Diffusion coefficients of oxygen, hydrogen peroxide and glucose in a hydrogel (original) (raw)
Related papers
Sensors and Actuators B: Chemical, 2015
The development of a sandwich-type biosensor for glucose quantification is presented. This work is focused on the optimization of the enzymatic matrix of the biosensor. The best performance was found for an enzymatic matrix composed by 30% w/w mucin, 70% w/w albumin, 1.35 U glucose oxidase (GOX) per sensor, and glutaraldehyde diluted to 3%. The crosslinking with glutaraldehyde transforms this mixture into a hydrogel that is entrapped between two membranes of polycarbonate. The selected sandwich-type biosensor showed very good response time, sensitivity, stability, and sensor-to-sensor reproducibility. According to the results presented in this manuscript, a biosensor prepared with very high amount of enzyme would not necessarily increase the analytical signal. Simulated curves are compared with experimental data to explain the dependence of sensitivity on the concentration of enzyme. In addition, this kind of comparison represents a quite simple way to estimate the value of v max ≈0.13 M s −1 from the amperometric response of a sensor prepared with 1.34 U of GOX. Considering that sandwich-type biosensors are commonly assembled as part of devices where the sample is diluted with buffer, the more than 3 orders of magnitude of linear behavior of this sensor would ensure the possibility for assessing any sample.
Hysteresis in the glucose permeability versus pH characteristic for a responsive hydrogel membrane
Macromolecular Rapid Communications, 1996
A side-by-side diffusion cell was used to study the permeability of glucose through a temperature-and pH-sensitive poly(N-isopropylacrylamide-co-methacrylic acid) hydrogel membrane. At fixed temperature (37"C), lowering pH in one side of the cell induced hydrogel volume collapse and strongly attenuated glucose permeation across the membrane. Hysteresis was observed in the glucose permeability versus pH characteristic.
Analytical and Bioanalytical Chemistry, 2009
The diffusion coefficient of glucose in different media is an important parameter in life sciences, as well as in biotechnology and microbiology. In this work a simple, fast method is proposed that is based on the electrochemical time of flight principle. In most of the earlier time of flight experiments performed, a constant flight distance was applied. In the present work a scanning electrochemical microscope (SECM) was applied as a measuring tool. With use of the SECM, the flying distance could be changed with high precision, making measurements with several flight distances more accurate and reliable values could be obtained for solutions as well as for gels. The conventional voltammetric methods are not applicable for glucose detection. In our work electrocatalytic copper oxide coated copper microelectrodes and micro-sized amperometric enzyme sensors were used as detectors, while microdroplet-ejecting pneumatically driven micropipettes were used as a source.
ACS Applied Bio Materials, 2018
A continuous glucose monitoring device that resides fully in the subcutaneous tissue has the potential to greatly improve the management of diabetes. Toward this goal, we have developed a competitive binding glucose sensing assay based on fluorescently labeled PEGylated concanavalin-A (PEGylated-TRITC-ConA) and mannotetraose (APTS-MT). In the present work, we sought to contain this assay within the hollow central cavity of a cylindrical hydrogel membrane, permitting eventual subcutaneous implantation and optical probing through the skin. A "self-cleaning" hydrogel was utilized because of its ability to cyclically deswell/reswell in vivo, which is expected to reduce biofouling and therefore extend the sensor lifetime. Thus, we prepared a hollow, cylindrical hydrogel based on a thermoresponsive electrostatic double network design composed of N-isopropylacrylamide and 2-acrylamido-2-methylpropanesulfonic acid. Next, a layer-by-layer (LbL) coating was applied to the inner wall of the central cavity of the cylindrical membrane. It consisted of 5, 10, 15, 30, or 40 alternating bilayers of positively charged poly(diallyldimethylammonium chloride) and negatively charged poly(sodium 4-styrenesulfonate). With 30 bilayers, the leaching of the smaller-sized component of the assay (APTS-MT) from the membrane cavity was substantially reduced. Moreover, this LbL coating maintained glucose diffusion across the hydrogel membrane. In terms of sensor functionality, the assay housed in the hydrogel membrane cavity tracked changes in glucose concentration (0 to 600 mg/dL) with a mean absolute relative difference of ∼11%.
J. of Membrane Science, 1993
coefficients, P ( cm2-sec-1), for glucose, oxygen, acetaminophen (paracetamol), p-aminophenol (PAP), 5-trihydroxybenzene (phloroglucinol) and ascorbate through polycarbonate (PC) neutron beam track-etch membranes of pore radii 0.015-0.4 pm have been determined at (22? 1'C) using a diffusion chamber and the principle of steady state analysis. P values were found to increase with increasing membrane pore radius. The ratio of glucose/O, P values for membranes of pore radii 0.4,0.05, 0.03 and 0.015 pm were determined to be 0.64,0.36,0.22 and 0.045 respectively and therefore decreased with decreasing pore radius. The P value ratios for glucose with respect to other organic species were in the range 0.7-1.2, but showed little dependence on membrane pore radius. It has been found that lower glucose/O, P ratios characteristic of smaller pore radii membranes, were associated with extended linearity ranges for glucose analysis when utilised as upper membranes in a conventional glucose oxidase enzyme laminate electrode construction.
The effect of hydronium ion transport on the transient behavior of glucose sensitive membranes
Journal of Controlled Release, 1993
Explicit expressions for the hydronium ion transport have been added to an existing theoretical model describing the steady-state and transient behavior of glucose-sensitive membranes. The glucose sensitive membrane is a hydrogel containing pendant amine groups and immobilized glucose oxidase creating a membrane which swells in response to changes in glucose concentration. The extent of membrane swelling and the time required for swelling depend upon the pH within the membrane. The membrane pH is a function of the rate of production of gluconic acid from glucose as well as the transport rate of the hydronium ion. Although the steady-state membrane (pH) was predicted by the new model to be lower than that predicted by the previous model, the ( pH) versus glucose curves produced by the two models were similar. The predicted steady-state membrane (pH) was found by the new model to be most affected by changes in the buffer concentration and diffusivity. Contrary to findings of the previous model, the steady-state (pH) was unaffected by the membrane's amine content. However, the amine content of the membrane was the most important factor affecting the transient behavior of the membrane (pH) . The time to reach steady-state with an amine content typically used for a glucose-sensitive membrane was in the order of hours. To achieve response times in the range of minutes rather than hours, both the model and experimental observations show that the concentration of fixed titrateable groups must be minimized.
Use of hydrogel coating to improve the performance of implanted glucose sensors
Biosensors & Bioelectronics, 2008
In order to protect implanted glucose sensors from biofouling, novel hydrogels (146-217% water by mass) were developed based on a copolymer of hydroxyethyl methacrylate (HEMA) and 2,3-dihydroxypropyl methacrylate (DHPMA). The porosity and mechanical properties of the hydrogels were improved using N-vinyl-2-pyrrolidinone (VP) and ethyleneglycol dimethacrylate (EGDMA). The results of SEM and DSC FT-IT analyses showed that the hydrogel (VP30) produced from a monomeric mixture of 34.5% HEMA, 34.5% DHPMA, 30% VP and 1% EDGMA (mol%) had an excellent pore structure, high water content at swelling equilibrium (W eq = 166% by mass) and acceptable mechanical properties. Two kinds of VP30-coated sensors, Pt/GOx/VP30 and Pt/GOx/epoxy-polyurethane (EPU)/VP30 sensors were examined in glucose solutions during a period of 4 weeks. The Pt/GOx/VP30 sensors produced large response currents but the response linearity was poor. Therefore, further studies were focused on the Pt/GOx/EPU/VP30 sensors. With a diffusion-limiting epoxy-polyurethane membrane, the linearity was improved (2-30 mM) and the response time was within 5 min. Eight Pt/GOx/EPU/VP30 sensors were subcutaneously implanted in rats and tested once per week over 4 weeks. All of the implanted sensors kept functioning for at least 21 days and 3 out of 8 sensors still functioned at day 28. Histology revealed that the fibrous capsules surrounding hydrogel-coated sensors were thinner than those surrounding Pt/GOx/EPU sensors after 28 days of implantation.
A glucose biosensor operating under non-isothermal conditions: the dynamic response
Biosensors and Bioelectronics, 1999
The results obtained with a glucose biosensor operating under non-isothermal conditions are presented and discussed. Glucose oxidase, immobilized onto Nylon membranes, was used as biological element. An amperometric two electrodes system was employed to measure the anodic current produced by oxidation of hydrogen peroxide. Non-isothermal conditions were characterised in terms of the temperature difference, DT= T w − T c , and of the average temperature of the system, T av = (T w +T c )/ 2, T w and T c being the temperature in the warm and cold half-cells constituting the biosensor. Comparison between the functioning of the biosensor under isothermal and non-isothermal conditions was performed. It was found that, under non-isothermal conditions, the dynamic response and sensitivity increased, while the response times and the detection limit decreased, if comparison was done with the same parameters measured under isothermal conditions. The increase of the dynamic response was found to be proportional to the applied temperature gradient.
Sensors and Actuators B-chemical, 2018
The first smart hydrogel that shrinks in response to glucose, fructose, or lactate Smart hydrogels shrink when binding of analyte reduces hydrogel net charge Direct electrostatic effects are important for determining smart hydrogel response Smart hydrogels with high isoelectric points are suitable for bioprocess monitoring Abstract: Continuous glucose sensors based upon polyampholytic smart hydrogels (PSHs) have been intensively studied for biomedical and bioprocess applications. Here we focus on the chemistry of PSHs designed for bioprocess monitoring, an application for which the relevant glucose concentration and pH ranges (1-50 mM and 6.8-7.8, respectively) are much wider than those required for biomedical monitoring. PSHs respond to glucose because they contain phenylboronic acid (PBA) moieties that become negatively charged when they reversibly bind to glucose. PSHs also contain positively charged amine groups. Several research groups have designed PSHs that shrink in response to increases in glucose concentration, yet swell in response to increases in fructose or lactic acid concentration. The shrinking behavior is usually attributed to an increase in reversible crosslink density that occurs when the hydrogel binds glucose. However, we show here for the first time that it is possible to design PSHs that shrink in response to increases in glucose, fructose or lactic acid concentration. This is significant because fructose and lactic acid, unlike glucose, are incapable of forming reversible crosslinks within the hydrogel. Therefore, reversible crosslinking cannot be the sole mechanism responsible for the shrinking response of PSHs. In order to obtain PSHs suitable for glucose sensing over wide pH and glucose concentration ranges, we show that it is important to adjust the isoelectric point (IEP) so that it always exceeds the environmental pH value.