Alcohol quantification: recent insights into amperometric enzyme biosensors

Immobilization of Enzyme Electrochemical Biosensors and Their Application to Food Bioprocess Monitoring

Electrochemical biosensors based on immobilized enzymes are among the most popular and commercially successful biosensors. The literature in this field suggests that modification of electrodes with nanomaterials is an excellent method for enzyme immobilization, which can greatly improve the stability and sensitivity of the sensor. However, the poor stability, weak reproducibility, and limited lifetime of the enzyme itself still limit the requirements for the development of enzyme electrochemical biosensors for food production process monitoring. Therefore, constructing sensing technologies based on enzyme electrochemical biosensors remains a great challenge. This article outlines the construction principles of four generations of enzyme electrochemical biosensors and discusses the applications of single-enzyme systems, multi-enzyme systems, and nano-enzyme systems developed based on these principles. The article further describes methods to improve enzyme immobilization by combining different types of nanomaterials such as metals and their oxides, graphene-related materials, metal-organic frameworks, carbon nanotubes, and conducting polymers. In addition, the article highlights the challenges and future trends of enzyme electrochemical biosensors, providing theoretical support and future perspectives for further research and development of high-performance enzyme chemical biosensors.

A novel amperometric biosensor for rapid detection of ethanol utilizing gold nanoparticles and enzyme coupled PVC reaction cell

This research was aimed at the fabrication of an improved enzyme-based amperometric biosensor for rapid quantification of ethanol. Alcohol oxidase (AOX) from Pichia pastoris was covalently immobilized on chemically treated polyvinylchloride (PVC) beaker and subsequently horseradish peroxidase (HRP), nafion (Nf), carboxylated multi-walled carbon nanotubes (c-MWCNTs), chitosan (CHIT) and gold nanoparticles (AuNPs) were immobilized onto Au electrode to fabricate a working electrode. The enzyme-coated PVC surface was analysed morphologically via scanning electron microscopy (SEM). At different stages of construction, the electrochemical properties of working electrode were deciphered by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The biosensor displayed optimal response in a short time span of 12 s at pH 7.5 and 35°C temperature. The working range exhibited by the proposed biosensor was 0.01-42 mM with a limit of detection (LOD) of 0.0001 µM and storage stability of 180 days at 4°C. When level of alcohol was evaluated in commercial samples via standard assay kit and existing biosensor, a good correlation (R²= 0.98) was observed which authenticates its reliability.

Calorimetric Sensor for Ethanol Using Ni2+-nitrilotriacetic Acid (NTA) Resin Immobilized Alcohol Dehydrogenase (ADH)

Background:

A simple, fast and economic analytical method for the determination of ethanol is important for clinical, biological, forensic and physico-legal purposes.

Methods:

Ni2+-NTA resin was used as an immobilization matrix for the simple one-step purification/ immobilization of his6-tagged ADH. Different alcohols with a concentration range of 0.5-50% V/V, namely methanol, ethanol and propanol were measured using prepared ADH enzyme thermistor. The ethanol content of Tsingtao beer was tested as a real sample containing alcohol. Reproducibility and stability of prepared ADH enzyme thermistor were also investigated by repeated measurements.

Results:

In comparison to the controlled pore glass (a common used support for the immobilization of enzyme) used in thermal biosensor, the use of Ni2+-NTA resin not only led to simple one-step purification/ immobilization by his6-tagged ADH binding to Ni2+-NTA resin, but also made the immobilizing supports reusable. The prepared biosensor can be used to determine ethanol and methanol by the calorimetric measurement. A linear range of 1 -32% (V/V) and 2-20% (V/V) was observed for ethanol and methanol, respectively. The detection limits were 0.3% (V/V) and 1% (V/V) for ethanol and methanol, respectively. The tested ethanol concentration of Tsingtao beer was 4.5% V/V, which is comparable with the labeled alcohol by volume (ABV) 4.80%.

Conclusion:

Ni2+-NTA resin, as an immobilization matrix in ET sensor, provides a simple one-step purification/immobilization for His6-tagged recombinase and a reusable immobilization matrix. The prepared biosensor exhibits good repeatability and stability. Such a new biosensor shows great promise for rapid, simple, and cost-effective analysis of ethanol and methanol, both in qualitative and in quantitative tests.

What Electrochemical Biosensors Can Do for Forensic Science? Unique Features and Applications

This article critically discusses the latest advances in the use of voltammetric, amperometric, potentiometric, and impedimetric biosensors for forensic analysis. Highlighted examples that show the advantages of these tools to develop methods capable of detecting very small concentrations of analytes and provide selective determinations through analytical responses, without significant interferences from other components of the samples, are presented and discussed, thus stressing the great versatility and utility of electrochemical biosensors in this growing research field. To illustrate this, the determination of substances with forensic relevance by using electrochemical biosensors reported in the last five years (2015–2019) are reviewed. The different configurations of enzyme or affinity biosensors used to solve analytical problems related to forensic practice, with special attention to applications in complex samples, are considered. Main prospects, challenges to focus, such as the fabrication of devices for rapid analysis of target analytes directly on-site at the crime scene, or their widespread use and successful applications to complex samples of interest in forensic analysis, and future efforts, are also briefly discussed.