Search

Abstract: A capillary electrophoresis method and a durable choline biosensor were developed for measuring serum cholinesterase (EC 3.1.1.8) activity, a useful clinical index for liver function. The former is based on separation of benzoate and benzoylcholine (the artificial substrate of cholinesterase) in an uncoated fused-silica capillary. The migration time of benzoylcholine and benzoate was 1.3min and 5.5min, respectively. By the peak areas of A 233 signals, the linear dynamic ranges for both analytes were 0.01–50.0mM, and the relative standard deviations of 1.0mM benzoylcholine and benzoate were less than 4% and 6%, respectively. The FIA-choline sensor was constructed with the working electrode of the flow cell covered with a natural chitinous membrane purified from Taiwanese soldier crab, Mictyris brevidactylus. The biomembrane served as the supporting material for enzyme immobilization (choline oxidase, EC 1.1.3.17), and also prevented protein adsorption on the electrode surface. The calibration curve was linear between 0.05 and 5.0mM (r =0.999). The relative standard deviations for 1.0mM choline (n =7) were less than 3%, and the activity of the bioactive membrane lasted for about 2 months. The analytical results of both methods correlated well (r =0.940). [Copyright &y& Elsevier]

Abstract: An amperometric flow-injection choline biosensor was assembled utilizing natural chitinous membrane as the supporting material for biocatalyst immobilization, and the membrane was purified from Taiwanese soldier crab, Mictyris brevidactylus. The chitinous membrane (<50.0μm in thickness) was covalently immobilized with choline oxidase (EC 3.1.1.17 from Alcaligenes sp.) and then attached onto the platinum electrode of an amperometric flow cell. The flow cell served as the choline sensing device of the proposed FIA system. The sensor signal (peak height of the FIAgram) was linearly related to choline concentration (r =0.999 for choline up to 5.0mM) with low detection limit (S/N>3 for 10.0μM choline) and high reproducibility (CV<3% for 1.0mM choline, n =7). The system was proved to be useful in measuring cholinesterase inhibitory activities of synthetic chemicals or natural products. [Copyright &y& Elsevier]

Abstract: This study investigated characteristics of a chitosan membrane from the carapace of the soldier crab Mictyris brevidactylus intended to construct an amperometric biosensor. Electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) were used in this study to characterize these chitosan membranes intended for constructing enzymatic biosensors. Chitosan membranes suffering various durations (>10 min) of deacetylation had small charge-transfer resistances (<7.88 kΩ) but large double-layer capacitances (>0.55 μF). They were found in EIS where both the solution resistance and Warburg impedance upon electrode interface were almost independent of the durations and degree of deacetylation. The degree of deacetylation and the thickness of chitosan membranes were also determined. Membrane thickness was slightly dependent with the duration but degree of deacetylation was slightly dependent on the duration. Chitosan membranes with various thicknesses suffered various durations of deacetylation, but this did not influence their electrochemical characteristics. The chitinous membrane was covalently immobilized with glucose oxidase (EC 1.3.4.3) and then attached onto the platinum electrode of a homemade amperometric flow cell. Sensor signal was linearly related to glucose concentration (r =0.999 for glucose up to 1.0 mM). The system was sensitive (S / N >5 for 10 μM glucose) and reproducible (CV<1.3% for 50 μM glucose, n =5). [Copyright &y& Elsevier]