On-line Monitoring Of Glucose Research Articles

An automatic glucose monitoring system based on periplasmic binding proteins for online bioprocess monitoring

Glucose is one of the most vital nutrients in all living organisms, so its monitoring is critical in healthcare and bioprocessing. Enzymatic sensors are more popular as a technology solution to meet the requirement. However, periplasmic binding proteins have been investigated extensively for their high sensitivity, enabling microdialysis sampling to replace existing complex and expensive glucose monitoring solutions based on enzymatic sensors. The binding proteins are used as optical biosensors by introducing an environment-sensitive fluorophore to the protein. The biosensor's construction, characterization, and potential application are well studied, but a complete glucose monitoring system based on it is yet to be reported. This work documents the development of the first glucose sensor prototype based on glucose binding protein (GBP) for automatic and continuous glucose measurements. The development includes immobilizing the protein into reusable chips and a low-cost solution for non-invasive glucose sampling in bioprocesses using microdialysis sampling technique. A program was written in LabVIEW to accompany the prototype for the complete automation of measurement. The sampling technique allowed glucose measurements of a few micromolar to 260 mM glucose levels. A thorough analysis of the sampling mode and the device's performance was conducted. The reported measurement accuracy was 81.78%, with an RSD of 1.83%. The prototype was also used in online glucose monitoring of E. coli cell culture. The mode of glucose sensing can be expanded to the measurement of other analytes by switching the binding proteins.

Continuous glucose metabolism monitoring platform for long-term analysis of tumor cell proliferation and drug response

Glucose metabolism monitoring has emerged as a crucial method for analyzing the metabolic state of tumor cells. Conventional glucose measurement techniques only provide endpoint information and lack the ability for real-time monitoring. Therefore, it is imperative to develop a continuous and long-term monitoring approach to gain insights into cellular behavior and metabolic regulation. We developed a selective permeation outer membrane specifically designed for high glucose concentrations in cell culture, allowing continuous operation in the range of 0–32 mM, significantly exceeding the linear range of typical continuous glucose sensing systems (CGMS). The platform enabled real-time and continuous monitoring of glucose consumption during tumor cell proliferation, demonstrating high linearity, stability, and anti-interference in the cell culture medium. More importantly, by optimizing the electrode design, we achieved accurate and long-term online glucose monitoring for over seven days, double the current capacity. The prepared sensors have enabled continuous monitoring of glucose metabolism parameters in different cell lines, cell numbers and cells treated with different drugs, providing a promising strategy to explore cellular metabolism. The glucose monitoring platform holds tremendous potential in various fields, including drug screening, toxicology, cancer therapy and personalized medicine.

Online Glucose Analysis System With High Precision and Wide Detection Range for Fermentation Monitoring

Online glucose monitoring during the fermentation process is critical for evaluating the microbial metabolism state and reaction course, achieving precise process control for industrial efficiency enhancement. However, the fast, wide-range and highly accurate test technique always presents a challenge for state-of-the-art analytical instruments. In this work, we proposed an online glucose analysis system based on a homemade screen-printed enzymatic biosensor chip composed of Prussian blue nanocubes with a high sensitivity of 83.404 mA mM <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> . To match the detection behavior of this chip, a specific signal conversion system was designed to realize the highly precise acquisition and treatment of nA-level currents by integrating hardware acquisition circuits and Kalman filtering algorithms. Focusing on the continuous change in glucose concentration during fermentation, an adaptive injection strategy for the sampling volume was proposed to achieve an ultrawide linear range from 1 g/L to 180 g/L. The results show that the online analytical system exhibits excellent detection performance with high accuracy and low relative error of detection (<2%) during the fermentation of sophorolipid and ethanol compared to high performance liquid chromatography and commercial analyzers.

In vivo monitoring of cerebral glucose with an updated on-line electroanalytical system.

Because cerebral species involve rapid events, increasing the temporal resolution to realize in vivo near-real-time measurements is desirable. Here, we aimed to improve the low resolution of our previous on-line electroanalytical system by decreasing the dead volume and reducing molecular dispersion. This updated system has advantages of elevated time resolution and accelerated analysis for on-line monitoring of glucose versus the previous system. Finally, this new system was successfully applied to continuous measurement of cerebral glucose in vivo during global ischemia/reperfusion events. This study is expected to offer a reliable on-line analytical platform for continuous monitoring of important species associated with fast physiological and pathological events in vivo. Graphical abstract.

On-line glucose monitoring by near infrared spectroscopy during the scale up steps of mammalian cell cultivation process development

NIR spectroscopy is a non-destructive tool for in-situ, on-line bioprocess monitoring. One of its most frequent applications is the determination of metabolites during cultivation, especially glucose. Previous studies have usually investigated the applicability of Near Infrared (NIR) spectroscopy at one bioreactor scale but the effect of scale up was not explored. In this study, the complete scale up from shake flask (1 L) through 20 L, 100 L and 1000 L up to 5000 L bioreactor volume level was monitored with on-line NIR spectroscopy. The differences between runs and scales were examined using principal component analysis. The bioreactor runs were relatively similar regardless of scales but the shake flasks differed strongly from bioreactor runs. The glucose concentration throughout five 5000 L scale bioreactor runs were predicted by partial least squares regression models that were based on pre-processed spectra of bioreactor runs and combinations of them. The model that produced the lowest error of prediction (4.18 mM on a 29 mM concentration range) for all five runs in the prediction set was based on the combination of 20 L and 100 L data. This result demonstrated the capabilities and the limitations of an NIR system for glucose monitoring in mammalian cell cultivations.

Online Glucose Measurement in DMEM for &lt;i&gt;In Vitro&lt;/i&gt; Cell Culture

In-vitro cell culture offers the ability to grow individual cells and monitor their behaviour in a controlled environment over a certain time. During culture, different parameters have to be controlled to ensure a vital growth of cells. The most important parameters are temperature, pH-value, oxygen and carbon dioxide levels as well as the glucose concentration. All of these parameters influence the growth ability of the cell culture and should be monitored online. The online monitoring of glucose was achieved with a novel GOD based sensor which enabled a real-time measurement of glucose during cell culture. A first-time characterisation of the sensor was carried out in the culture medium DMEM. In addition, material properties of the culture system were investigated. At first to establish a baseline measurement, the sensor was placed in different glucose concentrations dissolved in Water-KCl mixture at 25 °C inside a batch chamber under constant stirring. Afterwards, the temperature was increased to 37 °C to simulate a cell culture environment. In addition, the system was transferred into a flow-through reaction chamber. The highest response signal and the most stable signal was achieved at 37 °C with DMEM during flow-through measurement. Based on these measurements online glucose monitoring in cell culture was possible to determine the glucose consumption for each cell which is important for future human-on-a-chip devices to prevent diabetic metabolisms.

생물공정 모니터링을 위한 광섬유 포도당 및 젖산 센서의 개발

In this work the optical fiber glucose and lactate biosensors were developed by using fluorescent dye and enzyme immobilized on the end tip of an optical fiber. 3-Glycidyloxypropyl)methyldiethoxysilane (GPTMS), (3-Aminopropyl) trimethoxysilane (APTMS) and Methyltrimethoxysilane (MTMS) were used to immobilize glucose oxidase (GOD), lactate oxidase (LOD) and ruthenium(II) complex (tris(4,7-diphenyl-1,10-phenanthroline) ruthenium(II), <TEX>$Ru(dpp)_3^{2+}$</TEX>) as oxygen sensitive fluorescent dye. MTMS sol-gel was an excellent supporting material for the immobilization of <TEX>$Ru(dpp)_3^{2+}$</TEX>, GOD, and LOD on the optical fiber. Storage stability of the optical fiber glucose sensor was kept constant over 20 days, while the optical fiber lactate sensor had constant storage stability over 17 days. The optical fiber glucose and lactate biosensors also maintained good operational stability for 20 hours and 14 hours, respectively. The activities of the immobilized enzymes were most excellent at pH 7 and at <TEX>$25^{\circ}C$</TEX>. On-line monitoring of glucose and lactate in a simulated process was performed with the optical fiber glucose and lactate biosensors. On-line monitoring results were agreed with those of off-line data measured with high performance liquid chromatography (HPLC).

Accuracy assessment of online glucose monitoring by a subcutaneous enzymatic glucose sensor during exercise in patients with type 1 diabetes treated by continuous subcutaneous insulin infusion

AimOnline continuous glucose monitoring (CGM) during physical exercise would be highly useful in patients with insulin-treated diabetes. For this reason, this study assessed whether such a goal could be reached with a subcutaneous ‘needle-type’ enzymatic sensor. MethodsTen patients (five women/five men), aged 51±12 years, with type 1 diabetes for 24±11 years treated by continuous subcutaneous insulin infusion (CSII) for more than 1 year (HbA1c: 7.5±0.8%) performed a 30-min bout of exercise at a constant high-intensity load (15% above their individual ventilatory threshold) on a cycle ergometer. All patients wore a subcutaneous ‘needle-type’ enzymatic glucose sensor linked to a portable monitor (Guardian® RT, Medtronic-MiniMed, Northridge, CA, USA) that had been inserted the previous evening. Sensor calibration was performed against capillary blood glucose immediately before the exercise. CGM values were recorded every 5min from T–10 to T+30, then every 10min during the recovery period from T+30 to T+90. These recorded values were compared with blood glucose assays performed on simultaneously collected venous samples. ResultsSensor functioning and tolerability raised no problems except for one sensor that could not be adequately calibrated. Data from this patient were excluded from the data analysis. An average blood glucose decrease of 63±63mg/dL (3.5±3.5mmol/L) (median decrease: 58mg/dL [3.22mmol/L]; range: –3mg/dL [0.16mmol/L] to 178mg/dL [9.8mmol/L]) occurred during exercise bouts, while CGM values decreased by 38±49mg/dL (2.11±2.72mmol/L) (median: 32mg/dL [1.7mmmol/L]; range: –15mg/dL [0.83mmol/L] to 58mg/dL [3.22mmol/L]). Cumulative paired glucose values (n=135) could be analyzed. The correlation factor between CGM and blood glucose values was 0.957 with an intercept of 0.275. The mean difference between paired values according to Bland–Altman analysis was 10±31mg/dL (0.56±1.72mmol/L). Clarke error grid analysis showed 91% of paired points in A and B zones, while 0%, 9% and 0% of paired points were in the C, D and E zones, respectively. ConclusionBlood glucose changes during intensive physical-exercise bouts performed by CSII-treated type 1 diabetes patients can be estimated with acceptable clinical accuracy by online CGM.

Effectiveness and safety of a glucose data-filtering system with automatic response software to reduce the physician workload in managing type 2 diabetes

We conducted a randomized controlled trial to investigate the efficacy and safety of a system for online glucose monitoring of type 2 diabetes patients. The software automatically filtered the self-monitored blood glucose data to reduce physicians' time. In the control group, the physicians had to contact the patients manually. We measured the time spent by physicians for online management in a 24-week study. Seventy-nine patients were recruited. The frequency of physicians' online monitoring of the patients was decreased by 55% in patients with HbA(1c) ≤ 6.5% and by 29% when HbA(1c) > 6.5% (P < 0.01). Physicians' log-in time was reduced by 67% and 55% in patients with HbA(1c) ≤6.5% and >6.5%, respectively (P <0.05). HbA(1c) levels were maintained at <6.5% during the study period in both groups. The study showed the efficacy and safety of the software for online communication in diabetes management. The results suggest that it could improve the cost-effectiveness of online communication systems and form the basis of future clinical applications.

BioMEMS device with integrated microdialysis probe and biosensor array

The fabrication of a microdevice for continuous sampling and on-line monitoring of glucose is described. The device comprised a microdialysis sampling system integrated on the flow through channel of a microfabricated enzyme sensor. The sensor was produced by thin film technology and was assembled to a printed circuit board (PCB) that provided the means for both electrical and fluidic connections. A polyacrilonitrile fibre, with a cut-off of 50 kDa, was used in the fabrication of the sampling probe. The performance of the device was evaluated in-vitro. High sampling efficiency of the microdialysis probe was achieved by appropriate selection of the perfusion fluid flow rate. Response times varying from 1.5 to 3.0 min were determined for flow rates ranging between 1 and 0.2 μl/min. The linear response range was up to 30 mM glucose and interference from other electroactive substances was almost negligible. The device showed excellent stability under continuous operation for at least 5 days and sensitivity variation less than 3% over a period of 15 days.

Chemiluminescence flow sensor for in vivo on-line monitoring of glucose in awake rabbit by microdialysis sampling

A novel chemiluminescence (CL) flow sensor for in vivo on-line monitoring of glucose in blood by microdialysis sampling is described in this paper. The sol–gel method is introduced to co-immobilize horseradish peroxidase (HRP) and glucose oxidase (GOD) on the inside surface of the CL flow cell. The CL detection involved enzymatic oxidation of glucose to d-gluconic acid and H 2O 2, then H 2O 2 oxidizing luminol to produce CL in presence of HRP. The perfusion rate of the dialysate was 5.0 μl/min. The dialysate sample volume was 20 μl, and the sample throughput was 15 h −1. The variation of glucose level in blood of the rabbit was monitored after the administration of glucose to demonstrate the favorable resolution and reliability of the system for in vivo on-line monitoring.

On-line continuous monitoring of glucose or lactate by ultraslow microdialysis combined with a flow-through nanoliter biosensor based on poly(m-phenylenediamine) ultra-thin polymer membrane as enzyme electrode.

A miniaturised flow-through biosensor with a cell volume of only a few nanoliters was developed in our laboratory. The biosensor can be directly coupled to a microdialysis or ultrafiltration probe. Sampling and continuous on-line monitoring can thus be carried out at submicroliter levels and as a consequence quantitative recoveries of the analyte of interest are achieved. Via this method excessive calibration procedures, as are necessary with conventional microdialysis, are avoided. Here, the construction and the performance of such a biosensor for the continuous on-line monitoring of glucose and lactate will be presented. The biosensor is based on the amperometric detection of hydrogen peroxide after conversion of the analyte of interest by an immobilised oxidoreductase enzyme. Immobilisation of the enzyme is performed through electropolymerisation of m-phenylenediamine. Strategies to improve the performance (e.g. linearity, selectivity and stability) of the miniaturised biosensor are discussed and ex vivo and in vivo experiments carried out thus far demonstrate the potential of this miniaturised flow-through biosensor.

An automated flow injection analysis system for on-line monitoring of glucose and L-lactate during lactic acid fermentation in a recycle bioreactor

The study concerns on-line sequential analysis of glucose and L-lactate during lactic acid fermentation using a flow injection analysis (FIA) system. Enzyme electrodes containing immobilized glucose oxidase and L-lactate oxidase were used with an amperometric detection system. A 12-bit data acquisition card with 16 analog input channels and 8 digital output channels was used. The software for data acquisition was developed using Visual C++, and was devised for sampling every hour for sequential analyses of lactate and glucose. The detection range was found to be 2–100 g l−1 for glucose and 1–60 g l−1 for L-lactate using the biosensors. This FIA system was used for monitoring glucose utilization and L-lactate production by immobilized cells of Lactobacillus casei subsp. rhamnosus during a lactic acid fermentation process in a recycle batch reactor. After 13 h of fermentation, complete sugar utilization and maximal L-lactate production was observed. A good agreement was observed between analysis data obtained using the biosensors and data from standard analyses of reducing sugar and L-lactate. The biosensors exhibited excellent stability during continuous operation for at least 45 days.

Part II. Potentiodynamic on-line monitoring of the concentration of glucose in metal-walled bioreactors

Abstract Electronics, steam-sterilized membranes and disposable sensors for the on-line monitoring of glucose in the 1–20 mM range are described. The problems addressed, in addition to those common with, and addressed earlier in the context of, continuous amperometric in vivo monitoring of glycemia in diabetic patients, derive from (a) the need to monitor the glucose concentration in the total absence of oxygen, (b) the variation of the signal at low (1 mM) glucose concentration with the partial pressure of oxygen when the sensor is based on the electrical connection (wiring) of glucose oxidase reaction centers to an electrode through an electron conducting redox hydrogel and (c) the safety related requirement to ground the stainless steel-walled industrial bioreactor electrically. We show that the effect of oxygen is eliminated upon shielding the glucose anode (poised at +400 mV vs. Ag ∣ AgCl) by a glucose permeable, gold-coated membrane cathode (poised at −400 mV vs. Ag ∣ AgCl). We also describe a novel and simple circuit allowing the use of the grounded reactor wall as the counter-electrode and the poising of the nearby anode and cathode at their respective potentials.

Development of an On-Line Electrochemical Biosensor for Glucose Determination in Rat Brain Using Microdialysis Sampling

A biosensor for on-line monitoring of glucose in brain dialysates was developed. The biosensor was generated in the cross-flow amperometric cell by potentiostatic electropolymerization of phenol (50 mM) in the presence of glucose oxidase (935 U/mL) at +600 mV (vs. Ag/AgCl) at a flow-rate of 5 µL/min at the Pt electrode. The polyphenol film ensured low interferences of ascorbate. The on-line set-up was mathematically described and the model was used to calculate the extracellular concentration of glucose in the striatum of an anesthetized rat. The concentration of glucose was found to be 1.4±0.5 mM and 0.9±0.2 mM in two independent experiments.

Application of Convective Interaction Media disks with immobilised glucose oxidase for on-line glucose measurements

A new polymeric macroporous material, Convective Interaction Media (CIM) was applied as a support for glucose oxidase (GOD) immobilisation. CIM epoxy disks with the immobilised enzyme were integrated as an enzyme reactor in a flow injection analysis (FIA) system and applied to on-line monitoring of glucose during cultivation of Saccharomyces cerevisiae and citric acid production by Aspergillus niger. The developed CIM GOD disk–FIA system exhibited good signal reproducibility and satisfactory long-term stability with a linear response in the range 10–200 mg l −1. The CIM disk applied as an enzyme reactor proved to be a successful replacement for conventionally used packed-bed columns and as such it was well suited for on-line monitoring of bioprocesses.

Development and comparison of biosensors for in-vivo applications

Electrochemical biosensors have been of increasing interest, especially those developed to be directly applied in diagnostic areas, such as neuroscience. We have been interested in developing a range of biosensors for monitoring glucose, lactate, pyruvate, and glutamate in order to study on-line both brain function in the laboratory and to monitor brain health in neurointensive care. For a biosensor to function effectively in these situations, it has to combine the following characteristics: quick response and high sensitivity, good reproducibility and adequate stability. In this study we compared the performance of a number of different amperometric biosensors strategies. These included ferrocene mediation of immobilised enzymes (system A), a redox hydrogel based system (system B), and a conducting polymer approach using polyaniline (system C). All assays were operated as flow-injection systems with upstream immobilised enzyme beds if necessary. When calibrated for H2O2 systems A and B reacted quickly enough to give quantitative conversion up to 0.2 mM. Above this concentration the response was limited by horseradish peroxidase enzyme kinetics and eventually enzyme loading. System C showed a restricted H2O2 response. When calibrated for glucose (by use of immobilised glucose oxidase) system B exhibited the highest sensitivity but its analytical range was restricted because the system became limited by H2O2 response. System A had low sensitivity for analyte compared to H2O2 and system B, but a greater useful range. Problems of mediator cycling between the immobilised enzymes are discussed. System C gave an excellent linear range but sensitivity was limited by background noise. Stability and reproducibility of the systems are also described. In conclusion, from this study the ferrocene system proved to be overall most useful and has now been used in the first dual on-line monitoring of glucose and lactate in patients in neurointensive care.

Evaluation of cell recycling in continuous fermentation of enzymatic hydrolysates of spruce with Saccharomyces cerevisiae and on-line monitoring of glucose and ethanol

The maximum growth rate of Saccharomyces cerevisiae ATCC 96581, adapted to fermentation of spent sulphite liquor (SSL), was 7 times higher in SSL of hardwood than the maximum growth rate of bakers' yeast. ATCC 96581 was studied in the continuous fermentation of spruce hydrolysate without and with cell recycling. Ethanol productivity by ATCC 96581 in continuous fermentation of an enzymatic hydrolysate of spruce was increased 4.6 times by employing cell recycling. On-line analysis of CO2, glucose and ethanol (using a microdialysis probe) was used to investigate the effect of fermentation pH on cell growth and ethanol production, and to set the dilution rate. Cell growth in the spruce hydrolysates was strongly influenced by fermentation pH. The fermentation was operated in continuous mode for 210 h and a theoretical ethanol yield on fermentable sugars was obtained.

On-line monitoring of glucose in mammalian cell culture using a flow injection analysis (FIA) mediated biosensor

A flow injection analysis (FIA) biosensor system has been developed for on-line determination of glucose during mammalian cell cultivation. The culture sample was peristaltically withdrawn from the bioreactor and after cell separation by a steam sterilizable ceramic microfilter, the filtrate was continuously fed to the FIA mediated-biosensor system at 4 mLh(-1), whereas the cell-containing retentate was recirculated to the bioreactor. In the amperometric biosensor system, glucose oxidase was covalently immobilized onto a preactivated nylon membrane and attached to the sensing area of a platinum working electrode. The enzyme reaction was coupled with the mediator 1,1'-dimethylferricinium (DMFe(+))-cyclodextrin inclusion complex to recycle the reduced glucose oxidase to its original active state. 1,1'-Dimethylferrocene (DMFe) was then reoxidized to DMFe(+) at the surface of the platinum electrode poised at + 0.15 V vs silver/silver chloride. The FIA mediated-biosensor was linear up to 6 mM glucose, with a detection limit of 0.1 mM, and possessed excellent reproducibility (+/- 0.4 %, 95 % confidence interval) over 123 repeated analyses during a 62 h continuous operation. The immobilized glucose oxidase was stable for up to 7 days when applied to glucose measurement during 5-10 day fed-batch cultivation of 293S mammalian cells. The results obtained from the mediated-biosensor system compared well with the hexokinase and HPLC data.

Design and development of a miniaturised total chemical analysis system for on-line lactate and glucose monitoring in biological samples

A miniaturised Total chemical Analysis System (μTAS) for glucose and lactate measurement in biological samples constructed based on an integrated microdialysis sampling and detection system. The complete system incorporates a microdialysis probe for intravascular monitoring in an ex vivo mini-shunt arrangement, and a silicon micromachined stack with incorporated miniaturised flow cell/sensor array. The prototype device has been developed based on state-of-the-art membrane and printed circuit board technology. The flow-through detection system is based on a three-dimensional flow circuit incorporating silicon chips with stacked micromachined channels. An integrated biosensor array (comprising enzyme sensors specific for glucose and lactate) is placed at the base of the stack allowing the detector to be incorporated within the μTAS assembly. These glucose and lactate biosensors are prepared using photolithographic techniques, with measurement based on the detection of hydrogen peroxide at glucose oxidase and lactate oxidase modified platinum electrodes. The resulting amperometric current (at 500 mV vs. Ag/AgCl) is proportional to the concentration of analyte in the sample. All instrumentation is under computer control and the complete unit allows continuous on-line monitoring of glucose and lactate, with fast stable signals over the relevant physiological range for both analytes. The microdialysis system provides 100% sampling efficiency. Sensor performance studies undertaken include optimisation of sensitivity, linearity, operational stability, background current, storage stability and hydration time. The total system (sampling and detection) response time is of the order of 4 min, with sensor sensitivity 1–5 nA mM−1 for glucose and lactate over the range 0.1–35 and 0.05–15 mM, respectively.