RESUMEN

CONTEXT: Although the crystallization of monosodium urate monohydrate (MSUM) has a crucial role in the occurrence of gout, which is an inflammatory arthritis disease, theoretical models have not been able to describe all features observed in its seeded growth kinetics. In contrast to previous modeling approaches, we show that our model can reproduce qualitative features typically observed in experiments. In particular, our results show that the higher the initial supersaturation and the lower the viscosity, the faster the crystallization kinetics, and they also indicate that there are distinct growth regimes for low and high concentrations of seeds. METHODS: In this work, we introduce an alternative approach based on a master equation that allows us to incorporate hypotheses for the seeded growth crystallization of MSUM in a more transparent way. Such an approach includes not only effects that are related to the finite time-dependent supersaturation and concentration of seeds, but it can also be used to determine how the viscosity of the solution can affect the crystallization kinetics of MSUM molecules.

Asunto(s)

Cristalización , Ácido Úrico , Ácido Úrico/química , Viscosidad , Cinética , Modelos Químicos

RESUMEN

This work presents the synthesis and characterization of an innovative F,S-doped carbon dots/CuONPs hybrid nanostructure obtained by a direct mixture between F,S-doped carbon dots obtained electrochemically and copper nitrate alcoholic solution. The hybrid nanostructures synthesized were characterized by absorption spectroscopy in the Ultraviolet region (UV-vis), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), and different electrochemical techniques. The fluoride and sulfur-doped carbon dots/CuONPs nanostructures were used to prepare a non-enzymatic biosensor on a printed carbon electrode, exhibiting excellent electrocatalytic activity for the simultaneous determination of NADH, dopamine, and uric acid in the presence of ascorbic acid with a detection limit of 20, 80, and 400 nmol L-1, respectively. The non-enzymatic biosensors were also used to determine NADH, dopamine, and uric acid in plasma, and they did not suffer significant interference from each other.

Asunto(s)

Técnicas Biosensibles , Carbono , Cobre , Dopamina , Técnicas Electroquímicas , Límite de Detección , NAD , Ácido Úrico , Ácido Úrico/sangre , Ácido Úrico/química , Técnicas Biosensibles/métodos , Dopamina/sangre , Dopamina/análisis , Carbono/química , NAD/química , NAD/sangre , Cobre/química , Técnicas Electroquímicas/métodos , Humanos , Azufre/química , Fluoruros/química , Puntos Cuánticos/química , Nanoestructuras/química , Electrodos

RESUMEN

Clinical History: In a flock of approximately 180 peafowl, several were showing signs of a possible upper respiratory infection and had mouth gaping per the owner. They were also reported to be lethargic, to have excessive phlegm or mucus in the mouths, had trouble swallowing, and were losing weight. They were being treated with Baytril and Metronidazole with no improvement. Approximately eight had died. Five peafowl were submitted for necropsy and diagnostic work-up, including three peahens and two peacocks. Gross Findings: In all five peafowl, the oral cavity contained excess mucus. The oral, crop, and esophageal mucosa had disseminated, smooth, raised, round nodules with a central pore. The proximal esophagus was the most severely affected site. The nodules measured on average ~2 mm in diameter. Upon squeezing some of these nodules, pale tan, caseous material could be expressed. In all five peafowl, the heart was diffusely coated by abundant white, chalky, urate material. Similar though lesser amounts of urates partially coated the surface of the liver and other coelomic membranes. In one peahen, the ureters were multifocally distended and contained consolidated accumulations of tan to pale yellow, caseous material. The kidneys in this bird were pale. Follow-up questions: Morphologic diagnoses Cause Pathogenesis

Asunto(s)

Animales , Pavos/fisiología , Deficiencia de Vitamina A/veterinaria , Ácido Úrico/química

RESUMEN

BACKGROUND AND PURPOSE: Gouty arthritis is characterized by an intense inflammatory response to monosodium urate crystals (MSU), which induces severe pain. Current therapies are often ineffective in reducing gout-related pain. Resolvin D1 (RvD1) is a specialized pro-resolving lipid mediator with anti-inflammatory and analgesic proprieties. In this study, we evaluated the effects and mechanisms of action of RvD1 in an experimental mouse model of gouty arthritis, an aim that was not pursued previously in the literature. EXPERIMENTAL APPROACH: Male mice were treated with RvD1 (intrathecally or intraperitoneally) before or after intraarticular stimulation with MSU. Mechanical hyperalgesia was assessed using an electronic von Frey aesthesiometer. Leukocyte recruitment was determined by knee joint wash cell counting and immunofluorescence. IL-1ß production was measured by ELISA. Phosphorylated NF-kB and apoptosis-associated speck-like protein containing CARD (ASC) were detected by immunofluorescence, and mRNA expression was determined by RT-qPCR. CGRP release was determined by EIA and immunofluorescence. MSU crystal phagocytosis was evaluated by confocal microscopy. KEY RESULTS: RvD1 inhibited MSU-induced mechanical hyperalgesia in a dose- and time-dependent manner by reducing leukocyte recruitment and IL-1ß production in the knee joint. Intrathecal RvD1 reduced the activation of peptidergic neurons and macrophages as well as silenced nociceptor to macrophage communication and macrophage function. CGRP stimulated MSU phagocytosis and IL-1ß production by macrophages. RvD1 downmodulated this phenomenon directly by acting on macrophages, and indirectly by inhibiting CGRP release and CGRP-dependent activation of macrophages. CONCLUSIONS AND IMPLICATIONS: This study reveals a hitherto unknown neuro-immune axis in gouty arthritis that is targeted by RvD1.

Asunto(s)

Artritis Gotosa , Animales , Artritis Gotosa/inducido químicamente , Artritis Gotosa/tratamiento farmacológico , Péptido Relacionado con Gen de Calcitonina , Ácidos Docosahexaenoicos , Hiperalgesia/tratamiento farmacológico , Hiperalgesia/metabolismo , Inflamación/metabolismo , Activación de Macrófagos , Masculino , Ratones , Neuroinmunomodulación , Neuronas , Nociceptores/metabolismo , Dolor , Ácido Úrico/química , Ácido Úrico/farmacología

RESUMEN

For the first time the development of an electrochemical method for simultaneous quantification of Zn2+ and uric acid (UA) in sweat is described using an electrochemically treated 3D-printed working electrode. Sweat analysis can provide important information about metabolites that are valuable indicators of biological processes. Improved performance of the 3D-printed electrode was achieved after electrochemical treatment of its surface in an alkaline medium. This treatment promotes the PLA removal (insulating layer) and exposes carbon black (CB) conductive sites. The pH and the square-wave anodic stripping voltammetry technique were carefully adjusted to optimize the method. The peaks for Zn2+ and UA were well-defined at around - 1.1 V and + 0.45 V (vs. CB/PLA pseudo-reference), respectively, using the treated surface under optimized conditions. The calibration curve showed a linear range of 1 to 70 µg L-1 and 1 to 70 µmol L-1 for Zn2+ and UA, respectively. Relative standard deviation values were estimated as 4.8% (n = 10, 30 µg L-1) and 6.1% (n = 10, 30 µmol L-1) for Zn2+ and UA, respectively. The detection limits for Zn2+ and UA were 0.10 µg L-1 and 0.28 µmol L-1, respectively. Both species were determined simultaneously in real sweat samples, and the achieved recovery percentages were between 95 and 106% for Zn2+ and 82 and 108% for UA.

Asunto(s)

Técnicas Biosensibles/métodos , Técnicas Electroquímicas/métodos , Sudor/química , Ácido Úrico/química , Zinc/química

RESUMEN

A highly sensitive sensor for quantification of uric acid (UA) directly in body fluids (saliva and sweat) is reported, working at a potential as low as 0.0 V vs Ag/AgCl. New mixed hydroxide materials exhibiting stable electrocatalytic responses from alkaline to acidic media were prepared, their structure was thoroughly characterized, and the electrochemical properties of the modified FTO (fluorine-doped tin oxide) electrodes were evaluated for UA determination by cyclic voltammetry, chronoamperometry, and batch injection analysis. A very low limit of detection (2.3 × 10-8 mol L-1) with good repeatability (RSD = 3.2% for 30 successive analyses) was achieved based on a fast and simple BIA procedure. Finally, α-Ni0.75Zn0.25(OH)2 screen-printed electrodes (SPE) were developed for the measurement of UA directly in real saliva and sweat samples, without interference of ascorbic acid, acetaminophen, lactate, and glucose at their typical concentrations present in those body fluids, revealing high potential for application as disposable sensors in biological systems. Graphical abstract.

Asunto(s)

Técnicas Electroquímicas/métodos , Hidróxidos/química , Saliva/química , Sudor/química , Ácido Úrico/análisis , Catálisis , Técnicas Electroquímicas/instrumentación , Electrodos , Humanos , Límite de Detección , Níquel/química , Oxidación-Reducción , Reproducibilidad de los Resultados , Ácido Úrico/química , Zinc/química

RESUMEN

BACKGROUD: The mechanism by which monosodium urate (MSU) crystals induce inflammation is not completely understood. Few studies have shown that MSU is capable of stimulating the release of IL-1ß in the absence of LPS treatment. The purinergic P2X7 receptor is involved in the release of IL-1ß in inflammatory settings caused by crystals, as is the case in silicosis. METHODS: We investigated the role of P2X7 receptor in sterile MSU-induced inflammation by evaluating peritonitis and paw edema. In in vitro models, we performed the experiments using peritoneal macrophages and THP-1 cells. We measured inflammatory parameters using ELISA and immunoblotting. We measured cell recruitment using cell phenotypic identification and hemocytometer counts. RESULTS: Our in vivo data showed that animals without P2X7 receptors generated less paw edema, less cell recruitment, and lower levels of IL-1ß release in a peritonitis model. In the in vitro model, we observed that MSU induced dye uptake by the P2X7 receptor. In the absence of the receptor, or when it was blocked, MSU crystals induced less IL-1ß release and this effect corresponded to the concentration of extracellular ATP. Moreover, MSU treatment induced HMGB1 release; pre-treatment with P2X7 antagonist reduced the amount of HMGB1 in cell supernatants. CONCLUSIONS: IL-1ß secretion induced by MSU depends on P2X7 receptor activation and involves HMGB1 release. GENERAL SIGNIFICANCE: We propose that cell activation caused by MSU crystals induces peritoneal macrophages and THP-1 cells to release ATP and HMGB1, causing IL-1ß secretion via P2X7 receptor activation.

Asunto(s)

Proteína HMGB1/genética , Inflamación/genética , Interleucina-1beta/genética , Receptores Purinérgicos P2X7/genética , Ácido Úrico/toxicidad , Adenosina Trifosfato/genética , Animales , Modelos Animales de Enfermedad , Edema/inducido químicamente , Edema/genética , Edema/patología , Humanos , Inflamación/inducido químicamente , Macrófagos Peritoneales/efectos de los fármacos , Macrófagos Peritoneales/patología , Ratones , Peritonitis/inducido químicamente , Peritonitis/genética , Peritonitis/patología , Silicosis/genética , Silicosis/patología , Células THP-1 , Ácido Úrico/química

RESUMEN

This paper reports the comparison of the electrochemical properties of 3D PLA-graphene electrodes (PLA-G) under different activation conditions and through different processes. In this work, the performance of the electrodes was evaluated after polishing, electrochemical and chemical treatments and a combination of them. The best results were obtained with hydroxide activation using 1.0 mol L-1 NaOH for 30 min of immersion, which promoted the saponification of PLA exposing the graphene nanoribbon structures. The improvement was more evident also after electrochemical activation, which led to a great increase in surface area, defects, electron transfer rate and amount of edge sites. The analytical performance of the proposed PLA-GNaOH-30-EC electrode was evaluated in the presence of dopamine (DA) by three electrochemical techniques, presenting a broad linear range, and limits of detection of 3.49, 2.17 and 1.67 µmol L-1 were obtained by cyclic voltammetry (CV), differential pulse voltammetry (DPV) and square wave voltammetry (SWV), respectively. The separation and quantification of DA in the presence of AA and UA was also reported. The sensor showed good repeatability and reproducibility and was successfully applied to DA determination in synthetic urine and human serum, showing good recovery, from 88.8 to 98.4%. Therefore, the activation methods were essential for the improvement in the 3D PLA-G electrode properties, allowing graphene surface alteration and electrochemical enhancement in the sensing of molecular targets.

Asunto(s)

Dopamina/análisis , Electroquímica/instrumentación , Grafito/química , Poliésteres/química , Impresión Tridimensional , Electrodos , Límite de Detección , Reproducibilidad de los Resultados , Ácido Úrico/química

RESUMEN

A new disposable microfluidic electrochemical paper-based device (ePAD) consisting of two spot sensors in the same working electrode for the simultaneous determination of uric acid and creatinine was developed. The spot 1 surface was modified with graphene quantum dots for direct uric acid oxidation and spot 2 surface modified with graphene quantum dots, creatininase and a ruthenium electrochemical mediator for creatinine oxidation. The ePAD was employed to construct an electrochemical sensor (based on square wave voltammetry analysis) for the simultaneous determination of uric acid and creatinine in the 0.010-3.0 µmol L-1 range. The device showed excellent analytical performance with a very low simultaneous detection limit of 8.4 nmol L-1 to uric acid and 3.7 nmol L-1 to creatinine and high selectivity. The ePAD was applied to the rapid and successful determination of those clinical biomarkers in human urine samples.

Asunto(s)

Creatinina/orina , Técnicas Electroquímicas/instrumentación , Dispositivos Laboratorio en un Chip , Ácido Úrico/orina , Biomarcadores/química , Biomarcadores/orina , Creatinina/química , Electrodos , Grafito/química , Humanos , Oxidación-Reducción , Papel , Puntos Cuánticos/química , Rutenio/química , Ureohidrolasas/química , Ácido Úrico/química

RESUMEN

The use of invertebrate hemolymph chemistry analysis has the potential to become a major diagnostic tool. The goal of this study was to generate statistically sound hemolymph reference ranges from healthy tarantulas. Hemolymph was drawn from wild caught, acclimatized, and apparently healthy female Chilean rose tarantulas Grammostola rosea (Walkenaer, 1837) ( n = 43) using a modified technique. Hemolymph samples were separately analyzed using the Avian-Reptilian Profile Plus reagent rotor for VetScan® for the following chemistries: aspartate aminotransferase, bile acids, creatine kinase, uric acid, glucose, total calcium, phosphorus, total protein, albumin, potassium, and sodium. With this method the authors were able to establish statistically sound reference ranges for aspartate aminotransferase, creatine kinase, glucose, phosphorus, and total protein. Further in situ studies will determine the practical usability of these values in the evaluation of tarantula health.

Asunto(s)

Hemolinfa/química , Arañas/fisiología , Albúminas/química , Animales , Aspartato Aminotransferasas/química , Aspartato Aminotransferasas/metabolismo , Calcio/química , Creatina Quinasa , Femenino , Ácido Glucárico/química , Fósforo , Potasio/química , Proteínas/química , Valores de Referencia , Sodio/química , Ácido Úrico/química

RESUMEN

Uric acid is the final product of purine metabolism in humans and is considered to be quantitatively the main antioxidant in plasma. In vitro studies showed that the oxidation of uric acid by peroxidases, in presence of superoxide, generates urate free radical and urate hydroperoxide. Urate hydroperoxide is a strong oxidant and might be a relevant intermediate in inflammatory conditions. However, the identification of urate hydroperoxide in cells and biological samples has been a challenge due to its high reactivity. By using mass spectrometry, we undoubtedly demonstrated the formation of urate hydroperoxide and its corresponding alcohol, hydroxyisourate during the respiratory burst in peripheral blood neutrophils and in human leukemic cells differentiated in neutrophils (dHL-60). The respiratory burst was induced by phorbol myristate acetate (PMA) and greatly increased oxygen consumption and superoxide production. Both oxygen consumption and superoxide production were further augmented by incubation with uric acid. Conversely, uric acid significantly decreased the levels of HOCl, probably because of the competition with chloride by the catalysis of myeloperoxidase. In spite of the decrease in HOCl, the overall oxidative status, measured by GSH/GSSG ratio, was augmented in the presence of uric acid. In summary, the present results support the formation of urate hydroperoxide, a novel oxidant in neutrophils oxidative burst. Urate hydroperoxide is a strong oxidant and alters the redox balance toward a pro-oxidative environment. The production of urate hydroperoxide in inflammatory conditions could explain, at least in part, the harmful effect associated to uric acid.

Asunto(s)

Inflamación/sangre , Neutrófilos/metabolismo , Peróxidos/metabolismo , Especies Reactivas de Oxígeno/sangre , Ácido Úrico/análogos & derivados , Catálisis , Línea Celular Tumoral , Radicales Libres/química , Radicales Libres/metabolismo , Humanos , Inflamación/patología , Espectrometría de Masas , Neutrófilos/química , Oxidación-Reducción , Peroxidasa/genética , Peroxidasa/metabolismo , Peróxidos/química , Peróxidos/aislamiento & purificación , Especies Reactivas de Oxígeno/aislamiento & purificación , Superóxidos/química , Superóxidos/metabolismo , Ácido Úrico/química , Ácido Úrico/aislamiento & purificación , Ácido Úrico/metabolismo

RESUMEN

Uric acid is the end product of purine metabolism in humans and is an alternative physiological substrate for myeloperoxidase. Oxidation of uric acid by this enzyme generates uric acid free radical and urate hydroperoxide, a strong oxidant and potentially bactericide agent. In this study, we investigated whether the oxidation of uric acid and production of urate hydroperoxide would affect the killing activity of HL-60 cells differentiated into neutrophil-like cells (dHL-60) against a highly virulent strain (PA14) of the opportunistic pathogen Pseudomonas aeruginosa. While bacterial cell counts decrease due to dHL-60 killing, incubation with uric acid inhibits this activity, also decreasing the release of the inflammatory cytokines interleukin-1ß (IL-1ß) and tumor necrosis factor-α (TNF- α). In a myeloperoxidase/Cl-/H2O2 cell-free system, uric acid inhibited the production of HOCl and bacterial killing. Fluorescence microscopy showed that uric acid also decreased the levels of HOCl produced by dHL-60 cells, while significantly increased superoxide production. Uric acid did not alter the overall oxidative status of dHL-60 cells as measured by the ratio of reduced (GSH) and oxidized (GSSG) glutathione. Our data show that uric acid impairs the killing activity of dHL-60 cells likely by competing with chloride by myeloperoxidase catalysis, decreasing HOCl production. Despite diminishing HOCl, uric acid probably stimulates the formation of other oxidants, maintaining the overall oxidative status of the cells. Altogether, our results demonstrated that HOCl is, indeed, the main relevant oxidant against bacteria and deviation of myeloperoxidase activity to produce other oxidants hampers dHL-60 killing activity.

Asunto(s)

Neutrófilos/metabolismo , Peróxidos/metabolismo , Pseudomonas aeruginosa/efectos de los fármacos , Ácido Úrico/análogos & derivados , Ácido Úrico/metabolismo , Catálisis , Diferenciación Celular/genética , Radicales Libres/metabolismo , Glutatión/metabolismo , Células HL-60/metabolismo , Células HL-60/microbiología , Humanos , Peróxido de Hidrógeno/metabolismo , Ácido Hipocloroso/química , Neutrófilos/microbiología , Oxidantes/metabolismo , Oxidación-Reducción/efectos de los fármacos , Peróxidos/química , Pseudomonas aeruginosa/patogenicidad , Ácido Úrico/química

RESUMEN

Desde el desarrollo de la Diabetes Mellitus (DM) hasta la aparición de nefropatía transcurren varios años, siendo la albuminuria la primera evidencia de la misma. El Ácido Úrico (AU) parece ser importante en la génesis de nefropatía diabética. Objetivo: Determinar la relación entre niveles séricos de AU y valores de proteinuria en 24 horas en pacientes diabéticos que acudieron a las consultas de Diabetes y Nefrología. Métodos: Estudio de campo, transversal y correlacional. Se determinaron niveles séricos de glicemia, creatinina y AU, además de proteinuria en 24 horas en 94 pacientes, que fueron divididos en 2 grupos: ≤5 años y >5 años de diagnóstico de la DM. Resultados: La edad promedio fue 62,4+ 12,9 años. Predominó el género femenino (69,1%). La DM tipo 2 representó 97,1%. Las complicaciones crónicas más frecuentes fueron las Cardiovasculares (45,7%) y la Nefropatía (30,9%). El valor promedio de Glicemia en ayunas fue 138,1+ 58,5 mg/dl, Creatinina 1,15 + 0,84 mg/dl, AU 4,9+1,8 mg/dl. La mediana de Proteinuria en 24 horas fue 112,1mg/24horas / Varianza (σ) 697872 (mg/24 horas)2. 37, 2% presentó Enfermedad Renal Crónica estadio 2. Se encontró HTA en 72,7% de pacientes con AU elevado. El AU mostró correlación positiva con proteinuria en 24 horas mayor a 150 mg/dl. 4,75 mg/dl funcionó como punto de corte del AU, con 69% de sensibilidad y 69,23% de especificidad. Valores superiores a éste tradujeron 5 veces más riesgo de proteinuria >150 mg/dl. El AU resultó ser un fuerte indicador pronóstico para la aparición de proteinuria(AU)

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It often takes several years since the development of Diabetes Mellitus (DM) until the onset of ephropathy, and usually albuminuria is the first clinical evidence of kidney damage. Uric Acid (UA) seems to play an important role in diabetic nephropathy. Objective: To determine the relationship between serum UA and 24-hours Proteinuria in diabetic patients treated on the Diabetes and Nephrology outpatient consultations. Methods: A descriptive cross-sectional correlational study was conducted on 94 patients. Fasting plasma glucose, serum creatinine and UA were determined, as well as 24-hour Proteinuria. Patients were classified into 2 groups: ≤5 years and >5 years since the diagnosis of DM. Results: The mean age was 62, 4+ 12, 9 years. The majority of patients were females (69, 1%). DM2 accounted for 97,1% of all Diabetes types. Cardiovascular diseases (45,7%) and Nephropathy (30,9%) were the most common chronic complications. Fasting plasma glucose mean was 138,1+ 58,5 mg/dl, Creatinine 1,15 + 0,84 mg/dl, UA 4,9+1,8 mg/dl. 24-hours Proteinuria median was 112,1mg/24horas / Variance (σ) 697872 (mg/24- hours) 2. 37,2% showed stage 2 Chronic Kidney Disease. Arterial hypertension was found on 72,7% of the sample with increased UA levels. UA displayed a positive association with 24-hour roteinuria > 150 mg/24 h. 4,75 mg/dl was found as the cut-off point, with sensitivity of 69% and specificity of 69,23%. Subjects with Serum UA above 4,75 mg/dl had a 5 times higher risk of proteinuria>150 mg/dl. Conclusion: UA was a strong prognosis marker for the onset of proteinuria in diabetic patients(AU)

Asunto(s)

Humanos , Masculino , Femenino , Persona de Mediana Edad , Anciano , Anciano de 80 o más Años , Ácido Úrico/química , Diabetes Mellitus/fisiopatología , Hiperglucemia/complicaciones , Proteinuria/metabolismo , Enfermedades Metabólicas

Asunto(s)

Hiperuricemia/historia , Hiperuricemia/prevención & control , Leucemia-Linfoma Linfoblástico de Células Precursoras/historia , Leucemia-Linfoma Linfoblástico de Células Precursoras/prevención & control , Enfermedad Aguda , Alopurinol/química , Niño , ADN de Neoplasias , Historia del Siglo XX , Humanos , Hiperuricemia/terapia , Mercaptopurina/sangre , Pediatría/historia , Leucemia-Linfoma Linfoblástico de Células Precursoras/terapia , Síndrome de Lisis Tumoral , Ácido Úrico/química

RESUMEN

Surface plasmon resonance (SPR) biosensing is based on the detection of small changes in the refractive index on a gold surface modified with molecular recognition materials, thus being mostly limited to detecting large molecules. In this paper, we report on a SPR biosensing platform suitable to detect small molecules by making use of the mediator-type enzyme microperoxidase-11 (MP11) in layer-by-layer films. By depositing a top layer of glucose oxidase or uricase, we were able to detect glucose or uric acid with limits of detection of 3.4 and 0.27 µmol l-1, respectively. Measurable SPR signals could be achieved because of the changes in polarizability of MP11, as it is oxidized upon interaction with the analyte. Confirmation of this hypothesis was obtained with finite difference time domain simulations, which also allowed us to discard the possible effects from film roughness changes observed in atomic force microscopy images. The main advantage of this mediator-type enzyme approach is in the simplicity of the experimental method that does not require an external potential, unlike similar approaches for SPR biosensing of small molecules. The detection limits reported here were achieved without optimizing the film architecture, and therefore the performance can in principle be further enhanced, while the proposed SPR platform may be extended to any system where hydrogen peroxide is generated in enzymatic reactions.

Asunto(s)

Enzimas/química , Técnicas Biosensibles/métodos , Glucosa/química , Glucosa Oxidasa/química , Oro/química , Peróxido de Hidrógeno/química , Límite de Detección , Microscopía de Fuerza Atómica/métodos , Peroxidasas/química , Resonancia por Plasmón de Superficie/métodos , Urato Oxidasa/química , Ácido Úrico/química

RESUMEN

Density functional theory calculations, using the SMD continuum model, indicate that hydrogen transfer from totally protonated uric to a tryptophanyl radical in proteins corresponds to a sequential mechanism. Modeling in methyl butanoate indicates that this mechanism is more important in a hydrophobic medium than in water.

Asunto(s)

Modelos Teóricos , Ácido Butírico/química , Transporte de Electrón , Electrones , Hidrógeno/química , Proteínas/química , Protones , Teoría Cuántica , Termodinámica , Triptófano/química , Ácido Úrico/química , Agua/química

RESUMEN

The use of nanomaterials as an electroactive medium has improved the performance of bio/chemical sensors, particularly when synergy is reached upon combining distinct materials. In this paper, we report on a novel architecture comprising electrospun polyamide 6/poly(allylamine hydrochloride) (PA6/PAH) nanofibers functionalized with multiwalled carbon nanotubes, used to detect the neurotransmitter dopamine (DA). Miscibility of PA6 and PAH was sufficient to form a single phase material, as indicated by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC), leading to nanofibers with no beads onto which the nanotubes could adsorb strongly. Differential pulse voltammetry was employed with indium tin oxide (ITO) electrodes coated with the functionalized nanofibers for the selective electrochemical detection of dopamine (DA), with no interference from uric acid (UA) and ascorbic acid (AA) that are normally present in biological fluids. The response was linear for a DA concentration range from 1 to 70 µmol L(-1), with detection limit of 0.15 µmol L(-1) (S/N = 3). The concepts behind the novel architecture to modify electrodes can be potentially harnessed in other electrochemical sensors and biosensors.

Asunto(s)

Dopamina/análisis , Técnicas Electroquímicas , Nanofibras/química , Nanotubos de Carbono/química , Ácido Ascórbico/química , Técnicas Biosensibles , Rastreo Diferencial de Calorimetría , Caprolactama/análogos & derivados , Caprolactama/química , Electrodos , Nanofibras/ultraestructura , Poliaminas/química , Polímeros/química , Termogravimetría , Compuestos de Estaño/química , Ácido Úrico/química

RESUMEN

We describe the amperometric detection of glucose using oriented nanowires with magnetic switching of the bioelectrochemical process. The fabrication process of the nanowires was prepared through controlled nucleation and growth during a stepwise electrochemical deposition, and it was characterized using scanning electron microscopy. Cyclic voltammetry and amperometry were used to study the magnetoswitchable property; this control was accomplished by changing the surface orientation of nanowires. Under the optimal condition, the amperometric response was also linear up to a glucose concentration of 0.1-16.0 mmol L(-1) with a sensitivity of 81 µA mM(-1). The detection limit was estimated for 4.8×10(-8) mol L(-1), defined from a signal/noise ratio of 3. It also exhibits good reproducibility and high selectivity with insignificant interference from ascorbic acid, acetoaminophen, and uric acid. The resulting biosensor was applied to detect the blood sugar in human serum samples without any pretreatment, and the results were comparatively in agreement with the clinical assay.

Asunto(s)

Técnicas Biosensibles , Glucemia/análisis , Nanotecnología/métodos , Nanocables/química , Acetaminofén/química , Ácido Ascórbico/química , Catálisis , Técnicas Electroquímicas , Electrodos , Glucosa Oxidasa/química , Humanos , Concentración de Iones de Hidrógeno , Límite de Detección , Magnetismo , Microscopía Electrónica de Rastreo , Reproducibilidad de los Resultados , Ácido Úrico/química

RESUMEN

OBJECTIVE: To study several measurements from a single-energy noncontrast computed tomography (NCCT) that may distinguish calcium oxalate, uric acid, and cystine stones. METHODS: Patients with pure urinary stones who had at least 1 single-energy NCCT before the stone composition analysis from January 2008 to December 2012 were enrolled in this study. The analyzed data comprised stone size, volume, core Hounsfield unit (HU), periphery HU, absolute and relative HU differences between core and periphery, and HU density. After these measurements, an NCCT bone window was subjectively evaluated to study the homogeneity of each stone from core to periphery. The Spearman correlation test was used to determine the correlation between HU values and stone size and volume for each group. RESULTS: A total of 113 patients were found with pure urinary stones who also had a corresponding NCCT. There were 36, 47, and 30 patients in the calcium oxalate, uric acid, and cystine groups, respectively. The core HU, periphery HU, absolute and relative HU differences, and HU density were significantly different among the 3 groups (P<.001). Stone size and volume had a positive correlation with core and periphery HUs only for calcium oxalate and cystine stones. The subjective evaluation of the urinary calculi revealed a different pattern for each stone composition. CONCLUSION: Single-energy NCCT may predict calcium oxalate stones with a high degree of accuracy. There is an overlap in radiographic profiles of cystine and uric acid stones, making a definitive differentiation more challenging.

Asunto(s)

Cálculos/química , Cálculos/diagnóstico por imagen , Cistina/análisis , Tomografía Computarizada por Rayos X/métodos , Urolitiasis/diagnóstico por imagen , Adulto , Anciano , Oxalato de Calcio/análisis , Oxalato de Calcio/química , Estudios de Cohortes , Cistina/química , Femenino , Humanos , Masculino , Persona de Mediana Edad , Curva ROC , Estudios Retrospectivos , Sensibilidad y Especificidad , Ácido Úrico/análisis , Ácido Úrico/química , Urolitiasis/terapia

RESUMEN

The hydrophobicity of some photosensitizers can induce aggregation in biological systems, which consequently reduces photodynamic activity. The conjugation of photosensitizers with nanocarrier systems can potentially be used to overcome this problem. The objective of this study was to prepare and characterise hypericin-loaded solid lipid nanoparticles (Hy-SLN) for use in photodynamic therapy (PDT). SLN were prepared using the ultrasonication technique, and their physicochemical properties were characterised. The mean particle size was found to be 153 nm, with a low polydispersity index of 0.28. One of the major advantages of the SLN formulation is its high entrapment efficiency (EE%). Hy-SLN showed greater than 80% EE and a drug loading capacity of 5.22% (w/w). To determine the photodynamic efficiency of Hy before and after encapsulation in SLN, the rate constants for the photodecomposition of two (1)O2 trapping reagents, DPBF and AU, were determined. These rate constants exhibited an increase of 60% and 50% for each method, respectively, which is most likely due to an increase in the lifetime of the triplet state caused by the increase in solubility. Hy-SLN presented a 30% increase in cell uptake and a correlated improvement of 26% in cytotoxicity. Thus, all these advantages suggest that Hy-loaded SLN has potential for use in PDT.

Asunto(s)

Nanopartículas/química , Perileno/análogos & derivados , Fármacos Sensibilizantes a Radiaciones/química , Animales , Antracenos , Benzofuranos/química , Línea Celular Tumoral , Supervivencia Celular/efectos de los fármacos , Humanos , Luz , Lípidos/química , Ratones , Perileno/química , Perileno/farmacología , Fotoquimioterapia , Fármacos Sensibilizantes a Radiaciones/farmacología , Oxígeno Singlete/química , Ácido Úrico/química