RU2706705C1 - Water-soluble magnetoactive nanobiocomposites of flavonoid complexes of gadolinium based on a natural conjugate of arabinogalactan with bioflavonoids and a method of producing said nanobiocomposites - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to novel water-soluble nanocomposites, which are nanoparticles of metal complex compounds of bioflavonoids contained in crude arabinogalactan, and Gd(III) encapsulated in arabinogalactan macromolecules. Arabinogalactan-raw is a natural conjugate of arabinogalactan and bioflavonoids. Disclosed nanocomposite is presented in the form of stable water-soluble powders with size of nanoparticles of complexes of gadolinium 1–100 nm and content of gadolinium in composition of 0.8–9.1 %. Also disclosed is a method of producing water-soluble nanocomposites.

EFFECT: proposed nanocomposites have magnetic properties, namely, high ability to reduce time of magnetic relaxation of water protons, and also are stable for a long time, do not lose their properties during storage and can easily be transferred into water solution.

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Description

The invention relates to new water-soluble composite magnetic materials based on nanoparticles of gadolinium and bioflavonoid complexes encapsulated in macromolecules of the natural arabinogalactan polysaccharide, as well as to methods for producing these magnetic nanomaterials from renewable natural materials.

Nanocomposites contain water-soluble magnetic nanoparticles of metal complexes of bioflavonoids and gadolinium (III) with a size of 1-100 nm, stabilized by arabinogalactan macromolecules, and are obtained in one step by mixing aqueous solutions of gadolinium (III) salts and commercial non-essential and non-natural arabinogalactan.

The claimed solution relates to the fields of chemistry, materials science, as well as to biomedical theranostics (parallel therapy and diagnostics) and can be used to create new compositions with high magnetic characteristics in the form of polymer radio-absorbing coatings, sources of elastic vibrations with a frequency of a control alternating magnetic field (for example, for the generation of ultrasound, including in the body of a living organism), as well as in the form of aqueous solutions used as multipurpose magnetic fluids, in particular agnitokontrastnyh preparations to enhance the contrast of images of living organisms using magnetic resonance imaging (MRI). In the case of MRI diagnostic detection of pathology, these drugs also have the possibility of a parallel neutron capture therapeutic effect on the pathogenic target due to the presence of gadolinium in the preparation, which has the highest neutron capture efficiency among all chemical elements, or hyperthermia due to the controlled heating of magnetic nanoparticles under the action of alternating magnetic field. In addition, new magnetic preparations have the property of magnetization in an external magnetic field, therefore, they can be redirected and concentrated by the magnetic field of the MRI of the tomograph directly at the diagnostic and therapeutic target, thereby significantly increasing the informative detail of the diagnosis, as well as the effectiveness of therapeutic neutron capture or hyperthermic effects on target with a minimum total dose of the introduction of potentially toxic gadolinium into the body.

The ability of paramagnetic gadolinium (III) ions in an aqueous solution to significantly increase the rate of nuclear magnetic relaxation of water protons is known. Due to this, the contrast of the image sharply increases during biomedical MRI diagnostics. However, simple inorganic salts have little relaxation efficiency due to the high rotational mobility of the free paramagnetic gadolinium ion; accordingly, in order to achieve a magneto-contrasting diagnostic effect, large doses of gadolinium are required, which is associated with a high risk for the body of this potentially highly toxic heavy metal.

The introduction of bulk chelating organic ligands into the coordination environment of the gadolinium ion allows one to slow down the rotation of the resulting paramagnetic metal complex gadolinium-containing ion and thus increase relaxation efficiency, therefore, reduce the effective dose and, accordingly, the toxic load of gadolinium on the body with the same relaxation efficiency. So, there is known a contrast agent for MRI based on the complex salt of gadolinium and diethylene triamine pentaacetic acid [Pat. RF 2150961. Magnetic resonance contrast composition]. Its disadvantage is still relatively small relaxation efficiency, therefore, a sufficiently large dose of the introduction of toxic gadolinium into the body to achieve a diagnostic effect.

Self-association in water of gadolinium metal complexes based on bulk hydrophobic ligands also leads to a decrease in the rotational mobility of metal complex gadolinium-containing self-associates, and as a result to an increase in the relaxation efficiency of magnetocontraining agents [Pat. RF 2242477. Perfluoroalkyl-containing compounds, a method for their preparation (options) and a pharmaceutical agent containing these compounds; Lattuada L., Lux G. Synthesis of Gd-DTPA-cholesterol: a new lipophilic gadolinium complex as a potential MRI contrast agent // Tetrahedron Letters. 2003. V.44. P.3893-3895]. The main disadvantages of analogues are the complexity and multi-stage synthesis of both ligands and the metal complexes themselves, as well as the need to isolate and purify all (both target and intermediate) compounds.

The use of the most voluminous - polymer ligands surrounded by gadolinium ions leads to an even more significant decrease in their rotational mobility, respectively, to an increase in the relaxation efficiency of the resulting preparations. The closest analogue, selected as a prototype, are complex compounds of gadolinium with heteroatom high molecular weight ligands [US Pat. RF 2197495. Complexes of cascade polymers containing their diagnostic contrast agent and intermediates]. The essence of the technical solution proposed in the prototype is the use of original, specially synthesized complex-forming nitrogen-containing polymers to obtain multi-ion gadolinium polymer complexes of high molecular weight (from 10,000 to 80,000 Da), which leads to high relaxation efficiency. The disadvantages are the multi-stage and complexity of the synthesis of both complexing polymers (polymer ligands) and polymeric multi-ion gadolinium complexes proper, which requires a whole set of sophisticated specialized experimental equipment, as well as significant material and labor costs.

The objective of the claimed technical solution is the rational - one-stage creation of a new nanocomposite magnetically active metal complex gadolinium system, combining the advantages of self-associated metal complexes of gadolinium and high molecular weight gadolinium multi-ion coordination compounds, as well as devoid of most of the above disadvantages.

The essence of the proposed solution lies in the fact that, as sources of chelating complexing ligands, as well as a polymer matrix that stabilizes the resulting gadolinium complexes self-associated in nanoparticles, it is proposed to use commodity raw arabinogalactan, a natural bioconjugate of this polysaccharide and bioflavonoids [B. Sukhov and others. Proceedings of the Academy of Sciences. Chemical series. 2014. No. 9. S. 2189-2194; Pat. RF № 2611999. Silver nanocomposite based on conjugate of arabinogalactan and flavonoids with antimicrobial and antitumor effects, and a method for its preparation; Pat. RF № 2614363. An agent with antitumor activity based on nanocomposites of arabinogalactan with selenium, and methods for producing such nanobiocomposites]. The purpose of the invention is achieved in that an aqueous solution of gadolinium (III) salt is added to an aqueous solution of crude arabinogalactan at room temperature (20-25 ^° C) with vigorous stirring. After this, a 30% aqueous ammonia solution is added dropwise to a neutral reaction. Then the solution is stirred for 2 hours and the resulting target nanocomposite is isolated by precipitation into ethanol, acetone, another water-miscible organic solvent, the precipitate is filtered off, washed on the filter with the same solvent and dried in a desiccator (examples 1-5).

In the described mixing of aqueous solutions of raw arabinogalactan and gadolinium (III) salts, the bioflavonoids in macromolecules of arabinogalactan come into contact with the gadolinium cations and are chelated to coordinate them, as is the case with similar complexation of gamma-pyrons and other metal flavonoids with non-metal flavonoids Fly S.A. et al. Synthesis and properties of metal chelates based on natural γ-pyrone - maltol. Chemistry for sustainable development. 2007. T. 15, No. 4. P. 457-466; Sukhov BG et al. Nonlinear-optical bis (3-hydroxy-2-methyl-4h-pyran-4-onato) complexes of metals. Mendeleev Communication. 2007. V. 17, No. 3. P. 154-155; Sukhov BG et al. Stereoactive lone pair of electrons on bismuth (III): tris (3-hydroxy- 2-methyl-4h-pyran-4-onato) bismuth (III). Arkivoc. 2008.V. 2008, No. 8. P. 139-149; Fly S.A. New aspects of the chemistry and physical chemistry of maltol and its metal-containing complexes. Dis. Cand. Chem. sciences. Irkutsk 2008; Stolpovskaya E.V. Synthesis of biologically active complex compounds based on dihydroquercetin - a product of deep processing of larch wood. Dis. Cand. Chem. sciences. Irkutsk 2015]. However, in our case, complexation occurs directly in the cavities of arabinogalactan macromolecules, where there are chelating ligands - bioflavonoid molecules, and the water-insoluble molecules of chelated metal complexes of gadolinium and bioflavonoids self-associate in nanoparticles, which are automatically encapsulated in arabic 2 (apec). ) The fundamental difference from the above inventions [Pat. RF No. 2611999, Pat. RF No. 2614363] is the implementation in the process of producing nanocomposites of the exclusively complexation stage with the non-oxidizing cadmium gadolinium (III) in the absence of an oxidation-reduction stage, that is, in the present case, the bioflavonoid molecules are not spent on the reduction of the metal of the nanoparticles, but are completely included in the metal complex nanoparticles as gadolinium (III) ligands. Indeed, the presence in the IR spectrum of the obtained nanocomposites of the band at 1628-1642 cm ^{-1 of} flavonoids coordinated to the carbonyl metal, as well as in the UV spectrum of the band in the range of 230-400 nm of aromatic rings of flavonoids coordinated in the metal complex, indicates the continued presence of flavonoid molecules in the nanocomposite, however already coordinated to metal ions [Mukha S.A. et al. Synthesis and properties of metal chelates based on natural γ-pyrone - maltol. Chemistry for sustainable development. 2007. T. 15, No. 4. P. 457-466; Fly S.A. New aspects of the chemistry and physical chemistry of maltol and its metal-containing complexes. Dis. Cand. Chem. sciences. Irkutsk 2008; Stolpovskaya E.V. Synthesis of biologically active complex compounds based on dihydroquercetin - a product of deep processing of larch wood. Dis. Cand. Chem. sciences. Irkutsk 2015].

The gadolinium content in the obtained samples, determined by elemental analysis and X-ray energy dispersive microanalysis, varies in the range of 0.8-9.1 mass%, depending on the initial ratio of the gadolinium salt to the raw arabinogalactan (examples 1-5). According to transmission electron microscopy, the size of metal-complex nanoparticles is 1-100 nm (Figures 1, 2).

It was found that new nanobiocomposites even at room temperature are magnets with a very large width of the electron paramagnetic resonance (EPR) signal ΔH ≈ 2000 G (examples 1-5, Fig. 3).

The ability of the obtained nanobiocomposites to significantly reduce the magnetic relaxation time T1 of water protons in an aqueous solution is also detailed, which is the main characteristic when using such water-soluble magnetic substances in MRI (example 6). So, the relaxation time T1 of the protons of distilled water is 570 ms, however, after the obtained nanocomposite is dissolved in it, this time T1 becomes equal to 15 ms, that is, it is reduced by 38 times (example 6). Even stronger - the relaxation time T1 of the residual protons of deuterated water D ₂ O is reduced by a factor of 350: from 2800 ms to 8 ms after dissolution of the same nanocomposite in it (example 6).

Thus, the target nanocomposites are light cream colored magnetic powders that are readily soluble in water, insoluble in alcohol, acetone, ether and most other low and non-polar organic solvents. Nanocomposite powders are aggregatively stable for a long time, do not lose their properties during long-term storage, and can easily be re-transferred to an aqueous solution.

The proposed magneto-active nanocomposites and the method for their preparation are characterized by the following advantages:

- commodity arabinogalactan-raw material (already containing macromolecules of this polysaccharide and a molecule of chelating ligands - bioflavon) is used as sources of complexing chelating ligands, as well as a polymer matrix that stabilizes the metal complexes of gadolinium and flavonoids that are self-associated in nanoparticles;

- the preparation of a composite with nanoparticles of gadolinium flavonoid complexes based on the natural conjugate of arabinogalactan and bioflavonoids is notable for its simplicity and cost-effectiveness, as it consists of one stage, proceeds at room temperature (20-25 ^° C) and does not require any additional reagents (complexing ligands or polymers);

- gadolinium-containing magnetic nanocomposites are stable water-soluble powders and retain their properties for a long time.

Figure 1 shows a photo of nanoparticles of chelate complexes of bioflavonoids and Gd (III) encapsulated in arabinogalactan macromolecules with a minimum Gd content of 0.8 mass% (obtained using a transmission electron microscope).

Figure 2 shows a photo of nanoparticles of chelate complexes of bioflavonoids and Gd (III) encapsulated in arabinogalactan macromolecules, with a maximum Gd content of 9.1 mass% (obtained by transmission electron microscope).

Figure 3 shows a typical EPR spectrum of the obtained nanocomposites.

The following examples illustrate the invention.

Example 1

A portion of raw arabinogalactan (non-covalent conjugate of arabinogalactan and bioflavonoids: the band at 1641-1729 cm ^-1 in its IR spectrum refers to the carbonyl groups of flavonoids, the bands in the range of 230-430 nm in the UV spectrum also relate to the optical absorption of aromatic flavonoid rings) of mass 1.00 g was dissolved in 3 ml of water, and dissolved GdCl ₃ · 6H ₂ O m = 0.02 g in 2 ml of water was added dropwise to the resulting solution with constant stirring. Then, the pH value was adjusted to neutral 7.0 by adding a few drops of an aqueous solution of ammonia (the pH was monitored using an EV-74 ionomer). The reaction mixture turned brown. The mixture was stirred at room temperature ^(20-25 ° C) for 2 hours. The nanocomposite was precipitated in 100 ml of acetone, followed by filtration through a Schott funnel under vacuum. The precipitate was washed on a Schott with the same solvent, and the resulting nanocomposite was dried in an desiccator over anhydrous calcium chloride.

The yield of the obtained nanocomposite was 98% (in terms of gadolinium taken) with a gadolinium content of 0.8 mass%.

The presence in the IR spectrum of this nanocomposite of a band at 1628-1642 cm ^{-1 of} flavonoids coordinated to a carbonyl metal, and also in the UV spectrum, bands in the range of 230-400 nm of aromatic rings coordinated in a metal complex of flavonoids [Mukha S.A. et al. Synthesis and properties of metal chelates based on natural γ-pyrone - maltol. Chemistry for sustainable development. 2007. T. 15, No. 4. P. 457-466; Fly S.A. New aspects of the chemistry and physical chemistry of maltol and its metal-containing complexes. Dis. Cand. Chem. sciences. Irkutsk 2008; Stolpovskaya E.V. Synthesis of biologically active complex compounds based on dihydroquercetin - a product of deep processing of larch wood. Dis. Cand. Chem. sciences. Irkutsk 2015] indicates the continued presence in the nanocomposite of flavonoid molecules, however, already coordinated to metal ions.

The resulting nanocomposite contains a wide signal in the EPR spectrum (D H = 2015 ± 20 G, g _eff = 2.11).

Example 2

The preparation and characterization of the nanocomposite was carried out analogously to example 1, but an increased sample of GdCl ₃ • 6H ₂ O was taken to m = 0.13 g.

The yield of the obtained nanocomposite was 97% (in terms of gadolinium taken) with a gadolinium content of 4.9 mass% in it.

The resulting nanocomposite contains a wide signal in the EPR spectrum, as in example 1, but with a higher intensity.

Example 3

The preparation and characterization of the nanocomposite was carried out analogously to example 2, but instead of gadolinium (III) chloride, 0.25 g of gadolinium (III) nitrate was used.

The yield of the obtained nanocomposite was 95% (in terms of the taken gadolinium) with a gadolinium content of 7.8 mass% in it.

The resulting nanocomposite contains a wide signal in the EPR spectrum, as in example 1, but with a higher intensity.

Example 4

The preparation and characterization of the nanocomposite was carried out analogously to example 2, but instead of gadolinium (III) chloride, 0.20 g of gadolinium (III) sulfate was used.

The yield of the obtained nanocomposite was 97% (in terms of gadolinium taken) with a gadolinium content of 3.8 mass% in it.

The resulting nanocomposite contains a wide signal in the EPR spectrum, as in example 1, but with a higher intensity.

Example 5

The preparation and characterization of the nanocomposite was carried out analogously to example 2, but instead of gadolinium (III) chloride, 0.22 g of gadolinium (III) acetate was used.

The yield of the obtained nanocomposite was 94% (in terms of gadolinium taken) with a gadolinium content of 9.1 mass% in it.

The resulting nanocomposite contains a wide signal in the EPR spectrum, as in example 1, but with a higher intensity.

Example 6

0.036 g of a nanocomposite with gadolinium content of 7.8 mass% was dissolved in 2 ml of water (or deuterated water D ₂ O) and the relaxation time T1 of water protons (or residual protons of deuterated water D ₂ O) was determined on a Bruker DPX-400 NMR spectrometer according to the standard method inversion - signal recovery. "

The time T1 decreased from 570 ms to 15 ms for distilled water, and from 2800 ms to 8 ms for deuterated water.

Claims (2)

1. Water-soluble nanocomposites, which are nanoparticles of metal-complex compounds of bioflavonoids contained in raw arabinogalactan (a natural conjugate of arabinogalactan and bioflovanoids), and Gd (III) encapsulated in macromolecules of arabinogalactan, which have a high magnetic relaxation time , in the form of stable water-soluble powders with a nanoparticle size of gadolinium complexes of 1-100 nm and a gadolinium content in the composite of 0.8-9.1%. 2. The method for producing the water-soluble nanocomposites according to claim 1, comprising reacting an aqueous solution of the gadolinium salt with an aqueous solution of crude arabinogalactan (a natural conjugate of arabinogalactan and bioflavonoids) in the presence of an aqueous ammonia solution to create a neutral medium at room temperature of 20-25 ° C, followed by precipitation into acetone, or ethanol, or another water-miscible organic solvent and filtration.

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