Studies on enhancing operational stability of a reusable laccase-based biosensor probe for detection of ortho-substituted phenolic derivatives

Disposable Polyaniline/m-Phenylenediamine-Based Electrochemical Lactate Biosensor for Early Sepsis Diagnosis

Lactate serves as a crucial biomarker that indicates sepsis assessment in critically ill patients. A rapid, accurate, and portable analytical device for lactate detection is required. This work developed a stepwise polyurethane-polyaniline-m-phenylenediamine via a layer-by-layer based electrochemical biosensor, using a screen-printed gold electrode for lactate determination in blood samples. The developed lactate biosensor was electrochemically fabricated with layers of m-phenylenediamine, polyaniline, a crosslinking of a small amount of lactate oxidase via glutaraldehyde, and polyurethane as an outer membrane. The lactate determination using amperometry revealed the biosensor's performance with a wide linear range of 0.20-5.0 mmol L-1, a sensitivity of 12.17 ± 0.02 µA·mmol-1·L·cm-2, and a detection limit of 7.9 µmol L-1. The developed biosensor exhibited a fast response time of 5 s, high selectivity, excellent long-term storage stability over 10 weeks, and good reproducibility with 3.74% RSD. Additionally, the determination of lactate in human blood plasma using the developed lactate biosensor was examined. The results were in agreement with the enzymatic colorimetric gold standard method (p > 0.05). Our developed biosensor provides efficiency, reliability, and is a great potential tool for advancing lactate point-of-care testing applications in the early diagnosis of sepsis.

Nanomaterial-based electrochemical enzymatic biosensors for recognizing phenolic compounds in aqueous effluents

With the rapid development of industrial society, phenolic pollutants already identified in water are severe threats to human health. Traditional detection techniques like chromatography are poor in the ability of cost-effectiveness and on-site detection. In recent years, electrochemical enzymatic biosensors have attracted increasing attention for use in the recognition of phenolic compounds, which is considered an effective strategy for the product transfer of portable analytical devices. Although electrochemical enzymatic biosensors provide a fast, accurate on-site detection technique, the difficulties of enzyme deactivation, poor stability and low sensitivity remain to be solved. Thus, effective immobilization methods of enzymes and nanomaterials with excellent properties have been extensively researched to obtain a high-sensitivity and high-stability biosensing platform. Simultaneous detection of multiple phenols may become the focus of further research. In this review, we provide an overview of recent progress toward electrochemical enzymatic biosensors for the detection of phenolic compounds, including enzyme immobilization approaches and advanced nanomaterials, especially nanocomposites with attractive properties such as good conductivity, high specific surface area, and porous structure. We will comprehensively discuss the features and mechanisms of the main enzymes adopted in the construction of different phenolic biosensors, as well as traditional methods (e.g., adsorption, covalent bonding, entrapment, encapsulation, cross-linking) of enzyme immobilization. The most effective method is based on the properties of enzymes, supports and application objective because there is no one-size-fits-all method of enzymatic immobilization. The emphasis will be given to various advanced nanomaterials, including their special nanostructures, preparation methods and performance. Finally, the main challenges in future research on electrochemical phenolic biosensors will be discussed to provide further perspectives for practical applications in dynamic and on-site monitoring. We believe this review will deliver an important inspiration for the construction of novel and high-performance electrochemical biosensors from enzyme selection to nanomaterial design for the detection of various hazardous materials. We believe this review will deliver an important inspiration on the construction of novel and high-performance electrochemical biosensors from the enzyme selection to the nanomaterial design for detections of various hazardous materials.

Deep Eutectic Solvents (DESs) and Their Application in Biosensor Development

Deep Eutectic Solvents (DESs) are a new class of solvents characterized by a remarkable decrease in melting point compared to those of the starting components. The eutectic mixtures can be simply prepared by mixing a Hydrogen Bond Acceptor (HBA) with a Hydrogen Bond Donor (HBD) at a temperature of about 80 °C. They have found applications in different research fields; for instance, they have been employed in organic synthesis, electrochemistry, and bio-catalysis, showing improved biodegradability and lower toxicity compared to other solvents. Herein, we review the use of DESs in biosensor development. We consider the emerging interest in different fields of this green class of solvents and the possibility of their use for the improvement of biosensor performance. We point out some promising examples of approaches for the assembly of biosensors exploiting their compelling characteristics. Furthermore, the extensive ability of DESs to solubilize a wide range of molecules provides the possibility to set up new devices, even for analytes that are usually insoluble and difficult to quantify.

Laccase and Tyrosinase Biosensors Used in the Determination of Hydroxycinnamic Acids

In recent years, researchers have focused on developing simple and efficient methods based on electrochemical biosensors to determine hydroxycinnamic acids from various real samples (wine, beer, propolis, tea, and coffee). Enzymatic biosensors represent a promising, low-cost technology for the direct monitoring of these biologically important compounds, which implies a fast response and simple sample processing procedures. The present review aims at highlighting the structural features of this class of compounds and the importance of hydroxycinnamic acids for the human body, as well as presenting a series of enzymatic biosensors commonly used to quantify these phenolic compounds. Enzyme immobilization techniques on support electrodes are very important for their stability and for obtaining adequate results. The following sections of this review will briefly describe some of the laccase (Lac) and tyrosinase (Tyr) biosensors used for determining the main hydroxycinnamic acids of interest in the food or cosmetics industry. Considering relevant studies in the field, the fact has been noticed that there is a greater number of studies on laccase-based biosensors as compared to those based on tyrosinase for the detection of hydroxycinnamic acids. Significant progress has been made in relation to using the synergy of nanomaterials and nanocomposites for more stable and efficient enzyme immobilization. These nanomaterials are mainly carbon- and/or polymer-based nanostructures and metallic nanoparticles which provide a suitable environment for maintaining the biocatalytic activity of the enzyme and for increasing the rate of electron transport.

Polyphenol oxidase-based electrochemical biosensors: A review

The detection of phenolic compounds is relevant not only for their possible benefits to human health but also for their role as chemical pollutants, including as endocrine disruptors. The required monitoring of such compounds on-site or in field analysis can be performed with electrochemical biosensors made with polyphenol oxidases (PPO). In this review, we describe biosensors containing the oxidases tyrosinase and laccase, in addition to crude extracts and tissues from plants as enzyme sources. From the survey in the literature, we found that significant advances to obtain sensitive, robust biosensors arise from the synergy reached with a diversity of nanomaterials employed in the matrix. These nanomaterials are mostly metallic nanoparticles and carbon nanostructures, which offer a suitable environment to preserve the activity of the enzymes and enhance electron transport. Besides presenting a summary of contributions to electrochemical biosensors containing PPOs in the last five years, we discuss the trends and challenges to take these biosensors to the market, especially for biomedical applications.

Design and simulation of diatom-based microcantilever immunobiosensor for the early detection of Karnal bunt

Fungal pathogen, Tilletia indica, the cause of Karnal bunt disease in wheat, is severely affecting the yield and grain quality, worldwide. Thus, strict quarantine regulations by most wheat growing countries have to be followed, leading to trade barriers for wheat export. The conventional methods being used for pathogen detection at symptomatic stage requires the germination of Tilletia spores for the processing of samples. Thus, it is time-consuming and expensive. This study proposes a simulated microcantilever-based piezoelectric biosensor for the early detection of T. indica. Four different materials, SiO2, SiC, Si3N4, and Poly Si, were used for the microcantilever design. Microcantilever was coated with siliceous frustules of diatom that provides high surface area and enhanced sensitivity for specific antibody against the antigen, T. indica. Ansys software was used for the simulation analysis. Simulation results showed that microcantilever beam of SiO2 length of 150 µm, width of 30 µm and thickness 1 µm enhanced the sensitivity by two times against the antibody in comparison to normal microcantilever beam. The results concluded that SiO2 with coated diatom is the best material for the microcantilever fabrication, thus, providing an excellent protocol for fabrication of microcantilever-based biosensor which is both cost- and time effective.