Disposable glucose test strip for whole blood with integrated sensing/diffusion-limiting layer

The Impact of the Functional Layer Composition of Glucose Test-Strips on the Stability of Electrochemical Response

Herein, the impact of the chemical stability of RedOx mediator ferricyanide, K3[Fe(CN)6] (FC), a type of buffer solution used for bioreceptor preparation, gel composition (carboxymethylcellulose, CMC, Aerosile, AS, and alginate, ALG) on the long term stability of glucose test-strips and their analytical performance was examined. By simple addition of ALG to the functional gel aiming to improve its viscosity, we managed to enhance the sensitivity of conventional CMC-containing amperometric glucose test-strips from 3.3 µA/mM to 3.9 µA/mM and extend their shelf life from 8 months to 1.7 years. Moreover, during the course of investigations, it was revealed that the activity of enzyme in dependence with the used buffer did not linearly correlate with its activity in a dried functional layer, and the entire long-term electrochemical signal of glucose test-strips was determined by RedOx mediator FC chemical stability. The most stable and sensitive test-strips were obtained by the screen-printing approach from a gel containing 24 mg/mL GOx prepared in citrate buffer with pH 6, 200 mg/mL of FC and 10 mg/mL of CMC supplemented with 25 mg/mL of ALG.

Fluorimetric Mercury Test Strips with Suppressed "Coffee Stains" by a Bio-inspired Fabrication Strategy

A fluorimetric Hg²⁺ test strip has been developed using a lotus-inspired fabrication method for suppressing the “coffee stains” toward the uniform distribution of probe materials through creating a hydrophobic drying pattern for fast solvent evaporation. The test strips were first loaded with the model probes of fluorescent gold-silver nanoclusters and then dried in vacuum on the hydrophobic pattern. On the one hand, here, the hydrophobic constraining forces from the lotus surface-like pattern could control the exterior transport of dispersed nanoclusters on strips leading to the minimized “coffee stains”. On the other hand, the vacuum-aided fast solvent evaporation could boost the interior Marangoni flow of probe materials on strips to expect the further improved probe distribution on strips. High aqueous stability and enhanced fluorescence of probes on test strips were realized by the hydrophilic treatment with amine-derivatized silicane. A test strips-based fluorimetry has thereby been developed for probing Hg²⁺ ions in wastewater, showing the detection performances comparable to the classic instrumental analysis ones. Such a facile and efficient fabrication route for the bio-inspired suppression of “coffee stains” on test strips may expand the scope of applications of test strips-based “point-of-care” analysis methods or detection devices in the biomedical and environmental fields.

Technical and clinical accuracy of three blood glucose meters: clinical impact assessment using error grid analysis and insulin sliding scales

AIMS

Manufacturers of point-of-care testing (POCT) glucose systems must adhere to International Organisation for Standardisation (ISO) 15197 performance standards, a tightened version of which becomes mandatory in May 2016. Using methods deviating from the evaluation requirements of ISO 15197, we investigated the accuracy and clinical utility of three glucose testing systems.

METHODS

Whole blood glucose was measured on 62 EDTA-preserved samples with each system followed by plasma glucose determination with a laboratory hexokinase method. Technical accuracy was assessed using linear regression, Bland-Altman plots and bias. Clinical utility was evaluated using consensus error grid analysis and insulin dosing algorithms.

RESULTS

The correlation coefficient of the glucose measuring devices with the comparator method was between 0.979 and 0.993 (n=61). Bias against the reference method was +0.7-+4.4%. The FreeStyle Lite (0.7±4.4%) and ACCU-CHEK Aviva (1.3±7.3%) systems had the least bias to the reference. Error grid analysis depicts all meters to be clinically accurate, with all results falling within Zones A and B.

CONCLUSIONS

Conformité Européene-marked devices are presumed to have adequate accuracy, but postmarket evaluations are imperative to assess total system accuracy and whether regulatory targets are achieved.

Blood‐Glucose Biosensors, Development and Challenges

Diabetes mellitus is one of the major causes of premature illness and death worldwide. The World Health Organization estimated that by 2030, 439 million people, corresponding to 7.8% of the world adult population, will live with diabetes. With an increasing diabetic population, a Blood Glucose Monitoring System (BGMS) is becoming an ever important tool for diabetes management. The history of blood biosensor development can be traced back to 1932, when Warburg and Christian reported the “yellow enzyme” from yeast changed to colorless upon oxidizing its substrate and resumed the yellow color after its oxidation by oxygen. Since then a lot of research and development has taken place on blood glucose sensors, and the biosensor technology has gone through three generations, with the current commercially available BGMS predominantly relies on the second generation of technology. The advantages and challenges of each generation are discussed. This chapter will examine in detail topics covering the areas of electrode substrate and electrode material selection, fluid detection electrode, reaction chamber, chemistry (electrolyte, polymer, enzyme and mediator), detection method, analytical performance, regulatory requirements and the manufacturing process. The chapter will close with the clinical utility and future direction and application of glucose biosensor include a brief introduction to the Continuous Blood Glucose Monitoring System (CGMS).