Amperometric Biosensor Based on Enzymatic Reactor for Choline Determination in Flow Systems

Abstract

A simple, selective and stable biosensor with the enzymatic reactor based on choline oxidase (ChOx) was developed and applied for the determination of choline (Ch) in flow injection analysis with amperometric detection. The enzyme ChOx was covalently immobilized with glutaraldehyde to mesoporous silica powder (SBA‐15) previously covered by NH2‐groups. This powder was found as an optimal filling of the reactor. The detection of Ch is based on amperometric monitoring of consumed oxygen during the enzymatic reaction, which is directly proportional to Ch concentration. Two arrangements of an electrolytic cell in FIA, namely wall‐jet cell with working silver solid amalgam electrode covered by mercury film and flow‐through cell with tubular detector of polished silver solid amalgam were compared. The experimental parameters affecting the sensitivity and stability of the biosensor (i. e. pH of the carrier solution, volume of reactor, amount of the immobilized enzyme, the detection potential, flow rate, etc.) were optimized. Under the optimized conditions, the limit of detection was found to be 9.0×10−6 mol L−1. The Michaelis‐Menten constant for covalently immobilized ChOx on SBA‐15 was calculated. The proposed amperometric biosensor with the developed ChOx‐based reactor exhibits good repeatability, reproducibility, long‐term stability, and reusability. Its efficiency has been confirmed by the successful application for the determination of Ch in two commercial pharmaceuticals.

Choline Oxidase Based Composite ZrO2@AuNPs with Cu2O@MnO2 Platform for Signal Enhancing the Choline Biosensors

“…Additionally, the calibration curve shown in Figure 5B indicated that the developed biosensor had a wide linear response to choline concentration with good sensitivity (97.4 μA cm −2 mM −1 ), low detection limit (0.3 μM, S/N=3) and low quantitation limit (0.9 μM). According to the Michaelis‐Menten equation, the apparent Michaelis‐Menten constant ( K m ) was calculated to be 0.08 mM with I max of 0.67 μA, which is comparable to previously reported literatures [51–53]. This phenomenon suggested that our modified materials greatly encouraged enzymatic activity and improved the electron transfer process leading to the effective performance of the biosensor for quantitative choline detection covering possible choline levels found in real biological fluid samples i. e. plasma, human serum and human blood [54].…”

SPOOC (Sensor for Periodic Observation of Choline): An Integrated Lab‐on‐a‐Spoon Platform for At‐Home Quantification of Choline in Infant Formula

“…Other analysis methods for choline analysis have been developed based on electrochemical enzymatic biosensors. [21][22][23][24][25] Although these sensors are simple and relatively reliable, they have major drawbacks. Enzymes are sensitive to pH, temperature, and other environmental factors that makes it challenging to maintain the biosensor performance for a long time.…”