Mucin and carbon nanotube-based biosensor for detection of glucose in human plasma.

This work reports an amperometric enzyme-electrode prepared with glucose oxidase, which have been immobilized by a cross-linking step with glutaraldehyde in a mixture containing albumin and a novel carbon nanotubes-mucin composite (CNT-muc). The obtained hydrogel matrix was trapped between two polycarbonate membranes and then fixed at the surface of a Pt working electrode. The developed biosensor was optimized by evaluating different compositions and the analytical properties of an enzymatic matrix with CNT-muc. Then, the performance of the resulting enzymatic matrix was evaluated for direct glucose quantification in human blood plasma. The novel CNT-muc composite provided a sensitivity of 0.44 ±â€¯0.01 mA M-1 and a response time of 28 ±â€¯2 s. These values were respectively 20% higher and 40% shorter than those obtained with a sandwich-type biosensor prepared without CNT. Additionally, CNT-muc based biosensor exhibited more than 3 orders of magnitude of linear dynamic calibration range and a detection limit of 3 µM. The short-term and long-term stabilities of the biosensors were also examined and excellent results were obtained through successive experiments performed within the first 60 days from their preparation. Finally, the storage stability was remarkable during the first 300 days.

Effect of two mouthwashes on salivary ph.

To analyze the effect of two mouthwashes on salivary pH and correlate it with age, buffer capacity and saliva flow rate in healthy volunteers, a crossover phase IV clinical study involving three age-based groups was designed. Two commercial mouthwashes (MW), Cool Mint ListerineR (MWa) and Periobacter R (MWb) were used. The unstimulated saliva of each individual was first characterized by measuring flow rate, pH, and buffer capacity. Salivary pH was evaluated before rinsing with a given MW, immediately after rinsing, 5 minutes later, and then every 10 min (at 15, 25, 35 min) until the baseline pH was recovered. Paired t-test, ANOVA with a randomized block design, and Pearson correlation tests were used. Averages were 0.63 mL/min, 7.06, and 0.87 for flow rate, pH, and buffer capacity, respectively. An immediate significant increase in salivary pH was observed after rinsing, reaching average values of 7.24 (MWb) and 7.30 (MWa), which declined to an almost stable value 15 minutes. The great increase in salivary pH, after MW use shows that saliva is a dynamic system, and that the organism is capable of responding to a stimulus with changes in its composition. It is thus evident that pH of the external agent alone is not a good indicator for its erosive potential because biological systems tend to neutralize it. The results of this study enhance the importance of in vivo measurements and reinforce the concept of the protective action of saliva.

Effect of two mouthwashes on salivary pH

Etários de adultos voluntarios sanos, para analizar el efecto de dos colutorios sobre el pH salival y relacionarlo con la edad la capacidad buffer y el flujo salival. Se utilizaron dos marcascomerciales de colutorios (MW), ListerineCoolMint® (MWa) y eriobacter® (MWb). Primero se caracterizó la saliva sin estimular de cada individuo, se le midió el volumen minuto, el pH y la capacidad buffer. El pH salival se evaluó antes del buche con cada MW, inmediatamente después del enjuague bucal, 5 minutos después y luego cada 10 minutos (a los 15,25, 35 min) hasta que el pH inicial se recuperó. Para el análisis estadístico de los datos se utilizaron: ANOVA en bloque,test t apareado y el test de correlación de Pearson. Al caracterizar la saliva, se obtuvieron los siguientes valores promedio: 0.63 mL/min, 7.06 y 0.87 de volumen minuto,pH, y capacidadbuffer. Luego del enjuague se observó un incremento inmediato y significativo del pH salival alcanzando valores de 7.24 (MWb) y 7.30 (MWa) para descender a un valor estable luegode 15 minutos. El importante incremento del pH salival luego del uso del colutorio, muestra que la saliva es un sistema dinámico y que el organismo es capaz de responder a estímulos con cambios en su composición. Se hace evidente que el pH del agente externo, no es un buen indicador de su potencialerosivo sobre los elementos dentarios ya que los sistemas biológicos tienden a neutralizarlo. Los presentes resultadosponen de manifiesto la importancia de las mediciones en vivo y refuerzan el concepto de la función protectora de la saliva...

Amperometric biosensor for direct blood lactate detection.

An amperometric sensor for lactate quantification is presented. The developed biosensor requires only 0.2 U of lactate oxidase, which is immobilized in a mucin/albumin hydrogel matrix. By protecting the platinum surface with a Nafion membrane, typical interference related to negatively charged species such as ascorbic acid has been minimized to practically undetectable levels. Electrochemical properties associated with the Nafion membrane are assessed as a function of Nafion concentration. In a phosphate buffer solution of pH 7.0, linear dependence of the catalytic current upon lactate bulk concentration was obtained between 2 and approximately 1000 microM. A detection limit of 0.8 microM can be calculated considering 3 times the standard deviation of the blank signal divided by the sensitivity of the sensor. The lactate biosensor presents remarkable operational stability and sensitivity (0.537 +/- 0.007) mA.M(-1), where the error is the standard deviation of the slope calculated from the linear regression of the calibration curve of a fresh biosensor. In this regard, the sensor keeps practically the same sensitivity for 5 months, while the linear range decreases until an upper value of 0.8 mM is reached. Assays performed with whole blood samples spiked with 100 microM lactate gave (89 +/- 6)% of recovery.