High Reactivity of Supermolecular Nanoentities of a Vitamin B12 Derivative in Langmuir-Schaefer Films Toward Gaseous Toxins

Recently, we have described the first supermolecular nanoentities (SMEs) of a vitamin B12 derivative, viz., a monocyano form of heptabutyl cobyrinate ((CN-)BuCby), unique nanoparticles with strong noncovalent intermolecular interactions, and emerging optical and redox properties. In this work, the fast response of thin films based on the SMEs of the B12 derivative to gaseous toxins (viz., hydrogen cyanide, ammonia, sulfur dioxide, and hydrogen sulfide) particularly dangerous for humans was demonstrated. The reaction between SMEs of (CN-)BuCby in Langmuir-Schaefer (LS) films and HCN generates dicyano species and proceeds ca. 5-fold more rapidly than the process involving drop-coated films that contain (CN-)BuCby in molecular form. The highest sensitivity toward HCN was achieved by using thicker LS films. The reaction proceeds reversibly: upon exposure to air, the dicyano complex undergoes partial decyanation. The decyanated complex retains reactivity toward HCN for at least four subsequent cycles. The processes involving SMEs of (CN-)BuCby and NH3, SO2, and H2S are irreversible, and the sensitivity of the films toward these gases is lower in comparison with HCN. Presented data provides mechanistic information on the reactions involving solid vitamin B12 derivatives and gaseous toxins. In the case of NH3, deprotonation of the coordinated Co(III)-ion water molecule occurs, and the generated hydroxocyano species exhibit high air stability. After binding of SO2, a mixture of sulfito and dicyano species is produced, and the regenerated film contains aquacyano and diaqua or aquahydroxo species, which possess high reactivity toward gaseous toxins. Reaction with H2S produces a mixture of the Co(III)-dicyano form and Co(II)-species containing sulfide oxidation products, which are resistant to aerobic oxidation. Our findings can be used for the development of naked-eye, electronic optic, and chemiresistive sensors toward gaseous toxins with improved reactivity for prompt cyanide detection in air, blood, and plant samples and for analysis of exhaled gases for the diagnosis of diseases.

Bioinformatic and chemoneurocytological analysis of the pharmacological properties of vitamin B12 and some of its derivatives

More than three thousand five hundred biological properties of vitamin B[Formula: see text] and four of its derivatives (aquacobalamin, cyanoaquacobyrinic acid heptamethyl ester, dicyanocobyrinic acid heptamethyl ester and stable yellow corrinoid) have been assessed by bioinformation analysis. Based on the data obtained (including the assessments of the interaction of molecules with the proteins of rat proteome), conclusions were drawn about the potential effects and safety of the investigated substances. In particular, it has been shown that heptamethyl esters of cyanoaquacobyrinic and dicyanocobyrinic acids, as well as a stable yellow corrinoid (antivitamin), can be recommended for further study as analgesics, anti-inflammatory drugs and, also, antitumor agents aimed at the therapy of glioblastoma, hepatoblastoma and T-cell leukemia. Estimates of the LD50 constants for rats and the TD50 and IC50 constants for rat muscle cells in culture, along with the results of assessments of the interaction of molecules with the rat proteome, showed that all the compounds studied were of low toxicity. At the same time, cyanocobalamin and aquacobalamin are distinguished by the least cumulative properties in comparison with other studied compounds. Chemoneurocytological analysis of compounds showed that cyanocobalamin and aquacobalamin may have the greatest neuroprotective effects: increase in the concentration of the substances by 1 mmol/l causes the estimate of neuronal survival to increase by 25%.

Encapsulation of vitamin B12 into nanoengineered capsules and soft matter nanosystems for targeted delivery

Targeted delivery of vitamins to a desirable area is an active branch in a modern pharmacology. The most important and difficult delivery of vitamin B₁₂ is that to bone marrow and nerve cells. Herein we present a first step towards the development of two types of smart carriers, polymer capsules and lyotropic liquid-crystalline nanosystems, for vitamin B₁₂ targeted delivery and induced release. A vitamin B₁₂ encapsulation technique into nanoengineered polymeric capsules produced by layer-by-layer assembling of polymeric shells on CaCO₃ templates has been developed. The effectiveness of the process was demonstrated by optical absorption spectroscopy, transmission electron microscopy (TEM), atomic force microscopy (AFM) and small-angle X-ray diffraction. TEM and AFM analyses performed on capsules after their drying, confirmed the presence of the vitamin B₁₂ inside the capsules in the form of crystalline nanoaggregates, 50-300 nm in diameter. Soft lipid nanovectors consisting of amphiphilic phytantriol molecules, which in water excess spontaneously self-assembly in 3D well-ordered inverse bicontinuous cubic bulk phase, were used as alternative carriers for vitamin B₁₂. It was shown that about 30% of the vitamin added in the preparation of the soft lipid system was actually encapsulated in cubosomes and that no structural changes occurred upon loading. The Vitamin stabilizes the lipid system playing the role of its structure-forming element. The biocompatible nature, the stability and the feasibility of these systems make them good candidates as carriers for hydrophilic vitamins.

Magnesium Porphine Supermolecules and Two-Dimensional Nanoaggregates Formed Using the Langmuir-Schaefer Technique

Porphyrins are functional elements of important biomolecules, whose assemblies play a central role in fundamental processes such as electron transfer, oxygen transport, enzymatic catalysis, and light harvesting. Here we report an approach to formation of porphyrin supermolecules, a particular type of nanoparticles with unusually strong noncovalent intermolecular interactions. Key differences between the supermolecules and noncovalent nanostructures described earlier are as follows. (1) Supermolecules consist of molecules of the same type without side groups promoting the self-assembly and without any spacers; no surfactant or catalyst to assist the process is needed. (2) They exhibit unusual photophysical properties and remain stable even in organic solvents. Their formation occurs under specially selected conditions at the air-water interface at room temperature. Following this route, we have formed supermolecules of magnesium porphine, a functional element of chlorophyll. The properties of these supermolecules are markedly different from those of the constituent molecules. For example, in contrast to the pink color of the monomer solution, solutions of supermolecules are transparent for visible light and absorb in the ultraviolet and near-infrared regions. We also present atomic force microscopy visualization of the porphyrin two-dimensional nanoaggregates forming at the air-water interface that were predicted in our previous works. This approach offers a guideline for the discovery of new supermolecules, including complex biological ones, and the formation of supermolecular materials with novel properties.

Aggregation behavior of unsubstituted magnesium porphyrazine in monolayers at air–water interface and in Langmuir–Schaefer films

The aggregation behavior of unsubstituted magnesium porphyrazine (MgPz) was studied in layers at the water–air interface and in Langmuir–Schaefer films. Regions of existence and characteristics of the structure and properties of stable nanostructured monolayers of MgPz were determined with the method of quantitative analysis of compression isotherms of floating layers in a wide range of initial surface coverage degrees (ISCD). MgPz on the water surface forms monolayers of three types: a face-on type and two edge-on types that differ in the structure. The specific feature of the monolayers of the second type is the independence of the structure of two-dimensional MgPz nanoparticles formed on water on the ISCD. A mathematical model and a state diagram of the monolayer were constructed and a passport of MgPz monolayers was compiled. For the first time, the state diagram contains boundary isotherms based on data obtained from the model. Langmuir–Schaefer films of MgPz formed from layers of various types were prepared and studied by UV-vis absorption spectroscopy.

The influence of molecular structure and π-system extent on nano- and microstructure of Langmuir layers of copper azaporphyrins

Comparative analysis of the structure of floating layers formed by copper tetra-tert-butylsubstituted phthalocyanine ( CuPctBu4 ) and tetrabenzotriazaporphyrin ( CuThptBu4 ) dissolved in a number of solvents is performed. The influence of the π-system extent (tetra-tert-butylsubstituted copper porphyrazine and phthalocyanine: CuPaztBu4 and CuPctBu4 ) on the structure of Langmuir layers of copper azaporphyrins is studied. It is shown that both the lack of one meso-atom and the increase of the extent of the π-system cause the balance between intermolecular interactions (AP–AP) — (AP-water) to shift to the latter and lead to formation of stable monolayers with the most open face-on structure of nanoaggregates instead of the edge-on one, all other factors being equal, in Langmuir layers prepared from solutions in aromatic solvents. The micro-level structural difference of copper tetra-tert-butylsubstituted porphyrazine ( CuPaztBu4 ) and phthalocyanine ( CuPctBu4 ) resulted from the structural difference of two-dimensional nanoaggregates forming the layers was shown using Brewster angle microscopy.

Nanoaggregates in floating layers of azaporphyrins

An analysis of compression isotherms of floating layers of copper tetra-tert-butylphthalocyanine ( CuPctBu4 ) and copper tetrabenzotriazaporphyrine, obtained at varied initial conditions, is carried out. The structure of layers is determined by three methods: the traditional one (direct estimation of area per molecule from a π-A isotherm), by a quantitative analysis of compression isotherms (with the use of Volmer equation), and by Brewster angle microscopy. It is shown that in layers with edge-on arrangement of molecules (initial surface concentrations N0 > 0.15 μmol.m-2), the layer structure, determined by the quantitative method, may differ drastically from the structure obtained by the traditional one. The equation of state of the floating layer generalized to the case when structural units of 2D gas are molecular aggregates is used to describe the layer of azaporphyrines. Boundaries of existence and characteristics of structure and properties of floating layers in stable states (size of nanoaggregates formed in a layer, number of molecules in them, interaggregate spacing, compressibility) are determined. The quantitative model of floating layer of copper tetra-tert-butylphthalocyanine is proposed. Constants characterizing a stable monolayer, as well as the region where it may be formed, are determined on the base of the model created.