The Biological Molecular Imaging Section focuses on identification of disease-specific biomarkers; development of new molecular imaging probes with cellular and molecular biology oriented techniques and methods; application of the developed probes into multimodality imaging; and collaborates with the other two LOMIN sections to characterize novel imaging or therapeutic agents, both in vitro and in vivo.
Molecular imaging allows detection of specific targets in vivo, including visualization of the presence of targets, as well as the quantification of their spatial and temporal distribution. A target may be a single key protein or a particular pathway related to certain pathological processes. Our lab develops probes of small organic molecules, polypeptides, proteins, antibodies or aptamers by phage peptide display library screening, single chain antibody library screening, and systematic evolution of ligands by exponential enrichment (SELEX). The newly developed probes are then modified and optimized for in vivo molecular imaging application.
Fluorophores, isotopes, and other detectable labels are most commonly introduced into a protein through in vitro modifications with suitable amine or thiol reactive reagents. Non-specific labeling of protein probes will cause heterogeneity and inaccuracy of quantification in the imaging process. Our lab engineers protein probes to accomplish site-specific modification. For example, with a system utilizing an mRNA template with an amber codon (UAG), instead of a normal initiating codon (AUG) and a complementary misaminoacylated initiator suppressor tRNA capable of initiating protein synthesis from the UAG codon, an artificial amino acid can be introduced into the N-terminal of synthesized proteins. Enzymatic post-translational modification of proteins utilizing inteins-mediated protein splicing is an alternative approach for site-specific labeling.
Therapeutic efficacy is a key question that needs to be answered for ever drug or drug candidate. Molecular imaging is able to provide information to evaluate pharmacological effects. For instance, solid tumors are often characterized by having high glucose utilization, tumor cell proliferation, hypoxia with sustained angiogenesis and evasion of apoptosis. The influence of compounds targeting these characteristics of cancer biology can be selectively visualized by molecular imaging techniques. Examples include FDG PET to image glucose transport and metabolism, and FLT PET to evaluate the proliferating status. Additionally, some imaging strategies can focus on one particular pathway such as apoptosis and hypoxia or a single molecular target to access specific drugs.
As a unique branch of molecular imaging, various reporter genes have been developed, and expression of reporter genes can be evaluated by multiple imaging modalities, including optical imaging, SPECT/PET or MRI. With split reporter gene or bioluminescence resonance energy transfer (BRET) system, protein-protein interactions can be visualized in living organisms. Our lab develops and applies reporter gene imaging to corroborate probe-based non-invasive imaging.
The Biological Molecular Imaging Section is physically located in building 9 and building 10, room B3B25.
The laboratory is equipped with instruments to perform cell biology and molecular biology experiments, such as cell culture, western blot, PCR, and gene and protein engineering. A Zeiss Axio Imager A2 LED upright bright field microscope is equipped for tissue staining and histological observation. An Olympus X-81 epifluorescent microscope and an Olympus Fluoview F10i-LIV fully automated confocal laser-scanning microscope allow us to investigate fluorophores label probes in tissue section or live cells. The surgery and imaging room 10/B3B25 is equipped with a cryomicrotome, a storage phosphor system, gamma counters, and liquid scintillation counters for ex vivo investigation.
The lab is also equipped with a stereotaxic mounted cortical impactor, a surgical microscope, a rodent ventilator and a body temperature controller for animal model establishment including traumatic brain injury (TBI), myocardial infarction (MI), hindlimb ischemia and various orthotopic tumor inoculation.
For live animal imaging, we are equipped with a Siemens Inveon PET/CT docking system to explore radiolabeled tracers, a CRI Maestro II for fluorescence imaging, and an IVIS Lumina II for both bioluminescence imaging and fluorescence imaging. We also get access to the NIH/MIF (Mouse Imaging Facility) to perform MRI imaging. Recently, we have installed a Vevo 2100 high frequency ultrasound system with integrated Vevo LAZR for ultrasound and photoacoustic (PA) imaging.