A bimetallic nanocoral Au decorated with Pt nanoflowers (bio)sensor for H2O2 detection at low potential.

In this work, we have developed for the first time a method to make novel gold and platinum hybrid bimetallic nanostructures differing in shape and size. Au-Pt nanostructures were prepared by electrodeposition in two simple steps. The first step consists of the electrodeposition of nanocoral Au onto a gold substrate using hydrogen as a dynamic template in an ammonium chloride solution. After that, the Pt nanostructures were deposited onto the nanocoral Au organized in pores. Using Pt (II) and Pt (IV), we realized nanocoral Au decorated with Pt nanospheres and nanocoral Au decorated with Pt nanoflowers, respectively. The bimetallic nanostructures showed better capability to electrochemically oxidize hydrogen peroxide compared with nanocoral Au. Moreover, Au-Pt nanostructures were able to lower the potential of detection and a higher performance was obtained at a low applied potential. Then, glucose oxidase was immobilized onto the bimetallic Au-Pt nanostructure using cross-linking with glutaraldehyde. The biosensor was characterized by chronoamperometry at +0.15V vs. Ag pseudo-reference electrode (PRE) and showed good analytical performances with a linear range from 0.01 to 2.00mM and a sensitivity of 33.66µA/mMcm2. The good value of Kmapp (2.28mM) demonstrates that the hybrid nanostructure is a favorable environment for the enzyme. Moreover, the low working potential can minimize the interference from ascorbic acid and uric acid as well as reducing power consumption to effect sensing. The simple procedure to realize this nanostructure and to immobilize enzymes, as well as the analytical performances of the resulting devices, encourage the use of this technology for the development of biosensors for clinical analysis.

Comparison between a Direct-Flow SPR Immunosensor for Ampicillin and a Competitive Conventional Amperometric Device: Analytical Features and Possible Applications to Real Samples.

In this research, we developed a direct-flow surface plasmon resonance (SPR) immunosensor for ampicillin to perform direct, simple, and fast measurements of this important antibiotic. In order to better evaluate the performance, it was compared with a conventional amperometric immunosensor, working with a competitive format with the aim of finding out experimental real advantages and disadvantages of two respective methods. Results showed that certain analytical features of the new SPR immunodevice, such as the lower limit of detection (LOD) value and the width of the linear range, are poorer than those of a conventional amperometric immunosensor, which adversely affects the application to samples such as natural waters. On the other hand, the SPR immunosensor was more selective to ampicillin, and measurements were more easily and quickly attained compared to those performed with the conventional competitive immunosensor.

Inhibition-based first-generation electrochemical biosensors: theoretical aspects and application to 2,4-dichlorophenoxy acetic acid detection.

In this work, several theoretical aspects involved in the first-generation inhibition-based electrochemical biosensor measurements have been discussed. In particular, we have developed a theoretical-methodological approach for the characterization of the kinetic interaction between alkaline phosphatase (AlP) and 2,4-dichlorophenoxy acetic acid (2,4-D) as representative inhibitor studied by means of cyclic voltammetry and amperometry. Based on these findings, a biosensor for the fast, simple, and inexpensive determination of 2,4-D has been developed. The enzyme has been immobilized on screen-printed electrodes (SPEs). To optimize the biosensor performances, several carbon-based SPEs, namely graphite (G), graphene (GP), and multiwalled carbon nanotubes (MWCNTs), have been evaluated. AlP was immobilized on the electrode surface by means of polyvinyl alcohol with styryl-pyridinium groups (PVA-SbQ) as cross-linking agent. In the presence of ascorbate 2-phosphate (A2P) as substrate, the herbicide has been determined, thanks to its inhibition activity towards the enzyme catalyzing the oxidation of A2P to ascorbic acid (AA). Under optimum experimental conditions, the best performance in terms of catalytic efficiency has been demonstrated by MWCNTs SPE-based biosensor. The inhibition biosensor shows a linearity range towards 2,4-D within 2.1-110 ppb, a LOD of 1 ppb, and acceptable repeatability and stability. This analysis method was applied to fortified lake water samples with recoveries above 90%. The low cost of this device and its good analytical performances suggest its application for the screening and monitoring of 2,4-D in real matrices.

Amine oxidase-based biosensors for spermine and spermidine determination.

The present work describes the development and optimization of electrochemical biosensors for specific determination of the biogenic polyamine spermine (Spm) and spermidine (Spmd) whose assessment represents a novel important analytical tool in food analysis and human diagnostics. These biosensors have been prepared using novel engineered enzymes: polyamine oxidase (PAO) endowed with selectivity towards Spm and Spmd and spermine oxidase (SMO) characterized by strict specificity towards Spm. The current design entails biosensors in which the enzymes were entrapped in poly(vinyl alcohol) bearing styrylpyridinium groups (PVA-SbQ), a photocrosslinkable gel, onto an electrode surface. Screen-printed electrodes (SPEs) were used as electrochemical transducers for enzymatically produced hydrogen peroxide, operating at different potential vs Ag/AgCl according to the material of the working electrode (WE): +700 mV for graphite (GP) or -100 mV for Prussian blue (PB)-modified SPE, respectively. Biosensor performances were evaluated by means of flow injection amperometric (FIA) measurements. The modified electrodes showed good sensitivity, long-term stability and reproducibility. Under optimal conditions, the PAO biosensor showed a linear range 0.003-0.3 mM for Spm and 0.01-0.4 mM for Spmd, while with the SMO biosensor, a linear range of 0.004-0.5 mM for Spm has been obtained. The main kinetic parameters apparent Michaelis constant (K M), turnover number (K cat) and steady-state current (I max) were determined. The proposed device was then applied to the determination of biogenic amines in blood samples. The results obtained were in good agreement with those obtained with the GC-MS reference method.

Development of Carbon-Based Nano-Composite Materials for Direct Electron Transfer Based Biosensors.

Nafion, an ion exchange polymer that is very resistant to chemical attack, even by strong oxidant at high temperatures, has found great increasing use as a film material; however, its use as immobilizing agent in third-generation biosensors is hindered due to the low rate of charge transfer in the pure Nafion film. In this work we showed that the use of functionalized multi-walled carbon nanotubes Nafion/MWCNTs composite film for modification of the carbon-based electrode surfaces would increase the charge transfer rate greatly; the composite has proven to efficiently immobilize two different heme proteins (catalase and cytochrome c) and to enhance the electrochemical performances of several carbon electrode materials (glassy carbon, mesoporous graphite, graphite and graphene) either used as classical electrodes or screen printed ones. The electrochemical signal of both redox proteins becomes more reversible and the electron transfer kinetic constant increases. At the same time the biological activity is maintained indicating that the immobilization procedure allows the proteins to retain a native-like structure.

A new surface plasmon resonance immunosensor for triazine pesticide determination in bovine milk: a comparison with conventional amperometric and screen-printed immunodevices.

A detailed comparison was made of the analytical features of a new Surface Plasmon Resonance (SPR) immunodevice for triazine pesticide determination with those of two other amperometric (conventional and screen-printed) immunosensors and the advantages and disadvantages of the SPR method were thoroughly investigated. For conventional amperometric and screen-printed devices, "competitive" assays were used; conversely, the SPR transduction technique allowed a "direct" measurement format to be used. As far as the main analytical data are concerned, the SPR method does not seem to offer substantial advantages. Nevertheless the measurement time is much shorter and the measurement itself much easier to perform. Lastly several applications and recovery tests were carried out on bovine milk samples, before and after spiking, to check for triazine pesticides in the samples, obtaining satisfactory results.

Colonic Epithelial Circadian Disruption Worsens Dextran Sulfate Sodium-Induced Colitis.

BACKGROUND: Disruption of central circadian rhythms likely mediated by changes in microbiota and a decrease in gut-derived metabolites like short chain fatty acids (SCFAs) negatively impacts colonic barrier homeostasis. We aimed to explore the effects of isolated peripheral colonic circadian disruption on the colonic barrier in a mouse model of colitis and explore the mechanisms, including intestinal microbiota community structure and function. METHODS: Colon epithelial cell circadian rhythms were conditionally genetically disrupted in mice: TS4Cre-BMAL1lox (cBMAL1KO) with TS4Cre as control animals. Colitis was induced through 5 days of 2% dextran sulfate sodium (DSS). Disease activity index and intestinal barrier were assessed, as were fecal microbiota and metabolites. RESULTS: Colitis symptoms were worse in mice with peripheral circadian disruption (cBMAL1KO). Specifically, the disease activity index and intestinal permeability were significantly higher in circadian-disrupted mice compared with control animals (TS4Cre) (P < .05). The worsening of colitis appears to be mediated, in part, through JAK (Janus kinase)-mediated STAT3 (signal transducer and activator of transcription 3), which was significantly elevated in circadian-disrupted (cBMAL1KO) mice treated with DSS (P < .05). Circadian-disrupted (cBMAL1KO) mice also had decreased SCFA metabolite concentrations and decreased relative abundances of SCFA-producing bacteria in their stool when compared with control animals (TS4Cre). CONCLUSIONS: Disruption of intestinal circadian rhythms in colonic epithelial cells promoted more severe colitis, increased inflammatory mediators (STAT3 [signal transducer and activator of transcription 3]), and decreased gut microbiota-derived SCFAs compared with DSS alone. Further investigation elucidating the molecular mechanisms behind these findings could provide novel circadian directed targets and strategies in the treatment of inflammatory bowel disease.

Disruption of peripheral circadian rhythms of the colon epithelium results in worse colitis and increased intestinal permeability in mice when given dextran sulfate sodium. This may be mediated through alterations in microbiota, butyrate levels, and STAT3.

Attenuated Postprandial GLP-1 Response in Parkinson's Disease.

The incretin hormone glucagon-like peptide 1 (GLP-1) has neuroprotective effects in animal models of Parkinson's disease (PD), and GLP-1 receptor agonists are associated with clinical improvements in human PD patients. GLP-1 is produced and secreted by intestinal L-cells in response to consumption of a meal. Specifically, intestinal microbiota produce short chain fatty acids (SCFA) which, in turn, promote secretion of GLP-1 into the systemic circulation, from which it can enter the brain. Our group and others have reported that PD patients have an altered intestinal microbial community that produces less SCFA compared to age-matched controls. In this report, we demonstrate that PD patients have diminished GLP-1 secretion in response to a meal compared to their household controls. Peak postprandial GLP-1 levels did not correlate with PD disease severity, motor function, or disease duration. These data provide the scientific rationale for future studies designed to elucidate the role of GLP-1 in the pathogenesis of PD and test the potential utility of GLP-1-directed therapies.

A multi-methodological approach in the study of Italian PDO "Cornetto di Pontecorvo" red sweet pepper.

A multi-methodological approach was applied to study red sweet peppers (Capsicum annuum L.) ecotype "Cornetto di Pontecorvo" grown in a greenhouse or in open field. This approach includes morphological analysis, chemical composition determination, and biological activity evaluation of different extracts from pepper fruits. Untargeted analyses, namely NMR spectroscopy and mass spectrometry, allowed the comprehensive pepper metabolite profile of pepper pulp, peel and seeds hydroalcoholic and organic extracts to be determined, showing the presence of sugars, organic acids, amino acids and other secondary metabolites. Targeted analyses, such as HPLC-PDA, HPLC-TLC and spectrophotometric analyses allowed polyphenols, tannins, flavonoids and pigments content to be determined. Samples quality and freshness were verified by the low content of biogenic amines and mycotoxins, as determined using HPLC-FLD and HPLC-MS, respectively. Preliminary biological results demonstrated the ability of the organic extracts to inhibit α-amylase, a key enzyme in the control of glucose metabolism.

Application of a Nanostructured Enzymatic Biosensor Based on Fullerene and Gold Nanoparticles to Polyphenol Detection.

Electrochemical biosensors provide an attractive means of analyzing the content of a biological sample due to the direct conversion of a biological event to an electronic signal. The signal transduction and the general performance of electrochemical biosensors are often determined by the surface architectures that connect the sensing element to the biological sample at the nanometer scale. The most common surface modification techniques, the various electrochemical transduction mechanisms, and the choice of the recognition receptor molecules all influence the ultimate sensitivity of the sensor. We show herein a novel electrochemical biosensing platform based on the coupling of two different nanostructured materials (gold nanoparticles and fullerenols) displaying interesting electrochemical features. The use of these nanomaterials improved the electrochemical performance of the proposed biosensor.An application of the nanostructured enzyme-based biosensor has been developed for evaluating the detection of polyphenols either in buffer solution or in real wine samples.

Beyond graphene: Electrochemical sensors and biosensors for biomarkers detection.

Graphene's success has stimulated great interest and research in the synthesis and characterization of graphene-like 2D materials, single and few-atom-thick layers of van der Waals materials, which show fascinating and technologically useful properties. This review presents an overview of recent electrochemical sensors and biosensors based on graphene and on graphene-like 2D materials for biomarkers detection. Initially, we will outline different electrochemical sensors and biosensors based on chemically derived graphene, including graphene oxide and reduced graphene oxide, properly functionalized for improved performances and we will discuss the various strategies to prepare graphene modified electrodes. Successively, we present electrochemical sensors and biosensors based on graphene-like 2D materials, such as boron nitride (BN), graphite-carbon nitride (g-C3N4), transition metal dichalcogenides (TMDs), transition metal oxides and graphane, outlining how the new modified 2D nanomaterials will improve the electrochemical performances. Finally, we will compare the results obtained with different sensors and biosensors for the detection of important biomarkers such as glucose, hydrogen peroxide and cancer biomarkers and highlight the advantages and disadvantages of the use of graphene and graphene-like 2D materials in different sensing platforms.

A Flow SPR Immunosensor Based on a Sandwich Direct Method.

In this study, we report the development of an SPR (Surface Plasmon Resonance) immunosensor for the detection of ampicillin, operating under flow conditions. SPR sensors based on both direct (with the immobilization of the antibody) and competitive (with the immobilization of the antigen) methods did not allow the detection of ampicillin. Therefore, a sandwich-based sensor was developed which showed a good linear response towards ampicillin between 10(-3) and 10(-1) M, a measurement time of ≤20 min and a high selectivity both towards ß-lactam antibiotics and antibiotics of different classes.

Bubble electrodeposition of gold porous nanocorals for the enzymatic and non-enzymatic detection of glucose.

Au nanocorals are grown on gold screen-printed electrodes (SPEs) by using a novel and simple one-step electrodeposition process. Scanning electron microscopy was used for the morphological characterization. The devices were assembled on a three-electrode SPE system, which is flexible and mass producible. The electroactive surface area, determined by cyclic voltammetry in sulphuric acid, was found to be 0.07±0.01cm(2) and 35.3±2.7cm(2) for bare Au and nanocoral Au, respectively. The nanocoral modified SPEs were used to develop an enzymatic glucose biosensor based on H2O2 detection. Au nanocoral electrodes showed a higher sensitivity of 48.3±0.9µA/(mMcm(2)) at +0.45V vs Ag|AgCl compared to a value of 24.6±1.3µA/(mMcm(2)) at +0.70V vs Ag|AgCl obtained with bare Au electrodes. However, the modified electrodes have indeed proven to be extremely powerful for the direct detection of glucose with a non-enzymatic approach. The results confirmed a clear peak observed by using nanocoral Au electrode even in the presence of chloride ions at physiological concentration. Amperometric study carried out at +0.15V vs Ag|AgCl in the presence of 0.12M NaCl showed a linear range for glucose between 0.1 and 13mM.

Fast synthesis of platinum nanopetals and nanospheres for highly-sensitive non-enzymatic detection of glucose and selective sensing of ions.

Novel methods to obtain Pt nanostructured electrodes have raised particular interest due to their high performance in electrochemistry. Several nanostructuration methods proposed in the literature use costly and bulky equipment or are time-consuming due to the numerous steps they involve. Here, Pt nanostructures were produced for the first time by one-step template-free electrodeposition on Pt bare electrodes. The change in size and shape of the nanostructures is proven to be dependent on the deposition parameters and on the ratio between sulphuric acid and chloride-complexes (i.e., hexachloroplatinate or tetrachloroplatinate). To further improve the electrochemical properties of electrodes, depositions of Pt nanostructures on previously synthesised Pt nanostructures are also performed. The electroactive surface areas exhibit a two order of magnitude improvement when Pt nanostructures with the smallest size are used. All the biosensors based on Pt nanostructures and immobilised glucose oxidase display higher sensitivity as compared to bare Pt electrodes. Pt nanostructures retained an excellent electrocatalytic activity towards the direct oxidation of glucose. Finally, the nanodeposits were proven to be an excellent solid contact for ion measurements, significantly improving the time-stability of the potential. The use of these new nanostructured coatings in electrochemical sensors opens new perspectives for multipanel monitoring of human metabolism.