Project List

Continuous amperometry and fast scan cyclic voltammetry with diamond and carbon fiber microelectrodes are being used to study the sympathetic neural control mechanisms of arteries and veins and how these mechanisms are altered in salt-sensitive hypertension. Specifically, we are using these electroanalytical methods, video microscopy and neuropharmacological agents in in vitro mesenteric preparations (DOCA-salt model) to locally monitor the release of norepinephrine from periarterial and perivenous sympathetic nerves (which innervate the smooth muscle cells surrounding the vessel) and the elicited effect on vascular tone. It turns out that there is significant functional differentiation between arteries and veins. We are also employing LC-EC and CE-EC to measure norepinephrine and metabolite levels in different organs and plasma, as a function of the disease state, with the goal of better understanding how release, uptake and metabolism are altered.

In related work, we are studying the local compensatory role of co-innervating sensory nerves on vascular tone and sympathetic activity. Specifically, we are testing the hypothesis that TRPV channels of the sensory nerves are key proteins in sensing salt, osmotic and mechanical stimuli in the kidney and that dysfunction of these channels is critical to the initiation and maintenance of salt-sensitive hypertension. A key aspect of this work is monitoring sensory nerve function, in terms of the release of SubP and CGRP, and the relationship between sensory nerve function and sympathetic nerve output.

This research is being conducted collaboratively with researchers in the Pharmacology and Toxicology ,Neuroscience and Human Medicine at MSU.

SEM images of a nanocrystalline diamond thin film deposited on Si.

Thin-film diamond on quartz.

SEM images of boron-doped diamond powder (6-10 mm) particles.

SEM images of a boron-doped diamond microelectrode prepared by depositing a thin film on a sharpened Pt wire.

SEM image of a microcrystalline diamond film deposited on Si.

Michigan State University

Analytical Chemistry, Neuroscience and Materials Chemistry

Below is a brief description of the ongoing research projects. Depending on the project, our research involves aspects of electrochemistry, neurophysiology and neuropharmacology, and materials chemistry.

We are developing optically transparent diamond electrodes for use in chemical analysis. Of particular interest is the use of this new transparent electrode in UV/Vis and IR spectroelectrochemical measurements of redox proteins and enzymes. Thin diamond film on quartz (UV/Vis), Si (mid-IR) and in freestanding form (mid and far-IR) are being grown, characterized and used in electrochemical difference transmission measurements. Our goal is to better understand structure-function relationships of redox proteins and enzymes like cytochrome c and cytochrome c oxidase. A key feature of the method is the ability to obtain low frequency IR information on metal-ligand modes as a function of the oxidation state of the biomolecule.

seek to fabricate, characterize and apply optically transparent diamond thin-film electrodes for chemical analysis in UV/Vis and IR spectroelectrochemical measurements.

Boron-doped diamond is a new type of carbon electrode and much remains to be learned about why this material functions the way it does. In general, conducting diamond is characterized by a wide working potential window, low background current, relatively rapid electron transfer kinetics for several inorganic and organic redox systems without conventional pretreatment, and weak adsorption of polar molecules. All of these properties are attractive for electroanalysis. We are investigating how the homogeneity of the physical, chemical, electrical and electrochemical properties of microcrystalline and nanocrystalline diamond thin films are affected by the deposition conditions, boron-doping level, film microstructure and surface chemistry. Electrochemical methods of analysis, conductivity probe-atomic force microscopy and scanning electron microscopy are tools being employed to better understand structure-function relationships at diamond for a variety of redox systems.

We are collaborating with Professor James Galligan and Dr. Xiaochun Bian in the Department of Pharmacology at MSU and Dr. Bhavik Patel (Imperial College, UK) to identify the unique mechanisms by which neurotransmission occurs in the enteric nervous system to control gut function. We are using in vitro continuous amperometry to investigate serotonin (a principal neurotransmitter in the enteric nervous system) release and clearance by cells of the mucosa and neurons in the myenteric plexus of isolated preparations of guinea pig ileum and colon. These preparations are useful as most neural connections present in the intact intestine are preserved and the endogenous neural circuits that control gut function can be studied. We are also conducting similar studies with wild type and SERT-KO rats. Of particular interest, is the development of the neural control mechanisms with animal maturation. Similar strategies are also being employed to study the neurosignalling molecule, nitric oxide (NO), in order to understand its role in controlling gut function.

The degradation and corrosion of sp²carbon electrocatalyst support materials is currently a serious problem that limits the operational lifetime of polymer electrolyte membrane fuel cells (PEMFCs). While it is known that these carbons (e.g. Vulcan) undergo microstructural degradation and corrosion, the mechanisms by which this happens are unclear. In one aspect of the work, we are using high surface area carbon powders of different microstructure (graphite, glassy carbon, Vulcan) along with electrochemical methods, in situ Raman spectroscopy and in situ mass spectrometry to study the microstructural degradation and corrosion as a function of the applied potential, solution pH and temperature.

If the degradation mechanisms can be better understood, then approaches to effectively mitigate the problem may be possible. To this end, we are developing advanced sp³ carbon support materials (high surface area diamond and diamond-like carbon powders) and evaluating how effective these new materials are as an electrocatalyst support. For sure, microstructural degradation and corrosion are not an issue with the diamond powders. However, technical hurdles still need to be overcome including making the powders high surface area (100 m²/g) and electrically conducting (>10 S/cm).To date, we are working with conducting diamond powder in the 100-500 nm diameter range (50 m²/g).

Sympathetic Neural Control Mechanisms in Hypertension

Mechanisms of Neurotransmission in the Enteric Nervous System

Structure-Function Studies of Diamond Electrodes

Optically Transparent Diamond Electrodes

Advanced Carbon Electrocatalyst Supports for Fuel Cells

Research Projects

Mechanisms of Neurotransmission in the Enteric Nervous System