Effects of the modification of gas diffusion electrodes by organic redox catalysts for hydrogen peroxide electrosynthesis

This paper reports a comparative study of the electrochemical performance of in situ hydrogen peroxide electrogeneration on gas diffusion electrodes modified by organic redox catalysts 2-ethylanthraquinone, 2-terc-butylanthraquinone and azobenzene in medium of 0.1 mol L-1 H2SO4 plus 0.1 mol L-1 K2SO4, pH = 1. Hydrogen peroxide generation proved strongly dependent on the applied potential and on the concentration of added catalysts. Electrode modifications led to a significant increase in H2O2 yield (30%) reaching 850 mg L-1, and the overpotential for oxygen reduction shifted to less negative values (400 mV vs Ag/AgCl for electrodes modified by quinones and 300 mV vs Ag/AgCl for electrodes modified by azobenzene) compared to noncatalyzed gas diffusion electrodes, resulting in reduced energy consumption of 596.5 to 232.4 kWh kg-1. The results indicated that the best electrode for H2O2 electrogeneration is the gas diffusion electrode modified with 10% of 2-ethylanthraquinone, offering the best cost to benefit ratio.Este trabalho apresenta um estudo comparativo da eficiência eletroquímica na eletrogeração de peróxido de hidrogênio in situ usando eletrodos da difusão gasosa modificados com os catalisadores orgânicos redox: 2-etilantraquinona, 2-terc-butilantraquinona e azobenzeno em meio de 0,1 mol L-1 H2SO4 + 0,1 mol L-1 K2SO4, pH = 1. A produção de peróxido de hidrogênio está diretamente relacionada ao potencial aplicado e a concentração dos catalisadores adicionados. A modificação dos eletrodos resultou em um aumento significativo no rendimento de H2O2 (30%) alcançando 850 mg L-1 e o sobrepotencial da reação de redução do oxigênio foi deslocado para valores menos negativos (400 mV vs Ag/AgCl para os eletrodos modificados com quinonas e 300 mV vs. Ag/AgCl para os eletrodos modificados com azobenzeno) comparado ao eletrodo de difusão gasosa não modificado, reduzindo o consumo de energia de 596,5 para 232,4 kWh kg-1. Os resultados indicaram que o melhor eletrodo para a eletrogeração do H2O2 é o eletrodo de difusão gasosa modificado com 10% de 2-etilantraquinona, o qual apresentou a melhor relação custo/benefício.643650Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP

Hydrogen Peroxide Production in an Electrochemical Flow-by Reactor using Gas Diffusion Electrodes Modified with Organic Redox Catalysts

This paper presents a proposal to use an electrochemical flow-by reactor for hydrogen peroxide electrogeneration using cathodes formed from the incorporation of organic redox catalysts (2-ethylanthraquinone, 2-tert-butylanthraquinone, alizarin, and azobenzene) in the structure of gas diffusion electrodes. These electrodes help circumvent the low solubility of oxygen in aqueous solutions. Organic redox catalysts, which typically contain quinone or azo groups in their structure, were added to the electrode mass in a 10% proportion. The electrodes were used to study the electrogeneration of hydrogen peroxide in situ, in an acid medium (0.1 mol L-1 H2SO4 and 0.1 mol L-1 K2SO4, pH 1), inside an electrochemical flow-by reactor. Comparative analysis among the different catalysts indicated that the best electrode for hydrogen peroxide electrogeneration was the gas diffusion electrode modified with 10% of 2-ethylanthraquinone. With an underflow rate of 200 L h-1, hydrogen peroxide was formed with a maximum yield of 998.12 mg L-1 after 2 h at -2.0 V vs Pt//Ag/AgCl, for which the energy consumption was 11.21 kWh kg-1. The use of the electrochemical flow-by reactor was much more efficient, in that it yielded higher concentrations of hydrogen peroxide with extremely low energy consumption, compared to that obtained when using an electrochemical cell. In addition, for ensuring appropriate usage of the electrodes, optimizing their potential for the maximum generation of hydrogen peroxide, and obtaining the highest efficiency for the reduction of oxygen, a fuzzy algorithm was developed to help support the user’s decision

Low adenovirus vaccine doses administered to skin using microneedle patches induce better functional antibody immunogenicity as compared to systemic injection

Adenovirus-based vaccines are demonstrating promising clinical potential for multiple infectious diseases, including COVID-19. However, the immunogenicity of the vector itself decreases its effectiveness as a boosting vaccine due to the induction of strong anti-vector neutralizing immunity. Here we determined how dissolvable microneedle patches (DMN) for skin immunization can overcome this issue, using a clinically-relevant adenovirus-based Plasmodium falciparum malaria vaccine, AdHu5–PfRH5, in mice. Incorporation of vaccine into patches significantly enhanced its thermostability compared to the liquid form. Conventional high dose repeated immunization by the intramuscular (IM) route induced low antigen-specific IgG titres and high anti-vector immunity. A low priming dose of vaccine, by the IM route, but more so using DMN patches, induced the most efficacious immune responses, assessed by parasite growth inhibitory activity (GIA) assays. Administration of low dose AdHu5–PfRH5 using patches to the skin, boosted by high dose IM, induced the highest antigen-specific serum IgG response after boosting, the greatest skewing of the antibody response towards the antigen and away from the vector, and the highest efficacy. This study therefore demonstrates that repeated use of the same adenovirus vaccine can be highly immunogenic towards the transgene if a low dose is used to prime the response. It also provides a method of stabilizing adenovirus vaccine, in easy-to-administer dissolvable microneedle patches, permitting storage and distribution out of cold chain

Effects of the modification of gas diffusion electrodes by organic redox catalysts for hydrogen peroxide electrosynthesis

This paper reports a comparative study of the electrochemical performance of in situ hydrogen peroxide electrogeneration on gas diffusion electrodes modified by organic redox catalysts 2-ethylanthraquinone, 2-terc-butylanthraquinone and azobenzene in medium of 0.1 mol L-1 H2SO4 plus 0.1 mol L-1 K2SO4, pH = 1. Hydrogen peroxide generation proved strongly dependent on the applied potential and on the concentration of added catalysts. Electrode modifications led to a significant increase in H2O2 yield (30%) reaching 850 mg L-1, and the overpotential for oxygen reduction shifted to less negative values (400 mV vs Ag/AgCl for electrodes modified by quinones and 300 mV vs Ag/AgCl for electrodes modified by azobenzene) compared to noncatalyzed gas diffusion electrodes, resulting in reduced energy consumption of 596.5 to 232.4 kWh kg-1. The results indicated that the best electrode for H2O2 electrogeneration is the gas diffusion electrode modified with 10% of 2-ethylanthraquinone, offering the best cost to benefit ratio

A TLR9-adjuvanted vaccine formulated into dissolvable microneedle patches or cationic liposomes protects against leishmaniasis after skin or subcutaneous immunization

Re-emergence and geographic expansion of leishmaniasis is accelerating efforts to develop a safe and effective Leshmania vaccine. Vaccines using Leishmania recombinant antigens, such as LiHyp1, which is mostly present in the amastigote parasite form, are being developed as a next generation to crude killed parasite-based vaccines. The main objective of this work was to develop a LiHyp1-based vaccine and determine if it can induce protective immunity in BALB/c mice when administered using a dissolvable microneedle (DMN) patch by the skin route. The LiHyp1 antigen was incorporated into cationic liposomes (CL), with or without the TLR9 agonist, CpG. The LiHyp1-liposomal vaccines were characterized with respect to size, protein encapsulation rates and retention of their physical characteristics after incorporation into the DMN patch. DMN mechanical strength and skin penetration ability were tested. A vaccine composed of LiHyp1, CpG and liposomes and subcutaneously injected or a vaccine containing antigen and CpG in DMN patches, without liposomes, induced high antibody responses and significant levels of protection against L. donovani parasite infection. This study progresses the development of an efficacious leishmania vaccine by detailing promising vaccine formulations and skin delivery technologies and it addresses protective efficacy of a liposome-based dissolvable microneedle patch vaccine system

Combination oral therapy against Leishmania amazonensis infection in BALB/c mice using nanoassemblies made from amphiphilic antimony(V) complex incorporating miltefosine

8p.-3 fig.-1 tab.Clinically available drugs for mucocutaneous and cutaneous leishmaniases (CL) include mainly pentavalent antimony (Sb(V)) complexes, liposomal amphotericin B, and miltefosine (HePC). However, they present at least one of the following limitations: long-term parenteral administration through repeated doses, severe side effects, drug resistance, and high cost. HePC is the only oral drug available, but the appearance of resistance has resulted in changes of its use from monotherapy to combination therapy. Amphiphilic Sb(V) complexes, such as SbL8 obtained from reaction of Sb(V) with N-octanoyl-N-methylglucamide, were recently found to be orally active against experimental CL. The property of SbL8 to self-assemble in aqueous solution, forming nanostructures, led us to investigate the incorporation of HePC into SbL8 nanoassemblies and the therapeutic efficacy of SbL8/HePC nanoformulation by oral route in a murine model of CL. HePC incorporation into the SbL8 nanosystem was evidenced by using a fluorescent analog of HePC. The antileishmanial activity of SbL8/HePC nanoassemblies was evaluated after daily oral administration for 30 days in Leishmania amazonensis-infected BALB/c mice, in comparison with monotherapies (SbL8 or HePC) and saline control. All the treatments resulted in significant reduction in the lesion size growth, when compared with control. Strikingly, only SbL8/HePC nanoassemblies promoted a significant decrease of the parasite burden in the lesion. This work establishes the therapeutic benefit of SbL8/HePC association by oral route in a CL model and constitutes an important step towards the development of new orally active drug combination.This work was supported by the Brazilian agencies Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq, grant number: 425332/2018–7), Coordenação de Aperfeicoamento de Pessoal de Nível Superior (CAPES, grant number: PNPD20131163), and Fundação de Amparo a Pesquisa do Estado de Minas Gerais (FAPEMIG, grant number: APQ-03129-16) for financial support. F.F. was recipient of fellowship from CNPq (grant number: 305659/2017-0) and Chaire Jean d’Alembert, Université Paris-Saclay, France (ANR-11-IDEX-0003-02). L.R was supported by Program of Redes Temáticas de Investigación Cooperativa RETICS-FEDER (grant number: RD16/0027/0010).Peer reviewe

Degradation of dipyrone by electrogenerated H2O2 combined with Fe2+ using a modified gas diffusion electrode

The aim of the present study was to investigate the electrochemical degradation of dipyrone in a single compartment electrochemical cell equipped with a gas diffusion electrode (GDE) modified with cobalt (II) phthalocyanine. Degradations were performed under conditions of anodic oxidation (GDE pressurized with N-2) and under conditions promoting the electrogeneration of H2O2 (GDE pressurized with O-2) both in the absence and presence of 1 mmol FeSO4.7H2O (electro-Fenton conditions). The efficiency of the electro-Fenton process was satisfactory at all studied potentials, and achieved a maximum reduction of 67% in electrolyte absorbance at 262 nm after 90 min electrolysis at -0.7 V (vs. Ag/ AgCl). The reduction in dipyrone concentration attained 95% after 90 min of reaction with electrogenerated H2O2 in the absence or presence of Fe2+ ions at all potentials except -0.5 V (vs. Ag/ AgCl). The removal of total organic carbon (TOC) was most efficient under electro-Fenton conditions with a decrease of 54.4% in organic load attained at -0.9 V (vs. Ag/AgCl) and energy consumption (EC) of 270 kWh per kg of TOC removed. (C) 2014 The Electrochemical Society. All rights reserved.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES

Eletrodos De Difusão Gasosa Modificados Com Catalisadores Redox, Processo E Reator Eletroquìmico De Sìntese De Peróxido De Hidrogênio Utilizando Os Mesmos

ELETRODOS DE DIFUSÃO GASOSA MODIFICADOS COM CATALISADORES REDOR, PROCESSO E REATOR ELETROQUÍMICO DE SÍNTESE DE PERÓXIDO DE HIDROGÊNIO UTILIZANDO OS MESMOS. A presente invenção se refere a um processo para a síntese de peróxido de hidrogênio em meios com diferentes valores de pH, a eletrodos de difusão gasosa modificados com catalisadores redox e a um equipamento para a reação eletrolítica. Mais especificamente, o presente processo compreendendo as etapas de passagem de energia elétrica (corrente elétrica e/ou potencial elétrico) em uma solução aquosa eletrolitica, entre catodo e anodo, para promover a reação de redução de moléculas de oxigénio gasoso (02) à peróxido de hidrogénio (H202 ou H02); utilização de eletrodos de difusão gasosa (EDG) modificados com catalisadores orgânicos redox, ou equivalentes funcionais, corno catodo, independente do material empregado corno anodo, na síntese de peróxido de hidrogênio, a partir da reação de redução do oxigênio gasoso (O2); e utilização de eletrodos de difusão gasosa (EDG) modificados, simultaneamente, a partir da reação de oxidação da água no anodo. A presente invenção se refere ainda ao projeto, à construção e à operação de equipamentos denominados reatores eletroquinnicos, ou eletrolíticos, que utilizam eletrodos de difusão gasosa. Modificados ou não com catalisadores orgânico redox, ou equivalentes funcionais, como catodo, ou arranjos destes, para promover a síntese de peróxido de hidrogênio.BRPI0600460 (A)C25B1/30BR2006PI00460C25B1/3

Electrocatalysis of hydrogen peroxide generation using oxygen-fed gas diffusion electrodes made of carbon black modified with quinone compounds

Hydrogen peroxide (H2O2) is one of the most popular and widely used oxidants. Among the wide range of synthesis techniques used for the production of H2O2; the electrochemical method allows the use of gas diffusion electrodes to generate H2O2 without limiting the low solubility of O2 in water. The present work reports the modification of carbon black with quinone, where the generation of H2O2 occurs in an electrochemical/chemical mechanism. The results obtained by this technique were found to be highly promising. The use of the organic compound 1,2-dihydroxyanthraquinone to modify carbon black electrode resulted in greater production of H2O2. Carbon black electrode modified with 1% of 1,2-dihydroxyanthraquinone yielded 298 mg L−1 of H2O2 at the end of 90 min of experiment, reaching an electrical efficiency of approximately 25.5%. Based on the findings of this study, H2O2 generation is found to be directly associated with the chemical structure of the carbon modifier and not solely related to the presence of quinone groups113CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQCOORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPESFUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP465571/2014-0, 302874/2017-8 and 427452/2018-00012011/14314-1; 2016/22115-2; 2014/50945-4; 2013/02762-5; 2016/12597-0; 2019/00239-0; 2017/10118-

Nanoassemblies from Amphiphilic Sb Complexes Target Infection Sites in Models of Visceral and Cutaneous Leishmaniases

This work aims to evaluate whether nanoassemblies (NanoSb) made from antimony(V) complexes with octanoyl-N-methylglucamide (SbL8) or decanoyl-N-methylglucamide (SbL10) would effectively target the infection sites in visceral and cutaneous leishmaniases (VL and CL). NanoSb were investigated regarding stability at different pHs, accumulation of Sb in the macrophage host cell and liver, and in vitro and in vivo activities in models of leishmaniasis. The kinetic stability assay showed that NanoSb are stable at neutral pH, but release incorporated lipophilic substance after conformational change in media that mimic the gastric fluid and the parasitophorous vacuole. NanoSb promoted greater accumulation of Sb in macrophages and in the liver of mice after parenteral administration, when compared to conventional antimonial Glucantime®. SbL10 was much more active than Glucantime® against intramacrophage Leishmania amastigotes and less cytotoxic than SbL8 against macrophages. The in vitro SbL10 activity was further enhanced with co-incorporated miltefosine. NanoSb showed high antileishmanial activity in the L. donovani murine VL after parenteral administration and moderate activity in the L. amazonensis murine CL after topical treatment. This study supports the ability of NanoSb to effectively deliver a combination of Sb and co-incorporated drug to host cell and infected tissues, in a better way than Glucantime® does