Immobilization Of Acetylcholinesterase Research Articles

Facile synthesis of novel porphyrin-based covalent organic frameworks integrated with Au nanoparticles for highly sensitive detection of organophosphorus pesticide residues

Organophosphorus pesticides (OPs) residues in agricultural products such as vegetables, fruits, and grains pose a threat to food safety and human health. In this work, a novel and highly sensitive electrochemical biosensor was developed for OPs residues detection in real sample, based on the immobilization of acetylcholinesterase (AChE) by electrostatic adsorption on a glassy carbon electrode (GCE) modified with composite nanomaterials of porphyrin-based covalent organic frameworks (p-COFs) loaded by gold nanoparticles (AuNPs) and poly (diallyldimethylammonium chloride) (PDDA). Due to the synergistic effect of p-COFs, AuNPs and PDDA, the fabricated biosensor displayed the remarkable properties with the high electrocataytic activity, and excellent biocompatibility, resulting in a significant signal amplification of as-prepared biosensor. Under optimized conditions, the biosensor showed excellent sensing performances for the detection of methyl parathion (MP), with wide linear ranges from 1.9 × 10−9–3.8 × 10−5 M and a low detection limit as low as 2.3 × 10−10 M, as well as the satisfactory selectivity, excellent reproducibility, anti-interference properties and good stability. It was also successfully applied to the monitoring of MP content in vegetables and fruits, which may be explore a new opportunity for the potential utilization in analysis field.

Highly Sensitive Acetylcholine Biosensing Via Chemical Amplification of Enzymatic Processes in Single Track-Etched Nanochannels

Neurotransmitters are endogenous chemical messengers that play crucial roles in the transmission, enhancement and conversion of specific signals between neurons and other cells and are considered biomarkers of neurodegenerative diseases.[1] Neurodegenerative diseases cause progressive loss of cognitive and/or motor function and, as life expectancy rises, they imply major challenges for societies with rapidly aging populations.[2] As a result, monitoring neurotransmitters is becoming increasingly relevant in clinical environments. Acetylcholine (Ach) is a neurotransmitter that plays a key role in the communication between neurons in the spinal cord and nerve skeletal junctions in vertebrates. [3] Since an abnormal concentration of Ach has proven to be related to neurodegenerative diseases, novel strategies for highly sensitive and specific Ach (bio)sensing are in great demand.In this work we present the construction of Ach enzymatic biosensors with remarkable sensitivity by acetylcholinesterase immobilization on polyamine-modified single nanochannels via electrostatic self-assembly. [4] To fabricate bullet-shaped single nanochannels in polyethylene terephthalate (PET), 12 µm thick PET foils are irradiated with a single swift heavy ion. The resulting ion track consists of highly localized damaged material along the ion trajectory and is selectively dissolved in a highly basic aqueous solution under asymmetric conditions to obtain a bullet-shaped channel. The controlled PET hydrolysis exposes carboxylic groups at the channel surface (negative charge at pH < 4), which allows the immobilization of further functional groups to design and construct the biosensor.Here, we will discuss in detail the sensor design, the applied functionalization strategy, and the performance of the sensor. In short, changes in the surface charge of the nanochannel lead to measurable changes in the transmembrane current in a steady-state configuration. We will show experimental results that evidence that the designed sensor successfully transduces the presence of acetylcholine into measurable ionic signals with a 16 nM low limit of detection.[1] World Health Organization, Neurological Disorders: Public Health Challenges, World Health Organization Press, Geneva, Switzerland,2007.[2] L. Gan, M. R. Cookson, L. Petrucelli and A. R. La Spada,Nat. Neurosci., 2018, 21, 1300–1309.[3] M. Hasanzadeh, N. Shadjou and M. de la Guardia, TrAC, Trends Anal. Chem., 2017, 86, 107–121.[4] Yamili Toum Terrones, Gregorio Laucirica, Vanina M. Cayón, Gonzalo E. Fenoy, M. Lorena Cortez, María Eugenia Toimil-Molares, Christina Trautmann, Waldemar A. Mamisollé and Omar Azzaroni, Chem. Commun., 2022, 58, 10166

ZnO-rGO-based electrochemical biosensor for the detection of organophosphorus pesticides

The accurate determination of organophosphorus pesticide residues is of great importance for human disease monitoring and environmental safety. Numerous detection methods exist, among which sensitive monitoring of organophosphorus compounds using electrochemical sensors has gradually become a research hotspot. This paper used acetylcholinesterase (AChE) as an indicator anchored on a zinc oxide-reduced graphene oxide (ZnO-rGO) composite rich in active sites, in which green non-toxic zinc oxide (ZnO) nanomaterials were uniformly distributed on the reduced graphene for rapid detection of organophosphorus. The effects of different ratios of ZnO to reduced graphene on the performance of ZnO-rGO nanocomposites were investigated. The AChE/ZnO-rGO biosensor detects organophosphorus by electrochemical inhibition of acetylcholinesterase in the presence of organophosphorus. The developed electrochemical biosensor has high selectivity and good linearity, and the ZnO-rGO nanocomposite as a matrix for immobilization of acetylcholinesterase and detection of organophosphorus has the potential for highly sensitive pesticide detection.

Efficient Immobilization of Acetylcholinesterase onto Amino Functionalized Nitrogen‐doped Reduced Graphene Oxide for Highly Sensitive Pesticides Biosensors

AbstractThe residues of carbamates pesticides can cause a threat to human and animal health. Therefore, the exact and speedy detection of pesticides is very urgent. In this work, a novel acetylcholinesterase (AChE) biosensor based on amino functionalized nitrogen‐doped reduced graphene oxide (NrGO−NH2) has been developed for the determination of carbamates pesticides. The NrGO−NH2 can not only serve as electronic bridges and signal amplifiers, but also efficiently immobilize AChE. The detection linear range for carbofuran is ranged from 0.05 to 11 ng/mL, and the detection limit is 0.025 ng/mL. Under the optimum conditions, the developed biosensor has also been successfully used for pesticide residues detecting in vegetable samples.

Immobilization of Acetylcholinesterase onto Pyrrole-containing Photocured Thermosets

Acetylcholinesterase (AChE; EC 3.1.1.7) is a group of enzymes that catalyzes the hydrolysis of the neurotransmitter acetylcholine (ACh) into choline and acetate. AChE inhibition is commonly utilized as a biomarker for pesticides. In membrane based AChE biosensors the enzyme immobilization onto an electrode surface is of prime importance. In previous studies, conducting polymers-based supports have been used for the immobilization of AChE. In this study, a novel immobilization platform was developed. The simultaneous polymerization of pyrrole and functional thiol/ene monomers was performed to prepare conductive thermosets. AchE was covalently immobilized onto the membranes through the epoxy functional groups. After the immobilization process, the optimal temperature increased to 50 °C, displaying a better thermal stability and the optimum pH was elevated to 8.5. The activity of the immobilized enzyme was tested in the presence of several metals, and it was found that Cu2+ ions caused a noticable inhibition. After 10 cycles, the immobilized enzyme retained 51% of its original activity. In accordance with our results; the durability and the stability of the immobilized enzyme were improved. In future studies, the method applied here can be used in the design of an AchE biosensor.

Enzyme colorimetric cellulose membrane bioactivity strips based on acetylcholinesterase immobilization for inhibitors preliminary screening

To quickly screen the active pharmaceutical ingredient that can be used as acetylcholinesterase inhibitors (AChEIs) to treat Alzheimer's disease, an enzyme colorimetric cellulose membrane bioactivity strip (CBS) was developed for simple and rapid screening of AChEIs. The amino group of acetylcholinesterase (AChE) undergoes Schiff base reaction with the aldehyde group on the oxidized cellulose membranes, then the AChE was covalently cross-linking on the surface of cellulose membranes, enabling the screening based on Ellman's enzyme colorimetric method. When the enzyme activity of AChE was inhibited after incubation with inhibitors, the hydrolysis of S-Acetylthiocholine iodide decreased, consequently, the 5-thio-2-nitrobenzoic acid generated by the reaction with 5,5′-dithiobis (2-nitrobenzoic acid) also decreased, leading to a decreased color intensity. In addition, CBSs had fast chromogenic time, excellent specificity, and extraordinary storage stability. Tacrine and Donepezil were used as representative inhibitors during the detection, while their IC50 and limit of detection were determined.Therefore, our work not only established a platform for effective preliminary screening of AChEIs but also inspired the further development of other cellulose membrane-based biosensors.

A Novel Electrochemical Biosensor Based on Polyaniline-Embedded Copper Oxide Nanoparticles for High-Sensitive Paraoxon-Ethyl (PE) Detection.

This paper proposes a fabrication of a hyper-sensitive amperometric biosensor for paraoxon-ethyl (PE) detection. In this developed biosensor, polyaniline (PANI) and copper oxide (CuO)-based nanocomposite is used as a sensing platform. The homogeneous distribution of CuO onto the PANI matrix enhances the surface area and conductivity of the nanocomposite. Additionally, the PANI produces a compatible environment for enzyme immobilization, which further enhances the rate of electron transfer. For biosensor fabrication, the nanocomposite is deposited electrophoretically onto the ITO glass substrate and immobilization of acetylcholinesterase (AChE) enzyme is conducted onto the fabricated electrode surface. The results validate good reproducibility, good stability, and high selectivity of the fabricated biosensor (AChE/PANI@CuO/ITO). The inhibition rate of paraoxon-ethyl (PE) is recorded in the concentration range of 1-200nM with a low limit of detection of 0.096nM or 96pM. The sensitivity of the developed biosensor is found to be 49.86 µA(nM)-1. The developed biosensor is further successfully accomplished for the detection of PE in real samples like rice and pulse.

Biosensor Based on Covalent Organic Framework Immobilized Acetylcholinesterase for Ratiometric Detection of Carbaryl.

A ratiometric electrochemical biosensor based on a covalent organic framework (COFThi-TFPB) loaded with acetylcholinesterase (AChE) was developed. First, an electroactive COFThi-TFPB with a two-dimensional sheet structure, positive charge and a pair of inert redox peaks was synthesized via a dehydration condensation reaction between positively charged thionine (Thi) and 1,3,5-triformylphenylbenzene (TFPB). The immobilization of AChE on the positively charged electrode surface was beneficial for maintaining its bioactivity and achieving the best catalytic effect; therefore, the positively charged COFThi-TFPB was an appropriate support material for AChE. Furthermore, the COFThi-TFPB provided a stable internal reference signal for the constructed AChE inhibition-based electrochemical biosensor to eliminate various effects which were unrelated to the detection of carbaryl. The sensor had a linear range of 2.2–60 μM with a detection limit of 0.22 μM, and exhibited satisfactory reproducibility, stability and anti-interference ability for the detection of carbaryl. This work offers a possibility for the application of COF-based materials in the detection of low-level pesticide residues.

Development of nano Bio LC columns for the search of acetylcholinesterase molecular targets.

A novel acetylcholinesterase Nano liquid chromatography capillary column (75 μm i.d. × 50mm length) was developed for the fast screening of acetylcholinesterase inhibitors and the evaluation of their molecular recognition mechanism. Biotinylated acetylcholinesterase was immobilized on a streptavidin Nano liquid chromatography capillary column. Because of the very strong streptavidin-biotin interaction, the acetylcholinesterase immobilization step performed by frontal analysis is very fast (required less than 10min), and the amount of immobilized acetylcholinesterase was in the microgram range (1μg). The yellow anion obtained from the enzymatic reaction detected at 412nm was achieved within 60 s, and the immobilized acetylcholinesterase retained 96% of the initial activity beyond 90 days. This column was successfully applied for the discrimination of weak affinity ligands to acetylcholinesterase from nonbinders, which is the heart of fragment-based drug design. This column was used for the determination of the IC50 values of a series of inhibitor molecules. In addition, it was demonstrated that competitive experiments could be performed with our miniaturized system to confirm the existence and binding pocket of a ligand to acetylcholinesterase contained in a methanol plant extract. The results revealed that our acetylcholinesterase Nano liquid chromatography capillary column developed in this work represents a useful tool for the rapid screening of inhibitor candidates and evaluation of the action mechanism.

Introducing a covalent thiol-based protected immobilized acetylcholinesterase with enhanced enzymatic performances for biosynthesis of esters

Acetylcholinesterase covalent immobilization was performed on mercaptoacetic acid-functionalized magnetic nanoparticles. Upon the thiol-based protection of the enzyme active center, its kinetics, stability, and activity in organic solvents were enhanced and its initial activity was fully recovered. The optimal results for the immobilization (i.e., yield=98.3 ± 5.2 %; enzyme loading=1.20 ± 0.06 mg mg−1) were found at an acetylcholinesterase initial concentration of 12.0 mg mL−1 and an immobilization time of 4.0 hrs. The optimum pH of both enzymes was over 7.0–9.0. The optimal temperature was measured as 40.0–45.0 and 30 ºC for immobilized and free AChE, respectively. The immobilized enzyme retained about 92.1 ± 3.0 % and 91.5 ± 3.0 % of the initial activity after 65 days and 10 cycles, respectively. The Km and Vmax were calculated as 136.2 ± 8.2 µM and 4.3 ± 0.2 µmol mg−1 min−1for the immobilized and 162.0 ± 9.7 µM and 3.63 ± 0.20 µmol mg−1 min−1for the free enzyme. The novel biocatalyst was utilized for ultra-fast esterification, for the first time, revealing 73.0 ± 2.3 % yield after 30.0 min and 85.0 ± 2.7 % after 15.0 min along with fully saving the catalytic efficiency over 6 and 8 cycles for solvent-free and solvent-controlled reactions, respectively. As a consequence, this biocatalyst is an excellent candidate for the application of the AChE enzyme in the commercial synthesis of esters.

Highly Sensitive Detection of Carbaryl Pesticides Using Potentiometric Biosensor with Nanocomposite Ag/r-Graphene Oxide/Chitosan Immobilized Acetylcholinesterase Enzyme

Novel, sensitive, selective, efficient and portable electrochemical biosensors are needed to detect residual contaminants of the pesticide 1-naphthyl methylcarbamate (carbaryl) in the environment, food, and essential biological fluids. In this work, a study of nanocomposite-based Ag reduced graphene oxide (rGO) and chitosan (CS) that optimise surface conditions for immobilisation of acetylcholinesterase (AChE) enzyme to improve the performance of catalytic biosensors is examined. The Ag/rGO/CS nanocomposite membrane was used to determine carbaryl pesticide using a potentiometer transducer. The AChE enzyme-based biosensor exhibits a good affinity for acetylthiocholine chloride (ATCl). It can catalyse the hydrolysis of ATCl with a potential value of 197.06 mV, which is then oxidised to produce a detectable and rapid response. Under optimal conditions, the biosensor detected carbaryl pesticide at concentrations in the linear range of 1.0 × 10−8 to 1.0 μg mL−1 with a limit of detection (LoD) of 1.0 × 10−9 μg mL−1. The developed biosensor exhibits a wide working concentration range, detection at low concentrations, high sensitivity, acceptable stability, reproducibility and simple fabrication, thus providing a promising tool for pesticide residue analysis.

Effective biocatalyst developed via genipin mediated acetylcholinesterase immobilization on rice straw derived cellulose nanofibers for detection and bioremediation of organophosphorus pesticide

This study aims to utilize cellulose nanofibers (CNFs) derived from rice straw to immobilize acetylcholinesterase (AChE) and their effective use as fluorescent sensor cum biocatalyst for sensing and degradation of chlorpyrifos (CPF) into 3,5,6-trichloro-2-pyridinol (TCP) and benign metabolites. AChE immobilized CNFs (AChE@CFs) exhibited excellent selectivity towards CPF in presence of other pesticides, amino acids and heavy metal ions with limit of detection as 90 nM. As compared to free enzyme, a better storage stability, higher endurance to change in pH and temperature and recyclability upto 20 cycles with 8% loss of activity was achieved. AChE@CFs effectively degraded CPF in 36 h. Kinetics of degradation revealed first order kinetics with rate constant of 0.0611 h−1 and half-life of 11.34 h, better than the reported studies leading to conclusion that AChE@CFs is efficacious catalyst for degradation of CPF, not reported hitherto.

A sensitive and stable acetylcholinesterase biosensor with TiO2 nanoparticles anchored on graphitic carbon nanofibers for determination of organophosphate pesticides.

Electrode materials play a central role in assembling biosensors. In this work, a titanium dioxide nanoparticle loaded graphitized carbon nanofiber (TiO2/GNF) composite is prepared for the sensitive detection of organophosphorus pesticide residues (OPs). The TiO2/GNF composite with superior conductivity, catalytic activity and biocompatibility offers an extremely hydrophilic surface for the effective immobilization of acetylcholinesterase (AChE). Furthermore, the Ti atoms of TiO2/GNFs could coordinate with AChE to improve its stability, and TiO2 has a strong adsorption on OPs. The developed AChE/TiO2/GNFs/GCE biosensor showed a high affinity to acetylthiocholine chloride (ATCh) and could catalyze the hydrolysis of ATCh with an apparent Michaelis-Menten constant (Km) of 50 μM. The constructed AChE/TiO2/GNFs/GCE biosensor exhibits a wide detection linear range (1.0 × 10-13 M to 1.0 × 10-8 M) with a low detection limit (3.3 fM) for paraoxon determination (a model of OPs). In addition, the developed biosensor possesses remarkable anti-interference, acceptable reproducibility and good long-term stability, and is successfully used for the determination of OPs in lake water, providing a new strategy for the analysis of OPs in ecological environments.

An Acetylcholinesterase-Functionalized Biosensor for Sensitive Detection of Organophosphorus Pesticides Based on Solution-Gated Graphene Transistors

In this work, a highly sensitive and selective organophosphorus pesticide (OP) biosensor based on a solution-gated graphene transistor (SGGT) has been successfully constructed. The electrochemical performance of the device is improved by immobilization of acetylcholinesterase (AChE) on the gold gate electrode with chitosan (CHIT) for detection of OPs. The AChE/CHIT-functionalized SGGT sensor shows an ultralow detection limit of 10 nM for OPs and a wide linear range from 300 nM to 3 μM. We also proved that the SGGT-based OP sensor has good selectivity and recovery performance for efficient evaluation of the level of OPs in actual rice samples. This sensor provides a promising detection platform for rapid and sensitive analysis of OPs in real samples with complex components and can be readily applied to many other important analytes for agricultural and food safety using the corresponding enzymes.

Efficient acetylcholinesterase immobilization for improved electrochemical performance in polypyrrole nanocomposite-based biosensors for carbaryl pesticide

• Optimized surface conditions for the immobilization of an expressive amount of active acetylcholinesterase. • The carbaryl pesticide detection follows a Langmuir isotherm with high affinity adsorption constant. • Simple and straightforward methodology to immobilize a high density of active acetylcholinesterase. • Acetylcholinesterase with the active site close to the interface enabling a fast direct electron transfer. • Enzymatic electrochemical biosensor with low LOD and high sensitivity toward the determination of carbaryl pesticide. Efficient and portable sensors are required to monitor and evaluate pesticide contaminants in the environment, food supply and biological fluids. In this work, a study of indigo carmine and dodecyl sulphate doped polypyrrole - gold nanoparticle nanocomposite films revealed changes during the polymerization that optimized the surface conditions for the immobilization of acetylcholinesterase enzyme (from electric eel ), leading to improved catalytic performance. The results suggest a similar behavior to AChE from electric ray , as previously reported in a theoretical study, where the active site is orientated closer to the electrode when the enzyme is immobilized on a positively charged surface, promoting faster direct electron transfer. In addition, this interaction allows the immobilization of an expressive amount of active enzymes. The lack of hindrance led to a high binding interaction of the analyte (carbaryl) towards the adsorption sites of the enzyme (Langmuir isotherm constant of 7.39 × 10 8 ). This electrochemical enzymatic biosensor presented linear responses ranging from 0.05 to 0.25 ng mL −1 for carbaryl (a wide spectrum insecticide), with a detection limit of 0.033 ng cm 2 mL −1 , quantification limit of 0.11 ng cm 2 mL -1 and sensitivity of -59.5 × 10 3 A cm -2 mL g −1 . The biosensor showed good intra-electrode repeatability and inter-electrode reproducibility with the relative standard deviation of 1.8 % and 3.7 % towards thiocholine oxidation and carbaryl pesticide detection, respectively. The biosensor stability improved when stored at lower temperature (-15 °C).

Nitrogen-Doped Graphdiyne as a Robust Electrochemical Biosensing Platform for Ultrasensitive Detection of Environmental Pollutants.

Owing to its unique chemical structure, natural pores, high structure defects, good surface hydrophilicity and biocompatibility, and favorable electrical conductivity, nitrogen-doped graphdiyne (NGDY) has been attracting attention in the application of electrochemical sensing. Taking advantage of these fascinating electrochemical properties, for the first time, two types of electrochemical enzymatic biosensors were fabricated for the respective detection of organophosphorus pesticides (OPs) and phenols based on the immobilization of acetylcholinesterase or tyrosinase with NGDY. Results revealed that the sensitivities of the NGDY-based enzymatic biosensors were almost twice higher than that of the matching biosensor in the absence of NGDY, proving that NGDY plays a vital role in immobilizing the enzymes and improving the performance of the fabricated biosensors. The effects of nitrogen doping on improving the biosensing performance were studied in depth. Graphitic N atoms can enhance the electrical conductivity, while imine N and pyridinic N can help to adsorb and accumulate the substance molecules to the electrode surface, all of which contribute to the significantly improved performance. Furthermore, these two types of biosensors also demonstrated excellent reproducibility, high stability, and good recovery rate in real environmental samples, which showed a valuable way for the rapid detection of OPs and phenols in the environment. With these excellent performances, it is strongly anticipated that NGDY has tremendous potential to be applied to many other biomedical and environmental fields.

Acetylcholinesterase Immobilized on Glass Rod for Organophosphorus Pesticides Detection: Application on Milk Analysis

Immense use of an insecticide such as malathion has initiated a hindrance to the environment and has increased possible risk to human health via milk and milk products. The presence of insecticide residues in milk products is an alarming signal to set up a string monitoring system. Since their risk to human health, the determination of organophosphate pesticide levels in dairy products is essential. This study shows biosensors' development for the detection of residues of the pesticides generally used in agriculture to increase productivity, which has high toxicity and selective action, a significant part of which falls into crop and livestock products. The test system described in this paper is based on the immobilization of acetylcholinesterase on glass rods by colorimetry as a detection technique. The application of the biosensor to the analysis of the real sample confirmed its reliability. The developed biosensor test system showed excellent analytical performance with limits to detecting the concentration range of residual amounts of the acetylcholinesterase enzyme inhibitor - malathion insecticide (up to 0.089 mg/kg), along with acceptable reproducibility and stability. Distinct advantages of enzyme-based biosensors are high sensitivity, convenience, quick response, cost-effectiveness, portability, and a possibility to use for environmental detection purposes. The biosensor can be used for the analysis of organophosphorus pesticides with anticholinesterase action. It can be concluded that the benefits of using immobilized enzymes are significant since it will bring advantages for the food, pharmaceutical, and medical device industries.

A sensitive acetylcholinesterase biosensor based on NaOH etching glassy carbon electrode for electrochemical determination of 3-nitropropionic acid

Abstract In this study, a stable and sensitive acetylcholinesterase biosensor was developed for the electrochemical determination of 3-nitropropionic acid (3-NPA). To this end, NaOH etching was used to activate the surface of the glassy carbon electrode, and the morphologies and electrochemistry properties of the resulting electrodes were characterized by various analytical methods. The results indicated dramatic enhancement in the electrochemical properties of electrodes by NaOH etching. As a result, the etched electrodes were applied as novel platforms for the immobilization of acetylcholinesterase. Accordingly, a sensor based on inhibition of 3-NPA toward the activity of acetylcholinesterase was constructed for the electrochemical determination of 3-NPA. Under the optimal conditions, the inhibition rate was found to be proportional to the logarithm of the concentration of 3-NPA from 0.1 to 30 μg/L, and the limit of detection was recorded as 0.05 μg/L. In comparison to conventional detection method, the fabricated biosensor also has added advantages in the form of easy and convenient operation, high sensitivity and better linear range.

APLLICATION OF GOLD NANOPARTICLES FOR IMPROVEMENT OF ANALYTICAL CHARACTERISTICS OF CONDUCTOMETRIC ENZYME BIOSENSORS

In this work, the possibility of application of gold nanoparticles for modification of bioselective elements of conductometric biosensors to improve their analytical characteristics has been tested. A bioselective elements of biosensors based on acetylcholinesterase, butyrylcholinesterase and glucose oxidase have been studied as a model of such system. Immobilization of enzymes on the surface of conductometric transducers was carried out by covalent crosslinking of enzymes by using a crosslinking agent (glutaraldehyde). The conditions for immobilization of acetylcholinesterase with gold nanoparticles in BSA membranes were optimized. The optimal concentration of glutaraldehyde, time of immobilization process, ratio of an amount of enzyme and gold nanoparticles, and the concentration and size of gold nanoparticles were selected. The improved characteristics of the developed biosensors based on enzymes and gold nanoparticles were investigated and compared with the characteristics of biosensors based only on enzymes without nanoparticles addition. It was shown, how the addition of gold nanoparticles to the bioselective element of the biosensor affects the stability of biosensors. In particular, the reproducibility of signals during continuous operation of biosensors, the reproducibility of the manufacture of biosensors and their stability during storage were investigated. Thus, it was shown, that the application of gold nanoparticles in the composition of bioselective elements can improve some characteristics of biosensors, which may be promising for further biosensor application

Ensuring traceability of organophosphate pesticides (OPs) through enzyme immobilized spheres

Currently, pesticide residues increasingly lead to health problems. Acetylcholinesterase enzyme (AChE) plays a role in detoxification processes due to their ability to scavenge organophosphates. Thus, this enzyme has been selected for the detection of pesticides. Herein, this study describes the preparation and application of appropriate new immobilized spheres that could be used for the detection of organophosphorus pesticide residues. That is a simple colorimetric enzymatic assay for the practical discovery of N-(Mercaptomethyl) phthalimide S–(O, O–dimethylphosphorodithioate) from organophosphorus pesticides (OPs) widely used in the treatment of sugar beet, apple, nut, corn, and tobacco. The process is based on the immobilization of acetylcholinesterase onto tryptophan FMPS-Trp, (FMPS-Trp)Pd(II), and (FMPS-Trp)Pt(II) functionalized spheres. Spectroscopic and microscopic techniques were used in the characterization of the spheres where scanning electron microscopy (SEM) is an essential tool. The (FMPS-Trp)Pt(II)-AChE showed a good affinity to acetylthiocholine chloride (ATCl) and was found to have the ability to catalyze the hydrolysis of ATCl with an apparent Michaelis–Menten constant value of 288 mM. The developed colorimetric process showed good qualitative analytical performance for Phosmet (OPs) detection as low as 10−7 M.