P. G. Rudakovskaya

Enzyme-functionalized gold-coated magnetite nanoparticles as novel hybrid nanomaterials: Synthesis, purification and control of enzyme function by low-frequency magnetic field

The possibility of remotely inducing a defined effect on NPs by means of electromagnetic radiation appears attractive. From a practical point of view, this effect opens horizons for remote control of drug release systems, as well as modulation of biochemical functions in cells. Gold-coated magnetite nanoparticles are perfect candidates for such application. Herein, we have successfully synthesized core-shell NPs having magnetite cores and gold shells modified with various sulphur containing ligands and developed a new, simple and robust procedure for the purification of the resulting nanoparticles. The carboxylic groups displayed at the surface of the NPs were utilized for NP conjugation with a model enzyme (ChT). In the present study, we report the effect of the low-frequency AC magnetic field on the catalytic activity of the immobilized ChT. We show that the enzyme activity decreases upon exposure of the NPs to the field.

Nanoscale engineering of hybrid magnetite–carbon nanofibre materials for magnetic resonance imaging contrast agents

Magnetic nanomaterials show significant promise as contrast agents for magnetic resonance imaging (MRI). We have developed a new highly efficient one-step procedure for the synthesis of magnetically- functionalised hollow carbon nanofibres, where (i) the carbon nanofibres act as both a template and a support for the nucleation and growth of magnetite nanoparticles and (ii) the structural (size, dispersity and morphology) and functional (magnetisation and coercivity) properties of the magnetic nanoparticles formed on nanofibres are strictly controlled by the mass ratio of the magnetite precursor to the nanofibres and the solvent employed during synthesis. We have shown that our magnetite-nanofibre materials are effectively solubilised in water resulting in a stable suspension that has been employed as a ‘‘negative’’ MRI contrast agent with an excellent transverse relaxivity (r2) of (268 13) mM s 1, surpassing current commercial materials and state-of-the-art magnetic nanoscale platforms in performance for MRI contrast at high magnetic fields. The preparation and evaluation of this unique hybrid nanomaterial represents a critical step towards the realisation of a highly efficient ‘‘smart’’ MRI theranostic agent – a material that allows for the combined diagnosis (with MRI), treatment (with magnetic targeting) and follow-up of a disease (with MRI) – currently in high demand for various clinical applications, including stratified nanomedicine.

Synthesis of magnetite-gold nanoparticles with core-shell structure

Data on the synthesis of core-shell-type nanoparticles in which the core is magnetite and the shell is gold are summarized and systematized. Various approaches to the synthesis of the magnetic core and methods for coating magnetite with a gold shell are considered.

Development of bacteriochlorophyll a-based near-infrared photosensitizers conjugated to gold nanoparticles for photodynamic therapy of cancer

We report the synthesis and characterization of a new sulfur-containing derivative of bacteriochlorophyll a. The latter was isolated from biomass of the nonsulfur purple bacterium Rhodobacter capsulatus strain B10. The developed photosensitizer is N-aminobacteriopurpurinimide with an exocyclic amino group acylated with a lipoic acid moiety, which is a biogenic substance that acts as a cofactor of the pyruvate dehydrogenase and α-ketoglutarate dehydrogenase complexes in the body. The disulfide moiety of lipoic acid confers the compound aurophilicity, thus allowing its conjugation with gold nanoparticles (NP-Au) via S—Au bonds. The shape and the size of the resulting nanoconjugate with immobilized photosensitizer (PS—Au) were assessed by dynamic light scattering and transmission electron microscopy. The conjugated nanoparticles are spherical with hydrodynamic diameter of 100–110 nm. The PS—Au conjugate absorbs light at 824 nm and emits strong fluorescence at 830 nm, which allowed in vivo study of its dynamic biodistribution in rats bearing sarcoma M-1. Compared to the free photosensitizer, PS loaded on the gold nanoparticles (PS—Au) showed extended circulation time in the blood and enhanced tumor uptake due to nonspecific passive targeting when the drug accumulates in tumor sites through the leaky tumor neovasculature and does not return to the circulation.

Synthesis and optimization of methods for the production of magnetite nanoparticles with different sizes and morphology for biological application

Herein we report on the synthesis, optimization of the synthetic procedure, functionalization, and characterization of cubic and spherical superparamagnetic magnetite nanoparticles. Spherical nanoparticles (16 ± 2 nm) were synthesized using oleylamine and oleic acid, and cubic (20 ± 2, 5 ± 0.5 nm) nanoparticles were synthesized with oleic acid and small amounts of oleylamine. Covalent modification of the nanoparticles was carried out using heterobifunctional PEG with aminopropyltriethoxysilane and N-hydroxysuccinimide ester moieties. This modification makes both water emulsion stability and further modification of the nanoparticles with cytotoxic drugs possible.

Сore–shell magnetite–gold nanoparticles: Preparing and functionalization by chymotrypsin

In this work we present the results of the synthesis of magnetite–gold nanoparticles with a core–shell structure. The preparation is carried out in several stages: synthesis of the core, coating with a gold shell, purification of magnetite–gold particles from an uncoated magnetite, and functionalization of the surface with sulfur-containing ligands. The conditions needed for the functionalization of nanoparticles with lipoic acid and mercapto-methoxy polyethylene glycol are indicated in detail, making it possible to determine the optimal conditions needed to achieve an efficient purification and a maximum concentration of the particles in a solution required for biological tests. The possibility of remotely controlling the chymotrypsin properties using an alternating magnetic field has been demonstrated by the example of magnetite–gold nanoparticles. The magnetite–gold nanoparticles which we have obtained are promising for future biomedical applications.

Synthesis and characterization of PEG-silane functionalized iron oxide(II, III) nanoparticles for biomedical application

In this paper we report the synthesis, functionalization, and characterization of ferromagnetic iron oxide (II, III) nanoparticles with different shapes and sizes. Using a number of chemical methods, magnetite nanoparticles having a spherical shape and size of 9 ± 2 nm (coprecipitation), 22 ± 4 nm and 50 ± 6 nm (redox reaction), and 40 ± 5 nm cubes were synthesized. Special attention in this paper is devoted to the covalent modification of magnetite nanoparticles by polymers such as silane-polyethylene glycol (Peg-silane). The main advantage of magnetic nanoparticles modified by polymer is low toxicity, colloidal stability of the prepared magnetite nanoparticles, and the possibility for post functionalization. We determined coercivity and saturated magnetism. Also, the relaxivity T2 was measured by magnetic resonance imaging (MRI). Prepared nanoparticles are of great interest and potential for use in biomedical imaging.