Nanographene-based tyrosinase biosensor for rapid detection of bisphenol A

Luminescent Cd(II) Fumarate Bridging 1D Coordination Polymer: Ultra-Trace Level Detection of Cu2+ in Aqueous Medium and Fabrication of Semiconducting Device

In addressing the Sustainable Development Goals (SDGs) the UNDP has fixed 17 issues out of them clean water (SDG-6) and affordable energy (SDG-7) serve as decisive points towards sustenance of the society. Material chemistry plays a vital role to design new chemical compounds and exploring versatile activities towards the solution of pressing challenges. Copper, third abundant metal in human body following iron and zinc, is useful to monitor many metabolic processes. Exposure to high level Copper or its deficiency can cause various health issues. It is essential to determine quantity of Cu2+ in a wide range of consumables. A luminescent coordination polymer (LCP) of Cd2+(d10) as a metal node, fumaric acid (fuma2 -) as a linker and tripod N-coordinated 4'-Chloro-2,2',6',2"-terpyridine (4-Cltpy) as end-capping ligand, {[Cd(fuma)₂(4-Cltpy)].(H2O)}n (CP1), has been used in this research for trace quantity detection of Cu2+ in aqueous solution (LOD: 0.0307 μM (Cu(II)) (WHO recommended toxicity limit of Cu(II) is 3.15 μM). The band gap of CP1 (experimental value by Tauc's plot, 3.56 eV and theoretically calculated band gap, 3.54 eV) directs to fabricate Schottky semiconducting device (ITO/CP1/Al) which determines electrical conductivity, 4.52×10-4 Sm-1 at room temperature. Therefore, CP1 is a promising candidate as a conductive material and a sensor. Because of its dual purpose, CP1 may be very beneficial for device applications and a breakthrough in material science in near future.

Organic conjugated polymer nanoparticles enhanced tyrosinase electrochemical biosensor for selective, sensitive and rapid detection of bisphenol A

Bisphenol A (BPA) has been widely used in the production of polycarbonate (PC) plastics, flame retardants and epoxy resins, which is one of the most important endocrine disrupting chemicals and can cause damage to the estrogen system of human. In this work, organic conjugated polymer nanoparticles (CPNPs) were synthesized through nanoprecipitation method using liposome 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[methoxy (polyethylene glycol)-2000] (DSPE-mPEG2000) coated poly[(4,4'-bis(2-ethylhexyl)-dithieno[3,2-b:2',3'-d]silole)-2,6-diyl-alt-4,7-di(4-hexyl-2-thienyl)-5,6-difluoro-2,1,3-benzothiadiazole] (PDTS-hDTBT) and poly[(4,4'-bis(2-ethylhexyl)-dithieno[3,2-b:2',3'-d]silole)-2,6-diyl-alt-4,7-di(4-(2-ethylhexyl)-2-thienyl)-5,6-difluoro-2,1,3-benzothiadiazole] (PDTS-ehDTBT). These two polymers have different side chains, which can affect the configuration of the polymers, thereby affecting the π-π interaction between BPA and CPNPs. The resultant two CPNPs were explored as extremely attractive matrix for tyrosinase immobilization to construct electrochemical biosensing platforms for sensitive and rapid detection of BPA in water environments. The electrochemical performance of these two biosensors was significantly enhanced, benefiting from the large specific surface area and excellent biocompatibility of CPNPs, as well as the strong π-π interaction between CPNPs and BPA. The current response of PDTS-ehDTBT-Tyr-Chi/GCE exhibited a good linear relationship with BPA concentration ranging from 0.02 to 3.0 μM with a low detection limit of 11.83 nM and a high sensitivity of 0.9724 μA μM-1 cm-2. The fabricated biosensor was further used for BPA detection in actual samples with a recovery rate of 92.0 %-99.4 %. With the remarkable advantages, CPNPs-based biosensor provides a highly sensitive detection tool for rapid detection of BPA in actual samples, which has broad application prospects.

Facile Chemical Synthesis of Co-Ru-Based Heterometallic Supramolecular Polymer for Electrochemical Oxidation of Bisphenol A: Kinetics Study at the Electrode/Electrolyte Interface

Regardless of the adverse effects of Bisphenol A (BPA), its use in industry and in day-to-day life is increasing at a higher rate every year. In the present study, a simple and reliable chemical approach was used to develop an efficient BPA sensor based on a Co-Ru-based heterometallic supramolecular polymer (polyCoRu). Surface morphology and elemental analysis were examined using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX). Furthermore, functional group analysis was accomplished by Fourier transform infrared spectroscopy (FT-IR). UV-vis spectroscopy was used to confirm the complexation in the ratio of 0.5:0.5:1 (metal 1/metal 2/ligand). Electrochemical characterization of the synthesized polyCoRu was conducted using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) analyses. The study identified two distinct linear dynamic ranges for the detection of BPA, 0.197-2.94 and 3.5-17.72 μM. The regression equation was utilized to determine the sensitivity and limit of detection (LOD), resulting in values of 0.6 μA cm-2 μM-1 and 0.02 μM (S/N = 3), respectively. The kinetics of BPA oxidation at the polyCoRu/GCE were investigated to evaluate the heterogeneous rate constant (k), charge transfer coefficient (α), and the number of electrons transferred during the oxidation and rate-determining step. A probable electrochemical reaction mechanism has been presented for further comprehending the phenomena occurring at the electrode surface. The practical applicability of the fabricated electrode was analyzed using tap water, resulting in a high percentage of recovery ranging from 96 to 105%. Furthermore, the reproducibility and stability data demonstrated the excellent performance of polyCoRu/GCE.

Shield, Anchor, and Adhesive Roles of Methylene Blue in Tyrosinase Adsorbed on Carbon Felt for a Flow Injection Amperometric Enzyme Biosensor for Phenolic Substrates and Inhibitors

Methylene blue (MB) acted as a stabilizer for preventing surface-induced denaturation of tyrosinase (TYR) adsorbed on a carbon felt (CF) surface, which is based on shield and anchor roles preventing the unfavorable conformational change of TYR on the hydrophobic CF surface. Furthermore, MB acted as an effective adhesive for TYR immobilization on CF. The resulting TYR and MB coadsorbed CF (TYR/MB-CF) worked as an excellent working electrode unit in an electrochemical detector in a flow injection amperometric biosensor, which allowed highly sensitive consecutive determination of not only TYR substrates but also competitive inhibitors. Simultaneous adsorption of TYR and MB from their mixed solution was much useful as compared with step-wise separated adsorption of TYR on the MB-adsorbed CF, which suggests that the binding interaction of MB with TYR in the solution phase is important for this phenomenon. Fluorescence and UV-vis spectroscopy revealed that not only electrostatic forces between the cationic MB and anionic amino acid residues of TYR but also hydrophobic interactions via the phenothiazine ring of MB play a principal binding driving force of MB with TYR at the surface of the TYR molecules. Synchronous fluorescence, three-dimensional fluorescence, and circular dichroism (CD) spectroscopy clarified that the conformation and the secondary structure of TYR slightly changed upon the MB binding, implying that MB binding leads to the modification of the original intramolecular bonding in part.

Electrochemical (bio)sensors based on carbon quantum dots, ionic liquid and gold nanoparticles for bisphenol A

Electrochemical (bio)sensors were developed for bisphenol A (BPA) determination. Screen printed carbon electrode (SPCE) was modified with ionic liquid 1- butyl-3-methylimidazolium tetrafluoroborate (IL), carbon quantum dots (CQD) and gold nanoparticles (AuNP) for the fabrication of the BPA sensor. Electrode surface composition was optimized for the deposition time of AuNP, amount of CQD and percentage of IL using the central composite design (CCD) method. The results of the CCD study indicated that maximum amperometric response was recorded when 9.8 μg CQD, 3% IL and 284 s AuNP deposition time were used in modification. Tyrosinase (Ty) was further modified on the AuNP/CQD-IL/SPCE to fabricate the biosensor. Analytical performance characteristics of the BPA sensor were investigated by differential pulse anodic adsorptive stripping voltammetry and the AuNP/CQD-IL/SPCE sensor exhibited a linear response to BPA in the range of 2.0 × 10^-8 - 3.6 × 10^-6 M with a detection limit of 1.1 × 10^-8 M. Amperometric measurements showed that the linear dynamic range and detection limit of the Ty/AuNP/CQD-IL/SPCE were 2.0 × 10^-8 - 4.0 × 10^-6 M and 6.2 × 10^-9 M, respectively. Analytical performance characteristics such as sensitivity, reproducibility and selectivity were investigated for the presented (bio)sensors. The analytical applicability of the (bio)sensors to the analysis of BPA in mineral water samples was also tested.

Recent advances in the potential applications of luminescence-based, SPR-based, and carbon-based biosensors

Abstract

The need for biosensors has evolved in the detection of molecules, diseases, and pollution from various sources. This requirement has headed to the development of accurate and powerful equipment for analysis using biological sensing component as a biosensor. Biosensors have the advantage of rapid detection that can beat the conventional methods for the detection of the same molecules. Bio-chemiluminescence-based sensors are very sensitive during use in biological immune assay systems. Optical biosensors are emerging with time as they have the advantage that they act with a change in the refractive index. Carbon nanotube-based sensors are another area that has an important role in the biosensor field. Bioluminescence gives much higher quantum yields than classical chemiluminescence. Electro-generated bioluminescence has the advantage of miniature size and can produce a high signal-to-noise ratio and the controlled emission. Recent advances in biological techniques and instrumentation involving fluorescence tag to nanomaterials have increased the sensitivity limit of biosensors. Integrated approaches provided a better perspective for developing specific and sensitive biosensors with high regenerative potentials. This paper mainly focuses on sensors that are important for the detection of multiple molecules related to clinical and environmental applications.

Key points

• The review focusses on the applications of luminescence-based, surface plasmon resonance-based, carbon nanotube-based, and graphene-based biosensors

• Potential clinical, environmental, agricultural, and food industry applications/uses of biosensors have been critically reviewed

• The current limitations in this field are discussed, as well as the prospects for future advancement

A Porous Metal-Organic Framework as an Electrochemical Sensing Platform for Highly Selective Adsorption and Detection of Bisphenols

The design of artificial receptors with a specific recognition function and enhanced selectivity is highly desirable in the electrochemical sensing field, which can be used for detection of environmental pollutants. In this facet, metal-organic frameworks (MOFs) featured adjustable porosities and specific host-guest recognition properties. Especially, the large hydrophobic cavity formed in the porous MOFs may become a potential artificial receptor. We herein designed a new porous MOF [Zn₂(L)(IPA)(H₂O)]·2DMF·2MeOH·3H₂O (Zn-L-IPA) by using a functionalized sulfonylcalix[4]arene (L¹) and isophthalic acid (H₂IPA) (DMF = N,N'-dimethylformamide). The specific pore size and pore shape of Zn-L-IPA made it efficiently selective for absorption of bisphenol A (BPA), bisphenol F (BPF), and bisphenol S (BPS). Therefore, a rapid, highly selective, and ultrasensitive electrochemical sensing platform Zn-L-IPA@GP/GCE was fabricated by using Zn-L-IPA as a host to recognize and absorb bisphenol guests (GP = graphite powder, GCE = glassy carbon electrode). Most strikingly, the extremely low detection limits were up to 3.46 and 0.17 nM for BPA and BPF, respectively, using the Zn-L-IPA@GP/GCE electrode. Furthermore, the "recognition and adsorption" mechanism was uncovered by density functional theory with the B3LYP function. This work offered a prospective strategy for selective absorption and detection of harmful bisphenols with the MOF-based porous material.

Triple-signaling amplification strategy based electrochemical sensor design: boosting synergistic catalysis in metal-metalloporphyrin-covalent organic frameworks for sensitive bisphenol A detection

A covalent organic framework (COF) is a promising type of porous material with customizable surface characteristics. Confining multiple catalytic units within a mesoporous COF can generate abundant active sites and improve the catalytic performance. In this work, a COF with both metalloporphyrin and a metal nanoparticle complex denoted as hemin/TAPB-DMTP-COF/AuNPs (TAPB: 1,3,5-tris(4-amino-phenyl)benzene, DMTP: 2,5-dimethoxyterephaldehyde, AuNPs: Au nanoparticles) has been successfully fabricated through a hierarchical encapsulation method. The as-synthesized composite was then employed to construct an electrochemical sensing platform for the efficient detection of bisphenol A (BPA). Under the optimal conditions, the hemin/TAPB-DMTP-COF/AuNP sensor presented a linear range of 0.01-3 μmol L^-1 and a low detection limit of 3.5 nmol L^-1. The satisfactory signal amplification is based on a triple-signaling amplification strategy due to the abundant Fe³⁺ sites of Fe-porphyrin, high conductivity of AuNPs and a large specific surface area of the TAPB-DMTP-COF. The proposed method was used to measure the content of BPA in different water samples with a satisfactory recovery from 95.5 to 104.0%, suggesting the great potential of the sensor in practical applications.

Two-Dimensional Nanostructures for Electrochemical Biosensor

Current advancements in the development of functional nanomaterials and precisely designed nanostructures have created new opportunities for the fabrication of practical biosensors for field analysis. Two-dimensional (2D) and three-dimensional (3D) nanomaterials provide unique hierarchical structures, high surface area, and layered configurations with multiple length scales and porosity, and the possibility to create functionalities for targeted recognition at their surface. Such hierarchical structures offer prospects to tune the characteristics of materials-e.g., the electronic properties, performance, and mechanical flexibility-and they provide additional functions such as structural color, organized morphological features, and the ability to recognize and respond to external stimuli. Combining these unique features of the different types of nanostructures and using them as support for bimolecular assemblies can provide biosensing platforms with targeted recognition and transduction properties, and increased robustness, sensitivity, and selectivity for detection of a variety of analytes that can positively impact many fields. Herein, we first provide an overview of the recently developed 2D nanostructures focusing on the characteristics that are most relevant for the design of practical biosensors. Then, we discuss the integration of these materials with bio-elements such as bacteriophages, antibodies, nucleic acids, enzymes, and proteins, and we provide examples of applications in the environmental, food, and clinical fields. We conclude with a discussion of the manufacturing challenges of these devices and opportunities for the future development and exploration of these nanomaterials to design field-deployable biosensors.

Electrochemical Biosensor Based on HRP/Ti3C2/Nafion Film for Determination of Hydrogen Peroxide in Serum Samples of Patients with Acute Myocardial Infarction

Hydrogen peroxide (H₂O₂) has been reported to mediate a variety of physiological and pathological processes in living systems. In this work, a biosensor for determination of H₂O₂ was prepared by using an HRP/Ti₃C₂/Nafion film-modified glassy carbon electrode (GCE). Ti₃C₂ nanosheets with remarkable conductivity and high specific surface area were chosen as carriers for HRP. Moreover, this biosensor modified with HRP has a specific catalytic effect on H₂O₂. The difference in peak current could reflect the quantitative change of H₂O₂. The linear range of the biosensor is 5-8000 μM, and the detection limit is 1 μM (S/N = 3). This biosensor was used to detect H₂O₂ in clinical serum samples of normal controls and patients with acute myocardial infarction (AMI) before and after percutaneous coronary intervention (PCI). The results showed that the difference between normal controls and patients is significant (P < 0.05), as well as the difference for patients before and after PCI (P < 0.01), but no significant difference existed between postoperative patients and normal controls. This biosensor has the advantages of simple preparation, high sensitivity, and quick detection, showing potential application in clinical diagnosis.

Lipid-matrix effects on tyrosinase immobilization in Langmuir and Langmuir-Blodgett films

The immobilization of the enzyme tyrosinase (Tyr) in lipid matrices can be explored to produce biosensors for detecting polyphenols, which is relevant for the food industry. Herein, we shall demonstrate the importance of the lipid composition to immobilize the enzyme tyrosinase in Langmuir-Blodgett (LB) films. Tyr could be incorporated into Langmuir monolayers of arachidic acid (AA), 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and 1,2-dipalmitoyl-sn-glycero-3-phospho-(1'-rac-glycerol) (sodium salt) (DPPG), having as the main effect an expansion in the monolayers. Results from polarization-modulated infrared reflection-absorption spectroscopy (PM-IRRAS) pointed to electrostatic interactions between the charged residues of Try and the lipid headgroups, in addition to changes in the order of lipid chains. The interaction between Tyr and DPPC in Langmuir monolayers can be correlated with the superior performance of DPPC/Tyr LB films used as biosensors to detect catechol by cyclic voltammetry. The molecular-level interactions assessed via PM-IRRAS are therefore believed to drive an immobilization process for Tyr in the lipid LB matrix and may serve as a general criterion to identify matrices that preserve enzyme activity.

Electrochemical Detection of Bisphenol A by Tyrosinase Immobilized on Electrospun Nanofibers Decorated with Gold Nanoparticles

Bisphenol A (BPA) is an endocrine-disrupting chemical (EDC) employed in industrial processes that causes adverse effects on the environment and human health. Sensitive and inexpensive methods to detect BPA are therefore needed. In this paper, we describe an electrochemical biosensor for detecting low levels of BPA using polymeric electrospun nanofibers of polyamide 6 (PA6) and poly(allylamine hydrochloride) (PAH) decorated with gold nanoparticles (AuNPs), namely, PA6/PAH@AuNPs, which were deposited onto a fluorine-doped tin oxide (FTO) substrate. The hybrid layer was excellent for the immobilization of tyrosinase (Tyr), which allowed an amperometric detection of BPA with a limit of detection of 0.011 μM in the concentration range from 0.05 to 20 μM. Detection was also possible in real water samples with recoveries in the range of 92–105%. The improved sensing performance is attributed to the combined effect of the large surface area and porosity of PA6/PAH nanofibers, the catalytic activity of AuNPs, and oxidoreductase ability of Tyr. These results provide a route for novel biosensing architectures to monitor BPA and other EDCs in water resources.

Agaricus bisporus Crude Extract: Characterization and Analytical Application

In the present work crude Agaricus bisporus extract (ABE) has been prepared and characterized by its tyrosinase activity, protein composition and substrate specificity. The presence of mushroom tyrosinase (PPO3) in ABE has been confirmed using two-dimensional electrophoresis, followed by MALDI TOF/TOF MS-based analysis. GH27 alpha-glucosidases, GH47 alpha-mannosidases, GH20 hexosaminidases, and alkaline phosphatases have been also detected in ABE. ABE substrate specificity has been studied using 19 phenolic compounds: polyphenols (catechol, gallic, caffeic, chlorogenic, and ferulic acids, quercetin, rutin, dihydroquercetin, l-dihydroxyphenylalanine, resorcinol, propyl gallate) and monophenols (l-tyrosine, phenol, p-nitrophenol, o-nitrophenol, guaiacol, o-cresol, m-cresol, p-cresol). The comparison of ABE substrate specificity and affinity to the corresponding parameters of purified A. bisporus tyrosinase has revealed no major differences. The conditions for spectrophotometric determination have been chosen and the analytical procedures for determination of 1.4 × 10^-4-1.0 × 10^-3 M l-tyrosine, 3.1 × 10^-6-1.0 × 10^-4 M phenol, 5.4 × 10^-5-1.0 × 10^-3 M catechol, 8.5 × 10^-5-1.0 × 10^-3 M caffeic acid, 1.5 × 10^-4-7.5 × 10^-4 M chlorogenic acid, 6.8 × 10^-5-1.0 × 10^-3 M l-DOPA have been proposed. The procedures have been applied for the determination of l-tyrosine in food supplements, l-DOPA in synthetic serum, and phenol in waste water from the food manufacturing plant. Thus, we have demonstrated the possibility of using ABE as a substitute for tyrosinase in such analytical applications, as food supplements, medical and environmental analysis.

Analytical performance of functional nanostructured biointerfaces for sensing phenolic compounds

Electrochemical biointerfaces are constructed with a wide range of nanomaterials and conducting polymers that strongly affect the analytical performance of biosensors. The analysis of progress toward electrochemical sensing platforms offers opportunities to provide devices for commercial use. The investigation of different methods for the synthesis of phenol biointerfaces leads to design challenges in the field of monitoring phenolic compounds. This paper review the innovative strategies and feature techniques in the construction of phenolic compound biosensors. The focus was made on the preparation methods of nanostructures and nanomaterials design for catalytic improvements of sensing interfaces. The paper also provides a comprehensive overview in the field of enzyme immobilization approaches at solid supports and technical formation of polymer nanocomposites, as well as applications of hybrid organic-inorganic nanocomposites in phenolic biosensors. This review also highlights the recent progress in the electrochemical detection of phenolic compounds and summarizes analytical performance parameters including sensitivity, storage stability, limit of detection, linear range, and Michaelis-Menten kinetic analysis. It also emphasizes advances from the past decade including technical challenges for the construction of suitable biointerfaces for monitoring phenolic compounds.

Catalysis-based specific detection and inhibition of tyrosinase and their application

Tyrosinase is an important enzyme in controlling the formation of melanin in melanosome, and plays a key role in the pigmentation of hair and skin. The abnormal expression or activation of tyrosinase is associated with several diseases such as albinism, vitiligo, melanoma and Parkinson disease. Excessive deposition of melanin could cause diseases such as freckles and brown spots in the human body, and it is also closely related to browning of fruits and vegetables and insect molting. Detecting and inhibiting the activity of tyrosinase is of extraordinary value in the progress of diagnosis and treatment of these diseases. Therefore, many selective optical detection probes and small molecular inhibitors have been developed, and have made significant contributions to the basic and clinical research on these diseases. In this paper, the detection and inhibition of tyrosinase and their application in whitening products are reviewed, with special emphasis on development of fluorescent probes and inhibitors. Hopefully, this review will help design more efficient and sensitive tyrosinase probes and inhibitors, as well as shed light on novel treatment of diseases such as melanoma.

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The abnormal expression or activation of tyrosinase is the pathogenesis of several diseases such as albinism, vitiligo, and melanoma.

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Detecting and inhibiting tyrosinase activity is of great value in the diagnosis and treatment of these diseases.

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The detection/inhibition of tyrosinase and its application in whitening products are reviewed, with special emphasis on probes/inhibitors.

Analysis of Phenolic Content in Grape Seeds and Skins by Means of a Bio-Electronic Tongue

A bio-electronic tongue has been developed to evaluate the phenolic content of grape residues (seeds and skins) in a fast and easy way with industrial use in mind. A voltammetric electronic tongue has been designed based on carbon resin electrodes modified with tyrosinase combined with electron mediators. The presence of the phenoloxydase promotes the selectivity and specificity towards phenols. The results of multivariate analysis allowed discriminating seeds and skins according to their polyphenolic content. Partial least squares (PLS) has been used to establish regression models with parameters related to phenolic content measured by spectroscopic methods i.e., total poliphenol content (TPC) and Folin–Ciocalteu (FC) indexes. It has been shown that electronic tongue can be successfully used to predict parameters of interest with high correlation coefficients (higher than 0.99 in both calibration and prediction) and low residual errors. These values can even be improved using genetic algorithms for multivalent analysis. In this way, a fast and simple tool is available for the evaluation of these values. This advantage may be due to the fact that the electrochemical signals are directly related to the phenolic content.

Promotion effect of Zn on 2D bimetallic NiZn metal organic framework nanosheets for tyrosinase immobilization and ultrasensitive detection of phenol

Environmental monitoring of pollutants is essential to guarantee the human health and maintain the ecosystem. The exploration of both simple and sensitive detection method has aroused widespread attentions. Herein, 2D bimetallic metal organic framework nanosheets (NiZn-MOF NSs) with tunable Ni/Zn ratios were synthesized, and for the first time employed to construct a tyrosinase biosensor. It is revealed that Zn element not only tuned the porosity structure and electronic structure of MOF NSs, but also modified their electrochemical activity. As a result, enzyme immobilization and electrochemical sensing performance of the NiZn-MOF NSs based biosensor were significantly enhanced by a suitable Zn addition. The fabricated tyrosinase biosensor exhibited excellent analytical detections, with a wide linear range from 0.08 μM to 58.2 μM, a high sensitivity of 159.3 mA M^-1, and an ultralow detection limit of 6.5 nM. In addition, the proposed biosensing approach also demonstrated good repeatability, superior selectivity, long-term stability, and high recovery for phenol detection in the real tap water samples.

Laccase Electrochemical Biosensor Based on Graphene-Gold/Chitosan Nanocomposite Film for Bisphenol A Detection

Background:

Bisphenol A (BPA) is considered one of the most common chemicals that could cause environmental endocrine disrupting. Therefore, there is an increasing demand for simple, rapid and sensitive methods for BPA detection that result from BPA leaching into foods and beverages from storage containers. Herein, a simple laccase electrochemical biosensor was developed for the determination of BPA based on Screen-Printed Carbon Electrode (SPCE) modified graphenegold/ chitosan. The synergic effect of graphene-gold/chitosan nanocomposite as electrode modifier greatly facilitates electron-transfer processes between the electrolyte and laccase enzyme, thus leads to a remarkably improved sensitivity for bisphenol A detection.

Methods:

In this study, laccase enzyme is immobilized onto the Screen-Printed Carbon Electrode (SPCE) modified Graphene-Decorated Gold Nanoparticles (Gr-AuNPs) with Chitosan (Chit). The surface structure of nanocomposite was studied using different techniques including Field Emission Scanning Microscopy (FESEM), TRANSMISSION Electron Microscopy (TEM), Raman spectroscopy and Energy Dispersive X-ray (EDX). Meanwhile, the electrochemical performances of the modified electrodes were studied using Cyclic Voltammetry (CV) and Differential Pulse Voltammetry (DPV).

Results:

The developed laccase biosensor offered excellent analytical performance for the detection of BPA with a sensitivity of 0.271 μA/μM and Limit of Detection (LOD) of 0.023 μM, respectively. Moreover, the constructed biosensor showed good reproducibility, selectivity and stability towards BPA. The sensor has been used to detect BPA in a different type of commercial plastic products as a real sample and satisfactory result was obtained when compared with the HPLC method.

Conclusion:

The proposed electrochemical laccase biosensor exhibits good result which is considered as a promising candidate for a simple, rapid and sensitive method especially in the resource- limited condition.

A Coculture Based Tyrosine-Tyrosinase Electrochemical Gene Circuit for Connecting Cellular Communication with Electronic Networks

There is a growing interest in mediating information transfer between biology and electronics. By the addition of redox mediators to various samples and cells, one can both electronically obtain a redox "portrait" of a biological system and, conversely, program gene expression. Here, we have created a cell-based synthetic biology-electrochemical axis in which engineered cells process molecular cues, producing an output that can be directly recorded via electronics-but without the need for added redox mediators. The process is robust; two key components must act together to provide a valid signal. The system builds on the tyrosinase-mediated conversion of tyrosine to L-DOPA and L-DOPAquinone, which are both redox active. "Catalytic" transducer cells provide for signal-mediated surface expression of tyrosinase. Additionally, "reagent" transducer cells synthesize and export tyrosine, a substrate for tyrosinase. In cocultures, this system enables real-time electrochemical transduction of cell activating molecular cues. To demonstrate, we eavesdrop on quorum sensing signaling molecules that are secreted by Pseudomonas aeruginosa, N-(3-oxododecanoyl)-l-homoserine lactone and pyocyanin.

Detection of phenol by incorporation of gold modified-enzyme based graphene oxide thin film with surface plasmon resonance technique

In this study, the incorporation between gold modified-tyrosinase (Tyr) enzyme based graphene oxide (GO) thin film with surface plasmon resonance (SPR) technique has been developed for the detection of phenol. SPR signal for the thin film contacted with phenol solution was monitored using SPR technique. From the SPR curve, sensitivity, full width at half maximum (FWHM), detection accuracy (DA) and signal-to-noise ratio (SNR) have been analyzed. The sensor produces a linear response for phenol up to 100 µM with sensitivity of 0.00193° µM^-1. Next, it can be observed that deionized water has the lowest FWHM, with a value of 1.87° and also the highest value of DA. Besides, the SNR of the SPR signal was proportional to the phenol concentrations. Furthermore, the surface morphology of the modified thin film after exposed with phenol solution observed using atomic force microscopy showed a lot of sharp peaks compared to the image before in contact with phenol proved the interaction between the thin film and phenol.

Graphene based sensors

The two dimensional, honeycomb structured, single carbon layered graphene has extensively been used in the field of sensor detection due to its unique physicochemical properties. These properties such as excellent electrical conductivity, high electron mobility, tunable optical properties, room temperature quantum Hall effect, large surface to volume ratio, high mechanical strength, and ease of functionalization, make it an ideal nanomaterial for sensor development. This has enabled the fabrication of a large variety of highly sensitive sensors which include colorimetric, electrochemical, potentiometric, fluorescence, etc. based sensors. These sensors in conjugation with graphene or its derivatives such as graphene quantum dots, graphene oxide, reduced graphene oxide, etc. show highly desirable properties such as high sensitivity (detecting minute amounts of target analyte), specificity (no cross reactivity while detecting the target analyte), rapid results, low cost, extended storage shelf life and robustness (stability), and easy-to-use capabilities (user-friendly). This book chapter gives a detailed overview of all the advances made in the development and fabrication of novel graphene based sensors and their application in point of care (PoC) detection of various diseases as well as health monitoring devices. The different sensors, their methods of fabrication, their sensitivity and the analytes and biomolecules used have been discussed in detail and compared.

Progress in miRNA Detection Using Graphene Material-Based Biosensors

MicroRNAs (miRNAs) are short, endogenous, noncoding RNAs that play critical roles in physiologic and pathologic processes and are vital biomarkers for several disease diagnostics and therapeutics. Therefore, rapid, low-cost, sensitive, and selective detection of miRNAs is of paramount importance and has aroused increasing attention in the field of medical research. Among the various reported miRNA sensors, devices based on graphene and its derivatives, which form functional supramolecular nanoassemblies of π-conjugated molecules, have been revealed to have great potential due to their extraordinary electrical, chemical, optical, mechanical, and structural properties. This Review critically and comprehensively summarizes the recent progress in miRNA detection based on graphene and its derivative materials, with an emphasis on i) the underlying working principles of these types of sensors, and the unique roles and advantages of graphene materials; ii) state-of-the-art protocols recently developed for high-performance miRNA sensing, including representative examples; and iii) perspectives and current challenges for graphene sensors. This Review intends to provide readers with a deep understanding of the design and future of miRNA detection devices.

Novel Bacillus subtilis Spore-Displayed Tyrosinase Kit for Rapid Detection of Tyrosine in Urine: Pharmaceutical Applications for the Early Diagnosis of Kidney-Related Diseases

Purpose: Simple and cheap diagnostic kit development is one of the important aims of pharmaceutical developers and companies focused on public health improvement. The Bacillus subtilis spore surface-display technique is a genetic engineering method that is used to develop new-generation diagnostic kits applicable for the early detection of various types of diseases. In this study, we developed a novel simple, rapid, and inexpensive diagnostic paper-based kit to detect tyrosine in urine samples of humans and animals that is applicable for home or laboratory use.

Methods: The B. subtilis spore-displayed tyrosinase system developed by genetic engineering methods was used to prepare a paper-based kit to detect tyrosine in urine samples of different groups of patients (i.e., patients with diabetes, diabetes with chronic kidney disease (CKD), and chronic kidney disease) for the detection of tyrosine during the acute disease phase. To confirm the sensitivity and specificity of the kit, tyrosine was also detected in urine samples using conventional liquid chromatography/mass spectroscopy.

Results: Different concentrations of tyrosine (0.1–1 mM) were detected in urine samples based on visible changes of color from bright brownish-gray to dark brownish-gray within 1 hour. The kit could screen samples to distinguish the three groups of patients based on formation of a broad spectrum of colors reflecting the concentration of tyrosine.

Conclusion: To the best of our knowledge, this is the first diagnostic kit with potential to rapidly diagnose various diseases related to the production of tyrosine in biological samples. This kit is not only widely applicable, including for personal use in the home, but is also appropriate as a part of standard screening tests and health protection programs in countries with limited resources.

Electrochemical Enzyme Biosensor Bearing Biochar Nanoparticle as Signal Enhancer for Bisphenol A Detection in Water

An electrochemical tyrosinase enzyme (Tyr) biosensor using a highly conductive sugarcane derived biochar nanoparticle (BCNP) as a transducer and signal enhancer (BCNPs/Tyr/Nafion/GCE) was developed for the sensitive detection of bisphenol A (BPA). The BCNPs/Tyr/Nafion/GCE biosensor exhibited improved amperometric current responses such as higher sensing signal, decreased impedance and lowered reduction potential compared with the Tyr/Nafion/GCE due to high conductivity property of the biochar nanoparticle. Under the optimized conditions, it could detect BPA in good sensitivity with linear range from 0.02 to 10 μM, and a lowest detection limit of 3.18 nM. Moreover, it showed a low K_m value, high reproducibility and good selectivity over other reagents, and the BCNPs/Tyr complex solution also showed good stability with 86.9% of sensing signal maintained after one month storage. The biosensor was also successfully utilized for real water detection with high accuracy as validated by high performance liquid chromatography. Therefore, the biochar nanoparticle based enzyme biosensor proved to be a potential and reliable method for high performance detection of pollutants in the environment.

Tyrosinase-immobilized CNT based biosensor for highly-sensitive detection of phenolic compounds

Highly sensitive phenol biosensor was developed by using well-dispersed carbon nanotubes (CNTs) in enzyme solution and adding CNTs in enzyme electrodes. First, the intact CNTs were dispersed in aqueous tyrosinase (TYR) solution, and TYR molecules were precipitated and crosslinked to prepare the sample of enzyme adsorption, precipitation and crosslinking (EAPC). EAPC exhibited 10.5- and 5.4-fold higher TYR activity per mg of CNTs as compared to enzyme adsorption (EA) and enzyme adsorption/crosslinking (EAC), respectively. EAPC retained 29% of its initial activity after incubation at 40 °C for 128 h, while EA and EAC showed no residual activities, respectively. In biosensing a model phenolic compound of catechol, the sensitivities of EA, EAC and EAPC electrodes on glassy carbon electrode (GCE) were 34, 281 and 675 µA/mM/cm², respectively. When 90 w/w% CNTs were added to the enzyme electrodes, the sensitivities of EA, EAC, and EAPC electrodes were 146, 427, and 1160 µA/mM/cm², respectively, and the EAPC electrode showed a 2.3-fold increase in sensitivity upon CNT addition. Catechol and phenol could also be detected by EAPC on the screen-printed electrode (SPE), with sensitivities of 1340 and 1170 µA/mM/cm², respectively. The sensitivity of EAPC-SPE for phenol detection in the effluent from real municipal wastewater treatment plant was 1100 µA/mM/cm². The sensitivity of EAPC-SPE retained 74% of its initial sensitivity after incubation at 40 °C for 12 h. The combination of EAPC immobilization and CNT addition has great potential for application in the development of sensitive enzyme biosensors for various analytes and phenols in water environments.

Zinc/Aluminium⁻Quinclorac Layered Nanocomposite Modified Multi-Walled Carbon Nanotube Paste Electrode for Electrochemical Determination of Bisphenol A

This paper presents the application of zinc/aluminium-layered double hydroxide-quinclorac (Zn/Al-LDH-QC) as a modifier of multiwalled carbon nanotubes (MWCNT) paste electrode for the determination of bisphenol A (BPA). The Zn/Al-LDH-QC/MWCNT morphology was examined by a transmission electron microscope and a scanning electron microscope. Electrochemical impedance spectroscopy was utilized to investigate the electrode interfacial properties. The electrochemical responses of the modified electrode towards BPA were thoroughly evaluated by using square-wave voltammetry technique. The electrode demonstrated three linear plots of BPA concentrations from 3.0 × 10⁻⁸–7.0 × 10⁻⁷ M (R² = 0.9876), 1.0 × 10⁻⁶–1.0 × 10⁻⁵ M (R² = 0.9836) and 3.0 × 10⁻⁵–3.0 × 10⁻⁴ M (R² = 0.9827) with a limit of detection of 4.4 × 10⁻⁹ M. The electrode also demonstrated good reproducibility and stability up to one month. The presence of several metal ions and organic did not affect the electrochemical response of BPA. The electrode is also applicable for BPA determination in baby bottle and mineral water samples with a range of recovery between 98.22% and 101.02%.

Tyrosinase/Chitosan/Reduced Graphene Oxide Modified Screen-Printed Carbon Electrode for Sensitive and Interference-Free Detection of Dopamine

Tyrosinase, chitosan, and reduced graphene oxide (rGO) are sequentially used to modify a screen-printed carbon electrode (SPCE) for the detection of dopamine (DA), without interference from uric acid (UA) or ascorbic acid (AA). The use of tyrosinase significantly improves the detection’s specificity. Cyclic voltammetry (CV) measurements demonstrate the high sensitivity and selectivity of the proposed electrochemical sensors, with detection limits of 22 nM and broad linear ranges of 0.4–8 μM and 40–500 μM. The fabricated tyrosinase/chitosan/rGO/SPCE electrodes achieve satisfactory results when applied to human urine samples, thereby demonstrating their feasibility for analyzing DA in physiological samples.

Advances in sensing and biosensing of bisphenols: A review

Bisphenols (BPs) are well known endocrine disrupting chemicals (EDCs) that cause adverse effects on the environment, biotic life and human health. BPs have been studied extensively because of an increasing concern for the safety of the environment and for human health. They are major raw materials for manufacturing polycarbonates, thermal papers and epoxy resins and are considered hazardous environmental contaminants. A vast array of sensors and biosensors have been developed for the sensitive screening of BPs based on carbon nanomaterials (carbon nanotubes, fullerenes, graphene and graphene oxide), quantum dots, metal and metal oxide nanocomposites, polymer nanocomposites, metal organic frameworks, ionic liquids and molecularly imprinted polymers. This review is devoted mainly to a variety of sensitive, selective and reliable sensing and biosensing methods for the detection of BPs using electrochemistry, fluorescence, colorimetry, surface plasmon resonance, luminescence, ELISAs, circular dichroism, resonance Rayleigh scattering and adsorption techniques in plastic products, food samples, food packaging, industrial wastes, pharmaceutical products, human body fluids and many other matrices. It summarizes the advances in sensing and biosensing methods for the detection of BPs since 2010. Furthermore, the article discusses challenges and future perspectives in the development of novel sensing methods for the detection of BP analogs.