Nanozymes with reductase-like activities: antioxidant properties and electrochemical behavior

Novel Zn/Cd/Cubd nanozymes possesses the ability to mimic coenzyme-dependent selenite reductase. A new amperometric biosensor for determination of selenite was constructed.

Determination of Glucose with Cellulose Acetate/Glucose Oxidase Modified Carbon Paste Electrodes

An amperometric biosensor for glucose determination was developed using a carbon paste electrode (CPE) modified with cellulose acetate (CA)/glucose oxidase (GOx) bilayer membrane through the electrostatic interaction between them. The CA membrane was used as matrix for enzyme immobilization via microencapsulation technique, is enzyme placed between two membranes. CA/GOx membrane was attached to CPE surface containing ferrocene (Fc). By using proposed amperometric biosensor, glucose concentration was determined as well as its characteristic. The modified Fc–graphite electrode with CA/GOx bilayer membrane for glucose had optimum measurement conditions at work emf of 874 mV, CA concentration of 10% and amount Fc of 0.021 mg. The biosensor showed good performance at glucose concentration range of 0.05–3 mM and limit of detection was 0.024 mM. Proposed biosensor has good reproducibility with relative standard deviation (RSD) was less than 5% up to 7 times use (in the defined condition 4 ˚C). Glucose measurement result in human serum of diabetes mellitus patients showed conformity with result of reference method, MediSense Optium glucose test kit.

Simple Amperometric Biosensor for Sucrose Concentration Measurement Based on Principal Component Analysis

Sucrose is a type of sugar that is widely used in various types of foods and beverages. In Indonesia, sucrose consumption reaches 2.8 million tons on average per year. Effects of consuming too much sucrose can increase the risk of various diseases such as diabetes, dental caries and obesity. The level of maximum amount of sucrose that is safe for the body equal to 10% of the total energy or the equivalent of 50 g/person/day, so that the required detection system and the identification of the sucrose concentration. In this work, the identification process was carried out using an amperometric biosensor based on the yeast Saccharomyces cerevisiae as a bioreceptor. Measurements were made by immobilizing yeast cells and analyte samples into the biosensor electrodes and observed based on cellular respiration activity which was expressed as a parameter of dissolved oxygen (DO). The biosensor response is generated in the form of an output potential value, then processed using principal component analysis (PCA) to produce a sucrose concentration classification point with a percentage of variance of the two main components of 98.77% which states that the sensor is able to identify sucrose concentrations.

A Crosstalk- and Interferent-Free Dual Electrode Amperometric Biosensor for the Simultaneous Determination of Choline and Phosphocholine

Choline (Ch) and phosphocholine (PCh) levels in tissues are associated to tissue growth and so to carcinogenesis. Till now, only highly sophisticated and expensive techniques like those based on NMR spectroscopy or GC/LC- high resolution mass spectrometry permitted Ch and PCh analysis but very few of them were capable of a simultaneous determination of these analytes. Thus, a never reported before amperometric biosensor for PCh analysis based on choline oxidase and alkaline phosphatase co-immobilized onto a Pt electrode by co-crosslinking has been developed. Coupling the developed biosensor with a parallel sensor but specific to Ch, a crosstalk-free dual electrode biosensor was also developed, permitting the simultaneous determination of Ch and PCh in flow injection analysis. This novel sensing device performed remarkably in terms of sensitivity, linear range, and limit of detection so to exceed in most cases the more complex analytical instrumentations. Further, electrode modification by overoxidized polypyrrole permitted the development of a fouling- and interferent-free dual electrode biosensor which appeared promising for the simultaneous determination of Ch and PCh in a real sample.