Laccase bioconjugate and multi-walled carbon nanotubes-based biosensor for bisphenol A analysis

ZnO-Polyaniline Nanocomposite Functionalised with Laccase Enzymes for Electrochemical Detection of Cetyltrimethylammonuium Bromide (CTAB)

The direct discharge of cationic surfactants into environmental matrices has exponentially increased due to their wide application in many products. These compounds and their degraded products disrupt microbial dynamics, hinder plant survival, and affect human health. Therefore, there is an urgent need to develop electroanalytical assessment techniques for their identification, determination, and monitoring. In our study, ZnO-PANI nanocomposites were electrodeposited on a glassy carbon electrode (GCE), followed by the immobilization of laccase enzymes and the electrodeposition of polypyrrole (PPy), to form a biosensor that was used for the detection of CTAB. A UV-Vis analysis showed bands corresponding to the π-π* transition of benzenoid and quinoid rings, π-polaron band transition and n-π*polaronic transitions associated with the extended coil chain conformation of PANI, and the presence and interaction of ZnO with PANI and type 3 copper in the laccase enzymes. The FTIR analysis exhibited peaks corresponding to N-H and C-N stretches and bends for amine, C=C stretches for conjugated alkenes, and a C-H bend for aromatic compounds. A high-resolution scanning electron microscopy (HRSEM) analysis proved that PANI and ZnO-PANI were deposited as fibres with hairy topography resulting from covalent bonding with the laccase enzymes. The modified electrode (PPy-6/GCE) was used as a platform for the detection of CTAB with three linear ranges of 0.5-100 µM, 200-500 µM, and 700-1900 µM. The sensor displayed a high sensitivity of 0.935 μA μM-1 cm-2, a detection limit of 0.0116 µM, and acceptable recoveries of 95.02% and 87.84% for tap water and wastewater, respectively.

Emphasizing laccase based amperometric biosensing as an eventual panpharmacon for rapid and effective detection of phenolic compounds

Phenols and phenolic compounds are major plant metabolites used in industries to produce pesticides, dyes, medicines, and plastics. These compounds enter water bodies, soil, and living organisms via such industrial routes. Some polyphenolic compounds like phenolic acids, flavonoids have antioxidant and organoleptic qualities, as well as preventive effects against neurodegenerative illnesses, cardiovascular disease, diabetes, and cancer. However, many of the polyphenolic compounds, such as Bisphenol A, phthalates, and dioxins also cause major environmental pollution and endocrine disruption, once the dose level becomes objectionable. The development of reliable and rapid methods for studying their dose dependency, high-impact detrimental effects, and continuous monitoring of phenol levels in humans and environmental samples is a crucial necessity of the day. Enzymatic biosensors employing phenol oxidases like tyrosinase, peroxidase and laccase, utilizing electrochemical amperometric methods are innovative methods for phenol quantification. Enzymatic biosensing, being highly sensitive and efficacious technique, is illuminated in this review article as a progressive approach for phenol quantification with special emphasis on laccase amperometric biosensors. Even more, the review article discussion is extended up to nanozymes, composites of metal organic frameworks (MOFs), and molecularly imprinted polymers (MIPs) as some emerging species for electro-chemical sensing of phenols. Applications of phenol quantification and green biosensing are also specified. A concrete summary of the innovative polyphenol detection approaches with futuristic scope indicates a triumph over some existing constraints of the phenomenological approaches providing an informative aisle to the modern researchers towards the bulk readability.

Thermostabilization of a fungal laccase by entrapment in enzymatically synthesized levan nanoparticles

In this work, we present a comprehensive investigation of the entrapment of laccase, a biotechnologically relevant enzyme, into levan-based nanoparticles (LNPs). The entrapment of laccase was achieved concomitantly with the synthesis of LNP, catalyzed by a truncated version of a levansucrase from Leuconostoc mesenteroides. The study aimed to obtain a biocompatible nanomaterial, able to entrap functional laccase, and characterize its physicochemical, kinetic and thermal stability properties. The experimental findings demonstrated that a colloidal stable solution of spherically shaped LNP, with an average diameter of 68 nm, was obtained. An uniform particle size distribution was observed, according to the polydispersity index determined by DLS. When the LNPs synthesis was performed in the presence of laccase, biocatalytically active nanoparticles with a 1.25-fold larger diameter (85 nm) were obtained, and a maximum load of 243 μg laccase per g of nanoparticle was achieved. The catalytic efficiency was 972 and 103 (μM·min)-1, respectively, for free and entrapped laccase. A decrease in kcat values (from 7050 min-1 to 1823 min-1) and an increase in apparent Km (from 7.25 μM to 17.73 μM) was observed for entrapped laccase, compared to the free enzyme. The entrapped laccase exhibited improved thermal stability, retaining 40% activity after 1 h-incubation at 70°C, compared to complete inactivation of free laccase under the same conditions, thereby highlighting the potential of LNPs in preserving enzyme activity under elevated temperatures. The outcomes of this investigation significantly contribute to the field of nanobiotechnology by expanding the applications of laccase and presenting an innovative strategy for enhancing enzyme stability through the utilization of fructan-based nanoparticle entrapments.

Extremozyme-Based Biosensors for Environmental Pollution Monitoring: Recent Developments

Extremozymes combine high specificity and sensitivity with the ability to withstand extreme operational conditions. This work presents an overview of extremozymes that show potential for environmental monitoring devices and outlines the latest advances in biosensors utilizing these unique molecules. The characteristics of various extremozymes described so far are presented, underlining their stability and operational conditions that make them attractive for biosensing. The biosensor design is discussed based on the detection of photosynthesis-inhibiting herbicides as a case study. Several biosensors for the detection of pesticides, heavy metals, and phenols are presented in more detail to highlight interesting substrate specificity, applications or immobilization methods. Compared to mesophilic enzymes, the integration of extremozymes in biosensors faces additional challenges related to lower availability and high production costs. The use of extremozymes in biosensing does not parallel their success in industrial applications. In recent years, the "collection" of recognition elements was enriched by extremozymes with interesting selectivity and by thermostable chimeras. The perspectives for biosensor development are exciting, considering also the progress in genetic editing for the oriented immobilization of enzymes, efficient folding, and better electron transport. Stability, production costs and immobilization at sensing interfaces must be improved to encourage wider applications of extremozymes in biosensors.

A graphitized carbon@boron carbide-mediated laccase-based amperometric biosensor for epinephrine detection

The development of novel electron transfer mediator is important for laccase-based electrochemical biosensors. Here, graphitized carbon coated boron carbide (GC@B4C) was first used as the mediator to transfer electrons from laccase (Lac) to nickel foam (NF) electrode. The GC shell of GC@B4C particles was characterized and confirmed by HRTEM, XRD and Raman spectroscopy. The fabricated Lac/GC@B4C/NF electrode was applied for amperometric detection of epinephrine (EP). Detection results indicated Lac/GC@B4C/NF electrode has wide linear range (0.1 µM-2.6 mM), low detection limit (40 nM), high sensitivity (76.05 µA mM-1), strong anti-interference ability and favorable stability for EP detection. This work opened up the use of nonmetallic carbide as the mediator for enzyme-based electrochemical biosensors.

A new non-enzymatic biosensor for the determination of bisphenol-A

In this study, a new non-enzymatic carbon paste biosensor was developed for the determination of Bisphenol-A (BPA) based on Multiwalled Carbon Nanotube (MWCNT) modified Myoglobin (Mb). The measurement principle of the biosensor was developed based on the inhibition effect of BPA on the heme group of myoglobin in the presence of hydrogen peroxide. With the designed biosensor, measurements were taken in the potential range of (-0.15 V & +0.65 V) using the differential pulse voltammetry (DPV) method in the medium containing K₄[Fe(CN)₆]. The linear range for BPA was determined to be 100-1000 µM. Response time was calculated as 16 s. The limit of detection was set at 89 μM. As a result, it has been proven that MWCNT modified myoglobin based biosensor is an alternative method that can be used for BPA determination, giving very sensitive and fast results.

Recent Developments in the Design and Fabrication of Electrochemical Biosensors Using Functional Materials and Molecules

Electrochemical biosensors are superior technologies that are used to detect or sense biologically and environmentally significant analytes in a laboratory environment, or even in the form of portable handheld or wearable electronics. Recently, imprinted and implantable biosensors are emerging as point-of-care devices, which monitor the target analytes in a continuous environment and alert the intended users to anomalies. The stability and performance of the developed biosensor depend on the nature and properties of the electrode material or the platform on which the biosensor is constructed. Therefore, the biosensor platform plays an integral role in the effectiveness of the developed biosensor. Enormous effort has been dedicated to the rational design of the electrode material and to fabrication strategies for improving the performance of developed biosensors. Every year, in the search for multifarious electrode materials, thousands of new biosensor platforms are reported. Moreover, in order to construct an effectual biosensor, the researcher should familiarize themself with the sensible strategies behind electrode fabrication. Thus, we intend to shed light on various strategies and methodologies utilized in the design and fabrication of electrochemical biosensors that facilitate sensitive and selective detection of significant analytes. Furthermore, this review highlights the advantages of various electrode materials and the correlation between immobilized biomolecules and modified surfaces.

Recent Prospects of Carbonaceous Nanomaterials-Based Laccase Biosensor for Electrochemical Detection of Phenolic Compounds

Phenolic compounds (PhCs) are ubiquitously distributed phytochemicals found in many plants, body fluids, food items, medicines, pesticides, dyes, etc. Many PhCs are priority pollutants that are highly toxic, teratogenic, and carcinogenic. Some of these are present in body fluids and affect metabolism, while others possess numerous bioactive properties such as retaining antioxidant and antimicrobial activity in plants and food products. Therefore, there is an urgency for developing an effective, rapid, sensitive, and reliable tool for the analysis of these PhCs to address their environmental and health concern. In this context, carbonaceous nanomaterials have emerged as a promising material for the fabrication of electrochemical biosensors as they provide remarkable characteristics such as lightweight, high surface: volume, excellent conductivity, extraordinary tensile strength, and biocompatibility. This review outlines the current status of the applications of carbonaceous nanomaterials (CNTs, graphene, etc.) based enzymatic electrochemical biosensors for the detection of PhCs. Efforts have also been made to discuss the mechanism of action of the laccase enzyme for the detection of PhCs. The limitations, advanced emerging carbon-based material, current state of artificial intelligence in PhCs detection, and future scopes have also been summarized.

Applications and immobilization strategies of the copper-centred laccase enzyme; a review

Laccase is a multi-copper enzyme widely expressed in fungi, higher plants, and bacteria which facilitates the direct reduction of molecular oxygen to water (without hydrogen peroxide production) accompanied by the oxidation of an electron donor. Laccase has attracted attention in biotechnological applications due to its non-specificity and use of molecular oxygen as secondary substrate. This review discusses different applications of laccase in various sectors of food, paper and pulp, waste water treatment, pharmaceuticals, sensors, and fuel cells. Despite the many advantages of laccase, challenges such as high cost due to its non-reusability, instability in harsh environmental conditions, and proteolysis are often encountered in its application. One of the approaches used to minimize these challenges is immobilization. The various methods used to immobilize laccase and the different supports used are further extensively discussed in this review.

Genosensing Applications of Glassy Carbon Electrodes Modified with Multi-Walled Carbon Nanotubes Non-Covalently Functionalized with Polyarginine

We report the advantages of glassy carbon electrodes (GCE) modified with multi-walled carbon nanotubes (MWCNTs) non-covalently functionalized with polyarginine (PolyArg) for the adsorption and electrooxidation of different DNAs and the analytical applications of the resulting platform. The presence of the carbon nanostructures, and mainly the charge of the PolyArg that supports them, facilitates the adsorption of calf-thymus and salmon sperm double-stranded DNAs and produces an important decrease in the overvoltages for the oxidation of guanine and adenine residues and a significant enhancement in the associated currents. As a proof-of-concept of possible GCE/MWCNTs-PolyArg biosensing applications, we develop an impedimetric genosensor for the quantification of microRNA-21 at femtomolar levels, using GCE/MWCNTs-PolyArg as a platform for immobilizing the DNA probe, with a detection limit of 3fM, a sensitivity of 1.544 × 10³ Ω M^-1, and a successful application in enriched biological fluids.

Recent Advances in the Development of Laccase-Based Biosensors via Nano-Immobilization Techniques

Monitoring phenolic compounds is critical in the environmental, food, and medical sectors. Among many recent advanced detection platforms, laccase-based biosensing platforms gave very rapid, effective, online, and in situ sensing of phenolic compounds. In laccase-based biosensors, laccase immobilization techniques have a vital role. However, a detailing of the advancements in laccase immobilization techniques employed in laccase-based biosensors is lacking in the literature. Thus, in this review, we assessed how the nano-immobilization techniques shaped the laccase biosensing platforms. We discussed novel developments in laccase immobilization techniques such as entrapment, adsorption, cross-linking, and covalent over new nanocomposites in laccase biosensors. We made a comprehensive assessment based on the current literature for future perspectives of nano-immobilized laccase biosensors. We found the important key areas toward which future laccase biosensor research seems to be heading. These include 1. A focus on the development of multi-layer laccase over electrode surface, 2. The need to utilize more covalent immobilization routes, as they change the laccase specificity toward phenolic compounds, 3. The advancement in polymeric matrices with electroconductive properties, and 4. novel entrapment techniques like biomineralization using laccase molecules. Thus, in this review, we provided a detailed account of immobilization in laccase biosensors and their feasibility in the future for the development of highly specific laccase biosensors in industrial, medicinal, food, and environmental applications.

Fabrication of D–A–D type conducting polymer, carbon nanotubes and silica nanoparticle-based laccase biosensor for catechol detection

A sensing platform for catechol detection incorporating triple key materials based on SiNPs, D–A–D type conducting polymer, and MWCNTs.