The development of treatments for central nervous system disorders has been limited because of difficulties in translating positive preclinical findings in small animal models to clinical studies. One major limit in preclinical studies is that it is difficult to directly correlate biomarker expression to cognitive/behavioral results in longitudinal studies. Animals are generally sacrificed to evaluate biomarker expression. Therefore, there is a need for a morphological, functional, and cellular/molecular neuroimaging technique capable of longitudinal assessment of brain tissue in vivo, non-invasively, and in real time. The goal of our research program is to develop a preclinical neuroimaging system based on ultrasound and photoacoustic (USPA) imaging and to use gas microbubble- assisted focused ultrasound (FUS) disruption of the blood brain barrier (BBB) for delivery of targeted contrast agents. We believe that this system would improve the ability of neuroscientists to study the underlying mechanisms of diseases and to develop and evaluate potential treatments. The underlying hypothesis of this project is that non-invasive, high-resolution, high-sensitivity, in vivo imaging of the brain is possible and will provide marked advantages over existing imaging tools available to neuroscientists. USPA imaging, in combination with FUS and molecular probes, is of interest because it is non-invasive, cost-effective, and portable while also capable of imaging the whole rodent brain in vivo. The main goal of this exploratory R21 application is to develop and test a laboratory prototype of the USPA neuroimaging system and address known concerns in order to proceed with broader development efforts in the future. We will develop an FUS-mediated USPA imaging system to non-invasively visualize protein biomarkers in vivo in preclinical models of Alzheimer?s disease (AD). AD is a progressive neurodegenerative disease, which causes significant morbidity and mortality, characterized by pathogenic protein plaques composed of ?-amyloid. In order to visualize plaques, ?-amyloid-targeted gold nanorods (AuNRs) will be developed. AuNRs have been shown to be strong optical absorbers and good photoacoustic contrast agents that can be tuned to absorb in the near-infrared region. Specifically, anti-?-amyloid antibodies will be conjugated to AuNRs and tested in AD tissue samples as well as via surface plasmon resonance assays. After confirming targeting of the rods, an FUS positioning system will be developed for targeting the hippocampus of mice. The ability of this system to target the hippocampus will be confirmed with Evans Blue leakage as well as delivery of non-targeted AuNRs (visualized with USPA imaging). The distribution of AuNRs, clearance mechanisms, and clearance timeline will be assessed acutely and longitudinally. Finally, targeted AuNRs will be delivered to the hippocampus of AD and wild type mice using FUS and visualized with USPA in vivo, acutely and longitudinally. The ability to visualize ?-amyloid in the hippocampus with USPA in vivo longitudinally would prove the utility of our system. If successful, these studies will demonstrate that USPA imaging is a valuable neuroimaging tool that will help to translate the result of preclinical studies and facilitate the clinical success of disease diagnosis and therapy.
We propose to develop an ultrasound and photoacoustic neuroimaging system, in combination with focused ultrasound blood brain barrier disruption for delivery of targeted photoacoustic contrast agents and for the visualization of biomarkers in preclinical models of central nervous system diseases/disorders. We will design, optimize, and characterize a system to achieve focal blood brain barrier disruption in the hippocampus using focused ultrasound. Additionally, we will develop and characterize ?-amyloid targeted gold nanorods as a photoacoustic imaging contrast agent and use them to visualize ?-amyloid in the hippocampus of rodent models of Alzheimer?s disease. If our approach is successful, we will have developed a powerful tool for imaging biomarkers in vivo within the central nervous system, which would have numerous applications in research and aide in the translation of therapeutics to the clinic.
