Cheng-Teng Hsu

A disposable screen-printed silver strip sensor for single drop analysis of halide in biological samples

A screen-printed silver strip with three-electrode configuration of Ag-working, Ag-counter and Ag/Ag(x)O reference electrodes was developed for simultaneous determination of chloride, bromide and iodide in aqueous solutions. It was fabricated simply by screen-printing silver ink onto a polypropylene (PP) base. The in-situ prepared Ag/Ag(x)O reference electrode can avoid the leaching interference in chloride detection while using a conventional Ag/AgCl reference electrode. A single drop of analyte (50 microl) is enough to determine iodide, bromide and chloride by measuring the well-separated oxidation peak currents of respective silver halides. The calibration graph was linear from 10 microM to 20 mM for iodide and bromide and 100 microM to 20 mM for chloride and the detection limit (S/N=3) was 3.05 microM, 2.95 microM and 18.83 microM for iodide, bromide and chloride, respectively. The strip is designed to be disposable and as such manual polishing is not necessary. The proposed sensor is not only simple to manufacture and easy to operate but also fast and precise with little detection volume. It is successfully applied to the determination of halide ions in real samples.

Fabrication of a Glucose Biosensor Based on Inserted Barrel Plating Gold Electrodes

We demonstrate here the application of barrel plating gold electrodes for fabricating a new type of disposable amperometric glucose biosensor. It is prepared by inserting two barrel plating gold electrodes onto an injection molding plastic base followed by immobilizing with a bioreagent layer and membrane on the electrode surface. The primary function of barrel plating is to provide an economical way to electroplate manufactured parts. The manufacture procedure is simple and can increase the fabrication precision for automation in mass production. At the two-electrode system, the detection of glucose is linear up to 800 mg/dL (i.e., 44.5 mM, r(2) > 0.99) in pH 7.4 PBS with a sensitivity of 0.71 microA/mM. Excellent sensor-to-sensor reproducibility shows coefficients of variation of only 0.8-1.4% for the detection of 56.5-561.0 mg/dL glucose. In laboratory trials 176 capillary blood samples with a range of 30-572 mg/dL glucose are used to evaluate the clinical application of the biosensor. A good linear correlation is observed between the measured values of the proposed biosensor and laboratory reference. Error grid analysis verifies that the proposed technique is promising in fabricating biosensor strips on a mass scale. As successfully demonstrated by using whole blood glucose as a model analyte, the fabrication technique can extend into other barrel plating noble metal electrodes for various applications.

Assessing the quality of Bionime self-monitoring blood glucose system Rightest GM110: A critical evaluation of interference and ambient circumstances

BACKGROUND The key issue in preventing chronic diabetic complications is to maintain near-normoglycemia. Analytical evaluation of Bionime self-monitoring blood glucose (SMBG) Rightest GM110 was carried out in this study. METHODS The evaluation was executed according to the Standards for Reporting Diagnostic Accuracy (STARD) and the Clinical and Laboratory Standards Institute (CLSI). The evaluation procedure mainly focused on analytical performance. The accuracy tests included hematocrit, interferants, temperature, humidity, altitude and clinical evaluations. RESULTS Good linearity response (R(2)>0.99) and satisfactory precision (CVs: 1.1-2.8%) were observed in glucose concentrations of 0.6-30.5 mmol/l. In hematocrit test, the Rightest GM110 was suitable for use in sample containing hematocrit in the range of 30-55%. Interfering test indicated that almost all substances tested were insignificant, with bias <10% in medium- and hyper-glycemia samples. Satisfactory stability was also found under various ambient circumstances, with bias within +/-10%. In clinical trials, values within the acceptable zone (A+B) were 100% and values within zone A exceed 95% in error grid analysis. CONCLUSIONS The Bionime Rightest GM110 is reliable to display accurate glucose concentrations in specimens with irresistible interfering factors.

Superior long-term stability of a glucose biosensor based on inserted barrel plating gold electrodes

Disposable one shot usage blood glucose strips are routinely used in the diagnosis and management of diabetes mellitus and their performance can vary greatly. In this paper we critically evaluated the long-term stability of glucose strips made of barrel plating gold electrodes. Compared to other glucose biosensing platforms of vapor deposited palladium and screen printed carbon electrodes, the proposed glucose biosensor was found to show the best stability among the three biosensing platforms in thermal acceleration experiments at 40 degrees C for 6 months with an average bias of 3.4% at glucose concentrations of 5-20 mM. The precision test of this barrel plating gold glucose biosensor also showed the best performance (coefficients of variation in the range of 1.4-2.4%) in thermal acceleration experiments at 40 degrees C, 50 degrees C and 70 degrees C for 27 days. Error grid analysis revealed that all measurements fell in zone A and zone B. Regression analysis showed no significant difference between the proposed biosensor and the reference method at 99% confidence level. The amperometric glucose biosensor fabricated by inserting two barrel plating gold electrodes onto an injection-molding plastic base followed by immobilizing with a bio-reagent layer and membrane was very impressive with a long-term stability up to 2.5 years at 25 degrees C. Overall, these results indicated that the glucose oxidase/barrel plating gold biosensing platform is ideal for long-term accurate glycemic control.

Multiple screening of urolithic organic acids with copper nanoparticle-plated electrode: Potential assessment of urolithic risks

There is yet to be a reliable prediction of urolithiasis. To facilitate early diagnosis, a simple and rapid high performance liquid chromatography method with electrochemical detection using disposable copper-nanoparticle-plated electrodes (Cu(n)-SPE) was developed for multiple detection of creatinine and 4 urolithic organic acids. A total of 206 normal and urolithic human and canine urines and urolith samples were collected for direct analysis of creatinine, cystine, uric acid, oxalic acid, and citric acid without sample cleanup and derivatization processes. Urinary organic acids were separated in 11 min and were devoid of ascorbic acid interference. The detection limits (S/N>3) were at the nanomolar level with linear dynamic ranges spanning 2-3 orders of magnitude. Recoveries in urine ranged from 99.5% for creatinine to 86.5% for citric acid. The analytical variations (RSD) were less than 6.2% in phosphate buffer and 7.7% in urine. Important differences in organic acid levels/profiles between animal species and among normal and urolithic urines/urolith were unveiled and corresponded well (70-90%) with the urolithic risk in a retrospective assessment. The simplicity and reproducibility of this method using disposable Cu(n)-SPE has made routine urine analysis possible and can be of great clinical and diagnostic potential in the screening of urolithiasis and abnormal states related to excess secretion of organic acids and amino acids in humans and animals.