control group. The electron paramagnetic resonances spectra of the spin probe CAT16 in tear secretions obtained from patients revealed changes that can be related with ophthalmologic parameters.

Spin probe method of electron paramagnetic resonance spectroscopy – a qualitative test for measuring the evolution of dry eye syndrome under treatment

The spin probe 5-DSA binds to proteins from tears and can be used to monitor changes in tear composition.