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1.
Environ Res ; 258: 119371, 2024 Jun 13.
Artículo en Inglés | MEDLINE | ID: mdl-38876420

RESUMEN

Cu2ZnSnS4 (CZTS) was synthesized following hot injection method and the process was optimized by varying temperature conditions. Four samples at different temperatures viz., 200, 250, 300 and 350 °C were prepared and analyzed using different characterization techniques. Based on the correlation between XRD, Raman and XPS, we conclude that the formation of ZnS and SnS2 occurs at 350 °C but at 200 °C there is no breakdown of the complex as per XRD. According to Raman and XPS analysis, as the temperature rises, the bonds between the metals become weaker, which is visibly seen in Raman and XPS due to the minor peaks of copper sulfide. Scanning electron microscopic analysis confirmed nanometric particles which increase in size with temperature. The photocatalytic evaluation showed that CZTS synthesized at 200 °C performed efficiently in the removal of the two colorants, methylene blue and Rhodamine 6G, achieving 92.80% and 90.65%, respectively. The photocatalytic degradation efficiencies decreased at higher temperatures due to bigger sized CZTS particles as confirmed by SEM results. Computational simulations confirm that CZTS has a highly negative energy -25,764 Ry, confirming its structural stability and higher covalent than ionic character.

2.
J Eur Acad Dermatol Venereol ; 34(2): 349-356, 2020 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-31566809

RESUMEN

BACKGROUND: Mucosal involvement is frequently seen in cutaneous lupus erythematosus (CLE) and systemic lupus erythematosus (SLE). There is no consensus regarding the prevalence, and a wide range of lesions has been reported. Its prognostic significance is currently unknown and a matter of controversy. OBJECTIVE: To classify oral lesions in lupus, evaluate their prevalence and assess their possible association with disease activity. METHODS: We conducted a descriptive study between 2016 and 2017. A total of 150 lupus patients were matched by sex, age and smoking status with 151 healthy individuals. All subjects underwent a careful evaluation of oral mucosa. On the same day of the clinical assessment, each patient underwent a peripheral venous blood and urine analysis. All patients underwent a full medical history, physical examination and a careful examination of the oral cavity. For each one, we obtained photographs of ten areas of the oral cavity. Two dermatologists of our group blindly recorded the presence and morphology of oral lesions. The disease activity of CLE patients was scored using the Revised Cutaneous Lupus Erythematosus Disease Area and Severity Index, and in SLE patients, activity was measured using the Systemic Lupus Erythematosus Disease Activity Index. RESULTS: In CLE patients, there was a statistically significant correlation between higher cutaneous disease activity and the following oral findings: discoid plaques, cobblestone and red/brown-pigmented macules. In patients with CLE, red macules on jugal mucosa were statistically associated with anaemia and positive antinuclear antibodies titres; additionally, the presence of gingivitis was related to systemic inflammation. In SLE patients, gingival telangiectases were statistically significantly associated with leucopenia, hypocomplementemia and systemic inflammation. LIMITATIONS: Biopsies on mucosal lesions were not performed. CONCLUSION: Some specific oral lesions correlate with disease activity in CLE and SLE.


Asunto(s)
Lupus Eritematoso Cutáneo/complicaciones , Lupus Eritematoso Sistémico/complicaciones , Enfermedades de la Boca/complicaciones , Adulto , Femenino , Humanos , Masculino , Persona de Mediana Edad , Mucosa Bucal/patología
3.
Nanotechnology ; 30(2): 025601, 2019 Jan 11.
Artículo en Inglés | MEDLINE | ID: mdl-30387444

RESUMEN

Polyacrylonitrile nonwovens intercalated with graphene oxide (GO) sheets were prepared by a simultaneous electrospinning-spray deposition system. These hybrid nonwovens were carbonized in a two-stage process to obtain a mesostructured hybrid carbon containing carbon nanofibers (CNF) and reduced GO sheets (CNF/RGO). During the carbonization process, the CNF act as spacers between the RGO layers to prevent their compactation and restacking resulting in a three-dimensional structure. The presence of RGO increases the electrical conductivity in the CNF/RGO material. The resulting hybrid carbon is nitrogen-doped as indicated by x-ray photoelectron spectroscopy and Fourier transformed infrared spectroscopy. This N-doped porous carbon was used to prepare electrodes with improved sensitivity for the electrochemical detection of L-cysteine.

4.
Zygote ; 27(6): 398-404, 2019 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-31576792

RESUMEN

Quality of in vitro-produced embryos is influenced by changes in gene expression in response to adverse conditions. Gene markers for predicting 'good embryos' do not exist at present. We propose that the expression of pluripotency markers OCT4-SOX2-NANOG in D9 (day 9) bovine demi-embryos correlated with development at D13 (day 13). Day 8 in vitro-produced blastocysts were split in two cloned halves, one half (D9) was subjected to analysis of pluripotency markers and the other was kept in culture until D13 of development. Embryo development was scored and correlated with its own status at D9 and assigned to one of two categories: G1, arrested/dead; or G2, development up to D13. SOX2 and NANOG expression levels were significantly higher in embryos from G1 and there was also negative correlation between SOX2 and embryo survival to D13 (G3; r = -0.37; P = 0.03). We observed a significant reduction in the expression of the three studied genes from D9 to D13. Furthermore, there was a correlation between the expression of pluripotency markers at D9 and embryo diameter and the expression of trophoblastic markers at D13 (TP1-EOMES-FGF4-CDX2-TKDP1). Finally, the quotient between the relative expression of SOX2 and OCT4 in the D9 blastocysts from G1 and G2 showed that embryos that were considered as competent (G2) had a quotient close to one, while the other group had a quotient of 2.3 due to a higher expression of SOX2. These results might indicate that overexpression of SOX2 at the blastocyst stage had a negative effect on the control of embryonic developmental potential.


Asunto(s)
Blastocisto/metabolismo , Técnicas de Cultivo de Embriones/métodos , Embrión de Mamíferos/metabolismo , Desarrollo Embrionario/genética , Regulación del Desarrollo de la Expresión Génica , Factores de Transcripción SOXB1/genética , Animales , Blastocisto/citología , Bovinos , Embrión de Mamíferos/citología , Embrión de Mamíferos/embriología , Femenino , Factores de Tiempo
5.
Clin Exp Dermatol ; 42(1): 14-20, 2017 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-27943384

RESUMEN

BACKGROUND: An algorithm based on measurement of a serum tumour necrosis factor antagonists (anti-TNF) and antidrug antibodies (ADA) has been proposed previously to guide dose escalation or therapy switching in the early (i.e. the first months of) treatment of psoriasis by anti-TNF. In long-term treatment of responding patients with psoriasis, it is usual to empirically reduce standard doses of anti-TNF to reduce exposure while maintaining clinical response. The relationship between serum anti-TNF, ADA levels and clinical efficacy in long-term treated patients with psoriasis has not yet been determined, so the potential role of these parameters in guiding dose escalation in this scenario is unknown. AIMS: To evaluate the relationship between drug/ADA levels and clinical efficacy in a group of patients with psoriasis undergoing long-term treatment with adalimumab or etanercept. METHODS: This was a single-centre, prospective, cohort study of patients with psoriasis receiving adalimumab or etanercept for a minimum of 48 weeks. All patients were started on the standard dose, but some adalimumab users had a reduced frequency of administration. Clinical efficacy was measured using the Psoriasis Area and Severity Index. Serum concentrations were measured by ELISA. Clinical assessment and blood sample collection were carried out simultaneously within 24 h before the next drug administration. RESULTS: In total, 21 patients were enrolled (67 simultaneous clinical and serum determinations: 38 receiving adalimumab, 29 receiving etanercept). We did not find any association between serum anti-TNF levels and clinical response. None of the patients developed ADA. CONCLUSIONS: ADA and anti-TNF levels are not related to clinical effectiveness in patients with psoriasis undergoing long-term treatment with adalimumab or etanercept.


Asunto(s)
Adalimumab/farmacocinética , Anticuerpos/inmunología , Etanercept/farmacocinética , Factor de Necrosis Tumoral alfa/sangre , Adalimumab/administración & dosificación , Adalimumab/inmunología , Adulto , Anciano , Antiinflamatorios/administración & dosificación , Antiinflamatorios/inmunología , Antiinflamatorios/farmacocinética , Relación Dosis-Respuesta a Droga , Ensayo de Inmunoadsorción Enzimática , Etanercept/administración & dosificación , Etanercept/inmunología , Femenino , Estudios de Seguimiento , Humanos , Inmunosupresores/administración & dosificación , Inmunosupresores/inmunología , Inmunosupresores/farmacocinética , Masculino , Persona de Mediana Edad , Estudios Prospectivos , Psoriasis/tratamiento farmacológico , Factores de Tiempo , Resultado del Tratamiento , Factor de Necrosis Tumoral alfa/antagonistas & inhibidores
6.
Artículo en Inglés | MEDLINE | ID: mdl-37858455

RESUMEN

INTRODUCTION AND AIMS: Posttransplantation diabetes mellitus (PTDM) is a serious long-term complication that has a negative impact on graft and patient survival. The purpose of the present study was to describe the incidence of PTDM in a Mexican cohort and evaluate its association with a previous family history of diabetes (FHD). METHODS: A retrospective single-center cohort study was conducted on patients undergoing liver transplantation (LT). The primary outcome was time from LT to PTDM. The diagnosis of PTDM was established using the ADA criteria. A mediation analysis that used adjusted Cox regression models and considered pretransplant prediabetes a mediator was performed, to determine the total effect and direct effect of FHD on PTDM. RESULTS: A total of 152 patients were included, with a median follow-up time of 41 months; 19.2% (n = 29) had pretransplant diabetes. During the follow-up time, 15% of patients developed PTDM (n = 23), with an incidence rate of 4.71 cases/100 person-years. PTDM was significantly higher in patients with FHD, compared with those with no FHD (8.72 cases/100 person-years vs 2.04 cases/100 person-years, respectively; p = 0.001). The adjusted hazard ratio of PTDM for FHD was 4.14 (95% CI 1.60-10.7), p = 0.005) and 3.48 (95% CI 1.35-9.01, p = 0.010), when further controlled for pretransplant prediabetes. CONCLUSION: The occurrence of PTDM was similar to that reported in most international studies. As with type 2 diabetes, family history plays an important role in the development of PTDM, even after accounting for pretransplant prediabetes. Patients with FHD should undergo a stricter metabolic program.

8.
Vet Immunol Immunopathol ; 228: 110100, 2020 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-32871408

RESUMEN

Mesenchymal stem cells (MSC) are modern tools in regenerative therapies of humans and animals owed to their immunomodulatory properties, which are activated in a pro-inflammatory environment. Different preconditioning strategies had been devised to enhance the immunomodulatory properties of MSC. In this research, we evaluated the immunological attributes of equine adipose MSC (eAMSC) before and after preconditioning in vitro with prostaglandin E2 (PGE2), substance P (SP), their combination and IFNγ. PGE2/SP was the best combination to keep or enhance the mesodermal lineage differentiation of eAMSC. Alongside with this, preconditioning of eMSC with PGE2 and SP did not affect expression of stemness MSC surface phenotype: CD90+, CD44+, MHC class I+, MHC class II- and CD45-, assessed by cytometry. Both naïve and preconditioned eAMSC expressed genes related with immune properties, such as MHC-I, PTGES, IL6, IL1A, TNFα and IL8 assessed by qPCR. Only TNFα was under expressed in treated cells, while the other markers were either overexpressed or not changed. In no cases MHC-II expression was detected. The antiproliferative effect of preconditioned eAMSC exposed to activated peripheral blood mononuclear cells (PBMC) showed that SP treatment significantly inhibited proliferation of LPS stimulated PBMC. When eAMSC were stimulated with Poly I:C, all the treatments significantly inhibited proliferation of stimulated PBMC (p < 0.05). Direct contact (coculture) between the preconditioned eAMSC and PBMC, induced a shift of significantly more (CD4/CD25/FOXP3)+ T-regulatory PBMC than naïve eAMSC. In the experiments of this research, we investigated the secreted proteomic profile of naïve and preconditioned eAMSC, 42 up-regulated and 40 down-regulated proteins were found in the proteomic assay. Our proteomic data revealed profound changes in the secretory pattern of MSC exposed to different treatments, compared to naïve eAMSC as well as among treatments. In overall, compared to naïve cells, the protein profile of preconditioned cells resembled the mesenchymal-epithelial transition (MET). Here we showed that the combined use of PGE2 and SP provoked in overall the highest expression of anti-inflammatory markers as well as lead to an increased acquisition of a T-regulatory phenotype in preconditioned eAMSC without affecting their "stemness".


Asunto(s)
Dinoprostona/inmunología , Caballos/inmunología , Células Madre Mesenquimatosas/inmunología , Proteínas/metabolismo , Sustancia P/inmunología , Animales , Biomarcadores/metabolismo , Diferenciación Celular/inmunología , Proliferación Celular , Citometría de Flujo/veterinaria , Interferón gamma/inmunología , Masculino , Células Madre Mesenquimatosas/metabolismo , Mesodermo/citología , Proteoma , Vías Secretoras/inmunología
9.
Mater Today Bio ; 8: 100074, 2020 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-32995743

RESUMEN

The increasing demand in rapid wound dressing and healing has promoted the development of intraoperative strategies, such as intraoperative bioprinting, which allows deposition of bioinks directly at the injury sites to conform to their specific shapes and structures. Although successes have been achieved to varying degrees, either the instrumentation remains complex and high-cost or the bioink is insufficient for desired cellular activities. Here, we report the development of a cost-effective, open-source handheld bioprinter featuring an ergonomic design, which was entirely portable powered by a battery pack. We further integrated an aqueous two-phase emulsion bioink based on gelatin methacryloyl with the handheld system, enabling convenient shape-controlled in situ bioprinting. The unique pore-forming property of the emulsion bioink facilitated liquid and oxygen transport as well as cellular proliferation and spreading, with an additional ability of good elasticity to withstand repeated mechanical compressions. These advantages of our pore-forming bioink-loaded handheld bioprinter are believed to pave a new avenue for effective wound dressing potentially in a personalized manner down the future.

10.
Rev Gastroenterol Mex (Engl Ed) ; 85(3): 288-294, 2020.
Artículo en Inglés, Español | MEDLINE | ID: mdl-32466830

RESUMEN

INTRODUCTION: After the World Health Organization declared the COVID-19 outbreak a pandemic, the number of patients with confirmed SARS-CoV-2 infection (COVID-19) has increased exponentially, and gastroenterologists and other specialists most likely will be involved in the care of those patients. AIM: To evaluate the knowledge Latin American gastroenterologists and endoscopists (staff physicians and residents) have about the characteristics of COVID-19, as well as the prevention measures to be taken during endoscopic procedures. MATERIALS AND METHODS: We conducted a cross-sectional study that included gastroenterologists and endoscopists from 9 Latin American countries. An electronic questionnaire was applied that was designed to evaluate the knowledge of symptoms, risk groups for severe disease, prevention measures, and the reprocessing of endoscopes utilized in patients with COVID-19. RESULTS: Information was obtained from 133 physicians. Ninety-five percent of them correctly identified the most frequent symptoms of the virus, and 60% identified the 3 risk groups for severe disease. Sixty-six percent of those surveyed did not consider it necessary to use standard precautions during endoscopic procedures, and 30% did not consider contact precautions necessary. Forty-eight percent of the participants surveyed were not familiar with the protocol for reprocessing the endoscopes utilized in patients with COVID-19. CONCLUSION: The majority of the gastroenterologists and endoscopists surveyed were familiar with the signs and symptoms of COVID-19 and the populations at risk for complications. There was a lack of knowledge about prevention measures (during clinical care and endoscopic procedures) and the reprocessing of endoscopic equipment by 70% and 48%, respectively, of those surveyed. Dissemination and teaching strategies that increase the knowledge of specific biosafety measures must be carried out.


Asunto(s)
Infecciones por Coronavirus , Endoscopía Gastrointestinal , Gastroenterólogos , Conocimientos, Actitudes y Práctica en Salud , Pandemias , Neumonía Viral , COVID-19 , Infecciones por Coronavirus/prevención & control , Infecciones por Coronavirus/terapia , Estudios Transversales , Endoscopios , Humanos , América Latina , Pandemias/prevención & control , Neumonía Viral/prevención & control , Neumonía Viral/terapia , Factores de Riesgo , Esterilización , Encuestas y Cuestionarios
11.
Science ; 252(5011): 1415-7, 1991 Jun 07.
Artículo en Inglés | MEDLINE | ID: mdl-17772914

RESUMEN

The reaction of bis(benzene)vanadium with tetracyanoethylene, TCNE, affords an insoluble amorphous black solid that exhibits field-dependent magnetization and hysteresis at room temperature. The critical temperature could not be estimated as it exceeds 350 kelvin, the thermal decomposition temperature of the sample. The empirical composition of the reported material is V(TCNE)x.Y(CH(2)Cl(2)) with x approximately 2 and Y approximately 1/2. On the basis of the available magnetic and infrared data, threedimensional antiferromagnetic exchange of the donor and acceptor spins resulting in ferrimagnetic behavior appears to be the mode of magnetic coupling.

12.
Science ; 203(4376): 172-4, 1979 Jan 12.
Artículo en Inglés | MEDLINE | ID: mdl-17834720

RESUMEN

The structure of an unusual organometallic complex, {Th[(CH(3))(5)C(5)](2) H(micro-H)}(2) . C(6)H(5)CH(3), has been determined from neutron diffraction data, using only the direct-methods program MULTAN. Besides providing accurate metrical information on the first organometallic actinide hydride complex, these results have general and far-reaching implications concerning the complexity and size of crystal structures that can be elucidated solely on the basis of neutron diffraction data.

14.
J Hazard Mater ; 147(1-2): 588-93, 2007 Aug 17.
Artículo en Inglés | MEDLINE | ID: mdl-17314007

RESUMEN

Recent studies have shown that the light-absorption and photocatalytic efficiencies of TiO2 can be improved by coupling TiO2 nano-particles with nonmetallic dopants, such as carbon. In this paper, we describe the electrophoretic preparation of a novel TiO2-carbon nano-composite photocatalyst on a glass indium thin oxide (ITO) substrate. The objective is to take better advantage of the (e-/h+) pair generated by photoexcitation of semiconducting TiO2 particles. The transfer of electrons (e-) into adjacent carbon nano-particles promotes reduction of oxygen to produce hydrogen peroxide (H2O2) which, in the presence of iron ions, can subsequently form hydroxyl radicals (*OH) via the Fenton reaction. At the same time, *OH is formed from water by the (h+) holes in the TiO2. Thus, the *OH oxidant is produced by two routes. The efficiency of this photolytic-Fenton process was tested with a model organic compound, Orange-II (OG-II) azo dye, which is employed in the textile industry.


Asunto(s)
Carbono/química , Nanoestructuras/química , Fotoquímica/métodos , Titanio/química , Compuestos Azo/química , Bencenosulfonatos/química , Catálisis , Electroforesis , Peróxido de Hidrógeno , Hierro , Oxidación-Reducción , Adherencias Tisulares
15.
Theriogenology ; 87: 124-134, 2017 Jan 01.
Artículo en Inglés | MEDLINE | ID: mdl-27641677

RESUMEN

Embryo splitting has been used for the production of identical twins and to increase the pregnancy rate per available embryo. Split blastocysts can develop to term; however, little is known about the impact on gene expression of split embryos, especially at the whole transcriptome level. This work was aimed to evaluate the effect of blastocyst splitting on global gene expression profile at the elongation stage. For that, split and time-matched nonsplit (control group) bovine blastocysts were transferred to a bovine recipient and recovered at Day 17 of development. The number of collected embryos, their size, and global gene expression was compared between both groups. From 16 transferred split embryos, six (37.5%) were collected, whereas nine elongated were recovered from 17 nonsplit (52.9%). Neither the recovery rate nor the average length of the elongated embryos was significantly different between both groups. However more than 50% of embryos from the control group had a length surpassing 100 mm, whereas only 33% of the split embryos reached that size. Global gene expression was performed in individual elongated embryos from both groups using Two-Color Microarray-Based Gene Expression Analysis. From detected genes, 383 (1.31%) were differentially expressed between both groups, among them, 185 (0.63%) were downregulated and 198 (0.67%) genes were upregulated in split embryos. Bioinformatic analysis of differentially expressed genes revealed that embryo splitting affects transcriptomes of resulting elongated embryos, mainly downregulating genes involved in matrix remodelation, control of growth, detoxification, and transport of metabolites. These in turns might have a detrimental impact on the developmental potential of produced embryos.


Asunto(s)
Blastocisto/citología , Bovinos/embriología , Regulación del Desarrollo de la Expresión Génica/fisiología , Transcriptoma/fisiología , Animales , Blastocisto/fisiología , Desarrollo Embrionario , Femenino , Fertilización In Vitro , Embarazo
16.
J Biophotonics ; 10(8): 1074-1079, 2017 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-28009134

RESUMEN

In this study we identify and classify high and low levels of glycated hemoglobin (HbA1c) in healthy volunteers (HV) and diabetic patients (DP). Overall, 86 subjects were evaluated. The Raman spectrum was measured in three anatomical regions of the body: index fingertip, right ear lobe, and forehead. The measurements were performed to compare the difference between the HV and DP (22 well controlled diabetic patients (WCDP) (HbA1c <6.5%), and 49 not controlled diabetic patients (NCDP) (HbA1c ≥6.5%)). Multivariable methods such as principal components analysis (PCA) combined with support vector machine (SVM) were used to develop effective diagnostic algorithms for classification among these groups. The forehead of HV versus WCDP showed the highest sensitivity (100%) and specificity (100%). Sensitivity (100%) and specificity (60%), were highest in the forehead of WCDP, versus NCDP. In HV versus NCDP, the fingertip had the highest sensitivity (100%) and specificity (80%). The efficacy of the diagnostic algorithm by receiver operating characteristic (ROC) curve was confirmed. Overall, our study demonstrated that the combination of Raman spectroscopy and PCA-SVM are feasible non-invasive diagnostic tool in diabetes to classify qualitatively high and low levels of HbA1c in vivo.


Asunto(s)
Hemoglobina Glucada/análisis , Espectrometría Raman , Máquina de Vectores de Soporte , Algoritmos , Estudios de Casos y Controles , Diabetes Mellitus/sangre , Humanos , Análisis de Componente Principal , Sensibilidad y Especificidad
17.
Chem Commun (Camb) ; (7): 898-900, 2005 Feb 21.
Artículo en Inglés | MEDLINE | ID: mdl-15700074

RESUMEN

Gold electrodes, previously prepared with surface anchored PAMAM dendrimers, were further modified with a Ni-containing tetraazamacrocycle resulting in a novel electrocatalytic material which proved to be particularly efficient for the electrochemical oxidation of methanol in basic aqueous medium.


Asunto(s)
Dendrímeros/química , Membranas Artificiales , Metanol/química , Níquel/química , Compuestos Organometálicos/química , Poliaminas/química , Catálisis , Electroquímica , Estructura Molecular , Oxidación-Reducción , Propiedades de Superficie , Agua/química
18.
Anal Chim Acta ; 812: 18-25, 2014 Feb 17.
Artículo en Inglés | MEDLINE | ID: mdl-24491759

RESUMEN

Glassy carbon electrodes (GCE) were sequentially modified by cysteamine-capped gold nanoparticles (AuNp@cysteamine) and PAMAM dendrimers generation 4.5 bearing 128-COOH peripheral groups (GCE/AuNp@cysteamine/PAMAM), in order to explore their capabilities as electrochemical detectors of uric acid (UA) in human serum samples at pH 2. The results showed that concentrations of UA detected by cyclic voltammetry with GCE/AuNp@cysteamine/PAMAM were comparable (deviation <±10%; limits of detection (LOD) and quantification (LOQ) were 1.7×10(-4) and 5.8×10(-4) mg dL(-1), respectively) to those concentrations obtained using the uricase-based enzymatic-colorimetric method. It was also observed that the presence of dendrimers in the GCE/AuNp@cysteamine/PAMAM system minimizes ascorbic acid (AA) interference during UA oxidation, thus improving the electrocatalytic activity of the gold nanoparticles.


Asunto(s)
Ácido Ascórbico/química , Cisteamina/química , Electrodos , Oro/química , Nanopartículas del Metal , Poliaminas/química , Ácido Úrico/sangre , Carbono/química
20.
Langmuir ; 21(7): 3013-21, 2005 Mar 29.
Artículo en Inglés | MEDLINE | ID: mdl-15779979

RESUMEN

Gold bead electrodes were modified with submonolayers of 3-mercaptopropionic acid or 2-aminoethanethiol and further reacted with poly(amidoamine) (PAMAM) dendrimers (generation 4.0 and 3.5, respectively) to obtain films on which Prussian Blue (PB) was later absorbed to afford mixed and stable electrocatalytic layers. Experiments carried out with these novel materials not only showed an improved surface coverage of PB on the dendrimer modified electrodes as compared to PB modified gold electrodes prepared under acidic conditions, but also showed an increased stability at neutral pH values for one of the dendrimer containing substrates where the PB film on a bare gold electrode is simply not formed. The dendrimer modified electrodes were also tested as electrocatalytic substrates for the electroxidation of L(+)-ascorbic acid (AA), and it was found that their sensitivity as well as the corresponding detection limits were improved as compared to the voltammetric response of a Au-PB modified electrode. On the basis of UV-visible (UV-vis) spectroscopy and electrochemical experiments, it is suggested that the PB molecules are located within the dendritic structure of the surface attached PAMAM dendrimers.

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