Immobilization Of Tyrosinase Research Articles

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.

Development of an Innovative Biosensor Based on Graphene/PEDOT/Tyrosinase for the Detection of Phenolic Compounds in River Waters.

Phenolic compounds, originating from industrial, agricultural, and urban sources, can leach into flowing waters, adversely affecting aquatic life, biodiversity, and compromising the quality of drinking water, posing potential health hazards to humans. Thus, monitoring and mitigating the presence of phenolic compounds in flowing waters are essential for preserving ecosystem integrity and safeguarding public health. This study explores the development and performance of an innovative sensor based on screen-printed electrode (SPE) modified with graphene (GPH), poly(3,4-ethylenedioxythiophene) (PEDOT), and tyrosinase (Ty), designed for water analysis, focusing on the manufacturing process and the obtained electroanalytical results. The proposed biosensor (SPE/GPH/PEDOT/Ty) was designed to achieve a high level of precision and sensitivity, as well as to allow efficient analytical recoveries. Special attention was given to the manufacturing process and optimization of the modifying elements' composition. This study highlights the potential of the biosensor as an efficient and reliable solution for water analysis. Modification with graphene, the synthesis and electropolymerization deposition of the PEDOT polymer, and tyrosinase immobilization contributed to obtaining a high-performance and robust biosensor, presenting promising perspectives in monitoring the quality of the aquatic environment. Regarding the electroanalytical experimental results, the detection limits (LODs) obtained with this biosensor are extremely low for all phenolic compounds (8.63 × 10-10 M for catechol, 7.72 × 10-10 M for 3-methoxycatechol, and 9.56 × 10-10 M for 4-methylcatechol), emphasizing its ability to accurately measure even subtle variations in the trace compound parameters. The enhanced sensitivity of the biosensor facilitates detection and quantification in river water samples. Analytical recovery is also an essential aspect, and the biosensor presents consistent and reproducible results. This feature significantly improves the reliability and usefulness of the biosensor in practical applications, making it suitable for monitoring industrial or river water.

Disposable biosensor based on nanodiamond particles, ionic liquid and poly-l-lysine for determination of phenolic compounds

This study describes the development of a highly sensitive amperometric biosensor for the analysis of phenolic compounds such as catechol. The biosensor architecture is based on the immobilization of tyrosinase (Tyr) on a screen-printed carbon electrode (SPE) modified with nanodiamond particles (ND), 1-butyl-3-methylimidazolium hexafluorophosphate (IL) and poly-l-lysine (PLL). Surface morphologies of the electrodes during the modification process were evaluated by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX). Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were used to investigate the electrochemical characteristics of the modified electrodes. Owing to the synergistic effect of the modification materials, the Tyr/PLL/ND−IL/SPE exhibited high sensitivity (328.2 μA mM−1) towards catechol with a wide linear range (5.0 × 10−8 – 1.2 × 10−5 M) and low detection limit (1.1 × 10−8 M). Furthermore, the method demonstrated good reproducibility and stability. The amperometric response of the biosensor towards other phenolic compounds such as bisphenol A, phenol, p-nitrophenol, m-cresol, p-cresol and o-cresol was also investigated. The analytical applicability of the biosensor was tested by the analysis of catechol in tap water. The results of the tap water analysis showed that the Tyr/PLL/ND−IL/SPE can be used as a practical and effective method for catechol determination.

Covalent immobilization of tyrosinase on magnetic multi-walled carbon nanotubes for inhibitor screening.

The inhibition of tyrosinase is considered to be a common therapeutic strategy for some hyperpigmentation disorders. Screening of tyrosinase inhibitors is of great significance to the treatment of pigmentation diseases. In this study, tyrosinase was covalently immobilized on magnetic multi-walled carbon nanotubes for the first time, and the immobilized tyrosinase was applied for ligand fishing of tyrosinase inhibitors from complex medicinal plants. The immobilized tyrosinase was characterized by transmission electron microscopy, atomic force microscopy, Fourier-transform infrared spectroscopy, vibratingsamplemagnetometry, and thermo-gravimetric analyzer, which indicated that tyrosinase was immobilized onto magnetic multi-walled carbon nanotubes. The immobilized tyrosinase showed better thermal stability and reusability than the free one. The ligand was fished out from Radix Paeoniae Alba and identified as 1,2,3,4,6-pentagalloylglucose by ultra-performance liquid chromatography-quadrupole time-of-flight high-resolution mass spectrometry. 1,2,3,4,6-pentagalloylglucose was found to be a tyrosinase inhibitor with similar half maximal inhibitory concentration values of 57.13±0.91μM compared to kojic acid (41.96±0.78μM). This work not only established a new method for screening tyrosinase inhibitors but also holds considerable potential for exploring the new medicinal value of medicinal plants.

Immobilization of Tyrosinase and Its Application

Immobilized enzymes are more robust and resistant to environmental changes than free enzymes in solution. More crucially, the immobilized enzyme systems' heterogeneity enables facile recovery of enzymes and products, multiple reuses, continuous enzymatic processes, quick reaction termination, and a more comprehensive range of bioreactor designs. This paper examines recent findings on enzyme immobilization using diverse approaches for various uses. The information gathered from the reactions catalyzed by the encapsulated tyrosinase provided a good view of hetero-biocatalysts in the phenol biosensor industries. This review proposes an effective method for immobilizing tyrosinase biomolecules into a silica aerogel matrix. Silica matrix has been utilized to encapsulate a wide range of biomolecules, mainly in sol-gel composites. We also discovered that silica aerogel synthesized from sol-gel method retains all the immobilized enzyme activity. The use of a silica matrix for enzyme immobilization, in conjunction with a moderate immobilization method, results in the successful retention of enzyme activity. Future studies should explore practical encapsulating approaches and inventively modified supports to enhance the commercialization of immobilized enzymes and offer fresh perspectives to the industrial sector.

Immobilization of Agaricus bisporus Polyphenol Oxidase 4 on mesoporous silica: Towards mimicking key enzymatic processes in peat soils

HypothesisThe use of immobilized enzyme-type biocatalysts to mimic specific processes in soil can be considered one of the most promising alternatives to overcome the difficulties behind the structural elucidation of riverine humic-derived iron-complexes. Herein, we propose that the immobilization of the functional mushroom tyrosinase, Agaricus bisporus Polyphenol Oxidase 4 (AbPPO4) on mesoporous SBA-15-type silica could contribute to the study of small aquatic humic ligands such as phenols. ExperimentsThe silica support was functionalized with amino-groups in order to investigate the impact of surface charge on the tyrosinase loading efficiency as well as on the catalytic performance of adsorbed AbPPO4. The oxidation of various phenols was catalyzed by the AbPPO4-loaded bioconjugates, yielding high levels of conversion and confirming the retention of enzyme activity after immobilization. The structures of the oxidized products were elucidated by integrating chromatographic and spectroscopic techniques. We also evaluated the stability of the immobilized enzyme over a wide range of pH values, temperatures, storage-times and sequential catalytic cycles. FindingsThis is the first report where the latent AbPPO4 is confined within silica mesopores. The improved catalytic performance of the adsorbed AbPPO4 shows the potential use of these silica-based mesoporous biocatalysts for the preparation of a column-type bioreactor for in situ identification of soil samples.

Tyrosinase Immobilization Strategies for the Development of Electrochemical Biosensors-A Review.

The development of enzyme biosensors has successfully overcome various challenges such as enzyme instability, loss of enzyme activity or long response time. In the electroanalytical field, tyrosinase is used to develop biosensors that exploit its ability to catalyze the oxidation of numerous types of phenolic compounds with antioxidant and neurotransmitter roles. This review critically examines the main tyrosinase immobilization techniques for the development of sensitive electrochemical biosensors. Immobilization strategies are mainly classified according to the degree of reversibility/irreversibility of enzyme binding to the support material. Each tyrosinase immobilization method has advantages and limitations, and its selection depends mainly on the type of support electrode, electrode-modifying nanomaterials, cross-linking agent or surfactants used. Tyrosinase immobilization by cross-linking is characterized by very frequent use with outstanding performance of the developed biosensors. Additionally, research in recent years has focused on new immobilization strategies involving cross-linking, such as cross-linked enzyme aggregates (CLEAs) and magnetic cross-linked enzyme aggregates (mCLEAs). Therefore, it can be considered that cross-linking immobilization is the most feasible and economical approach, also providing the possibility of selecting the reagents used and the order of the immobilization steps, which favor the enhancement of biosensor performance characteristics.

Sulfonated Starch-Graft-Polyaniline@Graphene Electrically Conductive Nanocomposite: Application for Tyrosinase Immobilization

The interaction of tyrosinase with sulfonated starch-graft-polyaniline@graphene (SSt-g-PANI@G) nanocomposite was investigated by electrochemical methods. The activity of the immobilized tyrosinase (Tyase) was proved by the electrochemical detection of three substrates (L-dopa, caffeic acid, and catechol). The SSt-g-PANI@G nanocomposite was characterized by Fourier-transform infrared spectra (FT-IR), X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy-dispersive X-ray analysis (EDX), and thermogravimetric analysis (TGA). To immobilize tyrosinase on the surface of the nanocomposite, a simple drop-casting technique was used. The presence of sulfuric acid and hydroxyl groups in SSt, amine groups in PANI, and high surface-to-volume ratio and electrical conductivity of graphene in the prepared nanocomposite led to good enzyme immobilization on the electrode surface. The modified electrode showed a suitable catalytic effect on the electrochemical redox agent, compared with the bare electrode. The peak current responses for three substrates were studied with a calibration curve derived using cyclic voltammetry (CV) and differential pulse voltammetry (DPV). In addition, the fabricated SSt-g-PANI@G/Tyase/GCE showed a more suitable response to catechol, L-dopa, and caffeic acid substrates, respectively.

Tyrosinase Immobilization in Nickel-Cross-Linked Gellan Microspheres and Conversion of l-DOPA to Dopachrome

Enzymes are widely applied in different industries, like pharmaceutical, food, biofuel, and waste valorization. However, the enzyme operating conditions are very limited. So, in most industrial processes, enzymes are not efficient, due to the use of harsh conditions, like organic solvents, extreme pH, and temperature. Immobilization arises as a way to overcome the process restrictions by offering better stability, activity, and improved recovery of enzymes. Physical adsorption into a solid support is a simple method to achieve enzyme immobilization and is compatible with different materials, like gellan gum. Tyrosinase is an essential enzyme for the biosynthesis of melanin, flavonoids, and l-DOPA, which is a drug used by the pharmaceutical industry to treat Parkinson’s disease. Therefore, it is important to develop an easy and simple method for tyrosinase immobilization that will allow high efficiency and reusability, making the melanin biosynthesis more cost-effective. In the laboratory experiment of the enzymatic biotechnology class, nickel-cross-linked gellan microspheres were prepared and characterized by the students and used as a solid support for tyrosinase immobilization. The reaction catalyzed by tyrosinase was detected by visual observation. This experiment allows students in the biotechnology field to understand the importance of the immobilization process in catalysis since the industry is exploring environmentally friendly processes and also the impact on enzyme efficiency when catalyzing a reaction. Moreover, it helps the students to acquire laboratory handling in the preparation of immobilized systems, while developing their creativity and innovative ability to overcome problems in the enzymatic biotechnology field.

Oriented in situ immobilization of a functional tyrosinase on microcrystalline cellulose effectively incorporates DOPA residues in bioengineered mussel adhesive protein.

Catechol-containing polymers such as mussel adhesive proteins (MAPs) are attractive as biocompatible adhesive biomaterials, and the catecholic amino acid 3,4-dihydroxyphenyl-L-alanine (DOPA) is considered a key molecule in underwater mussel adhesion. Tyrosinases can specifically convert tyrosine to DOPA without any cofactors. However, their catalytic properties still need to be adjusted to minimize unwanted DOPA oxidation via their diphenolase activity and catechol instability at neutral and basic pH values in the reaction products. In this work, we constructed a novel functional tyrosinase, mTyr-CNK_CBM, by fusion of mTyr-CNK with a cellulose-binding motif (CBM) for oriented in situ immobilization on microcrystalline cellulose via the C-terminal CBM without any additional purification steps. mTyr-CNK_CBM showed optimal catalytic activity at pH 4.5-6.5 and room temperature and had a high monophenolase/diphenolase activity ratio (Vmax mono/Vmax di = 2.08 at pH 6 and 25°C). mTyr-CNK_CBM exhibited 2.17-fold higher (as a unimmobilized free enzyme) and similarly high (upon immobilization) in vitro DOPA modification of a bioengineered MAP compared to a commercially available mushroom tyrosinase. Moreover, the immobilized mTyr-CNK_CBM showed long-term storability and improved reusability. These results clearly demonstrate a strong potential for practical use of immobilized mTyr-CNK_CBM as a monophenol monooxygenase in preparing biocompatible DOPA-tethered biomaterials and other catechol-containing polymers.

A novel tyramine biosensor based on carbon nanofibers, 1-butyl-3-methylimidazolium tetrafluoroborate and gold nanoparticles

A novel amperometric tyramine biosensor based on the immobilization of tyrosinase (Ty) onto glassy carbon electrode (GCE) modified with the carbon nanofibers (CNFs), chitosan (CH), ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate (IL) and gold nanoparticles (AuNPs) composite film was fabricated. Scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), cylic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) techniques were performed to ensure the successful fabrication of the biosensor. Owing to the synergistic action of carbon nanofibers, gold nanoparticles and ionic liquid, the Ty/AuNPs/CNFs-IL-CH/GCE biosensor resulted in an accurate, practical, highly sensitive and selective analytical method for tyramine determination. Under optimal experimental conditions a linear working range of 2.0 × 10−7 M to 4.8 × 10−5 M, sensitivity of 176.6 µA mM−1 and detection limit of 9.3 × 10−8 M were obtained. Moreover, the Ty/AuNPs/CNFs-IL-CH/GCE biosensor exhibited high selectivity towards tyramine in the presence of other biogenic amines. The applicability of the tyramine biosensor was demonstrated by detecting tyramine level in soy sauce sample with good recoveries.

Engineered tyrosinases with broadened bio-catalysis scope: immobilization using nanocarriers and applications.

Enzyme immobilization is a widely used technology for creating more stable, active, and reusable biocatalysts. The immobilization process also improves the enzyme's operating efficiency in industrial applications. Various support matrices have been designed and developed to enhance the biocatalytic efficiency of immobilized enzymes. Given their unique physicochemical attributes, including substantial surface area, rigidity, semi-conductivity, high enzyme loading, hyper catalytic activity, and size-assisted optical properties, nanomaterials have emerged as fascinating matrices for enzyme immobilization. Tyrosinase is a copper-containing monooxygenase that catalyzes the o-hydroxylation of monophenols to catechols and o-quinones. This enzyme possesses a wide range of uses in the medical, biotechnological, and food sectors. This article summarizes an array of nanostructured materials as carrier matrices for tyrosinase immobilization. Following a detailed background overview, various nanomaterials, as immobilization support matrices, including carbon nanotubes (CNTs), carbon dots (CDs), carbon black (CB), nanofibers, Graphene nanocomposite, platinum nanoparticles, nano-sized magnetic particles, lignin nanoparticles, layered double hydroxide (LDH) nanomaterials, gold nanoparticles (AuNPs), and zinc oxide nanoparticles have been discussed. Next, applied perspectives have been spotlights with particular reference to environmental pollutant sensing, phenolic compounds detection, pharmaceutical, and food industry (e.g., cereal processing, dairy processing, and meat processing), along with other miscellaneous applications.

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.

Isolation, partial purification and immobilization of locally sourced tyrosinase on different fiber materials

Tyrosinase has diverse functions in biological systems including melanin synthesis for defense against harmful effects of ultraviolet light. It oxidizes tyrosine especiallyL-3, 4-dihydroxyphenylalanineto L-Dopaquinone. The objective is to isolate, partially purify and immobilize tyrosinase on coconut fiber and palm wood chips using gum Arabic as binder. Yam (Dioscorea rotundata) was used as source of tyrosinase. It was extracted by mashing yam with potassium phosphate buffer (PH 7). The slurry was centrifuged, supernatant decanted and mixed with solid ammonium sulphate [(NH4)2SO4] for partial purification of the enzyme. Its kinetic parameters were determined spectrophotometrically by measuring its activity at varying concentrations of substrate (L-DOPA). Line weaver-bulk double reciprocal plot was plotted to derive Michealis-Menten constant (Km) and maximum velocity (Vmax) while the optimum temperature and PH was determined by varying temperature and PH ranges (5.5-8.5) of reaction system. The immobilized tyrosinase activitywas compared with that of partially purified enzyme. Results showed that, crude enzyme activity was 7.2 micromoles/min, immobilized enzymes activity on coconut fiber was7.7micromoles/min and that on palm wood chip was 11.1micromoles/min. Km and Vmax of partially purified tyrosinase was 33.3mM and 0.016S-1, that of immobilized enzyme on coconut fiber was 28.5mM and 0.020s-1 while that on palm wood chips was 20.8mM and 0.033s-1 respectively. Optimum PH and temperature for partially purified and immobilized enzymes was 6.5 and 550C. Immobilization of yam tyrosinase on palm wood chips increased the activity of partially purified enzyme by 15%. Conclusively, palm wood chip is considered a better support to coconut fiber for immobilization of yam tyrosinase.

Electrochemical Determination of Hydroquinone Using a Tyrosinase-Based Cup-Stacked Carbon Nanotube (CSCNT)/Carbon Fiber Felt Composite Electrode

This work shows that the cup-stacked carbon nanotube/carbon fiber felt composite electrode (CSCNT/felt) is a promising electronic conductive matrix to develop biosensors. The device was prepared by combining this matrix with the well-studied enzyme tyrosinase. Atomic force microscopy and scanning electron microscopy confirm that tyrosinase remained well dispersed in the whole electrode and completely covered the CSCNT network surface deposited on the surface of each graphitic felt electrode fiber. The studied combination allows preparing a disposable biosensor to determine hydroquinone in water with remarkable selectivity and accuracy when applied in real samples. The limit of detection was 1.4 µM with a wide linear range between 9 and 545 µM. The device presented good reproducibility for construction, with relative error of 2.4% (n = 7). These results confirm that a simple and sensitive device has been constructed to quantify hydroquinone in natural water and that the CSCNT structure is attractive for the immobilization of tyrosinase without functionalization of their walls or the use of surfactants.

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.

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.

Development of a Novel Electrochemical Biosensor Based on Carbon Nanofibers-Gold Nanoparticles-Tyrosinase for the Detection of Ferulic Acid in Cosmetics.

The present paper deals with the electrochemical behavior of three types of sensors based on modified screen-printed electrodes (SPEs): a sensor based on carbon nanofibers (CNF/SPE), a sensor based on nanofibers of carbon modified with gold nanoparticles (CNF-GNP/SPE) and a biosensor based on nanofibers of carbon modified with gold nanoparticles and tyrosinase (CNF-GNP-Ty/SPE). To prepare the biosensor, the tyrosinase (Ty) was immobilized on the surface of the electrode already modified with carbon nanofibers and gold nanoparticles, by the drop-and-dry technique. The electrochemical properties of the three electrodes were studied by cyclic voltammetry in electroactive solutions, and the position and shape of the active redox peaks are according to the nature of the materials modifying the electrodes. In the case of ferulic acid, a series of characteristic peaks were observed, the processes being more intense for the biosensor, with the higher sensitivity and selectivity being due to the immobilization of tyrosinase, a specific enzyme for phenolic compounds. The calibration curve was subsequently created using CNF-GNP-Ty/SPE in ferulic acid solutions of various concentrations in the range 0.1–129.6 μM. This new biosensor allowed low values of the detection threshold and quantification limit, 2.89 × 10−9 mol·L−1 and 9.64 × 10−9 mol·L−1, respectively, which shows that the electroanalytical method is feasible for quantifying ferulic acid in real samples. The ferulic acid was quantitatively determined in three cosmetic products by means of the CNF-GNP-Ty/SPE biosensor. The results obtained were validated by means of the spectrometric method in the infrared range, the differences between the values of the ferulic acid concentrations obtained by the two methods being under 5%.

The response surface methodology for optimization of tyrosinase immobilization onto electrospun polycaprolactone–chitosan fibers for use in bisphenol A removal

Composite polycaprolactone–chitosan material was produced by an electrospinning method and used as a support for immobilization of tyrosinase by mixed ionic interactions and hydrogen bonds formation. The morphology of the fibers and enzyme deposition were confirmed by SEM images. Further, multivariate polynomial regression was used to model the experimental data and to determine optimal conditions for immobilization process, which were found to be pH 7, temperature 25 °C and 16 h process duration. Under these conditions, novel type of biocatalytic system was produced with immobilization yield of 93% and expressed activity of 95%. Furthermore, as prepared system was applied in batch experiments related to biodegradation of bisphenol A under various remediation conditions. It was found that over 80% of the pollutant was removed after 120 min of the process, in the temperature range 15–45 °C and pH 6–9, using solutions at concentration up to 3 mg/L. Experimental data collected proved that the stability and reusability of the tyrosinase were significantly improved upon immobilization: the immobilized biomolecule retained around 90% of its initial activity after 30 days of storage, and was still capable to remove over 80% of bisphenol A even after 10 repeated uses. By contrast, free enzyme was able to remove over 80% of bisphenol A at pH 7–8 and temperature range 15–35 °C, and retained less than 60% of its initial activity after 30 days of storage.

Simple and Cost-Effective Electrochemical Method for Norepinephrine Determination Based on Carbon Dots and Tyrosinase.

Although neurotransmitters are present in human serum at the nM level, any dysfunction of the catecholamines concentration may lead to numerous serious health problems. Due to this fact, rapid and sensitive catecholamines detection is extremely important in modern medicine. However, there is no device that would measure the concentration of these compounds in body fluids. The main goal of the present study is to design a simple as possible, cost-effective new biosensor-based system for the detection of neurotransmitters, using nontoxic reagents. The miniature Au-E biosensor was designed and constructed through the immobilization of tyrosinase on an electroactive layer of cysteamine and carbon nanoparticles covering the gold electrode. This sensing arrangement utilized the catalytic oxidation of norepinephrine (NE) to NE quinone, measured with voltammetric techniques: cyclic voltammetry and differential pulse voltammetry. The prepared bio-system exhibited good parameters: a broad linear range (1–200 μM), limit of detection equal to 196 nM, limit of quantification equal to 312 nM, and high selectivity and sensitivity. It is noteworthy that described method was successfully applied for NE determination in real samples.