Polymerized Hemin as An Electrocatalytic Platform for Peroxynitrite\u27s Oxidation and Detection

Peroxynitrite (ONOO−) constitutes a major cytotoxic agent, implicated in a host of pathophysiological conditions, thereby stimulating a tremendous interest in evaluating its role as an oxidant in vivo. Some of the detection methods for peroxynitrite include oxidation of fluorescent probes, EPR spectroscopy, chemiluminescence, immunohistochemistry, and probe nitration; however, these are more difficult to apply for real-time quantification due to their inherent complexity. The electrochemical detection of peroxynitrite is a simpler and more convenient technique, but the best of our knowledge there are only few papers to date studying its electrochemical signature, or reporting amperometric microsensors for peroxynitrite. Recently, we have reported the use of layered composite films of poly(3,4-ethylenedioxythiophene) (PEDOT) and hemin (iron protoporphyrin IX) as a platform for amperometric measurement of peroxynitrite. The main goal herein is to investigate the intrinsic catalytic role of hemin electropolymerized thin films on carbon electrodes in oxidative detection of peroxynitrite. The electrocatalytic oxidation of peroxynitrite is characterized by cyclic voltammetry. The catalytic current increased as a function of peroxynitrite\u27s concentration, with a peak potential shifting positively with peroxynitrite\u27s concentration. The catalytic efficiency decreased as the scan rate increased, and the peak potential of the catalytic oxidation was found to depend on pH. We show that optimized hemin-functionalized carbon electrodes can be used as simple platforms for peroxinitrite detection and quantification. We report dose–response amperometry as an electroanalytical determination of this analyte on hemin films and we contrast the intrinsic hemin catalytic role with its performance in the case of the PEDOT–hemin as a composite matrix. Finally, we include some work extending the use of simple hemin films for peroxynitrite determination on carbon microfiber electrodes in a flow system

Nanoscale Architectures for Smart Bio-Interfaces: Advances and Challenges

Volcanology & seismolog

Nitric Oxide Synthase Encapsulation in Liposomes: A Potential Delivery Platform to (Nitric Oxide)-Deficient Targets

Nitric oxide (NO) is a freely diffusible, gaseous free radical, associated with many physiological and pathological processes: such as neuronal signaling, immune response and inflammatory response. In mammalian organisms, NO is produced from L-arginine in an NADPH-dependent reaction catalyzed by a family of nitric oxide synthase (NOS) enzymes. Typically, large NO fluctuations in biological systems under/over a critical limit is associated with problems that range from transient dysfunctions to severe chronic disease states. In this regard, we explore the development of a potential delivery and release method of nitric oxide to NO-deficient sites using liposomes as vehicles. Liposomes have already been used as effective nano-carriers. In this short communication, we report on the preparation and characterization of liposomes carrying a recombinant NOS enzyme. We report on the efficacy of using liposomes to carry NOS enzymes, and on the extent of preservation of native NOS structure and function. In addition to the characterization of liposome stability and recovery of enzymatic activity after encapsulation in liposomes, we also measured the NO production upon NOS stimulation. The NO release was monitored with a nitric oxide ultrasensitive electrochemical microsensor placed near NOS-carrying liposomes. This method of NOS-carrying liposomes shows the promise of potential development as a platform for targeted NO-delivery

Peroxynitrite Activity of Hemin-Functionalized Reduced Graphene Oxide

Conducting interfaces modified with reduced graphene oxide (rGO) have shown improved electrochemical response for different analytes. The efficient formation of functionalized rGO based materials is thus of current interest for the development of sensitive and selective biosensors. Herein, we report a simple and environmentally friendly method for the formation of a hemin-functionalized rGO hybrid nanomaterial that exhibits remarkable sensitivity to peroxynitrite (ONOO−) in solution. The hemin-functionalized rGO hybrid nanomaterial was formed by mixing an aqueous solution of graphene oxide (GO) with hemin and sonicating the suspension for 5 h at room temperature. In addition to playing a key role in biochemical and electrocatalytic reactions, hemin has been proven to be a good reducing agent for GO. The sensitivity of the peroxynitrite sensor is ≈7.5 ± 1.5 nA mM−1 with a detection limit of 5 ± 1.5 nM

Polymerized Hemin as An Electrocatalytic Platform for Peroxynitrite\u27s Oxidation and Detection

Peroxynitrite (ONOO−) constitutes a major cytotoxic agent, implicated in a host of pathophysiological conditions, thereby stimulating a tremendous interest in evaluating its role as an oxidant in vivo. Some of the detection methods for peroxynitrite include oxidation of fluorescent probes, EPR spectroscopy, chemiluminescence, immunohistochemistry, and probe nitration; however, these are more difficult to apply for real-time quantification due to their inherent complexity. The electrochemical detection of peroxynitrite is a simpler and more convenient technique, but the best of our knowledge there are only few papers to date studying its electrochemical signature, or reporting amperometric microsensors for peroxynitrite. Recently, we have reported the use of layered composite films of poly(3,4-ethylenedioxythiophene) (PEDOT) and hemin (iron protoporphyrin IX) as a platform for amperometric measurement of peroxynitrite. The main goal herein is to investigate the intrinsic catalytic role of hemin electropolymerized thin films on carbon electrodes in oxidative detection of peroxynitrite. The electrocatalytic oxidation of peroxynitrite is characterized by cyclic voltammetry. The catalytic current increased as a function of peroxynitrite\u27s concentration, with a peak potential shifting positively with peroxynitrite\u27s concentration. The catalytic efficiency decreased as the scan rate increased, and the peak potential of the catalytic oxidation was found to depend on pH. We show that optimized hemin-functionalized carbon electrodes can be used as simple platforms for peroxinitrite detection and quantification. We report dose–response amperometry as an electroanalytical determination of this analyte on hemin films and we contrast the intrinsic hemin catalytic role with its performance in the case of the PEDOT–hemin as a composite matrix. Finally, we include some work extending the use of simple hemin films for peroxynitrite determination on carbon microfiber electrodes in a flow system

Chapter Nanoscale Architectures for Smart Bio-Interfaces: Advances and Challenges

Volcanology & seismolog

Responsive Polymers for Crop Protection

This review outlines the responsive polymer methods currently in use with their potential application to plant protection and puts forward plant-specific mechanisms as stimuli in newly devised methods for smart release of crop protection agents (CPAs). CPAs include chemicals (fungicides, insecticides, herbicides), biochemicals (antibiotics, RNA-based vaccines for plant viruses), semiochemicals (pheromones, repellents, allomones), microbial pesticides, growth regulators (insect and plant) or micronutrients, all with crop protection effects. This appraisal focuses on emerging uses of polymer nano-encapsulated CPAs. Firstly, the most interesting advances in controlled release methods are critically discussed with their advantages and drawbacks. Secondly, several plant-specific stimuli-based smart methods are anticipated for use alongside the polymer nano- or micro-capsules. These new CPA release methods are designed to (i) protect plants against infection produced by fungi or bacteria, and (ii) apply micro-nutrients when the plants need it the most. Thus, we foresee (i) the responsive release of nano- encapsulated bio-insecticides regulated by plant stress enzymes, and (ii) the delivery of micro-nutrients synchronized by the nature or intensity of plant root exudates. Such continued advances of nano-scale smart polymer-based CPAs for the protection of crops herald a “small revolution” for the benefit of sustainable agriculture

Nitric Oxide Synthase Encapsulation in Liposomes: A Potential Delivery Platform to (Nitric Oxide)-Deficient Targets

Nitric oxide (NO) is a freely diffusible, gaseous free radical, associated with many physiological and pathological processes: such as neuronal signaling, immune response and inflammatory response. In mammalian organisms, NO is produced from L-arginine in an NADPH-dependent reaction catalyzed by a family of nitric oxide synthase (NOS) enzymes. Typically, large NO fluctuations in biological systems under/over a critical limit is associated with problems that range from transient dysfunctions to severe chronic disease states. In this regard, we explore the development of a potential delivery and release method of nitric oxide to NO-deficient sites using liposomes as vehicles. Liposomes have already been used as effective nano-carriers. In this short communication, we report on the preparation and characterization of liposomes carrying a recombinant NOS enzyme. We report on the efficacy of using liposomes to carry NOS enzymes, and on the extent of preservation of native NOS structure and function. In addition to the characterization of liposome stability and recovery of enzymatic activity after encapsulation in liposomes, we also measured the NO production upon NOS stimulation. The NO release was monitored with a nitric oxide ultrasensitive electrochemical microsensor placed near NOS-carrying liposomes. This method of NOS-carrying liposomes shows the promise of potential development as a platform for targeted NO-delivery

Peroxynitrite and Nitroxidative Stress: Detection Probes and Micro-Sensors. A Case of A Nanostructured Catalytic Film

Peroxynitrite, the primary product of the reaction of superoxide ion and nitric oxide, emerged as an important species with profound biological roles. Relatively speaking, it is a new member of the nitroxidative array of reactive metabolites, and details of its actions, impact on biological systems in health and disease states are still accumulating. It has already been linked to a host of pathological conditions. At the same time, its cytoprotective roles including redox regulation of critical signaling pathways are also reported. Assessment of peroxynitrite’s deleterious versus potential protective/signaling roles strongly depends on the possibility to accurately measure and monitor its concentration. This will help build a clearer understanding of its physiological roles. However, peroxynitrite’s extremely short half-life under physiological conditions and its very complex reactivity with many cellular targets create a major analytical chemistry challenge, particularly at the single cell level. The dynamic concentration of peroxynitrite versus other reactive species generated in situ under various conditions modulates its role in many vital cell functions. In this chapter, we give a brief overview of peroxynitrite biochemistry, physiology, and related therapeutic efforts to control its impact under pathological conditions. We then discuss the challenges and accomplishments in terms of major analytical methods developed for peroxynitrite’s sensing up-to-date, as well as opportunities for the future