Christopher Wyatt - US grants

This proposal was received in response to Nanoscale Science and Engineering initiative, NSF 04-043, category NIRT. This Solid State Chemistry program (DMR) award to Virginia Polytechnic Institute and State University is to develop understanding the mechanism and fundamental dipole-dipole dynamic interactions (i.e., unpaired electron spin density inside/outside the carbon cage with water) responsible for the enhanced relaxivity in functionalized endohedral metallofullerenes (EMFs) when used as medical diagnostic agents and other imaging applications (e.g., polymers, composites). Endohedral metallofullerenes, because of their shape, and capacity for multiple endo encapsulants and exo functionalizability, are ideal nano-constructs on which to develop imaging agents. In addition, the high stability of the carbon cage is known to exhibit unusual resistance to any chemical cage-opening process. The ability to detect and measure low amplitude signals in noisy, complex environments is a fundamental challenge in imaging applications. Although there have been major improvements in biological imaging technology (MRI), the sensitivity and specificity of current techniques using contrast agents such as the one using small molecular chelates of gadolinium remain far from optimal. Although signal amplification is important to achieving this goal, it will not be sufficient; rather it will require a synergistic approach that incorporates multiple visibilities simultaneously into the same nano-construct (multi-modal), not only to increase sensitivity, but also the signal/noise ratio and provide the ability to generate quantitative data. Major goals of this award will be to: 1) provide a new model for understanding the spin-lattice relaxation time (T1) (or increasing relaxivity r1= 1/ T1) of water or tissue, 2) employ this model to optimize these nanoscale interactions, and 3) develop a new multi-modality nanosphere-based endohedral metallofullerene imaging agents. In addition to the Solid-State Chemistry program (MPS), the following programs are co-funding this award: Chemistry (MPS); Engineering Education and Centers (ENG); and Bioengineering and Environmental Systems (ENG).

With this award, new educational programs will be developed at the K-12, undergraduate, and graduate levels, especially in the sciences through Institute for Connecting Science Research to the Classroom (ICSRC), an interdisciplinary center established in the College of Human Resources and Education at the University. In addition, the existing short courses and hands-on laboratory experiments in nanomaterials will be expanded to include other students and faculty at Virginia Tech, Virginia Commonwealth University as well as other academic institutions across the region. These interactions would provide undergraduates and graduate students in other disciplines the opportunity to interact with each other in many areas of nanotechnology. Industrial collaborations with Luna Innovations are expected to produce nanomaterials with potential biomedical imaging applications.

X-ray computed tomography (CT) is a popular approach that reveals internal structures of an object based on its shadows from an x-ray source. Filling in the performance gap between light and electron microscopies, x-ray nano-CT depicts details as tiny as 50nm ("resolution") and has emerged as a powerful tool in various applications. However, a major barrier to realizing its full potential is the inaccuracy encountered when an internal region of interest (ROI) inside a large object is imaged only with x-rays through that region ("the interior problem"). Also, nano-CT demands an intensive x-ray beam that may damage biological samples. To overcome these challenges, contemporary mathematical and engineering methods will be used in this project to develop the next-generation nano-CT system.

The nano-CT system will accelerate progress in medicine, biology, nanotechnology, materials, and energy. When combined with our existing micro-CT scanners of 0.5-20ìm resolution, the resulting multiscale CT facility will quickly become a regional center serving many users. As the only 50nm resolution CT scanner on the East Coast and the only CT system with narrow beam targeting and accurate interior reconstruction capabilities in the world, this instrument will be invaluable to both institutions and industries in the US. Furthermore, this project will facilitate nanotechnology teaching and training at Virginia Tech and Wake Forest University, benefiting undergraduate and graduate students from underrepresented and diverse groups. Finally, this system will be commercialized in collaboration with the leading nano-CT company Xradia to create job opportunities and maintain US leadership in this area.

DESCRIPTION (provided by applicant): The carotid bodies are small organs located on the carotid arteries. They serve an essential biological function by detecting and relaying information regarding blood gas composition to the breathing centers of the brain. Thus, a deficit in blood oxygen (hypoxia) is 'sensed'by the carotid body, resulting in an increased firing frequency of the carotid sinus nerve and ultimately a change in the pattern of breathing. Recent research suggests that the exact molecular mechanism by which hypoxia is transduced into increased carotid sinus nerve activity is close to being resolved. Evidence indicates that activation of the energy- sensing enzyme AMP-activated protein kinase (AMPK) may be critical for the transduction of an acute hypoxic stimulus by the carotid bodies. The novel experimental protocols detailed in the current proposal will provide functional insights into the role of AMPK in acute oxygen-sensing. Specific Aim 1 will define the importance of AMPK in the generation of the carotid body mediated acute hypoxic ventilatory response in whole animals. Specific Aim 2 will address the importance of AMPK in the response of isolated oxygen-sensing cells from the carotid body to hypoxia. Specific Aim 3 will address the importance of regulators of AMPK in the generation of a hypoxic response by oxygen-sensing cells in the carotid body. This project will use genetically modified mice, plethysmography, immunocytochemistry, electrophysiology and calcium imaging to define the role of AMPK in mediating hypoxic transduction at the level of the whole animal and the oxygen-sensing cells of the carotid bodies. Meeting the aims of the current proposal will provide clinically relevant information pertaining to the basic physiology of the carotid bodies and to the generation of the ventilatory increase observed during hypoxia. Furthermore the conceptually novel hypothesis that AMPK is involved in oxygen-sensing by the carotid body raises the possibility of new therapeutic strategies for disorders such as sleep apnea and sudden infant death. PUBLIC HEALTH RELEVANCE: The carotid bodies are vital organs which detect a fall in blood oxygen and increase the drive to breathe in order to restore oxygen levels to normal. The mechanisms that underpin the response of these organs to changes in blood gases are not well understood. This research will test the hypothesis that the energy- sensing enzyme AMP-activated protein kinase is required for the generation of a complete ventilatory response to low oxygen.