A novel tyrosinase biosensor based on hydroxyapatite–chitosan nanocomposite for the detection of phenolic compounds

Calcium Orthophosphate (CaPO4) Containing Composites for Biomedical Applications: Formulations, Properties, and Applications

The goal of this review is to present a wide range of hybrid formulations and composites containing calcium orthophosphates (abbreviated as CaPO4) that are suitable for use in biomedical applications and currently on the market. The bioactive, biocompatible, and osteoconductive properties of various CaPO4-based formulations make them valuable in the rapidly developing field of biomedical research, both in vitro and in vivo. Due to the brittleness of CaPO4, it is essential to combine the desired osteologic properties of ceramic CaPO4 with those of other compounds to create novel, multifunctional bone graft biomaterials. Consequently, this analysis offers a thorough overview of the hybrid formulations and CaPO4-based composites that are currently known. To do this, a comprehensive search of the literature on the subject was carried out in all significant databases to extract pertinent papers. There have been many formulations found with different material compositions, production methods, structural and bioactive features, and in vitro and in vivo properties. When these formulations contain additional biofunctional ingredients, such as drugs, proteins, enzymes, or antibacterial agents, they offer improved biomedical applications. Moreover, a lot of these formulations allow cell loading and promote the development of smart formulations based on CaPO4. This evaluation also discusses basic problems and scientific difficulties that call for more investigation and advancements. It also indicates perspectives for the future.

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.

Electrochemical and Structural Characterization of Lanthanum-Doped Hydroxyapatite: A Promising Material for Sensing Applications

In the quest to find powerful modifiers of screen-printed electrodes for sensing applications, a set of rare earth-doped Ca_10-xRE_x(PO₄)₆(OH)₂ (RE = La, Nd, Sm, Eu, Dy, and Tm and x = 0.01, 0.02, 0.10, and 0.20) hydroxyapatite (HAp) samples were subjected to an in-depth electrochemical characterization using electrochemical impedance spectroscopy and cyclic and square wave voltammetry. Among all of these, the inorganic phosphates doped with lanthanum proved to be the most reliable, revealing robust analytical performances in terms of sensitivity, repeatability, reproducibility, and reusability, hence paving the way for their exploitation in sensing applications. Structural data on La-doped HAp samples were also provided by using different techniques, including optical microscopy, X-ray diffraction, Rietveld refinement from X-ray data, Fourier transform infrared, and Raman vibrational spectroscopies, to complement the electrochemical characterization.

Hierarchical and urchin-like chitosan/hydroxyapatite microspheres as drug-laden cell carriers

Biopolymer/hydroxyapatite (HAp) composites are one type of the most promising materials for a variety of biomedical applications. In this study, hierarchical and urchin-like chitosan/HAp nanowire (HU-CS/HAp NW) microspheres were for the first time synthesized by in situ hydrothermal treatment of chitosan/HAp (CS/HAp) microspheres in the acetic acid solution. The results indicate that HU-CS/HAp NW microspheres were spherical in morphology with a diameter of 100-300 μm. Their surface was mainly constructed by numerous HAp NWs with the diameter of 80-120 nm and showed a hierarchical and urchin-like nanofibrous architecture. It was found that the acidic hydrothermal treatment caused an in situ conversion of HAp NPs to HAp NWs. In vitro biocompatible evaluation indicates that HU-CS/HAp NW microspheres showed an enhanced cell attachment and proliferation due to the presence of hierarchical and urchin-like architecture. Furthermore, HU-CS/HAp NW microspheres showed a good adsorption capacity for tetracycline hydrochloride (model drug, one of the most representative antibiotics) with a higher adsorption capacity than CS/HAp microspheres and well maintained their antibacterial efficacy to inhibit the growth of bacteria: Escherichia coli and Staphylococcus aureus. Thus, the present HU-CS/HAp NW microspheres would be applicable as novel drug-laden cell carriers.

Facile Synthesis of Fe-Doped Hydroxyapatite Nanoparticles from Waste Coal Ash: Fabrication of a Portable Sensor for the Sensitive and Selective Colorimetric Detection of Hydrogen Sulfide

In this work, a new strategy has been reported for the portable detection of H₂S based on Fe-doped hydroxyapatite nanoparticles (Fe-HA) using a colorimetric paper test strip integrated with a smartphone platform. Fe-HA NPs were fabricated successfully via recycling waste coal ash. The obtained probe response toward H₂S was through a distinct visual color change. The sensing mechanism is based on the displacement reaction, in which PO₄ ^3- is replaced by S^2-. The prepared test strip shows high selectivity, and the other compounds containing thiol and sulfur anion have a negligible effect on the detection of H₂S. The designed scheme is applied for H₂S detection in the concentration range of 0.5-130 ppm with a limit of detection of 70 ppb. Furthermore, such a disposable sensor was used as a practical system for monitoring H₂S in actual water samples, suggesting the promising potential of this platform for suitable analysis of H₂S in an aqueous environment.

Marine Biological Macromolecules as Matrix Material for Biosensor fabrication

The Ocean covers two-third of our planet and has great biological heterogeneity. Marine organisms like algae, vertebrates, invertebrates, and microbes are known to provide many natural products with biological activities as well as potent sources of biomaterials for therapeutic, biomedical, biosensors, and climate stabilization. Over the years, the field of biosensors have gained huge attention due to their extraordinary ability to provide early disease diagnosis, rapid detection of various molecules and substances along with long term monitoring. This review aims to focus on the properties and employment of various biomaterials (Carbohydrate polymers, proteins, polyacids etc) of marine origin such as Alginate, Chitin, Chitosan, Fucoidan, Carrageenan, Chondroitin Sulfate (CS), Hyaluronic acid (HA), Collagen, marine pigments, marine nanoparticles, Hydroxyapatite (HAp), Biosilica, lectins, and marine whole cell in the design and development of biosensors. Further, this review also covers the source of such marine biomaterials and their promising evolution in the fabrication of biosensors that are potent to be employed in the biomedical, environmental science and agricultural sciences domains. The use of such fabricated biosensors harness the system with excellent specificity, selectivity, biocompatibility, thermally stable and minimal cost advantages. This article is protected by copyright. All rights reserved.

An easily fabricated nano-hydroxyapatite modified glassy carbon electrode for the degradation of methylene blue

According to the existing photocatalytic properties and adsorption properties of hydroxyapatite, the electrochemical properties of hydroxyapatite have been studied to provide ideas for the design of new mineral electrocatalysts.

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.

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.

Iron and zinc ions, potent weapons against multidrug-resistant bacteria

Drug-resistant bacteria are becoming an increasingly widespread problem in the clinical setting. The current pipeline of antibiotics cannot provide satisfactory options for clinicians, which brought increasing attention to the development and application of non-traditional antimicrobial substances as alternatives. Metal ions, such as iron and zinc ions, have been widely applied to inhibit pathogens through different mechanisms, including synergistic action with different metabolic enzymes, regulation of efflux pumps, and inhibition of biofilm formation. Compared with traditional metal oxide nanoparticles, iron oxide nanoparticles (IONPs) and zinc oxide nanoparticles (ZnO-NPs) display stronger bactericidal effect because of their smaller ion particle sizes and higher surface energies. The combined utilization of metal NPs (nanoparticles) and antibiotics paves a new way to enhance antimicrobial efficacy and reduce the incidence of drug resistance. In this review, we summarize the physiological roles and bactericidal mechanisms of iron and zinc ions, present the recent progress in the research on the joint use of metal NPs with different antibiotics, and highlight the promising prospects of metal NPs as antimicrobial agents for tackling multidrug-resistant bacteria.

Cantilever Nanobiosensor Functionalized with Tyrosinase for Detection of Estrone and β-estradiol in Water

This work aimed to develop cantilever nanobiosensor functionalized with tyrosinase enzyme to detect 17β-estradiol and estrone hormones. In this system, the tyrosinase enzyme was covalently immobilized by self-assembled monolayer onto the cantilever sensor surface. It was possible to verify that the high hormone concentration investigated resulted in high voltage response. The nanobiosensor presented a distinction between the concentrations evaluated and was verified sensitivities of 0.497 and 0.101 V/μg, limit of detection of 0.1 and 0.4 ng/L for the hormones 17β-estradiol and estrone, respectively. The device showed good reversibility and during 30 days of storage maintained about 99% of the original signal. The cantilever nanobiosensor applied in different water samples (ultrapure, river, tap, and mineral) showed good performance, so could be readily extended toward the on-site monitoring of the other trace small molecular pollutants in environmental water matrices.

Development of photo-magnetic drug delivery system by facile-designed dual stimuli-responsive modified biopolymeric chitosan capped nano-vesicle to improve efficiency in the anesthetic effect and its biological investigations

Though anesthetic drug delivery system and drug vehicles is generally applied for pain relief, there are have many difficulties and issues due to its short duration carrier and low biocompatibility, effectiveness at the conditions of inflammation at acidic pH. To resolve this issue, we have designed and developed the dual (pH and temperature) responsive bio-nanomaterial to improve the efficiency anesthetic drug delivery system. Chitosan is a unique class of biomaterials that is widely used in medical devices. The surface engineering of ZnFe₂O₄ nanoparticles was performed by coating with chitosan using simple precipitation method. Then, multi-active anesthetic drug (Lidocaine) was loaded into nano-ferrite to form a drug delivery vehicle. The prepared drug-vesicle was characterized by using XRD, FTIR, SEM, XPS and TGA analysis. XRD analysis proved the face center cubic structure of zinc nanoferrite. The sustained delivery of Lidocaine (LDC) from CS coated nanoferrite (CS/ZnFe₂O₄) was stimulated by pH and temperature responsive characteristics of vesicles. The in vitro cytotoxicity of the CS/ZnFe₂O₄ particles towards fibroblast cells was analyzed by using MTT assay. The drug loaded CS/ZnFe₂O₄ particles exhibit high biocompatibility and sustained drug release in the physiological pH environment (4.8, 5.5 and 7.4) and temperature responsive (25 and 37 °C) of normal tissues and also drug loading efficiency was measured.

Monitoring of Chemical Risk Factors for Sudden Infant Death Syndrome (SIDS) by Hydroxyapatite-Graphene-MWCNT Composite-Based Sensors

Sensing properties of chemical sensors based on ternary hydroxyapatite-graphene-multiwalled carbon nanotube (HA-GN-MWCNT) nanocomposite in the detection of chemical substances representing risk factors for sudden infant death syndrome (SIDS), have been evaluated. Characterization data of the synthesized composite have shown that the graphene-MWCNT network serves as a matrix to uniformly disperse the hydroxyapatite nanoparticles and provide suitable electrical properties required for developing novel electrochemical and conductometric sensors. A HA-GN-MWCNT composite-modified glassy carbon electrode (HA-GN-MWCNT/GCE) has been fabricated and tested for the simultaneous monitoring of nicotine and caffeine by cyclic voltammetry (CV) and square wave voltammetry (SWV), whereas a HA-GN-MWCNT conductive gas sensor has been tested for the detection of CO2 in ambient air. Reported results suggest that the synergic combination of the chemical properties of HA and electrical/electrochemical characteristics of the mixed graphene-MWCNT network play a prominent role in enhancing the electrochemical and gas sensing behavior of the ternary HA-GN-MWCNT hybrid nanostructure. The high performances of the developed sensors make them suitable for monitoring unhealthy actions (e. g. smoking, drinking coffee) in breastfeeding women and environmental factors (bad air quality), which are associated with an enhanced risk for SIDS.

The facile fabrication of wound compatible anti-microbial nanoparticles encapsulated Collagenous Chitosan matrices for effective inhibition of poly-microbial infections and wound repairing in burn injury care: Exhaustive in vivo evaluations

Treatment of burn injury is clinically challenging one, therefore several steps and noteworthy approaches have been taken to improve wound mechanisms. Citrus pectin plays a stabilizing agent to synthesis of ZnO nanoparticles (ZnO NPs). The present study is focused on ZnO loaded collagen/chitosan nanofibrous were synthesized by electrospinning method using ZnO NPs. The chemical structure, phase purity and morphological observation were investigated under spectroscopic and mircoscopic techniques and demonstrated their suitable properties as a wound healing material. In addition, that prepared nanoparticles loaded biopolymeric fibrous nanomaterial showed suitable antibacterial activity against S. aureus and E. coli bacterial pathogens and also in vitro studies was confirmed the enhanced proliferation, cell viability and biocompatibility. In vitro evaluations have been exhibited acceptable cell proliferation is observed throughout the ZnO loaded Coll/CS nanofibrous within 3 days, which was comparable to the control material. In vivo wound healing ability was monitored on the rat wound experimental model. From the in vivo observations, revealed that the loaded of ZnO NPs with Coll/CS nanofibrous can effectively quicken wound healing mechanism, expressed in the initial stage healing process. These results suggest that ZnO loaded collagen/chitosan nanofibrous is a potential candidate for wound healing applications with enhanced biological properties.

A high-throughput screening method for improved R-2-(4-hydroxyphenoxy)propionic acid biosynthesis

R-2-(4-hydroxyphenoxy)propionic acid (R-HPPA) is a key intermediate of the enantiomerically pure phenoxypropionic acid herbicides. R-HPPA could be biosynthesized through selective introduction of a hydroxyl group (-OH) into the substrate R-2-phenoxypropionic acid (R-PPA) at C-4 position, facilitated by microorganisms with hydroxylases. In this study, an efficient high-throughput screening method for improved R-HPPA biosynthesis through microbial hydroxylation was developed. As a hydroxylated aromatic product, R-HPPA could be oxidized by oxidant potassium dichromate to form brown-colored quinone-type compound. The concentration of R-HPPA can be quantified according to the absorbance of the colored compound at a suitable wavelength of 570 nm; and the R-HPPA biosynthetic capability of microorganism strains could also be rapidly evaluated. After optimization of the assay conditions, the high-throughput screening method was successfully used in identification of Beauveria bassiana mutants with enhanced R-HPPA biosynthesis capacity. A positive mutant C-7 with high tolerance to 20 g/L R-PPA was rapidly selected from 1920 mutants. The biomass and R-HPPA titer were 12.5- and 38.19-fold higher compared with the original strain at 20 g/L R-PPA. This high-throughput screening method developed in this work could also be a potential tool for screening strains producing other important phenolic compounds.

Tyrosinase based amperometric biosensor for determination of tyramine in fermented food and beverages with gold nanoparticle doped poly(8-anilino-1-naphthalene sulphonic acid) modified electrode

The aim of the present work was to develop an amperometric biosensor for tyramine (Tyr) measurement in food and beverages. The biosensor architecture is based on tyrosinase (Tyr_ase) immobilization on glassy carbon electrode modified by a nanocomposite consisting of gold nanoparticles (AuNP) synthesized by a green method and poly(8-anilino-1-naphthalene sulphonic acid) modified glassy carbon electrode. Under optimized experimental conditions for fixed potential amperometric detection, the biosensor exhibited a linear response to tyramine in the range 10-120 µM and the limit of detection was estimated to be 0.71 µM. The novel platform showed good selectivity, long-term stability, and reproducibility. The strong interaction between tyrosinase and the nanocomposite was revealed by the high value of the Michaelis-Menten constant (79.3 μM). The fabricated biosensor was successfully applied to the determination of Tyr in dairy products and fermented drinks with good recoveries, which makes it a promising biosensor for quantification of tyramine.

Fast and direct amperometric analysis of polyphenols in beers using tyrosinase-modified screen-printed gold nanoparticles biosensors

In this work it is explored a real applicability of miniaturised and portable biosensing technology for the estimation of total phenolic content in 15 different commercial beers by applying direct amperometry. Gold nanoparticles screen-printed electrodes were thoroughly modified with tyrosinase (Tyr-AuNPS-SPCEs), which was immobilised on the surface by crosslinking with glutaraldehyde. All chemical and instrumental variables involved in the electrochemical method were optimised to develop a reliable and powerful tool to estimate rapidly the content of phenolic compounds in complex beer samples. Catechol, phenol, caffeic acid and tyrosol were analysed individually using the proposed methodology and good analytical and kinetic performances were obtained. Total phenolic content in tested beers (high fermented, low fermented and non-alcoholic) were expressed as mg L^-1 of tyrosol, which is one of the major phenolic compound reported in beer. Moreover, the developed amperometric methodology was successfully benchmarked against standardised Folin-Ciocalteau spectrophotometric method with a good Pearson correlation (r = 0.821, p < 0.01). Hierarchical Cluster Analysis (HCA) was also applied on electrochemical results and a good capability to group tested beers based on their tyrosol concentration was demonstrated.

A dual-channel homogeneous aptasensor combining colorimetric with electrochemical strategy for thrombin

In this protocol, a dual-channel homogeneous aptasenor was proposed for protein molecule determination, employing thrombin as target analyte. The colorimetric and electrochemical transducers were combined in a single analytical system for signal readout. In this dual-channel sensing strategy, the G-quadruplex sequence was released and incorporated with hemin to form DNAzyme for naked-eye colorimetric detection. Meanwhile, the hydroxyapatite nanoparticle as signal probe was combined with magnetic nanoparticles to construct sandwich-type structure for generating the electrochemical current when thrombin was present in solution. By introducing two kinds of reporter probes and transducers, this dual-channel sensor produced two different kinds of signal to improve the analytical accuracy and diversity. The results revealed that the dual-channel sensor achieved the quantatitive determination of thrombin with low limit of detection (0.40 fM) and wide range (0.1 fM to 1 nM), which offer a promise for rapid and accurate detection of biomolecule.

Development of a Polyphenol Oxidase Biosensor from Jenipapo Fruit Extract (Genipa americana L.) and Determination of Phenolic Compounds in Textile Industrial Effluents

In this work, an innovative polyphenol oxidase biosensor was developed from Jenipapo (Genipa americana L.) fruit and used to assess phenolic compounds in industrial effluent samples obtained from a textile industry located in Jaraguá-GO, Brasil. The biosensor was prepared and optimized according to: the proportion of crude vegetal extract, pH and overall voltammetric parameters for differential pulse voltammetry. The calibration curve presented a linear interval from 10 to 310 µM (r² = 0.9982) and a limit of detection of 7 µM. Biosensor stability was evaluated throughout 15 days, and it exhibited 88.22% of the initial response. The amount of catechol standard recovered post analysis varied between 87.50% and 96.00%. Moreover, the biosensor was able to detect phenolic compounds in a real sample, and the results were in accordance with standard spectrophotometric assays. Therefore, the innovatively-designed biosensor hereby proposed is a promising tool for phenolic compound detection and quantification when environmental contaminants are concerned.

Hydroxyapatite nanoparticle based fluorometric determination and imaging of cysteine and homocysteine in living cells

Fluorescent hydroxyapatite nanoparticles (HAP-NPs) were prepared by reacting calcium ion with phosphate in the presence of Eu(III) ion. The HAP-NPs display large Stokes' shift and two strong fluorescence emissions with peaks at 590 nm and 615 nm when excited at 250 nm. The HAP-NPs also have good photostability and water solubility. The HAP-NPs combined with Cu(II) were applied to fluorometric determination of cysteine and homocysteine in biological samples and in living cells. In this detection scheme, the fluorescence of HAP-NPs is initially quenched by Cu(II). The addition of biothiols results in the formation of Cu(II)-thiol complexes and leads to fluorescence recovery. The assay allows cysteine to be detected with a 110 nM detection limit, and homocysteine with a 160 nM detection limit. The assay was successfully applied to the analysis of cysteine in spiked human serum samples and to imaging of cysteine in HeLa cells, and this demonstrates its potential for clinical testing and in biomedical research. Graphical abstract Fluorescent hydroxyapatite nanoparticles were synthesized and combined with Cu²⁺ for fluorescence sensing of biothiols (cysteine and homocysteine) in complex biological samples and in living cells.

Electrochemical Biosensors: A Solution to Pollution Detection with Reference to Environmental Contaminants

The increasing environmental pollution with particular reference to emerging contaminants, toxic heavy elements, and other hazardous agents is a serious concern worldwide. Considering this global issue, there is an urgent need to design and develop strategic measuring techniques with higher efficacy and precision to detect a broader spectrum of numerous contaminants. The development of precise instruments can further help in real-time and in-process monitoring of the generation and release of environmental pollutants from different industrial sectors. Moreover, real-time monitoring can also reduce the excessive consumption of several harsh chemicals and reagents with an added advantage of on-site determination of contaminant composition prior to discharge into the environment. With key scientific advances, electrochemical biosensors have gained considerable attention to solve this problem. Electrochemical biosensors can be an excellent fit as an analytical tool for monitoring programs to implement legislation. Herein, we reviewed the current trends in the use of electrochemical biosensors as novel tools to detect various contaminant types including toxic heavy elements. A particular emphasis was given to screen-printed electrodes, nanowire sensors, and paper-based biosensors and their role in the pollution detection processes. Towards the end, the work is wrapped up with concluding remarks and future perspectives. In summary, electrochemical biosensors and related areas such as bioelectronics, and (bio)-nanotechnology seem to be growing areas that will have a marked influence on the development of new bio-sensing strategies in future studies.

The Investigation of Electrochemistry Behaviors of Tyrosinase Based on Directly-Electrodeposited Grapheneon Choline-Gold Nanoparticles

A novel catechol (CA) biosensor was developed by embedding tyrosinase (Tyr) onto in situ electrochemical reduction graphene (EGR) on choline-functionalized gold nanoparticle (AuNPs-Ch) film. The results of UV-Vis spectra indicated that Tyr retained its original structure in the film, and an electrochemical investigation of the biosensor showed a pair of well-defined, quasi-reversible redox peaks with E_pa = -0.0744 V and E_pc = -0.114 V (vs. SCE) in 0.1 M, pH 7.0 sodium phosphate-buffered saline at a scan rate of 100 mV/s. The transfer rate constant k_s is 0.66 s^-1. The Tyr-EGR/AuNPs-Ch showed a good electrochemical catalytic response for the reduction of CA, with the linear range from 0.2 to 270 μM and a detection limit of 0.1 μM (S/N = 3). The apparent Michaelis-Menten constant was estimated to be 109 μM.

Tyrosinase-Based Biosensors for Selective Dopamine Detection

A novel tyrosinase-based biosensor was developed for the detection of dopamine (DA). For increased selectivity, gold electrodes were previously modified with cobalt (II)-porphyrin (CoP) film with electrocatalytic activity, to act both as an electrochemical mediator and an enzyme support, upon which the enzyme tyrosinase (Tyr) was cross-linked. Differential pulse voltammetry was used for electrochemical detection and the reduction current of dopamine-quinone was measured as a function of dopamine concentration. Our experiments demonstrated that the presence of CoP improves the selectivity of the electrode towards dopamine in the presence of ascorbic acid (AA), with a linear trend of concentration dependence in the range of 2–30 µM. By optimizing the conditioning parameters, a separation of 130 mV between the peak potentials for ascorbic acid AA and DA was obtained, allowing the selective detection of DA. The biosensor had a sensitivity of 1.22 ± 0.02 µA·cm⁻²·µM⁻¹ and a detection limit of 0.43 µM. Biosensor performances were tested in the presence of dopamine medication, with satisfactory results in terms of recovery (96%), and relative standard deviation values below 5%. These results confirmed the applicability of the biosensors in real samples such as human urine and blood serum.

Biosensor Based on Tyrosinase Immobilized on Graphene-Decorated Gold Nanoparticle/Chitosan for Phenolic Detection in Aqueous

In this research work, electrochemical biosensor was fabricated based on immobilization of tyrosinase onto graphene-decorated gold nanoparticle/chitosan (Gr-Au-Chit/Tyr) nanocomposite-modified screen-printed carbon electrode (SPCE) for the detection of phenolic compounds. The nanocomposite film was constructed via solution casting method. The electrocatalytic activity of the proposed biosensor for phenol detection was studied using differential pulse voltammetry (DPV) and cyclic voltammetry (CV). Experimental parameters such as pH buffer, enzyme concentration, ratio of Gr-Au-Chit, accumulation time and potential were optimized. The biosensor shows linearity towards phenol in the concentration range from 0.05 to 15 μM with sensitivity of 0.624 μA/μM and the limit of detection (LOD) of 0.016 μM (S/N = 3). The proposed sensor also depicts good reproducibility, selectivity and stability for at least one month. The biosensor was compared with high-performance liquid chromatography (HPLC) method for the detection of phenol spiked in real water samples and the result is in good agreement and comparable.

How cutting-edge technologies impact the design of electrochemical (bio)sensors for environmental analysis. A review

Through the years, scientists have developed cutting-edge technologies to make (bio)sensors more convenient for environmental analytical purposes. Technological advancements in the fields of material science, rational design, microfluidics, and sensor printing, have radically shaped biosensor technology, which is even more evident in the continuous development of sensing systems for the monitoring of hazardous chemicals. These efforts will be crucial in solving some of the problems constraining biosensors to reach real environmental applications, such as continuous analyses in field by means of multi-analyte portable devices. This review (with 203 refs.) covers the progress between 2010 and 2015 in the field of technologies enabling biosensor applications in environmental analysis, including i) printing technology, ii) nanomaterial technology, iii) nanomotors, iv) biomimetic design, and (v) microfluidics. Next section describes futuristic cutting-edge technologies that are gaining momentum in recent years, which furnish highly innovative aspects to biosensing devices.

Amperometric Biosensor Based on Zirconium Oxide/Polyethylene Glycol/Tyrosinase Composite Film for the Detection of Phenolic Compounds

A phenolic biosensor based on a zirconium oxide/polyethylene glycol/tyrosinase composite film for the detection of phenolic compounds has been explored. The formation of the composite film was expected via electrostatic interaction between hexacetyltrimethylammonium bromide (CTAB), polyethylene glycol (PEG), and zirconium oxide nanoparticles casted on screen printed carbon electrode (SPCE). Herein, the electrode was treated by casting hexacetyltrimethylammonium bromide on SPCE to promote a positively charged surface. Later, zirconium oxide was mixed with polyethylene glycol and the mixture was dropped cast onto the positively charged SPCE/CTAB. Tyrosinase was further immobilized onto the modified SPCE. Characterization of the prepared nanocomposite film and the modified SPCE surface was investigated by scanning electron microscopy (SEM), Electrochemical Impedance Spectroscopy (EIS), and Cyclic voltamogram (CV). The developed biosensor exhibits rapid response for less than 10 s. Two linear calibration curves towards phenol in the concentrations ranges of 0.075–10 µM and 10–55 µM with the detection limit of 0.034 µM were obtained. The biosensor shows high sensitivity and good storage stability for at least 30 days.

Response Characteristics of Bisphenols on a Metal-Organic Framework-Based Tyrosinase Nanosensor

Bisphenols (BPs), which have more than ten kinds of structural analogues, are emerging as the most important endocrine disrupting chemicals that adversely affect human health and aquatic life. A tyrosinase nanosensor based on metal-organic frameworks (MOFs) and chitosan was developed to investigate the electrochemical response characteristics and mechanisms of nine kinds of BPs for the first time. The developed tyrosinase nanosensor showed a sensitive response to bisphenol A, bisphenol F, bisphenol E, bisphenol B, and bisphenol Z, and the responsive sensitivities were highly dependent on their respective log Kow values. However, the nanosensor showed no response to bisphenol S (BPS), bisphenol AP (BPAP), bisphenol AF (BPAF), or tetrabromobisphenol A, although BPS, BPAP, and BPAF have structures similar to those of the responsive BPs. The obtained results reveal that the electrochemical response of different BPs is affected not only by the molecular structure, especially the available ortho positions of phenolic hydroxyl groups, but also by the substituent group properties (electron acceptor or electron donor) on the bisphenol framework. The electronic cloud distribution of the phenolic hydroxyl groups, which is affected by the substituent group, determines whether the available ortho positions of phenolic hydroxyl groups can be oxidized by the tyrosinase biosensor. These response mechanisms are very significant as they can be used for predicting the response characteristics of many BPs and their various derivatives and metabolites on biosensors. The unexpected anti-interference ability of the biosensor to nine heavy metal ions was also discovered and discussed. The MOF-chitosan nanocomposite proves to be a promising sensing platform for the construction of diverse biosensors for selective detection of targets even in the presence of a high concentration of heavy metal ions.

An electrochemical biosensing platform based on 1-formylpyrene functionalized reduced graphene oxide for sensitive determination of phenol

A novel electrochemical biosensing platform is proposed. New tyrosinase-based biosensor can be used to detect phenols.

Calcium Orthophosphate-Containing Biocomposites and Hybrid Biomaterials for Biomedical Applications

The state-of-the-art on calcium orthophosphate (CaPO4)-containing biocomposites and hybrid biomaterials suitable for biomedical applications is presented. Since these types of biomaterials offer many significant and exciting possibilities for hard tissue regeneration, this subject belongs to a rapidly expanding area of biomedical research. Through the successful combinations of the desired properties of matrix materials with those of fillers (in such systems, CaPO4 might play either role), innovative bone graft biomaterials can be designed. Various types of CaPO4-based biocomposites and hybrid biomaterials those are either already in use or being investigated for biomedical applications are extensively discussed. Many different formulations in terms of the material constituents, fabrication technologies, structural and bioactive properties, as well as both in vitro and in vivo characteristics have been already proposed. Among the others, the nano-structurally controlled biocomposites, those containing nanodimensional compounds, biomimetically fabricated formulations with collagen, chitin and/or gelatin, as well as various functionally graded structures seem to be the most promising candidates for clinical applications. The specific advantages of using CaPO4-based biocomposites and hybrid biomaterials in the selected applications are highlighted. As the way from a laboratory to a hospital is a long one and the prospective biomedical candidates have to meet many different necessities, the critical issues and scientific challenges that require further research and development are also examined.

Tyrosinase-based biosensor for determination of bisphenol A in a flow-batch system

A tyrosinase-based amperometric biosensor is proposed for determination of bisphenol A (BPA) in a flow-batch monosegmented sequential injection system. The enzyme was entrapped in a sol-gel TiO2 matrix modified with multi-walled carbon nanotubes (MWCNTs), polycationic polymer poly(diallyldimethylammonium chloride), (PDDA) and Nafion. Morphology of TYR/TiO2/MWCNTs/PDDA/Nafion matrix composite was studied via scanning electron microscopy (SEM). Electrochemical behavior of the developed biosensor towards bisphenol A was examined and analytical characteristics were assessed with respect to linear range, biosensor sensitivity, limit of detection, long term stability, repeatability and reproducibility. Linear range of biosensor response was found between 0.28 and 45.05 µM with high sensitivity of 3263 µA mM(-1) cm(-2) and detection limit 0.066 µM. The approach was successfully employed for determination of BPA in natural samples.

Chemically glycosylation improves the stability of an amperometric horseradish peroxidase biosensor

We constructed a biosensor by electrodeposition of gold nano-particles (AuNPs) on glassy carbon (GC) and subsequent formation of a 4-mercaptobenzoic acid self-assembled monolayer (SAM). The enzyme horseradish peroxidase (HRP) was then covalently immobilized onto the SAM. Two forms of HRP were employed: non-modified and chemically glycosylated with lactose. Circular dichroism (CD) spectra showed that chemical glycosylation did neither change the tertiary structure of HRP nor the heme environment. The highest sensitivity of the biosensor to hydroquinone was obtained for the biosensor with HRP-lactose (414 nA μM(-1)) compared to 378 nA μM(-1) for the one employing non-modified HRP. The chemically glycosylated form of the enzyme catalyzed the reduction of hydroquinone more rapidly than the native form of the enzyme. The sensor employing lactose-modified HRP also had a lower limit of detection (74 μM) than the HRP biosensor (83 μM). However, most importantly, chemically glycosylation improved the long-term stability of the biosensor, which retained 60% of its activity over a four-month storage period compared to only 10% for HRP. These results highlight improvements by an innovative stabilization method when compared to previously reported enzyme-based biosensors.

Disposable screen printed electrochemical sensors: tools for environmental monitoring

Screen printing technology is a widely used technique for the fabrication of electrochemical sensors. This methodology is likely to underpin the progressive drive towards miniaturized, sensitive and portable devices, and has already established its route from "lab-to-market" for a plethora of sensors. The application of these sensors for analysis of environmental samples has been the major focus of research in this field. As a consequence, this work will focus on recent important advances in the design and fabrication of disposable screen printed sensors for the electrochemical detection of environmental contaminants. Special emphasis is given on sensor fabrication methodology, operating details and performance characteristics for environmental applications.

Mesoporous carbon nitride based biosensor for highly sensitive and selective analysis of phenol and catechol in compost bioremediation

Herein, we reported here a promising biosensor by taking advantage of the unique ordered mesoporous carbon nitride material (MCN) to convert the recognition information into a detectable signal with enzyme firstly, which could realize the sensitive, especially, selective detection of catechol and phenol in compost bioremediation samples. The mechanism including the MCN based on electrochemical, biosensor assembly, enzyme immobilization, and enzyme kinetics (elucidating the lower detection limit, different linear range and sensitivity) was discussed in detail. Under optimal conditions, GCE/MCN/Tyr biosensor was evaluated by chronoamperometry measurements and the reduction current of phenol and catechol was proportional to their concentration in the range of 5.00 × 10(-8)-9.50 × 10(-6)M and 5.00 × 10(-8)-1.25 × 10(-5)M with a correlation coefficient of 0.9991 and 0.9881, respectively. The detection limits of catechol and phenol were 10.24 nM and 15.00 nM (S/N=3), respectively. Besides, the data obtained from interference experiments indicated that the biosensor had good specificity. All the results showed that this material is suitable for load enzyme and applied to the biosensor due to the proposed biosensor exhibited improved analytical performances in terms of the detection limit and specificity, provided a powerful tool for rapid, sensitive, especially, selective monitoring of catechol and phenol simultaneously. Moreover, the obtained results may open the way to other MCN-enzyme applications in the environmental field.