Valutazione del potenziale antiossidante e neuroprotettivo di cellule staminali neurali adulte prelevate dalla zona subventricolare di topi C57BL/6

Neural stem cells (aNSC) are presently employed by many researchers as a restorative therapy for neurodegenerative diseases, including PD. The subventricular zone (SVZ) contains NSCs capable of giving rise to new neurons in adult mammalian brains. MPTP-induced degeneration of dopaminergic SNpc-SVZ fibres impairs NSC proliferation in primates and in mice. This study shows the DA-induced increase in NSC viability in vitro. L-DOPA and DA, being catechol-containing compounds, may undergo autoxidation in vivo in the striatal extracellular compartment, with the consequent generation of quinone derivatives. The results from this study demonstrate the inhibitory effects on NSC viability in vitro induced by Mn alone or in association with L-DOPA and the antagonism exerted by ascorbic acid (AA) . Furthermore, we demonstrated the inhibitory effects of MPTP and MPP+ on NSC viability in vitro and the complete recovery of viability exerted by DA+L-DOPA+AA. DA, L- DOPA and AA are physiological components of the striatal extracellular compartment. Therefore, the striatal levels of DA and AA, coupled with administration of exogenous L-DOPA, might help NSCs in their restorative effort in the MPTP model of PD. The main finding of this study is that aNSC possess SVCT2 which allows the cell to accumulate AA. Moreover, aNSC are able to induce the DHAA reduction back to AA. The later data consistent with the ability of stem cells to protect DA and L-DOPA from autoxidation

Design and construction of a distributed sensor NET for biotelemetric monitoring of brain energetic metabolism using microsensors and biosensors

Neurochemical pathways involved in brain physiology or disease pathogenesis are mostly unknown either in physiological conditions or in neurodegenerative diseases. Nowadays the most frequent usage for biotelemetry is in medicine, in cardiac care units or step-down units in hospitals, even if virtually any physiological signal could be transmitted (FCC, 2000; Leuher, 1983; Zhou et al., 2002). In this chapter we present a wireless device connected with microsensors and biosensors capable to detect real-time variations in concentrations of important compounds present in central nervous system (CNS) and implicated in brain energetic metabolism (Bazzu et al., 2009; Calia et al., 2009)

Real-Time Monitoring of Brain Tissue Oxygen Using a Miniaturized Biotelemetric Device Implanted in Freely Moving Rats

A miniaturized biotelemetric device for the amperometric detection of brain tissue oxygen is presented. The new system, derived from a previous design, has been coupled with a carbon microsensor for the real-time detection of dissolved O(2) in the striatum of freely moving rats. The implantable device consists of a single-supply sensor driver, a current-to-voltage converter, a microcontroller, and a miniaturized data transmitter. The oxygen current is converted to a digital value by means of an analog-to-digital converter integrated in a peripheral interface controller (PIC). The digital data is sent to a personal computer using a six-byte packet protocol by means of a miniaturized 434 MHz amplitude modulation (AM) transmitter. The receiver unit is connected to a personal computer (PC) via a universal serial bus. Custom developed software allows the PC to store and plot received data. The electronics were calibrated and tested in vitro under different experimental conditions and exhibited high stability, low power consumption, and good linear response in the nanoampere current range. The in vivo results confirmed previously published observations on oxygen dynamics in the striatum of freely moving rats. The system serves as a rapid and reliable model for studying the effects of different drugs on brain oxygen and brain blood flow and it is suited to work with direct-reduction sensors or O(2)-consuming biosensors

Biotelemetric Monitoring of Brain Neurochemistry in Conscious Rats Using Microsensors and Biosensors

In this study we present the real-time monitoring of three key brain neurochemical species in conscious rats using implantable amperometric electrodes interfaced to a biotelemetric device. The new system, derived from a previous design, was coupled with carbon-based microsensors and a platinum-based biosensor for the detection of ascorbic acid (AA), O2 and glucose in the striatum of untethered, freely-moving rats. The miniaturized device consisted of a single-supply sensor driver, a current-to-voltage converter, a microcontroller and a miniaturized data transmitter. The redox currents were digitized to digital values by means of an analog-to-digital converter integrated in a peripheral interface controller (PIC), and sent to a personal computer by means of a miniaturized AM transmitter. The electronics were calibrated and tested in vitro under different experimental conditions and exhibited high stability, low power consumption and good linear response in the nanoampere current range. The in-vivo results confirmed previously published observations on striatal AA, oxygen and glucose dynamics recorded in tethered rats. This approach, based on simple and inexpensive components, could be used as a rapid and reliable model for studying the effects of different drugs on brain neurochemical systems

Electropolymerized phenol derivatives as permselective polymers for biosensor applications

Amperometric biosensors are often coated with a polymeric permselective film to avoid electroactive interference by reducing agents present in the target medium. Phenylenediamine and phenol monomers are commonly used to form these permselective films in the design of microsensors and biosensors. This paper aims to evaluate the permselectivity, stability and lifetime of polymers electrosynthesized using either constant potential amperometry (CPA) or cyclic voltammetry (CV) from naturally occurring phenylpropanoids in monomeric and dimeric forms (eugenol, isoeugenol, dehydrodieugenol and magnolol). Sensors were characterized by scanning electron microscopy and permselectivity analysis. Magnolol formed an electro-deposited polymer with a more defined three-dimensional texture in comparison with the other films. The phenol-derived films showed different permselectivity towards H2O2 over ascorbic acid and dopamine, likely to be related to the thickness and compactness of the polymer. The CV-derived films had a better permselectivity compared to the CPA-corresponding polymers. Based on these results, the permselectivity, stability and lifetime of a biosensor for glucose were studied when a magnolol coating was electro-deposited. The structural principles governing the permselectivity of the magnololderived film are suggested to be mainly related to the conformational flexibility of this monomer. Newly designed biosensors, coated with electropolymerized natural phenol derivatives, may represent promising analytical devices for different application fields.NPRP 4-259-2-083 from the Qatar National Research Fun

Low electro-synthesis potentials improve permselectivity of polymerized natural phenols in biosensor applications

First-generation amperometric biosensors are often based on the electro-oxidation of oxidase-generated H2O2. At the applied potential used in most studies, other molecules such as ascorbic acid or dopamine can be oxidized. Phenylenediamines are commonly used to avoid this problem: when these compounds are electro-deposited onto the transducer surface in the form of poly-phenylenediamine, a highly selective membrane is formed. Although there is no evidence of toxicity of the resulting polymer, phenylenediamine monomers are considered carcinogenic. An aim of this work was to evaluate the suitability of natural phenols as non-toxic alternatives to the ortho isomer of phenylenediamine. Electrosynthesis over Pt-Ir electrodes of 2-methoxy phenols (guaiacol, eugenol and isoeugenol), and hydroxylated biphenyls (dehydrodieugenol and magnolol) was achieved. The potentials used in the present study are significantly lower than values commonly applied during electro-polymerization. Polymers were obtained by means of constant potential amperometry, instead of cyclic voltammetry, in order to achieve multiple polymerizations, hence decreasing the time of realization and variability. Permselective properties of natural phenols were significantly improved at low polymerization potentials. Among the tested compounds, isoeugenol and magnolol, polymerized respectively at +25mV and +170mV against Ag/AgCl reference electrode, proved as permselective as poly-ortho-phenylenediamine and may be considered as effective polymeric alternatives. The natural phenol-coated electrodes were stable and responsive throughout 14 days. A biosensor prototype based on acetylcholine esterase and choline oxidase was electro-coated with poly-magnolol in order to evaluate the interference-rejecting properties of the electrosynthesized film in an amperometric biosensor; a moderate decrease in ascorbic acid rejection was observed during in vitro calibration of biosensors.This work was supported by the Qatar National Research Fund (a member of Qatar Foundation) [NPRP grant # 8-392-4-003]

Development of a distributed, fully automated, bidirectional telemetry system for amperometric microsensor and biosensor applications

A new bidirectional telemetry system for amperometric sensor applications has been developed. A fully automated peripheral unit (PU), constituted by a potentiostat, a two-channel I/V converter, a microcontroller unit (MCU) and a signal transmitter, was designed, constructed, and tested. A peripheral interface controller (PIC) MCU drives a digital-to-analog converter (DAC), which polarized the sensor, while the resulting anodic current is converted to a digital value by an analog-to-digital converter (ADC). The PIC firmware is developed in assembly and transferred to the MCU through a bootloader algorithm. The digital data are sent to a personal computer using a 4-byte packet protocol by means of a miniaturized 433 MHz frequency modulation (FM) transceiver with a linear range up to 200 m. The central unit (CU) is connected to a PC via Universal Serial Bus (USB). Custom developed software, implemented in Basic and C, allows the PC to control several PUs and record, plot and handle received data. The development and operation of the hardware and software are described. The system performance was evaluated using an automated dummy cell connected to the PU. The amperometric response of nitric oxide (NO), dopamine (DA) microsensors and a glucose biosensor was determined in vitro. This apparatus serves as a basic model to realize an in vivo bidirectional telemetry system built with standard components readily available at low cost

New ultralow-cost telemetric system for a rapid electrochemical detection of vitamin C in fresh orange juice

Ascorbic acid (AA), one of the principal micronutrients in horticultural crops, plays a key role in the human metabolism, and its determination in food products has a great significance. Citrus fruits are rich in AA, but its content is highly susceptible to change during postharvest processing and storage. We present a new ultralow-cost system, constituted of an amperometric microsensor composed of three rod carbon electrodes connected to a telemetric device, for online detection of AA in orange juice, as an alternative to conventional analytical methods. The in vitro calibration, ranged from 0 to 5 mM, and AA juice content was calculated by adding low volumes of sample into an acetate buffer solution at a constant potential of +120 mV vs carbon pseudoreference. This new approach, which is simple, expandable, and inexpensive, seems appropriate for large scale commercial use