New approach to control ischemic severity ex vivo.

Background: It is advantageous to be able to both control and define a metric for ischemia severity in ex vivo models to enable more precise comparisons to in vivo models and to facilitate more sophisticated mechanistic studies. Currently, the primary method to induce and study ischemia ex vivo is to completely deplete oxygen and glucose in the culture media; however, in vivo ischemia often involves varying degrees of severities.

New Method: In this work, we have successfully developed an approach to both control and characterize three different ischemic severities ex vivo and we define these standard condition metrics via an oxygen sensor: normoxia (control), mild ischemia (partial oxygen-glucose deprivation), and severe ischemia (complete oxygen-glucose deprivation).

Plasma-treated gold microelectrodes for subsecond detection of Zn(II) with fast-scan cyclic voltammetry.

The sensitivity of zinc (Zn(II)) detection using fast-scan cyclic voltammetry (FSCV) with carbon fiber microelectrodes (CFMEs) is low compared to other neurochemicals. We have shown previously that Zn(II) plates to the surface of CFME's and we speculate that it is because of the abundance of oxide functionality on the surface. Plating reduces sensitivity over time and causes significant disruption to detection stability.

Surface-Roughened Graphene Oxide Microfibers Enhance Electrochemical Reversibility.

Here, we provide an optimized method for fabricating surface-roughened graphene oxide disk microelectrodes (GFMEs) with enhanced defect density to generate a more suitable electrode surface for dopamine detection with fast-scan cyclic voltammetry (FSCV). FSCV detection, which is often influenced by adsorption-based surface interactions, is commonly impacted by the chemical and geometric structure of the electrode's surface, and graphene oxide is a tunable carbon-based nanomaterial capable of enhancing these two key characteristics. Synthesized GFMEs possess exquisite electronic and mechanical properties.

A microfluidic chip for sustained oxygen gradient formation in the intestine .

The oxygen gradient across the intestine influences intestinal physiology and the microbial environment of the microbiome. The microbiome releases metabolites that communicate with enterochromaffin cells, neuronal cells, and resident immune cells to facilitate the bidirectional communication across the gut-brain axis. Measuring communication between various cell types within the intestine could provide essential information about key regulators of gut and brain health; however, the microbial environment of the intestine is heavily dependent on the physiological oxygen gradient that exists across the intestinal wall.

Subsecond Codetection of Dopamine and Estradiol at a Modified Sharkfin Waveform.

17β-Estradiol (E2) is a ubiquitously expressed hormone that is active in a wide range of neuroprotective and regenerative roles throughout the brain. In particular, it is a well-known dopamine (DA) regulator and is responsible for modulating the expression of dopaminergic receptors and transporters. Recent studies point to E2 release occurring on a rapid time scale and having impacts on DA activity within seconds to minutes.

Development of an Electrochemical, Aptamer-Based Sensor for Dynamic Detection of Neuropeptide Y.

The ability to monitor dynamic changes in neuropeptide Y (NPY) levels in complex environments can have an impact on many fields, including neuroscience and immunology. Here, we describe the development of an electrochemical, aptamer-based (E-AB) sensor for the dynamic (reversible) measurement of physiologically relevant (nanomolar) concentrations of neuropeptide Y. The E-AB sensors are fabricated using a previously described 80 nucleotide aptamer reported to specifically bind NPY with a binding affinity = 0.

Measuring neuron-regulated immune cell physiology via the alpha-2 adrenergic receptor in an ex vivo murine spleen model.

The communication between the nervous and immune systems plays a crucial role in regulating immune cell function and inflammatory responses. Sympathetic neurons, which innervate the spleen, have been implicated in modulating immune cell activity. The neurotransmitter norepinephrine (NE), released by sympathetic neurons, influences immune cell responses by binding to adrenergic receptors on their surface.

Graphene oxide fiber microelectrodes with controlled sheet alignment for sensitive neurotransmitter detection.

Here, we synthesized and characterized graphene oxide (GO) fiber microelectrodes with controllable nanosheet orientation to study the extent to which sheet alignment and orientation impacts electrochemical detection of neurochemicals. The alignment of the GO nanosheets was characterized by scanning electron microscopy, Raman spectroscopy, and cyclic voltammetry. The electrochemical performance of GO microelectrodes and its suitability for subsecond detection of neurotransmitters was further evaluated by fast-scan cyclic voltammetry (FSCV).

Genetic mapping of craniofacial traits in the Mexican tetra reveals loci associated with bite differences between cave and surface fish.

Background: The Mexican tetra, Astyanax mexicanus, includes interfertile surface-dwelling and cave-dwelling morphs, enabling powerful studies aimed at uncovering genes involved in the evolution of cave-associated traits. Compared to surface fish, cavefish harbor several extreme traits within their skull, such as a protruding lower jaw, a wider gape, and an increase in tooth number. These features are highly variable between individual cavefish and even across different cavefish populations.

Open multi-organ communication device for easy interrogation of tissue slices.

Here, we have developed an open multi-organ communication device that facilitates cellular and molecular communication between organ slices. Measuring communication between organs is vital for understanding the mechanisms of health regulation yet remains difficult with current technology. Communication between organs along the gut-brain-immune axis is a key regulator of gut homeostasis.

Porous Carbon Nanofiber-Modified Carbon Fiber Microelectrodes for Dopamine Detection.

We present a method to modify carbon-fiber microelectrodes (CFME) with porous carbon nanofibers (PCFs) to improve detection and to investigate the impact of porous geometry for dopamine detection with fast-scan cyclic voltammetry (FSCV). PCFs were fabricated by electrospinning, carbonizing, and pyrolyzing poly(acrylonitrile)--poly(methyl methacrylate) (PAN--PMMA) block copolymer nanofiber frameworks. Commonly, porous nanofibers are used for energy storage applications, but we present an application of these materials for biosensing which has not been previously studied.

Nanostructured carbon-fiber surfaces for improved neurochemical detection.

Fundamental insight into the extent to which the nanostructured surface and geometry impacts neurochemical interactions at electrode surfaces could provide significant advances in our ability to design and fabricate ultrasensitive neurochemical detection probes. Here, we investigate the extent to which the nanostructure of the carbon-fiber surface impacts detection of catecholamines and purines with fast-scan cyclic voltammetry (FSCV). Carbon-fibers were treated with argon (Ar) plasma to induce variations in the nano- and micro-structure without changing the functionalization of the surface.

Extended sawhorse waveform for stable zinc detection with fast-scan cyclic voltammetry.

Zinc (Zn(II)) is a divalent cation involved in regulating intracellular signal transduction and gene expression through transcription factor activity, and can act as a metal neurotransmitter by modulating synaptic activity and neuronal plasticity. Previous research has demonstrated spatial heterogeneity of Zn(II) in the brain, has estimated extracellular concentrations of Zn(II) across various brain regions, and has measured rapid intracellular changes in Zn(II) concentration during glutamate flux. Despite this work, quantification of rapid extracellular Zn(II) release from neurons, on a millisecond time scale, in real time has remained difficult with existing technologies.

Amine-functionalized carbon-fiber microelectrodes for enhanced ATP detection with fast-scan cyclic voltammetry.

Here, we provide evidence that functionalizing the carbon-fiber surface with amines significantly improves direct electrochemical adenosine triphosphate (ATP) detection with fast-scan cyclic voltammetry (FSCV). ATP is an important extracellular signaling molecule throughout the body and can function as a neurotransmitter in the brain. Several methods have been developed over the years to monitor and quantitate ATP signaling in cells and tissues; however, many of them are limited in temporal resolution or are not capable of measuring ATP directly.

High Young's modulus carbon fibers are fouling resistant with fast-scan cyclic voltammetry.

We report evidence that high Young's modulus carbon-fibers resist detrimental chemical fouling at their surface similarly to carbon nanotube fibers with fast-scan cyclic voltammetry. This provides a new method for stable monitoring of neurochemicals like serotonin, without the need to purchase costly carbon nanotube microfibers or perform complicated electrode immobilizations.

A microfluidic electrochemical flow cell capable of rapid on-chip dilution for fast-scan cyclic voltammetry electrode calibration.

Here, we developed a microfluidic electrochemical flow cell for fast-scan cyclic voltammetry which is capable of rapid on-chip dilution for efficient and cost-effective electrode calibration. Fast-scan cyclic voltammetry (FSCV) at carbon-fiber microelectrodes is a robust electroanalytical technique used to measure subsecond changes in neurotransmitter concentration over time. Traditional methods of electrode calibration for FSCV require several milliliters of a standard.

Plasma-treated carbon-fiber microelectrodes for improved purine detection with fast-scan cyclic voltammetry.

Here, we developed N2 and O2 plasma-treated carbon-fiber microelectrodes (CFME) for improved purine detection with fast-scan cyclic voltammetry (FSCV). Plasma treatment affects the topology and functionality of carbon which impacts the electrode-analyte interaction. CFME's are less sensitive to purines compared to catecholamines.

Defect Sites Modulate Fouling Resistance on Carbon-Nanotube Fiber Electrodes.

Carbon nanotube (CNT) fiber electrodes have become increasingly popular electrode materials for neurotransmitter detection with fast-scan cyclic voltammetry (FSCV). The unique properties of CNT fiber electrodes like increased electron transfer, sensitivity, waveform application frequency independence, and resistance to fouling make them ideal biological sensors for FSCV. In particular, their resistance to fouling has been observed for several years, but the specific physical properties which aid in fouling resistance have been debated.

Subsecond detection of guanosine using fast-scan cyclic voltammetry.

Guanosine is an important neuromodulator and neuroprotector in the brain and is involved in many pathological conditions, including ischemia and neuroinflammation. Traditional methods to detect guanosine in the brain, like HPLC, offer low limits of detection and are robust; however, subsecond detection is not possible. Here, we present a method for detecting rapid fluctuations of guanosine concentration in real-time using fast-scan cyclic voltammetry (FSCV) at carbon-fiber microelectrodes.

Phage display library screening for identification of interacting protein partners.

Phage display is a versatile high-throughput screening method employed to understand and improve the chemical biology, be it production of human monoclonal antibodies or identification of interacting protein partners. A majority of cell proteins operate in a concerted fashion either by stable or transient interactions. Such interactions can be mediated by recognition of small amino acid sequence motifs on the protein surface.

Detection of disulfide linkage by chemical derivatization and mass spectrometry.

The location of disulfide linkage(s) or status of unpaired cysteines is a critical structural feature required for the characterization of three-dimensional structure of a protein and for the correlation of protein structure-function relationships. Cysteine, with its reactive thiol group, can undergo enzymatic or oxidative posttranslational modification in response to changing redox conditions to signal a cascade of downstream reactions. In such a situation, it becomes even more critical to obtain the information on the pair of cysteines involved in such a redox switch operation.