Two new neutral binuclear tetranitrosyl iron complexes of general formula [Fe2R2(NO)4] with R = 2,4-difluorothiophenyl (complex 1) and 3,4-difluorothiophenyl (complex 2), donors of nitrogen monoxide (NO), were prepared. The complexes were characterized by single-crystal X-ray diffraction, IR, Mössbauer, EPR spectroscopy, and elemental analysis. The antibacterial activity and cytotoxicity of complex 1, complex 2, and previously synthesized [(NO)4] with R'= 2,4-dichlorothiophenyl (complex 3) were studied for the first time. The “amount of NO–biological activity” correlations were analyzed depending on the nature and position of the substituent in the thiophenyl ligand. Complex 2 was found to have antibacterial activity that was four times as high as that of the known antibiotic kanamycin. The anti-biofilm activity of complex 2 was studied; it inhibited 46% of biofilm formation and destroyed 32% of M. Luteus biofilms, surpassing the effects of the reference drugs kanamycin and ampicillin.

The synthesis and data on the physicochemical characteristics and biological activity of the new iron nitrosyl complex (Q + ) 2 [Fe 2 (S 2 O 3 ) 2 (NO) 4 ] 2– ( I ), where Q + is protonated 2-ethyl-4-pyridinecarbothioamide (C 8 H 11 N 2 S), are presented. The structure and properties of the complex were studied by X-ray diffraction, elemental analysis, IR and Mössbauer spectroscopy, and amperometry. The complex showed antibacterial activity and efficiently inhibited cyclic guanosine monophosphate phosphodiesterase (cGMP PDE), which may suggest its antihypertensive, anti-aggregation, and vasodilator activities.

We studied the possibility of inhibition of histone deacetylases (HDAC) in the nuclear extract of HeLa cells by N1-hydroxy-N4-(pyridin-4-yl)succinamide (compound 1). Compound 1 inhibits HDAC and showed low toxicity for A-172, HepG2, HeLa, MCF-7, and Vero cells. HeLa cells were most sensitive to the compound. Increasing the interval between administration of compound 1 and the chemotherapeutic agent to 8 h led to an increase in the cytotoxic effect of cisplatin (actinomycin D) on HeLa cells. The combination of compound 1 with cisplatin (actinomycin D) reduced the cytotoxic effect of these drugs for non-tumor Vero cells.

Two new neutral binuclear tetranitrosyl iron complexes of general formula [Fe 2 R 2 (NO) 4 ] with R = 2,4-difluorothiophenyl (complex 1 ) and 3,4-difluorothiophenyl (complex 2 ), donors of nitrogen monoxide (NO), were prepared. The complexes were characterized by single-crystal X-ray diffraction, IR, Mössbauer, EPR spectroscopy, and elemental analysis. The antibacterial activity and cytotoxicity of complex 1 , complex 2 , and previously synthesized [ Fe_2R_2^' (NO) 4 ] with R'= 2,4-dichlorothiophenyl (complex 3 ) were studied for the first time. The “amount of NO–biological activity” correlations were analyzed depending on the nature and position of the substituent in the thiophenyl ligand. Complex 2 was found to have antibacterial activity that was four times as high as that of the known antibiotic kanamycin. The anti-biofilm activity of complex 2 was studied; it inhibited 46

The structure of 2-ethyl-3-hydroxy-6-methylpyridinium nitroxysuccinate (2) was studied. The cytotoxicity of this compound and its ability to have an effect on the level of intracellular nitrogen monoxide, as well as on the formation of reactive oxygen species and lipid peroxidation processes under conditions of induced oxidative stress, were evaluated. It was found that compound 2 has low in vitro cytotoxicity in normal and cancer cell models. It was shown that compound 2 can increase the level of intracellular nitrogen monoxide due to the presence of nitroxysuccinate in its structure. Compound 2 suppresses the lipid peroxidation in mouse brain homogenate in contrast to 2-ethyl-3-hydroxy-6-methylpyridinium succinate (1) . Besides, compound 2 more effectively reduces the level of intracellular reactive oxygen species under tert -butyl peroxide-induced oxidative stress and has a greater ability to bind superoxide compared to compound 1 . The results of this study show that compound 2 is promising for the development of drugs with antioxidant activity.

Amphiphilic copolymers of N-vinylpyrrolidone and methacrylic acid, and triethylene glycol dimethacrylate (branching agent) are synthesized by radical copolymerization in toluene and ethanol; their main physicochemical characteristics (monomer composition, absolute weight-average molecular weight, polydispersity, and hydrodynamic radius in water and aqueous media with various рН) are determined. It is shown that in weakly acidic media copolymer solutions exhibit the lower critical temperature which shifts to high values in neutral and alkaline aqueous buffered solutions. Water-soluble nanoscale systems of red-fluorescent dye zinc tetraphenylporphyrinate having a hydrodynamic radius of about 50 nm (in aqueous neutral buffered solution) and stable in the physiologically important temperature range are obtained. Using the МТТ assay on various cell lines, normal (FetMSC, Vero) and tumor (HepG2, HeLa), ternary copolymers are found to be low toxic. The dynamics of accumulation of dye-loaded polymer particles in HeLa and Vero cells is studied by fluorescence microscopy. It is concluded that the synthesized copolymers show promise as carriers and means of delivery of biologically active compounds.

The cytotoxic activity of a series of dinitrosyl iron complexes (DNICs) with thioureas against cells of different origin has been studied in this work. The cytotoxicity of the studied DNICs proved to be substantially different depending on the structure of the complexes and cell line. Complexes with thiourea and 1,3-dimethylthiourea were found to induce notable cell death in different cell lines of both cancerous and non-cancerous origin, while the N-ethylthiourea-bearing complex induced cell death in cells derived from brain tumors. The studied DNICs effectively release NO while decomposing in solutions, as follows from the electrochemical analysis. It was found that the cytotoxic effects of the studied DNICs did not correlate with their NO-donating ability, hence suggesting that their cytotoxic activity is, in a big part, defined by the long-lived nitrosyl iron-sulfur intermediates formed during the decomposition of the complexes. The structures of the products formed upon hydrolytic decomposition of all studied DNICs have been studied by electrospray ionization mass spectrometry. Stable high-molecular cluster ions containing NO groups namely [Fe4S3(NO)7]- (Roussin's "black salt" anion), [Fe4S3(NO)5]-, [Fe4S4(NO)4]-, [Fe4S3(NO)4]- and [Fe4S3(NO)6]- have been detected in the solution of the N-ethylthiourea-bearing complex. The mechanism of Roussin's "black salt" anion formation in a solution of DNIC with N'-ethylthiourea was studied using density functional theory. This moved us near understanding the reasons for the formation of biologically active intermediates upon the decomposition of the complex with N'-ethylthiourea, which are apparently responsible for the unique antiglioma activity of the complex.

The performance of a bioanode based on living cells Escherichia coli in the electrochemical oxidation of glucose is studied. It is shown that potassium ferricyanide can serve as the mediator in this bioelectrocatalytic system. The efficiency of this bioelectrocatalytic reaction with living cells depends on the mediator concentration. It is shown that the nature of buffer can affect the electrochemical responses of this system.

Abstract Single-crystal XRD structure of binuclear tetranitrosyliron complex [Fe2(SR)2(NO)4] (1), R = 4-aminothiophenyl, has been described. The properties of 1 were studied by IR, Mössbauer, mass spectroscopy, and amperometry. Complex 1 was shown to form long-living nitrosyl intermediates in solution, which underlies its prolonged NO donor activity. In HeLa cells, 1 caused accumulation of NF-κB p50 but decreased the levels of NF-κB p65 in the nucleus, which led to inhibition of NF-κB dependent genes. The complex also induced increase of p53 protein levels and p21 gene activity, which led to the apoptotic cell death after G2/M cell cycle phase. Graphical Abstract

The synthesis of water-soluble dyads PFD-Chl(1), PFD-Chl(Zn) and PFD-Chl(2) based on a polyanionic fullerene [60] derivative PFD covalently linked to chlorin e 6 was described. Photophysical properties, generation of superoxide and singlet oxygen in water and liposomes, and photodynamic activity on HeLa cancer cells of obtained dyads were analyzed. The significant influence of linker length between fullerene[60] core and dye, presence of metal (Zn) atom in chlorin moiety on photophysical properties, and photodynamic activity of the dyads was demonstrated. All dyads exhibit quenching of chlorin fluorescence by 7-120 times due to the electron transfer from the dye to fullerene and they formed nanoassociates in aqueous solutions with an effective radius in the range of 30-500 nm due to their pronounced amphiphilic properties. Such nanoassociates were able to effectively interact with membranes of liposomes, which led to a sharp increase of fluorescence signal. This effect could be applied for the design of various fullerene-based nanoscale switch-off systems. The dyad PFD-Chl(1) - with the shortest linker and metal-free dye - had the superoxide generation efficiency 5.6 and 3.4 times higher compared to free chlorin Ce6 in water and liposomes, respectively, while its singlet oxygen generation was reduced. The phototoxicity of this dyad in HeLa cells was almost equal to that of the native chlorin, despite the reduction of singlet oxygen generation efficiency. Upon the incorporation of zinc atom into a chlorin moiety of this dyad, photodynamic activity and phototoxicity of PFD-Chl(Zn) dyad became negligible. The PFD-Chl(2) dyad - with the longest linker and metal-free chlorin - had about two times lower photodynamic activity and phototoxicity compared to Ce6 due to weak interaction between fullerene core and the dye. A significant increase of the type I pathway efficiency, demonstrated in the PFD-Chl(1) dyad, could be applied for the creation of photosensitizers, highly effective against hypoxic tumors. The demonstrated approach opens up vast opportunities for a directional design of highly efficient fullerene-based water-soluble photosensitizers for photodynamic therapy.

The effect of inhibition of the tumor suppressor p53 on the antioxidant system genes expression under the influence of cytotoxic compounds of the platinum group was studied. It was found that the action of platinum(II) and platinum(IV) complexes induced accumulation of p53 protein with a maximum in 12 h, which was confirmed by an increase in the expression of the P21 gene, the target gene of the p53 protein. It was shown that the action of platinum complexes activated the expression of catalase and superoxide dismutase 2 genes. Suppression of p53 protein functions with specific inhibitor α-piphitrin under the action of platinum complexes reduced the expression of catalase and superoxide dismutase 2 genes and the target gene P21, which attested to the p53-dependent regulation of these genes.

A new binuclear μ-NSC-type nitrosyl iron complex [Fe 2 (SR) 2 (NO) 4 ] (R is 5-phenyl-1 H -1,2,4-triazole-3-thiolyl) was synthesized. The composition and structure of the newly synthesized complex were determined by atomic absorption, IR, EPR, and Mössbauer spectroscopy and SQUID magnetometry. Amperometric analysis showed that the new complex is an effective nitric oxide (NO) donor in a 1% aqueous DMSO solution. The amounts of NO generated by the complex [Fe 2 (SR) 2 (NO) 4 ] in aqueous solutions at physiological pH values were determined. The new complex was shown to have higher antibacterial activity against the gram-positive bacteria Micrococcus luteus compared to kanamycin and streptomycin. According to assays, sulfur-containing ligands of the 1,2,4-triazole-3-thiol series are promising for the design of new antibacterial agents containing the {Fe(NO) 2 } structural moiety.

The conditions for obtaining stable aqueous solutions of a lipophilic aminonitroxyl platinum complex, namely, e -amine- d -(4-amino-2,2,6,6-tetramethylpiperidine 1-oxyl)- a, f -bis(octanoato)- b, c -dichloroplatinum( iv ), by means of its encapsulation into nanoparticles of copolymers of N -vinylpyrrolidone with triethylene glycol dimethacrylate with various monomer compositions and topologies were found. Aqueous solutions of the complex encapsulated into polymer particles were investigated by dynamic light scattering, the temperature dependence of nanostructure sizes was studied. Transmission electron microscopy established that the hybrid nanostructures are core—shell particles, in which the platinum complex forms small clusters (∼4 nm). The parameters of ESR spectra of aqueous dispersions indicate a high mobility of nitroxyl contained in hybrid nanostructures. Voltammetric measurements demonstrate a similarity of the redox reactions related to the free radical fragment of the aminonitroxyl Pt IV complex and of the 4-acetylamino-2,2,6,6-tetramethylpiperidine 1-oxyl radical. Polymer products containing the platinum complex were studied by IR spectroscopy, TGA, and DSC. The cytotoxicity index (IC 50 ) of the free and the encapsulated complex was determined for HeLa tumor cells. The cytotoxicity of the latter (IC 50 47–205 nmol L −1 ) depends on the monomeric composition of the nanoparticles and the incubation time.

The cytotoxicity and antioxidant effects of chitosan-(poly)nitoxides of different molecular weights containing a nitroxide radical of the piperidine structure were studied on tumor (HeLa, A172, and HepG2) and normal (Vero) cell lines. The chitosan-(poly)nitroxides exhibited low cytotoxicity. Under conditions of oxidative stress induced with tert -butyl hydroperoxide, the most pronounced decrease in ROS levels in the presence of chitosan-(poly)nitroxides was observed in normal cells. In cell homogenates, the decrease in malondialdehyde levels was observed only in the presence of low-molecular-weight chitosan-(poly)nitroxide irrespective of the cell line. Our data demonstrate that the cell-specific antioxidant properties of chitosan-(poly)nitroxides are related to their penetration into cells and interaction with intracellular membranes.

A protein extract of microbe cells is studied as a bioelectrocatalyst for glucose oxidation. The microbial protein extract prepared from Escherichia coli BB, which comprises all enzymes of the life cycle of these bacteria, is considered here as a model system. This system demonstrates the mediator mechanism of interaction with an inert glassy-carbon electrode in a buffer containing glucose as the substrate. The efficiency of the bioelectrocatalytic process was shown to depend on the type of mediator system and also on the nature of buffer, its temperature, pH, and ionic strength. The protein extract is shown to contain NAD-dependent Fe-glucosodehydrogenase and demonstrate the current densities in mediator-assisted glucose oxidation well comparable with the known data for pure dehydrogenase enzymes and E. coli microbial systems. The prospects for further studies and practical applications of this new bioelectrocatalyst type are outlined.

The biological activity of a series of sulfur-nitrosyl iron complexes (NICs) depends on the structure of the ligands and the position of the functional groups in the aromatic ring of the ligand. Differences in susceptibility of the gram-positive and gram-negative bacteria to the NICs was found. The series of the studied NICs suppresses the formation of biofilms of Micrococcus luteus bacteria. The obtained results demonstrate that the studied complexes can serve as the basis for the preparation of antibacterial agents.

Activities of superoxide dismutase and catalase and content of reduced glutathione in cells of drug-resistant murine leukemia P388 strains were studied without or after administration of antitumor compounds. In the absence of chemotherapeutic agents, no significant differences in activities of the studied enzymes in cells of the initial strain and strains resistant to cyclophosphamide, cisplatin, and rubomycin were observed. Compounds to which resistance was developed did not significantly affect activity of enzymes in cells of drug-resistant strains, while the use of compounds that were not resistance inductors was accompanied by a significant decrease in enzyme activity in cells resistant to cisplatin and rubomycin. In cells of strains resistant to cisplatin and cyclophosphamide, the content of reduced glutathione significantly differed from that in the initial strain. In addition, the concentration of reduced glutathione in cells of cyclophosphamide-resistant strain considerably decreased upon addition of the drug producing a therapeutic effect. Our findings suggest that the mechanism of resistance of in vivo derived cyclophosphamide resistant cell strain is related to increased level of reduced glutathione and activity of its metabolism.