Review: Recent Developments in Enzyme-Based Biosensors for Biomedical Analysis

The need for simple, rapid, cost-effective, and portable screening methods has boosted the development of practical biosensors with applications in clinical monitoring, and diagnosis of disease. Compared with traditional analytical methods, enzyme-based bioanalytical devices have several distinct advantages such as high sensitivity and specificity, portability, cost-effectiveness, and the possibilities for miniaturization and mass production. Additionally, they can be developed for point-of-care diagnostic testing. This paper reviews recent advances in the development of enzyme biosensors, design characteristics, performances, and applications with a focus on electrochemical and optical sensors. Recent emerging technologies and innovative biosensing designs, such as nanosensors, paper based-sensors, lab-on-a-chip, biochips, and microfluidic devices are discussed. Specific applications in bioanalysis, clinical diagnosis, and pharmacology are discussed.     

In Vivo Electrochemical Biosensors for Reactive Oxygen Species Detection: A Mini-Review

Due to the significance of reactive oxygen species (ROS) in numerous physiological processes including pathogen response, apoptosis, and induction of defense genes, various methods have been developed for their quantitative analysis. However, the conventional methods using exogenous tracers lack the capability to conduct real-time in vivo measurements. The electrochemical biosensors have shown their potentials for in vivo applications with the rapid and reagentless detection processes. In this article, electrochemical biosensors that are capable of making in vivo ROS detections are reviewed. The different configurations of these biosensors with corresponding strategies to enhance sensitivity and selectivity are discussed in detail. With further studies to promote the biosensor performance, these devices promise to provide more facile ways for ROS research in life sciences.     

DNA Hydrolysis and Voltammetric Determination of Guanine and Adenine Using Different Electrodes

Abstract

This work reports the development of a biosensor method for the label‐free detection of specific DNA sequences. In the initial phase, square wave voltammetry (SWV) was used in a comparative investigation into the electrochemical oxidation of purines (guanine and adenine) and DNA fragments at various electrode surfaces: carbon paste (CPE), glassy carbon electrode (GCE), and gold (AuE). Relative to the carbon electrodes, an approximate 4.0‐fold, 6.0‐fold, and 3.25‐fold increase in the anodic response was observed when guanine, adenine, and hydrolyzed DNA, respectively, were measured on the AuE. It was shown that the guanine and adenine bases could be successfully determined by use of SWV for a deoxyribonucleic acid sample following acid hydrolysis. This label‐free detection of hydrolyzed DNA on gold electrodes has significant advantages over methods using existing carbon electrode materials because of its higher sensitivity and the potential applicability of microfabrication techniques for the production of the requisite gold electrodes.

In another phase of development, the times and conditions for DNA hydrolysis and purine release were investigated. It was shown that under optimal conditions, trace levels of the purine bases could be readily detected following 20 min of hydrolysis at room temperature. The proposed method can be used to estimate the guanine and adenine contents in DNA with in a linear range of 5–30 ng ml^?1.

Finally, when appropriate probe sequences were first adsorbed on the surface of the screen‐printed gold electrode (SPGE), this electrochemical biosensor could be used to specifically detect sequences from ss corona virus aviair following hybridization and hydrolysis reactions on the sensor surface. No enhancement of the voltammetric response was observed when the sensor was challenged with a non‐complementary DNA sequence.     

A Piezoelectric Biosensor For DNA Hybridisation Detection

Abstract

In this paper the realisation of a piezoelectric biosensor for DNA hybridisation detection is reported. A biotinylated 25-mer, was immobilised on a (strept)avidin coated piezoelectric crystal; avidin was covalently bound to the thiol/dextran modified gold surface of the crystal. Hybridisation of the probe with a complementary sequence was detected. The device was able to distinguish among targets of different lengths. Many cycles of measurements could be performed on the same crystal surface regenerating the single strand with HCl (ImM). No signal was detected when the probe reacted with a non complementary sequence. The same experiments were performed immobilising the biotinylated DNA probe on the gold surface coated with avidin by adsorption and the results were compared.     

Simultaneous Detection and Removal of Mercury Ions in Aqueous Solution with Fluorescent Conjugated Polymer‐Based Sensor Ensemble

A water‐soluble, sulfur‐containing fluorescent conjugated polymer exhibits a visible fluorescence color change for detection of mercury in the presence of thymine. A new concept provides the design of a sensor ensemble using a simple combination method. This strategy avoids the need for complicated design and synthesis of a recognition group, eliminating the tedious synthetic efforts for the preparation of a sensor material.

     

Allosteric Indicator Displacement Enzyme Assay for a Cyanogenic Glycoside

Indicator displacement assays (IDAs) represent an elegant approach in supramolecular analytical chemistry. Herein, we report a chemical biosensor for the selective detection of the cyanogenic glycoside amygdalin in aqueous solution. The hybrid sensor consists of the enzyme β‐glucosidase and a boronic acid appended viologen together with a fluorescent reporter dye. β‐Glucosidase degrades the cyanogenic glycoside amygdalin into hydrogen cyanide, glucose, and benzaldehyde. Only the released cyanide binds at the allosteric site of the receptor (boronic acid) thereby inducing changes in the affinity of a formerly bound fluorescent indicator dye at the other side of the receptor. Thus, the sensing probe performs as allosteric indicator displacement assay (AIDA) for cyanide in water. Interference studies with inorganic anions and glucose revealed that cyanide is solely responsible for the change in the fluorescent signal. DFT calculations on a model compound revealed a 1:1 binding ratio of the boronic acid and cyanide ion. The fluorescent enzyme assay for β‐glucosidase uses amygdalin as natural substrate and allows measuring Michaelis–Menten kinetics in microtiter plates. The allosteric indicator displacement assay (AIDA) probe can also be used to detect cyanide traces in commercial amygdalin samples.