Laccase stabilized on β-D-glucan films on the surface of carbon black/gold nanoparticles: A new platform for electrochemical biosensing

Incorporation of carbon black into a sonogel matrix: improving antifouling properties of a conducting polymer ceramic nanocomposite

A new electrochemical sensor device has been developed through the modification of a polyaniline-silicon oxide network with carbon black (CB). Enhanced electrical conductivity and antifouling properties have been achieved due to the integration of this cheap nanomaterial into the bulk of the sensor. The structure of the developed material was characterized using Fourier transform infrared spectroscopy, energy-dispersive X-ray spectroscopy, and scanning electron microscopy techniques. Cyclic voltammetry was used to characterize electrochemically the Sonogel-Carbon/Carbon Black-PANI (SNG-C/CB-PANI) sensor device. In addition, differential pulse voltammetry was employed to evaluate the analytical response of the sensor towards sundry chlorophenols, common environmental hazards in aqueous ecosystems. The modified sensor material showed excellent antifouling properties, which led to a better electroanalytical performance than the one displayed with the bare sensor. Notably, a sensitivity of 5.48 × 10³ μA mM^-1 cm^-2 and a limit of detection of 0.83 μM were obtained in the determination of 4-chloro-3-methylphenol (PCMC) at a working potential of 0.78 V (vs. 3 M Ag/AgCl/KCl), along with proficient values of reproducibility and repeatability (relative standard deviation < 3%). Finally, the analysis of PCMC was carried out in multiple validated water samples using the synthesized SNG-C/CB-PANI sensor device, obtaining excellent results of recovery values (97-104%). The synergetic effect of polyaniline and carbon black leads to novel antifouling and electrocatalytic effects that improve the applicability of this sensor in sample analysis versus complex conventional devices.

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.

Carbon Black Functionalized with Naturally Occurring Compounds in Water Phase for Electrochemical Sensing of Antioxidant Compounds

A new sustainable route to nanodispersed and functionalized carbon black in water phase (W-CB) is proposed. The sonochemical strategy exploits ultrasounds to disaggregate the CB, while two selected functional naturally derived compounds, sodium cholate (SC) and rosmarinic acid (RA), act as stabilizing agents ensuring dispersibility in water adhering onto the CB nanoparticles’ surface. Strategically, the CB-RA compound is used to drive the AuNPs self-assembling at room temperature, resulting in a CB surface that is nanodecorated; further, this is achieved without the need for additional reagents. Electrochemical sensors based on the proposed nanomaterials are realized and characterized both morphologically and electrochemically. The W-CBs’ electroanalytical potential is proved in the anodic and cathodic window using caffeic acid (CF) and hydroquinone (HQ), two antioxidant compounds that are significant for food and the environment. For both antioxidants, repeatable (RSD ≤ 3.3%; n = 10) and reproducible (RSD ≤ 3.8%; n = 3) electroanalysis results were obtained, achieving nanomolar detection limits (CF: 29 nM; HQ: 44 nM). CF and HQ are successfully determined in food and environmental samples (recoveries 97–113%), and also in the presence of other phenolic classes and HQ structural isomers. The water dispersibility of the proposed materials can be an opportunity for (bio) sensor fabrication and sustainable device realization.

A carbon dots-enhanced laccase-based electrochemical sensor for highly sensitive detection of dopamine in human serum

Enzyme-based electrochemical sensor possesses a significant advantage in the highly efficient detection of small molecules, however, the poor electron transport efficiency limits their wide application. In this study, taking advantage of the distinct biocatalytic activity of laccase and the excellent electroconductibility of carbon dots, a carbon dots-enhanced laccase-based electrochemical sensor for the detection of dopamine (DA) is established. Thereinto, laccase can specifically recognize DA and promote its electrocatalytic oxidation on the electrode, while, the carbon dots can be used as the immobilization substrate of laccase and enhance its electron transfer efficiency, thus achieving the highly sensitive detection of dopamine. The electrochemical performance of the modified electrode interface is studied by electrochemical impedance spectroscopy and differential pulse voltammetry. As demonstrated, the electrocatalytic activity of the proposed electrochemical sensor for DA is significantly improved and exhibits a low detection limit (0.08 μM) and a wide linear range (0.25 μM-76.81 μM). The excellent selectivity allows the sensor has the capacity for specific discrimination the DA from other interferents. Furthermore, by analyzing the DA in human serum verifies the practicability of this assay in real sample analysis.

Using nanostructured carbon black-based electrochemical (bio)sensors for pharmaceutical and biomedical analyses: A comprehensive review

The outstanding electronic properties of carbon black (CB) and its economic advantages have fueled its application as nanostructured electrode material for the development of new electrochemical sensors and biosensors. CB-based electrochemical sensing devices have been found to exhibit high surface area, fast charge transfer kinetics, and excellent functionalization. In the present work, we set forth a comprehensive review of the recent advances made in the development and application of CB-based electrochemical devices for pharmaceutical and biomedical analyses - from quantitative monitoring of drug formulations to clinical diagnoses - and the underlying challenges and constraints that need to be overcome. We also present a thorough discussion about the strategies and techniques employed in the development of new electrochemical sensing platforms and in the enhancement of their analytical properties and biocompatibility for anchoring active biomolecules, as well as the combination of these sensing devices with other materials aiming at boosting the performance and efficiency of the sensors.

Improved stability and promoted activity of laccase by One-Pot encapsulation with Cu (PABA) nanoarchitectonics and its application for removal of Azo dyes

Immobilization of laccase helps protect the laccase and realizes repeated use. However, excessive encapsulation protection will also limit the release of laccase activity. This work introduces an effective one-pot method encapsulating laccase in the porous material of metal organic framework (MOF) containing specific metal ions, which provided a new way to solve the problem of limited laccase activity. The immobilization process was mathematically modeled. The morphological and encapsulated properties of the prepared materials were confirmed by the characterization results of SEM, FTIR, XRD, TGA, XPS and CLSM. The results showed that laccase was successfully encapsulated, and the Cu (PABA) with Cu2+ as the central structure promoted the laccase activity, the activity of immobilized laccase increased by 1.7 times. The prepared laccase@Cu (PABA) (Lac@Cu (PABA)) showed enhanced stability to extreme pH, high temperature and storage time. More importantly, the Lac@Cu (PABA) exhibited superior reusability, maintaining 70% removal rate of Direct Red 31 (DR31) even after 10 cycles. The dye removal rate of immobilized laccase reached 92% in 6 h under optimal conditions. This research improved the stability of laccase while releasing the activity of laccase, which not only broadened the applicable environment of laccase, but also increased the rate of degradation, and provided a new idea for the clean and efficient treatment of water pollution in textile industry.

Electrochemical Characterization of the Laccase-Catalyzed Oxidation of 2,6-Dimethoxyphenol: an Insight into the Direct Electron Transfer by Enzyme and Enzyme-Mediator System

The oxidation process of 2,6-dimethoxyphenol (2,6-DMP) by laccase from Botryosphaeria rhodina MAMB-05 and the corresponding enzyme-mediator systems was studied using cyclic voltammetry (CV). The enzyme was classified as a high oxidation potential laccase (> 0.70) V vs. NHE) based on its Redox potential at different pHs. The cyclic voltammograms for 2,6-DMP (- 58.7 mV pH^-1) showed that its oxidation potential decreased more significantly compared to the enzyme (- 50.2 mV pH^-1) by varying the pH. The 2,2'-azino-bis[3-ethyl-benzothiazoline-6-sulfonic acid] diammonium salt (ABTS) and 2,2,6,6-tetramethylpiperidine 1-oxyl radical (TEMPO) mediators were effectively oxidized by laccase from B. rhodina MAMB-05. The influence of laccase on the comproportionation of ABTS and the ionic step of the oxidation of TEMPO was also studied using CV. A higher potential difference was observed between laccase and the substrate, and correlated with higher enzyme activity. For the laccase-mediator systems, there was no clear correlation of potential difference between laccase and mediators with enzyme activity towards 2,6-DMP. This observation suggests that there are other limiting parameters for enzyme activity despite Redox potential difference, especially during ionic steps of the mechanism.

Silver Nanowires as Electron Transfer Mediators in Electrochemical Catechol Biosensors

The integration of nanomaterials as electron mediators in electrochemical biosensors is taking on an essential role. Due to their high surface-to-volume ratio and high conductivity, metallic nanowires are an interesting option. In this paper, silver nanowires (AgNWs) were exploited to design a novel catechol electrochemical biosensor, and the benefits of increasing the aspect ratio of the electron mediator (nanowires vs. nanoparticles) were analyzed. Atomic force microscopy (AFM) studies have shown a homogeneous distribution of the enzyme along the silver nanowires, maximizing the contact surface. The large contact area promotes electron transfer between the enzyme and the electrode surface, resulting in a Limit of Detection (LOD) of 2.7 × 10⁻⁶ M for tyrosinase immobilized onto AgNWs (AgNWs-Tyr), which is one order of magnitude lower than the LOD of 3.2 × 10⁻⁵ M) obtained using tyrosinase immobilized onto silver nanoparticles (AgNPs-Tyr). The calculated K_M constant was 122 mM. The simultaneous use of electrochemistry and AFM has demonstrated a limited electrochemical fouling that facilitates stable and reproducible detection. Finally, the biosensor showed excellent anti-interference characteristics toward the main phenols present in wines including vanillin, pyrogallol, quercetin and catechin. The biosensor was able to successfully detect the presence of catechol in real wine samples. These results make AgNWs promising elements in nanowired biosensors for the sensitive, stable and rapid voltammetric detection of phenols in real applications.

A photoelectrochemical enzyme biosensor based on functionalized hematite microcubes for rutin determination by square-wave voltammetry

A photoelectrochemical biosensing strategy for the highly sensitive detection of the flavonoid rutin was developed by synergizing the photoelectrocatalytic properties of hematite (α-Fe₂O₃) decorated with palladium nanoparticles (PdNPs) and the biocatalysis towards laccase-based reactions. The integration of α-Fe₂O₃.PdNPs with a polyphenol oxidase as a biorecognition element yields a novel biosensing platform. Under visible light irradiation, the photoactive biocomposite can generate a stable photocurrent, which was found to be directly dependent upon the concentration of rutin. Under the optimal experimental conditions, the cathodic photocurrent, measured at 0.33 V vs. Ag/AgCl, from the square-wave voltammograms presented a linear dependence on the rutin concentration within the range of 0.008-30.0 × 10^-8 mol L^-1 (sensitivity: 1.7 μA·(× 10^-8 M^-1)·cm^-2), with an experimental detection limit (S/N = 3) of 8.4 × 10^-11 mol L^-1. The proposed biosensor device presented good selectivity towards rutin in the presence of various organic compounds and inorganic ions, demonstrating the potential application of this biosensing platform in complex matrices. This bioanalytical device also exhibited excellent operational and analytical properties, such as intra-day (standard deviation, SD = 0.21%) and inter-day (SD = 1.30%) repeatability, and long storage stability (SD = 2.80% over 30 days).Graphical abstract.

Covalent attachment of laccase to carboxymethyl-botryosphaeran in aqueous solution for the construction of a voltammetric biosensor to quantify quercetin

Laccase from Botryosphaeria rhodina MAMB-05 was covalently immobilized on carboxymethyl-botryosphaeran by 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide and N-hydroxysuccinimide (EDC/NHS) in aqueous solution. This approach was employed to fabricate a novel laccase-based biosensor to electrochemically quantify quercetin (QCT), using a simple carbon black paste electrode as a transducer. The proposed biosensor was characterized by electrochemical impedance spectroscopy and Nyquist plots were used to evaluate the immobilization of the enzyme. For determining QCT, variables were optimized, that included experimental conditions for laccase immobilization, pH of the supporting electrolyte, and instrumental parameters of the electroanalytical technique. From square-wave-voltammograms, a linear dependence between the cathodic current peak and QCT concentration was observed within the range 4.98-50.0 × 10^-8 mol L^-1, with a theoretical detection limit of 2.6 × 10^-8 mol L^-1. The proposed method was successfully applied to determine QCT in beverages, pharmaceuticals, and biological samples. The proposed biosensor device presented good selectivity in the presence of uric acid, various inorganic ions, as well as other phenolic compounds, demonstrating the potential application of this biosensing platform in chemically complex solutions. Operational and analytical stability of the laccase-biosensor were evaluated, and good intra-day (SD = 1.23%) and inter-day (SD = 2.32%) repeatability, and long storage stability (SD = 3.47%) are presented.

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.

FTacV study of electroactive immobilized enzyme/free substrate reactions: Enzymatic catalysis of epinephrine by a multicopper oxidase from Thermothelomyces thermophila

In the present work, a kinetic analysis is made concerning the reaction of an electroactive immobilized enzyme with a free substrate, based on a Michaelis-Menten scheme. The proposed kinetic equations are investigated numerically for conditions describing large amplitude fast Fourier transform alternating current voltammetry (FTacV), under different reaction states (transient or steady state for the reaction intermediate as well as quasi or complete reversibility of the electrochemical step). The dependence of two chief observables that occur from the analysis of the results of the method, that is, the maximum of the harmonics and the potential shift of the corresponding dominant peaks, on substrate concentration is presented. The FTacV method is applied experimentally for an immobilized laccase-like multicopper oxidase from Thermothelomyces thermophila, TtLMCO1, and its reaction with epinephrine. From the experimental findings it is shown that the intrinsic characteristics of the system do not lead to the extraction of the desired kinetic data although indications on the relation between the kinetic constants is revealed. Finally, the response of the third harmonic for the first additions of epinephrine at subnanomolarity range can be exploited for the detection of epinephrine at rather low concentrations.

Carbon black as an outstanding and affordable nanomaterial for electrochemical (bio)sensor design

Advances in cutting-edge technologies including nanotechnology, microfluidics, electronic engineering, and material science have boosted a new era in the design of robust and sensitive biosensors. In recent years, carbon black has been re-discovered in the design of electrochemical (bio)sensors thanks to its interesting electroanalytical properties, absence of treatment requirement, cost-effectiveness (c.a. 1 €/Kg), and easiness in the preparation of stable dispersions. Herein, we present an overview of the literature on carbon black-based electrochemical (bio)sensors, highlighting current trends and possible challenges to this rapidly developing area, with a special focus on the fabrication of carbon black-based electrodes in the realisation of sensors and biosensors (e.g. enzymatic, immunosensors, and DNA-based).

Chemometric-assisted construction of a biosensing device to measure chlorogenic acid content in brewed coffee beverages to discriminate quality

In this work we propose the use of statistical mixture design in the construction of a biosensor device based on graphite oxide, platinum nanoparticles and biomaterials obtained from Botryosphaeria rhodina MAMB-05. The biosensor was characterized by electrochemical impedance spectroscopy. Under optimized experimental parameters by factorial design, the biosensor was applied to the voltammetric determination of chlorogenic acid (CGA) measured as 5-O-caffeoylquinic acid (5-CQA). The biosensor response was linear (R² = 0.998) for 5-CQA in the concentration range 0.56-7.3 µmol L^-1, with limit of detection and quantification of 0.18 and 0.59 µmol L^-1, respectively. The new biosensing device was applied to quality control analysis based upon the determination of CGA content in specialty and traditional coffee beverages. The results indicated that specialty coffee had a significantly higher content of CGA. Principal component analysis of the voltammetric fingerprint of brewed coffees revealed that the laccase-based biosensor can be used for their discrimination.