Electron Spin-Dependent Electrocatalysis for the Oxygen Reduction Reaction in a Chiro-Self-Assembled Iron Phthalocyanine Device

The chiral-induced spin selectivity effect (CISS) is a breakthrough phenomenon that has revolutionized the field of electrocatalysis. We report the first study on the electron spin-dependent electrocatalysis for the oxygen reduction reaction, ORR, using iron phthalocyanine, FePc, a well-known molecular catalyst for this reaction. The FePc complex belongs to the non-precious catalysts group, whose active site, FeN4, emulates catalytic centers of biocatalysts such as Cytochrome c. This study presents an experimental platform involving FePc self-assembled to a gold electrode surface using chiral peptides (L and D enantiomers), i.e., chiro-self-assembled FePc systems (CSAFePc). The chiral peptides behave as spin filters axial ligands of the FePc. One of the main findings is that the peptides' handedness and length in CSAFePc can optimize the kinetics and thermodynamic factors governing ORR. Moreover, the D-enantiomer promotes the highest electrocatalytic activity of FePc for ORR, shifting the onset potential up to 1.01 V vs. RHE in an alkaline medium, a potential close to the reversible potential of the O2 /H2 O couple. Therefore, this work has exciting implications for developing highly efficient and bioinspired catalysts, considering that, in biological organisms, biocatalysts that promote O2 reduction to water comprise L-enantiomers.

Nurse follow-up visit after the atrial complex ablation: a cross-sectional descriptive study

Funding Acknowledgements

Type of funding sources: None.

Background

Atrial fibrillation (AF) and flutter are complex arrhythmias to ablation because their anatomical location. A navigation system is required to map the ablationable area and in addition, the patient are under general anesthesia. In our hospital, the expert nurse control these patients 10 days afters discharge.

Purpose

To identify the complications and recurrences of arrhythmia that the nurse has detected early and how it has been managed.

Methods

Cross-sectional descriptive study, from September 2020 to January 2022, all patients who underwent complex atrial ablation under total anaesthesia and who were assessed by a nurse 10 days later were included. In the event that any problem arises, the nurse is in charge of managing the network of referrals to specialist doctors.

Results

A total of 159 patients were included with a mean age of 62 years (SD 10.4) and 34% were women. Arrhythmias were 73.5% AF, 11.3% flutter, 14.5% re-do ablations mixed AF/Flutter. CHA2DS2-VASc scale mean 2 points (SD 1.2). Nine cardioversions were scheduled due to early AF recurrence documented. 35% (n=55) of the patients underwent a blood test to control risk factors such as cholesterol, diabetes, kidney failure or thyroid problems. 17.6% (n=28) were programmed for a polysomnography. Cardiologist was consulted in 6.3% (n=10) due to edema of the lower legs, ventricular extrasystoles, asthenia and bradycardia. Interconsultations were also made with endocrinology 1.2%, urology 0.6%, vascular surgery 6.2% and neurology 2.5%. Finally, 12% of patients were referred to their GP for minor controls.

Conclusion

There is little evidence to suggest that nursing consultation could be useful for the early detection of complications and the management of arrhythmia recurrences. More experimental studies are necessary to know the impact of nurse follow-up in the management of patients undergoing complex atrial ablation.

Selective growth of palladium and titanium dioxide nanostructures inside carbon nanotube membranes

Hybrid nanostructured arrays based on carbon nanotubes (CNT) and palladium or titanium dioxide materials have been synthesized using self-supported and silicon-supported anodized aluminum oxide (AAO) as nanoporous template. It is well demonstrated that carbon nanotubes can be grown using these membranes and hydrocarbon precursors that decompose at temperatures closer to 600°C without the use of a metal catalyst. In this process, carbonic fragments condensate to form stacked graphitic sheets, which adopt the shape of the pores, yielding from these moulds' multi-walled carbon nanotubes. After this process, the ends of the tubes remain open and accessible to other substances, whereas the outer walls are protected by the alumina. Taking advantage of this fact, we have performed the synthesis of palladium and titanium dioxide nanostructures selectively inside carbon nanotubes using these CNT-AAO membranes as nanoreactors.

Growth of carbon nanostructures using a Pd-based catalyst

Carbon nanostructures were synthesized by decomposition of different carbon sources over an alumina supported palladium catalyst via Chemical Vapor Deposition (CVD). Several experimental conditions were varied to verify their influence in the synthesis products: temperature ramping rate, pre-annealing conditions, hydrogen pre-treatment, synthesis temperature and time, together with the use of different carbon sources. Depending on the experimental conditions carbon nanotubes and nanofibers with different shapes and structural characteristics were obtained. Straight, coiled and branched morphologies are the most common. Among our findings, the addition of hydrogen plays a significant role in the structure of the carbonaceous products. For example, the decomposition of acetylene on palladium catalysts at 800 degrees C in the absence of hydrogen produces only carbon micro- spheres as synthesis products. The incorporation of increasing amounts of hydrogen modifies the outcome, from thick fibers to carbon nanotubes. To verify the level of graphitization of the synthesis products we have used high resolution transmission electron microscopy (HRTEM) in addition to Raman spectroscopy. Our results, based on these complementary techniques, indicate the decomposition of acetylene on a palladium based catalyst, produces the best degree of graphitization in carbon nanotubes for a temperature of 800 degrees C and 100 cc/min of hydrogen flow. Similar hydrogen flows on the same catalyst, produced highly graphitized nanofibers by the decomposition of methane at 850 degrees C.

Growth morphology and spectroscopy of multiwall carbon nanotubes synthesized by pyrolysis of iron phthalocyanine

Carbon nanotubes (CNTs) were synthesized by Chemical Vapor Deposition (CVD) from the pyrolytic decomposition of Iron Phthalocyanine (FePc) molecules, on SiO2/Si(111) substrates in the presence of a hydrogen flow. FePc molecules contribute simultaneously both to the formation of the precursor Fe nanoparticles and also as a Carbon source. Different experimental conditions were examined. Samples were characterized by scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, and inverse photoemission. The resulting samples are highly oriented multiwall carbon nanotubes films, with heights in the range between: 4 and 20 microm. The tubes diameter is strongly dependent on growth temperature. Our experimental results show evidence of a transition in the growth mechanism, from a tip growth to a base growth mode, as the decomposition temperature is increased. Preliminary spectroscopic measurements performed on these MWCNTs, show the unoccupied density of states has several resonances close to Fermi level, related both to the graphene electronic structure and the formation of the tube.

Association between the NOS3 (-786 T/C) and the ACE (I/D) DNA genotypes and early coronary artery disease

DNA polymorphisms at the endothelium constitutive nitric oxide synthase gene (NOS3) have been linked to the risk of developing coronary artery disease (CAD). In vitro, a polymorphism in the 5' region of the NOS3 gene (-786 T/C) influences promoter activity. This polymorphism has been associated with coronary spasms among Japanese. The genetic variation at the angiotensin-converting enzyme (ACE) is associated with plasma ACE activities and has also been linked with susceptibility to cardiovascular disease. Our objective was to determine if DNA polymorphisms in the NOS3 and ACE genes were associated with early CAD. We analyzed the -786 T/C polymorphism in the 5' flanking region and the 27-bp repeat polymorphism in NOS3 intron 4, as well as the ACE-I/D polymorphism. A total of 170 male smokers (CAD patients) younger than 50 years and 300 male smokers (healthy controls) were genotyped. Frequencies were compared by the chi(2) test, and odds ratios (ORs) and their 95% confidence intervals (CI) were also calculated. Only the -786 T/C polymorphism in the 5' flanking region of the NOS3 gene was significantly associated with early CAD in our population. The frequency of the CC genotype was significantly increased (P = 0.039) in patients compared to controls (OR = 1.67; 95% CI = 1.01, 2.72). We found a synergistic effect between the NOS3-CC and the ACE-DD genotypes in the risk of developing early CAD. The frequency of CC + DD was significantly increased among patients (P = 0.002). Thus, those with a NOS3-CC and an ACE-DD genotype would have a significantly increased risk of suffering an early episode of coronary artery disease (OR = 2.82; 95% CI = 1.40, 5.70). Although based on a limited number of patients, our work suggests that individuals who are NOS3-CC + ACE-DD are at a higher risk for early CAD, probably as a consequence of increased endothelial dysfunction.

Synergistic effect between apolipoprotein E and angiotensinogen gene polymorphisms in the risk for early myocardial infarction

BACKGROUND

Several studies based on different populations worldwide have described an association between cardiovascular diseases and genetic variations in the apolipoprotein E (A:POE), angiotensinogen (A:GT), angiotensin receptor type 1 (A:T1R), and angiotensin-converting enzyme (A:CE) genes. In addition, there is growing evidence of an interaction between hypercholesterolemia and the renin-angiotensin system in the risk for hypertension and atherosclerosis.

METHODS

To determine whether the DNA polymorphisms in A:POE (epsilon2, epsilon3, and epsilon4 alleles), A:GT (M235T), A:T1R (1166 A:/C:), and ACE (I:/D:) are associated with early onset of myocardial infarction (MI), we genotyped 220 patients and 200 controls <55 years of age. Patients and controls were males from the same homogeneous Caucasian population. Data concerning hypertension, diabetes, and tobacco consumption were recorded. The lipid profiles of patients and controls were also determined.

RESULTS

APOE, ACE, AGT, and AT1R allele and genotype frequencies did not differ between patients and controls. None of these polymorphisms was related to the biochemical values in patients or controls. The frequency of individuals who were both APOE epsilon4 allele carriers and AGT-TT homozygotes was significantly higher in patients than in controls (11% vs 3.5%; P: = 0.0037). In patients, the frequency of epsilon4 carriers was significantly higher (P: <0.00001) in those who were AGT-TT (46%) than those who were AGT-MT/MM (14%). Mean cholesterol was significantly higher in AGT-TT + APOE epsilon34/44 patients than in the TM/MM + epsilon34/44 or TT + epsilon23/33 genotypes (P: = 0. 029).

CONCLUSIONS

Our data suggest a synergistic effect between the APOE and AGT polymorphisms and early MI. The increased risk could be mediated in part through higher cholesterol concentrations among individuals who are AGT-TT + APOE epsilon4 allele carriers.

Apolipoprotein A1 gene polymorphisms and risk of early coronary disease

Genetic studies have identified polymorphisms at the apolipoprotein (Apo) A1 gene associated with HDL cholesterol and apolipoprotein levels, and a relationship between the severity of coronary artery disease and polymorphisms at the 5'-end of Apo A1 has been also reported. This study was designed to examine the relationship between polymorphism at the Apo A1 gene and the risk of early coronary artery disease. Furthermore, the association of the polymorphism with the classical risk factors was analyzed. A total of 176 male patients (mean age 43 +/- 5 years) diagnosed as having unstable angina (53 cases) or myocardial infarction (123 cases) were prospectively evaluated. Data referring to hypertension, diabetes and tobacco consumption were recorded. The levels of total cholesterol, HDL cholesterol, Apo A1 and B and triglycerides were determined. DNA was obtained from the 176 patients and from 200 controls. In order to determine the Apo A1 genotypes at two polymorphic sites (G/A at -75 bp, and C/T at +83 bp), DNA was PCR amplified and digested with MspI. The frequency of carriers of the rare allele at the -75 bp site (M1-) was 0.34 in cases and 0.24 in controls (p < 0.05). The frequencies of the M1- allele among patients with angina and myocardial infarction were 0.43 (p = 0.009, angina vs. controls) and 0.30, respectively. No significant association between this polymorphism and other cardiovascular risk factors was found. No difference in the frequencies for carriers of the rare allele at the +83-bp polymorphism (M2) was observed among patients with angina (0.08 vs. 0.07) or myocardial infarction (0.04 vs. 0.07), and no association between this polymorphism and tobacco, hypertension and diabetes was noted. Patients carrying the rare M2- allele had a lower concentration of total cholesterol compared to those without this allele (183 +/- 29 vs. 223 +/- 54, p < 0.04) and HDL cholesterol was also lower among patients carrying the M2- (26 +/- 4 vs. 33 +/- 9, p < 0.02). In our community male patients with a diagnosis of coronary artery disease and age less than 50 years showed a higher frequency of the M1- allele at the -75-bp site of the Apo A1 gene. There was a significant increase in the frequency of the M1- allele in patients with unstable angina and no association with risk factors. In the +83-bp polymorphism there was no difference in the allelelic frequencies or the risk factors, except for the HDL cholesterol and total cholesterol where the patients with the allele M2- had lower levels than those homozygous for the M2+.

Immune complex-mediated haemolytic anaemia and Evans syndrome induced by diclofenac

BACKGROUND AND OBJECTIVES

Sodium diclofenac is one of the most widely used nonsteroidal anti-inflammatory drugs. Cases of acute haemolytic anaemia have been ascribed to the drug. We describe such a case, mediated by immune complexes.

MATERIALS AND METHODS

Standard serologic tests were carried out for blood grouping and the detection and identification of red cell allo- and autoantibodies. Drug-anti-drug complexes were detected with an ex-vivo method.

RESULTS

Warm IgG drug-independent red cell and platelet autoantibodies were detected in the serum. At first, the patient was diagnosed as having the Evans syndrome, and corticosteroids were administered. Later, because of the severity of the anaemia, the possibility of an immune complex mechanism was considered. This was confirmed by the detection of diclofenac-dependent antibodies that reacted with RBC only in the presence of urine from a volunteer receiving diclofenac as a source of ex-vivo antigen. The antibodies neither reacted with an in-vitro solution of the drug nor with the volunteer's serum. Diclofenac and corticosteroids were stopped, and the clinical condition of the patient completely normalised within 15 days.

CONCLUSIONS

We describe a patient with acute haemolytic anaemia caused by diclofenac through an immune complex mechanism.