Design of multicomponent reagents for enzymatic assays

Enzymes Immobilized into Starch- and Gelatin-Based Hydrogels: Properties and Application in Inhibition Assay

The present work is a review of the research on using hydrogels based on natural biodegradable polymers, starch, and gelatin for enzyme immobilization. This review addresses the main properties of starch and gelatin that make them promising materials in biotechnology for producing enzyme preparations stable during use and storage and insensitive to chemical and physical impacts. The authors summarize their achievements in developing the preparations of enzymes immobilized in starch and gelatin gels and assess their activity, stability, and sensitivity for use as biorecognition elements of enzyme inhibition-based biosensors.

A Multicomponent Butyrylcholinesterase Preparation for Enzyme Inhibition-Based Assay of Organophosphorus Pesticides

A new method of producing butyrylcholinesterase (BChE) preparations, stable in storage and use, has been proposed. The BChE preparation is the enzyme co-immobilized with 0.2 M 5-5′-dithiobis (2-nitrobenzoic acid) in starch or gelatin gel. All experimental preparations retain enzyme activity for at least 300 d. The preparations based on gelatin gel show higher activity but lower sensitivity to the toxicants tested in this study compared to the starch gel-based preparations. A method has been proposed for integrated detection of anti-cholinesterase substances in aqueous solutions using the experimental preparation with immobilized BChE. After the additional incubation of the preparation with the immobilized enzyme in the solution of the analyte, the detection limits of malathion and pirimiphos-methyl determined using the IC20 values were below their maximum allowable concentrations—0.005 µM and 0.03 µM, respectively.

Design of bioluminescent biosensors for assessing contamination of complex matrices

The presence of potentially toxic xenobiotics in complex matrices has become rather the rule than the exception. Therefore, there is a need for highly sensitive inexpensive techniques for analyzing environmental and food matrices for toxicants. Enzymes are selectively sensitive to various toxic compounds, and, thus, they can be used as the basis for detection of contaminants in complex matrices. There are, however, a number of difficulties associated with the analysis of complex matrices using enzyme assays, including the necessity to take into account properties and effects of the natural components of the test media for accurate interpretation of results. The present study describes the six-stage procedure for designing new enzyme sensors intended for assessing the quality of complex matrices. This procedure should be followed both to achieve the highest possible sensitivity of the biosensor to potentially toxic substances and to minimize the effect of the uncontaminated components of complex mixtures on the activity of the biosensor. The proposed strategy has been tested in designing a bioluminescent biosensor for integrated rapid assessment of the safety of fruits and vegetables. The biosensor is based on the coupled enzyme system NAD(P)H:FMN-oxidoreductase and luciferase as the biorecognition element. The study describes methods and techniques for attaining the desired result in each stage. The proposed six-stage procedure for designing bioluminescent enzyme biosensors can be used to design the enzymatic biosensors based on other enzymes.

Thermal Inactivation of Butyrylcholinesterase in Starch and Gelatin Gels

The present study demonstrates a simple approach to enhancing thermal stability of butyrylcholinesterase (BChE) by using natural polymers. Analysis of thermal inactivation of the tetrameric BChE in starch and gelatin gels at 50–64 °C showed that thermal inactivation followed second-order kinetics and involved two alternating processes of BChE inactivation, which occurred at different rates (fast and slow processes). The activation enthalpy ΔH# and the activation entropy ΔS# for BChE in starch and gelatin gels were evaluated. The values of ΔH# for the fast and the slow thermal inactivation of BChE in starch gel were 61 ± 3, and 22 ± 2 kcal/mol, respectively, and the values of ΔS# were 136 ± 12 and −2.03 ± 0.05 cal∙K−1∙mol−1, respectively. Likewise, the values of ΔH# for BChE in gelatin gel were 58 ± 6 and 109 ± 11 kcal/mol, and the values of ΔS# were 149 ± 16 and 262 ± 21 cal∙K−1∙mol−1, respectively. The values of the activation parameters obtained in this study suggest that starch gel produced a stronger stabilizing effect on BChE exposed to elevated temperatures over long periods compared with gelatin gel.