Liliana P. Ferreira

Effects of Sitagliptin Treatment on Dysmetabolism, Inflammation, and Oxidative Stress in an Animal Model of Type 2 Diabetes (ZDF Rat)

The purpose of this paper is to evaluate the chronic effect of sitagliptin on metabolic profile, inflammation, and redox status in the Zucker Diabetic Fatty (ZDF) rat, an animal model of obese type 2 diabetes. Diabetic and obese ZDF (fa/fa) rats and their controls (ZDF +/+) were treated during 6 weeks with vehicle (control) and sitagliptin (10 mg/kg/bw). Glucose, HbA1c, insulin, Total-c, TGs, IL-1β, TNF-α, CRPhs, and adiponectin were assessed in serum and MDA and TAS in serum, pancreas, and heart. Pancreatic histology was also evaluated. Sitagliptin in diabetic rats promoted a decrease in glucose, HbA1c, Total-c, and TGs accompanied by a partial prevention of insulinopenia, together, with a decrease in CRPhs and IL-1β. Sitagliptin also showed a positive impact on lipid peroxidation and hypertension prevention. In conclusion, chronic sitagliptin treatment corrected the glycaemic dysmetabolism, hypertriglyceridaemia, inflammation, and hypertension, reduced the severity of the histopathological lesions of pancreatic endocrine and exocrine tissues, together with a favourable redox status, which might be a further advantage in the management of diabetes and its proatherogenic comorbidities.

Synthesis and Reactivity of Four- and Five-Coordinate Low-Spin Cobalt(II) PCP Pincer Complexes and Some Nickel(II) Analogues

Anhydrous CoCl2 or [NiCl2(DME)] reacts with the ligand PCPMe-iPr (1) in the presence of nBuLi to afford the 15e and 16e square planar complexes [Co(PCPMe-iPr)Cl] (2) and [Ni(PCPMe-iPr)Cl] (3), respectively. Complex 2 is a paramagnetic d7 low-spin complex, which is a useful precursor for a series of Co(I), Co(II), and Co(III) PCP complexes. Complex 2 reacts readily with CO and pyridine to afford the five-coordinate square-pyramidal 17e complexes [Co(PCPMe-iPr)(CO)Cl] (4) and [Co(PCPMe-iPr)(py)Cl] (5), respectively, while in the presence of Ag+ and CO the cationic complex [Co(PCPMe-iPr)(CO)2]+ (6) is afforded. The effective magnetic moments μeff of all Co(II) complexes were derived from the temperature dependence of the inverse molar magnetic susceptibility by SQUID measurements and are in the range 1.9 to 2.4 μB. This is consistent with a d7 low-spin configuration with some degree of spin–orbit coupling. Oxidation of 2 with CuCl2 affords the paramagnetic Co(III) PCP complex [Co(PCPMe-iPr)Cl2] (7), while the synthesis of the diamagnetic Co(I) complex [Co(PCPMe-iPr)(CO)2] (8) was achieved by stirring 2 in toluene with KC8 in the presence of CO. Finally, the cationic 16e Ni(II) PCP complex [Ni(PCPMe-iPr)(CO)]+ (10) was obtained by reacting complex 3 with 1 equiv of AgSbF6 in the presence of CO. The reactivity of CO addition to Co(I), Co(II), and Ni(II) PCP square planar complexes of the type [M(PCPMe-iPr)(CO)]n (n = +1, 0) was investigated by DFT calculations, showing that formation of the Co species, 6 and 8, is thermodynamically favorable, while Ni(II) maintains the 16e configuration since CO addition is unfavorable in this case. X-ray structures of most complexes are provided and discussed. A structural feature of interest is that the apical CO ligand in 4 deviates significantly from linearity, with a Co–C–O angle of 170.0(1)°. The DFT-calculated value is 172°, clearly showing that this is not a packing but an electronic effect.

Hyperthermia studies of ferrite nanoparticles synthesized in the presence of cotton

MFe2O4 (M = Co, Fe, Mn) compounds were synthesized using hydrothermal treatment in the presence of medicinal cotton. Two sets of nanoparticles were produced for each composition and subsequently characterized by XRD, TEM and SEM. The nanoparticles obtained from the solution display the expected spinel structure and different mean sizes (below 16 nm); the nanoparticles embedded in cotton were subjected to a calcination process for cotton elimination. Regarding these calcinated samples, the spinel structure was maintained for CoFe2O4, a mixture of phases was identified for the M = Mn sample and, in the case of iron, the magnetite phase was converted to hematite (α-Fe2O3). After cotton elimination the samples exhibit a morphology which evidences the role of cotton as a template. To evaluate the quality of the nanoparticles for hyperthermia, SQUID magnetometry and Mossbauer spectroscopy were used to perform the magnetic characterization of all products, and the specific loss power (SLP) was determined by induction heating measurements. All the ferrite NP obtained by hydrothermal synthesis in the presence of cotton display good hyperthermia performance. MnFe2O4 nanoparticles exhibit the highest SLP value, 90 W g−1, followed by Fe3−xO4, and CoFe2O4. In the case of CoFe2O4, the specific loss power of the NP obtained after cotton elimination is enhanced by 50% which is explained by the NP morphology adopted from the cotton template during the synthesis.

A study of muon localization and diffusion in Hf2Co and Hf2CoH3

Muon spin relaxation ( mu SR) experiments were carried out in zero field on polycrystalline samples of Hf2Co and Hf2CoH3. In the unhydrided alloy the muon preferentially occupies octahedral interstices and diffuses through a tunnelling mechanism within the network made of adjacent octahedra above 220 K. In contrast, the muon occupies tetrahedral interstices in the hydrided alloy. Muon diffusion takes place through two distinct phonon-assisted tunnelling mechanisms with a possible contribution of overbarrier hopping above 250 K and appears to be strongly enhanced hy the presence of hydrogen. This effect is attributed to the different pathways taken by the muon in hydrided and unhydrided Hf2Co. A comparison with the hydrogen jump rate measured by perturbed angular correlation in the same hydride provides confirmation that the hydrogen mobility is indeed faster than that of the muon, which appears to be a quite general result in concentrated metallic hydrides.

Electrochemical studies and potential anticancer activity in ferrocene derivatives

Abstract Several ferrocene derivatives (five mononuclear and two binuclear), including the new N-(p-chlorophenyl)-carboxamidoferrocene (1), were synthesized and their anticancer activity investigated. Two of them, 3 and 7, bearing a benzimidazole backbone were the most active against HeLa cells achieving IC50 values of ~5 μM along with 4 with a dipyridylamine ligand (~6 μM). Complex 6, also with a benzimidazole backbone, displayed slightly higher values (~11 μM). Cyclic voltammetry studies show that while the non-cytotoxic ferrocene derivatives 1, 2, and 5 follow a ferrocene-based redox behavior, derivatives 3, 4, 6, and 7 exhibit a more complex mechanism. These complex mechanisms are consistent with a more effective cytotoxic activity. Mössbauer spectroscopy parameters reflect a very small influence of the substituents.

A magnetization and neutron powder diffraction study of compounds (R = Y, Dy, Ho, Er)

Neutron powder diffraction experiments and magnetic measurements were performed on compounds of the series (R = Y, Dy, Ho and Er). The influence of the R element on both the structural and the magnetic properties of the different compounds is discussed, as well as the possible correlation between the iron environments and the local moments. Comparison is made with a previous Mossbauer study on the same compounds.

Gelatine-assisted synthesis of magnetite nanoparticles for magnetic hyperthermia

Magnetite nanoparticles were synthesized by the co-precipitation method exploring the use of gelatine and agar as additives. For comparison, magnetite nanoparticles were also prepared by standard co-precipitation, by co-precipitation with the addition of a surfactant (sodium dodecyl sulphate) and by the thermal decomposition method. The structure and morphology of the synthesized nanoparticles were investigated by powder X-ray diffraction and transmission electron microscopy. Their magnetic properties were studied by SQUID magnetometry and 57Fe Mössbauer spectroscopy. The nanoparticles potential for applications in magnetic hyperthermia was evaluated through heating efficiency under alternating magnetic field. The results show that all synthesis methods produce Fe3−xO4 nanoparticles with similar sizes. The nanoparticles synthesized in the gelatine medium display the narrowest particle size distribution, the lowest oxidation degree, one of the highest saturation magnetization values and the best hyperthermia efficiency, proving that this gelatine-assisted synthesis is an efficient, environmental friendly, and low-cost method to produce magnetite nanoparticles.Graphical AbstractA new gelatine-assisted method is an efficient and low-cost way to synthesize magnetite nanoparticles with enhanced magnetic hyperthermia.

Di- versus Trinuclear Copper(II) Cryptate for the Uptake of Dicarboxylate Anions

Searching for receptors selective for the binding of dicarboxylate anions, the copper(II) complexes of the known ditopic octaazacryptand (t2pN8), derived from bistren [tren = tris(2-aminoethyl)amine] linked by p-xylyl spacers, were re-examined, with the expectation of observing a selective binding of oxalate or malonate by bridging the two copper centers of the [Cu2(t2pN8)(H2O)2](4+) receptor. Solution studies involving the supramolecular species formed by the receptor and oxalate (oxa(2-)), malonate (mal(2-)), and succinate (suc(2-)) anions are reported. The determined association constants revealed the unexpected formation of a 3:1:1 Cu/t2pN8/anion stoichiometry for the cascade species with oxa(2-) and mal(2-), and the single crystal X-ray structural characterization confirmed the presence of tricopper(II) complexes, with an unusual binding mode for the dicarboxylate anions. Each of the two copper atoms binds four nitrogen donor atoms of the t2pN8 cryptand and one additional hydroxide group, which bridges to the third copper. The square planar environment of this one is complete with two oxygen atoms from the oxalate (or the malonate). The two copper centers bound to the tren heads are ∼6.5 Å apart, each one at about 3.5 Å from the third Cu center. These studies were complemented by SQUID magnetization measurements and DFT calculations. The magnetic susceptibility measurements of the oxalate cascade complex showed a strong magnetic coupling (J = - 210 cm(-1)) between the Cu centers at a short distance (3.5 Å), while the coupling between the two equivalent Cu atoms (∼6.5 Å) was only -70 cm(-1). This result was well reproduced by DFT calculations.

Six-coordinate high-spin iron(II) complexes with bidentate PN ligands based on 2-aminopyridine – new Fe(II) spin crossover systems

Several new octahedral iron(ii) complexes of the type [Fe(PN(R)-Ph)2X2] (X = Cl, Br; R = H, Me) containing bidentate PN(R)-Ph (R = H, Me) (1a,b) ligands based on 2-aminopyridine were prepared. (57)Fe Mössbauer spectroscopy and magnetization studies confirmed in all cases their high spin nature at room temperature with magnetic moments very close to 4.9μB reflecting the expected four unpaired d-electrons in all these compounds. While in the case of the PN(H)-Ph ligand an S = 2 to S = 0 spin crossover was observed at low temperatures, complexes with the N-methylated analog PN(Me)-Ph retain an S = 2 spin state also at low temperatures. Thus, [Fe(PN(H)-Ph)2X2] (2a,3a) and [Fe(PN(Me)-Ph)2X2] (2b,3b) adopt different geometries. In the first case a cis-Cl,P,N-arrangement seems to be most likely, as supported by various experimental data derived from (57)Fe Mössbauer spectroscopy, SQUID magnetometry, UV/Vis, Raman, and ESI-MS as well as DFT and TDDFT calculations, while in the case of the PN(Me)-Ph ligand a trans-Cl,P,N-configuration is adopted. The latter is also confirmed by X-ray crystallography. In contrast to [Fe(PN(Me)-Ph)2X2] (2b,3b), [Fe(PN(H)-Ph)2X2] (2a,3a) is labile and undergoes rearrangement reactions. In CH3OH, the diamagnetic dicationic complex [Fe(PN(H)-Ph)3](2+) (5) is formed via the intermediacy of cis-P,N-[Fe(κ(2)-P,N-PN(H)-Ph)2(κ(1)-P-PN(H)-Ph)(X)](+) (4a,b) where one PN ligand is coordinated in a κ(1)-P-fashion. In CH3CN the diamagnetic dicationic complex cis-N,P,N-[Fe(PN(H)-Ph)2(CH3CN)2](2+) (6) is formed as a major isomer where the two halide ligands are replaced by CH3CN.

Magnetic phase transitions in RFe9.5Mo2.5 intermetallics studied by 57Fe Mössbauer spectroscopy, magnetisation and μ+SR

Abstract A series of RFe 12− x M x -type alloys were stabilised with M = Mo and x = 2.5 for R = Y, Nd, Dy and Er. Magnetisation, ac susceptibility measurements and μ + SR spectroscopy results are in good agreement with a systematic 57 Fe Mossbauer spectroscopy analysis. The strength of all local iron magnetic moments (and the related hyperfine fields), as well as the long range magnetic ordering, have been found to be markedly affected by the substitution of iron by molybdenum in Fe(8i) sites. It was found that the temperature dependence of the order/disorder phenomenology is well described by local magnetic correlation.