RESUMEN
Boronic acids have been used as receptors for the detection of diols and alpha-hydroxy acids. The incorporation of 3-acrylamide phenyl boronic acid (3-APB) into a hydrogel generates a suitably responsive and fully reversible holographic sensor for L-lactate. However, it was also found that the use of 3-APB resulted in the sensor being responsive towards a number of other compounds containing two hydroxy groups. This report details the further investigation into the reaction between L-lactate and three boronic acid-based receptors, both in the holograms and in solution, in order to establish the mechanism of binding. A novel boronate receptor is proposed based on this understanding.
Asunto(s)
Ácidos Borónicos/química , Ácido Láctico/química , Glucosa/química , Holografía , Concentración de Iones de Hidrógeno , Espectroscopía de Resonancia Magnética , Estructura Molecular , SolucionesRESUMEN
BACKGROUND: Current methods of glucose monitoring rely predominantly on enzymes such as glucose oxidase for detection. Phenylboronic acid receptors have been proposed as alternative glucose binders. A unique property of these molecules is their ability to bind glucose in a fully reversible covalent manner that facilitates direct continuous measurements. We examined (1) the ability of a phenylboronic-based sensor to measure glucose in blood and blood plasma and (2) the effect on measurement accuracy of a range of potential interferents. We also showed that the sensor is able to track glucose fluctuations occurring at rates mimicking those experienced in vivo. METHOD: In vitro static measurements of glucose in blood and blood plasma were conducted using holographic sensors containing acrylamide, N,N'-methylenebisacrylamide, 3-acrylamidophenylboronic acid, and (3-acrylamidopropyl) trimethylammonium chloride. The same sensors were also used for in vitro measurements performed under flow conditions. RESULTS: The opacity of the liquid had no affect on the ability of the optical sensor to measure glucose in blood or blood plasma. The presence of common antibiotics, diabetic drugs, pain killers, and endogenous substances did not affect the measurement accuracy, as shown by error grid analysis. Ex vivo flow experiments showed that the sensor is able to track changes accurately in concentration occurring in real time without lag or evidence of hysteresis. CONCLUSIONS: The ability of phenylboronic acid sensors to measure glucose in whole blood was demonstrated for the first time. Holographic sensors are ideally suited to continuous blood glucose measurements, being physically and chemically robust and potentially calibration free.
RESUMEN
BACKGROUND: We recently described a holographic optical sensor with improved selectivity for glucose over fructose that was based on a thin-film polymer hydrogel containing phenylboronic acid receptors. The aim of the present work was to measure glucose in human blood plasma as opposed to simple buffers and track changes in concentration at a rate mimicking glucose changes in vivo. METHODS: We used holographic sensors containing acrylamide, N,N'-methylenebisacrylamide, 3-acrylamidophenylboronic acid, and (3-acrylamidopropyl)trimethylammonium chloride to measure 7 human blood plasma samples at different glucose concentrations (3-33 mmol/L) in static mode. Separately, using a flow cell, the glucose concentration was varied at approximately 0.17-0.28 mmol(-1) x L(-1) x min(-1), and the sensor's ability to continuously monitor glucose was investigated over an extended period. RESULTS: We subjected the results of the ex vivo static measurements to error grid analysis. Of 46 measurements, 42 (91.3%) fell in zone A of a Clarke error grid, and the remainder (8.7%) fell in zone B. The ex vivo flow experiments showed that the sensor is able to accurately track changes in concentration occurring in real time without lag or evidence of hysteresis. CONCLUSIONS: We demonstrate the ability of a phenylboronic acid-based sensor to measure glucose in human blood plasma for the 1st time in vitro. Holographic glucose sensors can be used without recourse to recalibration. Their robust nature, coupled with their format flexibility, makes them an attractive alternative to conventional electrochemical enzyme-based methods of glucose monitoring for people with diabetes.
Asunto(s)
Glucemia/análisis , Ácidos Borónicos , Acrilamida , Acrilamidas , Tampones (Química) , Holografía , Humanos , Hidrogeles , Compuestos de Amonio CuaternarioRESUMEN
Measurement of blood l-lactate is used to assess and monitor exercise performance in sports medicine. This report describes the initial development of a holographic sensor, which employs a synthetic receptor, to enable the selective and continuous real-time measurement of l-lactate for eventual in vivo application. Three boronic acid-based receptors have been synthesized, integrated into thin acrylamide hydrogel films, and then subsequently transformed into holographic sensors. Changes in the replay wavelength of the sensors were used to characterize the swelling behavior of the matrix as a function of l-lactate concentration. It was found that the incorporation of 3-acrylamidophenyl boronic acid into an acrylamide hydrogel produced the largest response toward l-lactate. The effects of hydrogel composition, fluctuating l-lactate concentrations, and the response of potential interfering agents to the sensor have been investigated.
Asunto(s)
Técnicas Biosensibles/métodos , Holografía/métodos , Ácido Láctico/sangre , Acrilamida/química , Ácidos Borónicos/química , Humanos , Hidrogel de Polietilenoglicol-Dimetacrilato/químicaRESUMEN
A novel holographic sensor system capable of detecting dynamic changes in glucose concentration has been developed. The hologram is recorded within a bio-compatible hydrogel matrix containing phenylboronic acid derivatives. On binding glucose, the colour of the hologram red-shifts to longer wavelengths as the hydrogel expands and this colour change is used to quantify glucose concentration. However, phenylboronic acids are non-selective and bind a wide variety of cis-diols. In blood, glucose is the only sugar found free at high concentration, whilst other sugars are typically found as part of glycoproteins and macromolecular structures. Although glycoproteins have been shown to have no effect on the sensor, phenylboronic acids can bind lactate much more readily than glucose. We have designed two polymer hydrogel systems to increase the selectivity of the sensor for glucose over lactate. The first involved the use of high concentrations of 3-acrylamidophenylboronic acid (3-APB) whilst the second system utilised 2-acrylamido-5-fluorophenylboronic acid (5-F-2-MAPB). Both systems displayed an increased selectivity to glucose over lactate at physiological pH and ionic strength and could be deployed as selective holographic sensors for glucose detection in physiological fluids.