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1.
J Phys Condens Matter ; 36(15)2024 Jan 12.
Artigo em Inglês | MEDLINE | ID: mdl-38171319

RESUMO

Nodal-line semimetals, characterized by Dirac-like crossings along one dimensionalk-space lines, represent a unique class of topological materials. In this study, we investigate the intriguing properties of room-temperature antiferromagneticMnC4and its nodal-line features both with and without spin-orbit coupling (SOC). In the absence of SOC, we identify a doubly degenerate Dirac-nodal line, robustly protected by a combination of time-reversal, mirror, and partial-translation symmetries. Remarkably, this nodal line withstands various external perturbations, including isotropic and anisotropic strain, and torsional deformations, due to the ionic-like bonding between Mn atoms and C clusters. With the inclusion of SOC, we observe a distinctive quasi-Dirac-nodal line that emerges due to the interplay between antiferromagnetism and SOC-induced spin-rotation symmetry breaking. Finally, we observed a robust spin Hall conductivity that aligns with the energy range where the quasi-nodal line appears. This study presents a compelling example of a robust symmetry-protected Dirac-nodal line antiferromagnetic monolayer, which has potential for applications in next-generation spintronic devices.

2.
Arch. Soc. Esp. Oftalmol ; 97(8): 457-463, ago. 2022. ilus, tab
Artigo em Espanhol | IBECS | ID: ibc-209096

RESUMO

Objetivo Describir la restauración anatómica y funcional observada a largo plazo en pacientes intervenidos por agujero macular (AM) grande empleando distintas técnicas de interposición macular. Método Análisis retrospectivo de los resultados obtenidos en una serie de 9 pacientes sometidos a cirugía de AM grande (≥450μm) realizando 4 técnicas de interposición macular distintas: flap invertido de membrana limitante interna en 4 casos, plegado de membrana limitante interna en 2, injerto de membrana amniótica en 2 e injerto autógeno de cápsula anterior en uno. El tiempo de seguimiento medio fue de 11 meses. Anatómicamente las medidas de resultados exploradas fueron la restauración de las capas externas de la retina y el patrón de cierre macular. Funcionalmente se valoró la agudeza visual final y la calidad visual. Resultados La restauración de las capas externas fue parcial en 6 casos. La tasa de cierre macular fue del 100%, apreciándose un patrón incompleto en 4 casos. La agudeza visual mejoró en 7 pacientes, manteniéndose estable en 2. Tres casos mostraron un patrón de fijación excéntrico y/o metamorfopsias. Conclusiones El desarrollo de nuevas técnicas quirúrgicas ha incrementado la tasa de cierre macular en AM grandes. Sin embargo, la restauración anatómica y funcional sigue siendo impredecible. En este trabajo se logró el cierre macular en todos los pacientes y una mayor tasa de cierre completo empleando flap invertido de membrana limitante interna. La restauración de las capas externas fue más favorable en los grupos en los que se había empleado membrana limitante interna. La recuperación funcional fue independiente de la técnica empleada (AU)


Objective To describe the long-term anatomical and functional restoration observed in patients operated on for a large macular hole (MH) using different macular interposition techniques. Method Retrospective analysis of the results obtained in a series of 9 patients undergoing large MH surgery (≥450μm) performing 4 different macular interposition techniques: inverted internal limiting membrane flap in 4 cases, autotransplantation of internal limiting membrane in 2, amniotic membrane graft in 2, and autologous anterior capsule graft in one. The mean follow-up time was 11 months. Anatomically, the outcome measures explored were the restoration of the outer layers of the retina and the pattern of MH closure. The final visual acuity and visual quality were functionally assessed. Results The restoration of the outer layers was partial in 6 cases. The macular closure rate was 100%, showing an incomplete pattern in 4 cases. Visual acuity improved in 7 patients, remaining stable in 2. Three cases showed an eccentric fixation pattern and/or metamorphopsia. Conclusion The development of new surgical techniques has increased the rate of macular closure in large MHs. However, the anatomical and functional restoration remains unpredictable. In this work, macular closure was achieved in all patients and a higher rate of complete closure using inverted internal limiting membrane flap. The restoration of the outer layers was more favorable in the groups in which internal limiting membrane had been used. Functional recovery was independent of the technique used (AU)


Assuntos
Humanos , Masculino , Feminino , Idoso , Perfurações Retinianas/cirurgia , Tomografia de Coerência Óptica , Estudos Retrospectivos , Vitrectomia/métodos , Acuidade Visual
3.
Arch Soc Esp Oftalmol (Engl Ed) ; 97(8): 457-463, 2022 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-35331671

RESUMO

OBJECTIVE: To describe the long-term anatomical and functional restoration observed in patients operated on for a large macular hole (MH) using different macular interposition techniques. METHOD: Retrospective analysis of the results obtained in a series of 9 patients undergoing large MH surgery (≥450µm) performing 4 different macular interposition techniques: inverted internal limiting membrane flap in 4 cases, autotransplantation of internal limiting membrane in 2, amniotic membrane graft in 2, and autologous anterior capsule graft in one. The mean follow-up time was 11 months. Anatomically, the outcome measures explored were the restoration of the outer layers of the retina and the pattern of MH closure. The final visual acuity and visual quality were functionally assessed. RESULTS: The restoration of the outer layers was partial in 6 cases. The macular closure rate was 100%, showing an incomplete pattern in 4 cases. Visual acuity improved in 7 patients, remaining stable in 2. Three cases showed an eccentric fixation pattern and/or metamorphopsia. CONCLUSIONS: The development of new surgical techniques has increased the rate of macular closure in large MHs. However, the anatomical and functional restoration remains unpredictable. In this work, macular closure was achieved in all patients and a higher rate of complete closure using inverted internal limiting membrane flap. The restoration of the outer layers was more favorable in the groups in which internal limiting membrane had been used. Functional recovery was independent of the technique used.


Assuntos
Perfurações Retinianas , Humanos , Perfurações Retinianas/cirurgia , Estudos Retrospectivos , Tomografia de Coerência Óptica , Acuidade Visual , Vitrectomia/métodos
6.
J Gynecol Obstet Hum Reprod ; 51(1): 102240, 2022 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-34610488

RESUMO

OBJECTIVES: Intra-Uterine Device (IUD) insertion is possible in early postpartum. Although this contraception method is recognized and used in lots of country, it seems infrequent and poorly known in France. Our study aims to assess the barriers to the application of this method in France. METHODS: A questionnaire was sent to obstetricians-gynaecologist professionals and midwives in France, through the affiliation to CNGOF (French National College of Obstetricians and Gynecologists) and to CNSF (French National College of Midwives). Questions were focused on the practices and knowledge about the insertion of IUD in early postpartum. RESULTS: four hundred eight practitioners responded. Amongst them, 63% knew about the possibility to use IUDs after a vaginal delivery and 31% knew it could be inserted during cesarean section. Ten percent of them used this method. Most of these practitioners (80% of them) would like to discuss the insertion of an IUD in early postpartum with their patients and 71% would like to perform the insertion themselves after training. Besides, this study shows that contraception is rarely addressed by physicians during the follow-up of pregnancies. Less than 15% of respondents report discussing the topic systematically with the patient during the pregnancy follow during pregnancy follow. CONCLUSION: insertion of IUDs in early postpartum is uncommon in France. The main limitation seems to be a lack of knowledge, but practitioners seem to be interested in this practice. Training courses could be created in order to rase up the adoption of this practice.


Assuntos
Competência Clínica/normas , Dispositivos Intrauterinos , Obstetrícia/normas , Adulto , Competência Clínica/estatística & dados numéricos , Feminino , França , Humanos , Masculino , Pessoa de Meia-Idade , Obstetrícia/métodos , Obstetrícia/estatística & dados numéricos , Período Pós-Parto , Gravidez , Inquéritos e Questionários
7.
Rev Chilena Infectol ; 38(3): 317-323, 2021 Jun.
Artigo em Espanhol | MEDLINE | ID: mdl-34479286

RESUMO

BACKGROUND: The monitoring of antimicrobial therapy through plasma levels makes it possible to determine the optimal dosage of antimicrobials, an essential approach in pediatrics. AIM: To describe the monitoring of plasma antimicrobial levels and dose adjustment in the pediatric population to determine if the doses used reach therapeutic ranges. METHODS: Retrospective, descriptive study using a database with measurement of plasma levels of amikacin and vancomycin in pediatric patients at San Borja Arriarán Hospital between 2015-2018. The number of patients who reached the therapeutic range with the initial dose, how many required adjustment and their characteristics were determined. RESULTS: 104 total levels were monitored. For vancomycin 65 plasmatic levels were baseline, being outside the therapeutic range 56.5%; 25% of those requiring adjustment were neonates with a higher probability of being out of range versus others (p = 0.022). For amikacin, Cpeak was in range in 60% of measurements; 15.4% required adjustment, including patients with cystic fibrosis and cancer, without adjustments in patients without comorbidity. CONCLUSION: Measurement of plasma levels is necessary to individually adjust the dose, especially in pediatric patients with cystic fibrosis, oncology and in neonatology where it is more likely not to reach a therapeutic range with initial doses.


Assuntos
Pediatria , Vancomicina , Amicacina , Antibacterianos/uso terapêutico , Criança , Monitoramento de Medicamentos , Humanos , Recém-Nascido , Estudos Retrospectivos
8.
Eur J Contracept Reprod Health Care ; 26(5): 404-412, 2021 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-34096440

RESUMO

PURPOSE: To evaluate the different techniques for Essure® microinserts removal and to assess the risk of fracture of the device and the intra- and post-operative complications in relation to surgical technique variants. METHODS: Electronic search in Medline, Scopus and Embase databases using the following keywords: Essure; Essure removal; Essure surgical technique. RESULTS: Out of 95 articles in the initial database, 17 studies were eligible for inclusion in our literature review. Several surgical techniques have been described in which the most frequent were laparoscopic salpingectomy (LS), laparoscopic cornuectomy (LC), laparoscopic or vaginal hysterectomy (LH, VH) with en-bloc salpingectomy. There were more fractures of the device with the LS procedure (6.25%) followed by the LC technique (2.77%), while there was no fracture with hysterectomy. However, peri-and post-operative complications were more severe and frequent with hysterectomy in comparison with the LC and LS procedures (respectively 8.1% Clavien Dindo grade 3 for the hysterectomy group, 1.11% for the LC procedure and 0.69% for the LS technique). CONCLUSION: Due to the lack of standardised surgical treatment guidelines, a system of care networks for symptomatic patients with adverse effects related to Essure® headed by specialised centres may offer a suitable and high-quality management with the appropriate removal techniques within two objectives: limiting the risk of fracture (with an en-bloc removal of the Essure® microinserts) and avoiding intra- and post-operative complications.


Assuntos
Remoção de Dispositivo/métodos , Histerectomia/efeitos adversos , Dispositivos Intrauterinos/efeitos adversos , Laparoscopia/efeitos adversos , Salpingectomia/efeitos adversos , Esterilização Tubária/efeitos adversos , Feminino , Humanos , Histerectomia/métodos , Complicações Pós-Operatórias , Salpingectomia/métodos , Esterilização Tubária/métodos , Inquéritos e Questionários , Resultado do Tratamento
9.
Rev. chil. infectol ; 38(3): 317-323, jun. 2021. tab, graf
Artigo em Espanhol | LILACS | ID: biblio-1388242

RESUMO

INTRODUCCIÓN: La monitorización de antimicrobianos mediante sus concentraciones plasmáticas permite determinar la posología óptima de éstos, conducta esencial en pediatría. OBJETIVOS: Describir la monitorización de concentraciones plasmáticas de antimicrobianos y el ajuste de dosis en población pediátrica para determinar si las dosis utilizadas alcanzan rangos terapéuticos. PACIENTES Y MÉTODOS: Estudio descriptivo, retrospectivo, utilizando una base de datos con medición de concentraciones plasmáticas de amikacina y vancomicina en pacientes pediátricos del Hospital San Borja Arriarán, entre 2015-2018. Se determinó el número de pacientes que alcanzó rango terapéutico con dosis inicial, cuántos requirieron ajuste y sus características. RESULTADOS: Se monitorizó 104 concentraciones totales. Para vancomicina 65 concentraciones plasmáticas eran basales encontrándose fuera de rango terapéutico 56,5%; de los que requirieron ajuste, 25% fueron neonatos con mayor probabilidad de estar fuera de rango versus otros (p = 0,022). Para amikacina la Cpeak estuvo en rango en 60% de mediciones; 15,4% requirió ajuste incluyendo pacientes con fibrosis quística y oncológicos. No fue necesario efectuar ajustes en pacientes sin co-morbilidad. CONCLUSIÓN: La medición de concentraciones plasmáticas es necesaria para ajustar de forma individualizada la dosis, especialmente en pacientes pediátricos con fibrosis quística, oncológicos y en neonatología, donde es más probable no alcanzar rango terapéutico con las dosis iniciales.


BACKGROUND: The monitoring of antimicrobial therapy through plasma levels makes it possible to determine the optimal dosage of antimicrobials, an essential approach in pediatrics. AIM: To describe the monitoring of plasma antimicrobial levels and dose adjustment in the pediatric population to determine if the doses used reach therapeutic ranges. METHODS: Retrospective, descriptive study using a database with measurement of plasma levels of amikacin and vancomycin in pediatric patients at San Borja Arriarán Hospital between 2015-2018. The number of patients who reached the therapeutic range with the initial dose, how many required adjustment and their characteristics were determined. RESULTS: 104 total levels were monitored. For vancomycin 65 plasmatic levels were baseline, being outside the therapeutic range 56.5%; 25% of those requiring adjustment were neonates with a higher probability of being out of range versus others (p = 0.022). For amikacin, Cpeak was in range in 60% of measurements; 15.4% required adjustment, including patients with cystic fibrosis and cancer, without adjustments in patients without comorbidity. CONCLUSION: Measurement of plasma levels is necessary to individually adjust the dose, especially in pediatric patients with cystic fibrosis, oncology and in neonatology where it is more likely not to reach a therapeutic range with initial doses.


Assuntos
Humanos , Masculino , Feminino , Recém-Nascido , Lactente , Pré-Escolar , Criança , Adolescente , Pediatria , Amicacina/administração & dosagem , Vancomicina/administração & dosagem , Estudos Retrospectivos , Monitoramento de Medicamentos , Antibacterianos/administração & dosagem
10.
Gynecol Obstet Fertil Senol ; 49(12): 930-935, 2021 12.
Artigo em Francês | MEDLINE | ID: mdl-34051425

RESUMO

Synechiae are intrauterine adhesions that affect the fertility of women. They are most often of post-traumatic origin. The management of pregnancy abortions in the first trimester and post-delivery retention are the main contributing factors. Synechiae is responsible for cycle disorders and repeated pregnancy loss. Hysteroscopy is the reference method for its diagnosis and treatment. The surgical objective is the restoration of a normal sized cavity and a functional endometrium to allow fertilization and implantation. The use of small diameter (5mm) hysteroscopes and no energy or bipolar energy instruments are recommended. Echo guidance facilitates the treatment of severe synechiae and limits the risk of intraoperative perforation. The main risk of treatment is recurrence, particularly in severe cases where multiple operating times are sometimes necessary. An office hysteroscopy at 6 weeks is recommended to identify and treat these recurrences. Different physical, molecular or cellular methods are studied as primary and secondary prevention of postoperative synechiae. The objective of this review is to provide an update on the treatment of synechiae in the context of infertility.


Assuntos
Infertilidade Feminina , Infertilidade , Doenças Uterinas , Endométrio , Feminino , Humanos , Histeroscopia/métodos , Infertilidade Feminina/etiologia , Infertilidade Feminina/terapia , Gravidez , Aderências Teciduais/complicações , Aderências Teciduais/cirurgia , Doenças Uterinas/cirurgia
11.
Prog Urol ; 31(7): 422-429, 2021 Jun.
Artigo em Francês | MEDLINE | ID: mdl-33863637

RESUMO

INTRODUCTION: The French Department of Health published on October 23, 2020 a decree governing acts associated with mid-urethral sling (MUS) operations. The aim of this study was to evaluate the changes in practice following this new legislation. METHODS: A cross-sectional study was carried out among French urologists and gynecologists using an online survey to collect changes in practices since the publication of the decree. RESULTS: From January to February 2021, 436 surgeons participated in the survey. Among these surgeons, 87% were aware of the new legislation and 56% of them considered the decree as useless. The order resulted in an increase in working time in 81% of cases. Among these surgeons, 66% of the surgeons worked in tertiary referral centers for the management of incontinence, of which 55% had a multidisciplinary meeting in urogynecology. Among the surgeons, 31% considered this meeting to be useful but 80% considered that it did not lead to any change in surgical indications, even though 33% of complications of BSU were discussed there. In conclusion, 61% of surgeons felt more reluctant to schedule a BSU placement with this new legislation. CONCLUSION: The majority of questioned surgeons considered the decree as useless. It generated few changes in practices which already respected the law on information, consultation, consent, experience and training. Most urologists and gynecologists are more reluctant to offer MUS after this new legislation. LEVEL OF EVIDENCE: 4.


Assuntos
Utilização de Equipamentos e Suprimentos/legislação & jurisprudência , Utilização de Equipamentos e Suprimentos/tendências , Ginecologia , Padrões de Prática Médica , Slings Suburetrais/tendências , Urologia , Estudos Transversais , Utilização de Equipamentos e Suprimentos/estatística & dados numéricos , França , Humanos , Slings Suburetrais/estatística & dados numéricos
13.
Syst Biol ; 70(3): 576-592, 2021 04 15.
Artigo em Inglês | MEDLINE | ID: mdl-32785670

RESUMO

The Amazon and neighboring South American river basins harbor the world's most diverse assemblages of freshwater fishes. One of the most prominent South American fish families is the Serrasalmidae (pacus and piranhas), found in nearly every continental basin. Serrasalmids are keystone ecological taxa, being some of the top riverine predators as well as the primary seed dispersers in the flooded forest. Despite their widespread occurrence and notable ecologies, serrasalmid evolutionary history and systematics are controversial. For example, the sister taxon to serrasalmids is contentious, the relationships of major clades within the family are inconsistent across different methodologies, and half of the extant serrasalmid genera are suggested to be non-monophyletic. We analyzed exon capture to reexamine the evolutionary relationships among 63 (of 99) species across all 16 serrasalmid genera and their nearest outgroups, including multiple individuals per species to account for cryptic lineages. To reconstruct the timeline of serrasalmid diversification, we time-calibrated this phylogeny using two different fossil-calibration schemes to account for uncertainty in taxonomy with respect to fossil teeth. Finally, we analyzed diet evolution across the family and comment on associated changes in dentition, highlighting the ecomorphological diversity within serrasalmids. We document widespread non-monophyly of genera within Myleinae, as well as between Serrasalmus and Pristobrycon, and propose that reliance on traits like teeth to distinguish among genera is confounded by ecological homoplasy, especially among herbivorous and omnivorous taxa. We clarify the relationships among all serrasalmid genera, propose new subfamily affiliations, and support hemiodontids as the sister taxon to Serrasalmidae. [Characiformes; exon capture; ichthyochory; molecular time-calibration; piscivory.].


Assuntos
Caraciformes , Dieta , Filogenia , Animais , Caraciformes/genética , Dieta/veterinária , Fósseis
16.
Artigo em Inglês | MEDLINE | ID: mdl-31497757

RESUMO

OBJECTIVE: To report long term pregnancy rate in polycystic ovary syndrome (PCOS) treated by ovarian drilling. To evaluate predictive factors of pregnancy and possibility of a second drilling. DESIGN: Retrospective, observational, multicenter study. SETTING: Gynecologic departments of two teaching's hospitals. PATIENTS: All infertile women with PCOS who were treated by ovarian drilling from 2004 to 2013. The Rotterdam criteria were applied to define PCOS. INTERVENTIONS: Surgical ovarian drilling by laparoscopy and trans vaginal hydro laparoscopy. MAIN OUTCOME MEASURES: The primary endpoint was pregnancy rate after ovarian drilling. The secondary endpoints were the predictive factors of pregnancy and the possibility of a second ovarian drilling. RESULTS: 289 women were included in the study. The mean follow-up period was 28.4 months (25.3-31.5). A pregnancy was obtained in at least 137 (47.4%) women after a drilling, and 71 (51.8%) of these pregnancies were spontaneous, 48 (16.6%) women achieved at least two pregnancies after drilling, and 27 (56.3%) of these were spontaneous. The predictive factors for effectiveness were a normal body mass index (BMI), an infertility period of less than three years, an AFC of less than 50, and an age of less than 35. Second drillings were performed on 33 women. Among them, 19 (57.6%) achieved at least one pregnancy, and 10 (52.6%) of these were spontaneous. It appeared that a second drilling was effective either when the first drilling had been successful (pregnancy achieved after drilling) or when it had failed in cases of high AFC (greater than 55). CONCLUSION: Ovarian drilling permitted to obtain spontaneous pregnancy for women with PCOS. This surgery could have durably effect permitted to obtain more than one pregnancy.

17.
Arch Microbiol ; 201(10): 1447-1452, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31302710

RESUMO

Acanthamoeba castellanii is a free-living amoeba found mainly in humid environments and Arcobacter butzleri is an emerging zoonotic pathogen, both can establish in vitro endosymbiotic relationships in the absence of bacterial replication. We analyzed the localization of A. butzleri within A. castellanii establishing their association with endoplasmic reticulum vesicles and mitochondria. Through confocal microscopy, we observed that during the early stages of endosymbiosis, there is not colocalization between amoebic vacuoles containing A. butzleri and mitochondria or ER vesicles of A. castellanii. Considering that energy production of this bacterium occurs via metabolism of amino acids or the tricarboxylic acid cycle, these results contribute to explain the absence of bacterial replication, since A. butzleri would not have access to the nutrients found in endoplasmic reticulum vesicles and mitochondria. In addition, we observe that A. butzleri induces significantly the actin polymerization of A. castellanii during the early stages of endosymbiosis.


Assuntos
Acanthamoeba castellanii/microbiologia , Arcobacter/fisiologia , Simbiose , Vacúolos/microbiologia
18.
Lett Appl Microbiol ; 69(3): 190-197, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31220348

RESUMO

This research aims to compare the culturing conditions for enterohepatic Helicobacter, evaluating culture media, incubation atmosphere and susceptibility to antimicrobials used to generate selective conditions. Four common media for the closely related genus Campylobacter (Columbia, Bolton, Brucella and CCDA agar), as well as the need for hydrogen in the microaerobic incubation atmosphere, were evaluated. Serial dilutions of 13 strains belonging to six species (H. apodemus, H. bilis, H. canicola, H. canis, H. equorum and Helicobacter sp.) were inoculated in each media and incubated at 37°C for 48 to 96 h using CampyGen (OXOID) and gaseous exchange (including hydrogen) in parallel. Columbia or Brucella agars were the most appropriate for culturing EHH (P < 0·05). However, there was no significant difference between the atmospheres evaluated (P = 0·13). In addition, minimal inhibitory concentration for six antibiotics showed that all isolates were resistant to trimethoprim, whereas for the rest of the antibiotics (cephalothin, cefoperazone, cefsulodin, teicoplanin and vancomycin) the inhibition range was between 8 and 64 µg ml- 1 . Our findings suggest that Columbia or Brucella media, regardless of the use of hydrogen, can be used for the EHH isolation. In addition, the concentration of antibiotics included in commercial campylobacteria supplements is suitable for EHH species recovery. SIGNIFICANCE AND IMPACT OF THE STUDY: Enterohepatic Helicobacter (EHH) infections have been associated with several diseases in humans such as acute gastroenteritis, inflammatory bowel disease and hepatobiliary diseases. Although they are frequently detected in clinical samples by molecular methods, only occasionally they are isolated using culture conditions described for the taxonomic related pathogen Campylobacter sp. This is because the optimal conditions for the isolation of EHH have not yet been described, which results in an underestimation of the prevalence and clinical importance of these emerging pathogens. Therefore, this study provides insight for culturing EHH species.


Assuntos
Ágar/química , Antibacterianos/farmacologia , Meios de Cultura/química , Helicobacter/crescimento & desenvolvimento , Helicobacter/metabolismo , Campylobacter/crescimento & desenvolvimento , Gastroenterite/microbiologia , Helicobacter/classificação , Infecções por Helicobacter/tratamento farmacológico , Humanos , Testes de Sensibilidade Microbiana
20.
Talanta ; 194: 253-258, 2019 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-30609527

RESUMO

A third-generation enzymatic biosensor was developed to quantify sterigmatocystin (STEH). It was based on a glassy carbon electrode modified with a composite of the soybean peroxidase enzyme (SPE) and chemically reduced graphene oxide. The optimal conditions to construct the biosensor were obtained through an experimental design based on the response surfaces methodology. The experiments were performed in 0.1 mol L-1 phosphate buffer solution, pH 5. Amperometric measurements were carried out at - 0.09 V vs Ag/AgCl (3 mol L-1 NaCl). The biosensor showed a lineal response in the concentration range from 6.9 × 10-9 to 5.0 × 10-7 mol L-1. The limit of detection was 2.3 × 10-9 mol L-1 for a signal: noise ratio of 3: 1. Values of the apparent Michaellis-Menten constant, KMapp, obtained by using both Lineweaver-Burk and Eadi-Hofstee methods were (1.5 ± 0.2) × 10-6 and (1.2 ± 0.2) × 10-6 mol L-1, respectively. STEH was analyzed in corn samples spiked with STEH, with an average recovery of 96.5%. The biosensor was also used to determine STEH in corn samples inoculated with the Aspergillus flavus fungus, which is an aflatoxins producer. Considering that STEH is a precursor of aflatoxin B1 (AFB1) in its biological transformation, its decrease over time was related to the production of AFB1. The STEH concentration determined using the biosensor was in very good agreement with that determined by HPLC.


Assuntos
Aflatoxina B1/análise , Técnicas Biossensoriais/métodos , Peroxidase/metabolismo , Esterigmatocistina/análise , Técnicas Biossensoriais/instrumentação , Carbono/química , Eletroquímica , Eletrodos , Limite de Detecção , Zea mays/química
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