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1.  Deglycosylated Anti-Aβ Antibody Dose–Response Effects on Pathology and Memory in APP Transgenic Mice 
Anti-Aβ antibody administration to amyloid-depositing transgenic mice can reverse amyloid pathology and restore memory function. However, in old mice, these treatments also increase vascular leakage and promote formation of vascular amyloid deposits. Deglycosylated antibodies with reduced affinity for Fcγ receptors and complement are associated with reduced vascular amyloid and microhemorrhage while retaining amyloid-clearing and memory-enhancing properties of native intact antibodies. In the current experiment, we investigated the effect of 3, 10, or 30 mg/kg of deglycosylated antibody (D-2H6) on amyloid pathology and cognitive behavior in old Tg2576 mice. We found that low doses of deglycosylated antibody appear more efficacious than higher doses in reducing pathology and memory loss in amyloid precursor protein (APP) transgenic mice. These data suggest that excess antibody unbound to antigen can interfere with antibody-mediated Aβ clearance, possibly by saturating the FcRn antibody transporter.
doi:10.1007/s11481-008-9114-6
PMCID: PMC5072283  PMID: 18607758
Alzheimer’s disease; amyloid; angiopathy; microglia; transgenic mice; immunization; hemorrhage; Aβ; immunotherapy; behavior
2.  Near-Infrared Intraoperative Chemiluminescence Imaging 
ChemMedChem  2016;11(18):1978-1982.
Intraoperative imaging technologies recently entered the operating room, and their implementation is revolutionizing how physicians plan, monitor, and perform surgical interventions. In this work, we present a novel surgical imaging reporter system: intraoperative chemiluminescence imaging (ICI). To this end, we have leveraged the ability of a chemiluminescent metal complex to generate near-infrared light upon exposure to an aqueous solution of Ce4+ in the presence of reducing tissue or blood components. An optical camera spatially resolves the resulting photon flux. We describe the construction and application of a prototype imaging setup, which achieves a detection limit as low as 6.9 pmol cm−2 of the transition-metal-based ICI agent. As a proof of concept, we use ICI for the in vivo detection of our transition metal tracer following both systemic and subdermal injections. The very high signal-to-noise ratios make ICI an interesting candidate for the development of new intraoperative imaging technologies.
Glow in the dark
A preclinical imaging setup was developed to detect chemiluminescence in fresh tissues after intravenous or subdermal administration of a ruthenium metal complex. High signal-to-noise ratios were obtained without the need for excitation light. This could be a novel technology for intraoperative imaging and surgical margin evaluation.
doi:10.1002/cmdc.201600301
PMCID: PMC5061038  PMID: 27471800
chemiluminescence; intraoperative imaging; lymph node imaging; near infrared; ruthenium
3.  MOLECULAR IMAGING OF PROSTATE CANCER: translating molecular biology approaches into the clinical realm 
European radiology  2015;25(5):1294-1302.
The epidemiology of prostate cancer has dramatically changed since the introduction of prostate-specific antigen (PSA) screening in the 1980’s. Most prostate cancers today are detected at early stages of the disease and are considered “indolent”, however some patients’ prostate cancers demonstrate a more aggressive behavior which leads to rapid progression and death. Increasing understanding of the biology underlying the heterogeneity that characterizes this disease has lead to a continuously evolving role of imaging in the management of prostate cancer. Functional and metabolic imaging techniques are gaining importance as the impact on the therapeutic paradigm has shifted from structural tumor detection alone to distinguishing patients with indolent tumors that can be managed conservatively (e.g., by active surveillance) from patients with more aggressive tumors that may require definitive treatment with surgery or radiation. In this review, we discuss advanced imaging techniques that allow direct visualization of molecular interactions relevant to prostate cancer and their potential for translation to the clinical setting in the near future. The potential use of imaging to follow molecular events during drug therapy as well as the use of imaging agents for therapeutic purposes will also be discussed.
doi:10.1007/s00330-014-3539-5
PMCID: PMC4994516  PMID: 25693661
prostate cancer; molecular imaging; MRI; PET; optical imaging; Cerenkov imaging
4.  Multifunctional MRI/PET Nanobeacons Derived from the in Situ Self-Assembly of Translational Polymers and Clinical Cargo through Coalescent Intermolecular Forces 
Nano letters  2015;15(12):8032-8043.
Novel multifunctional platforms are needed for oncology in order to assist physicians during surgery and chemotherapy. In the present study, we show that polymeric nanobeacons, consisting of the glucose-based polymer dextran, can be used to guide surgery and improve drug delivery. For imaging, the nanobeacons stably retained the positron emitter 89-zirconium and the MRI contrast agent gadolinium, without the need of a chelator. In addition to using them for PET imaging, the 89Zr-nanobeacons guided the surgical resection of sentinel lymph nodes, utilizing their inherent Cerenkov luminescence. Through weak electrostatic interactions, the nanoparticles carried combinations of chemotherapeutics for the simultaneous inhibition of oncogenic pathways, resulting in enhanced tumor regression. The nanobeacons also allowed monitoring of drug release via MRI, through the quenching of the gadolinium signal by the coloaded drug, making them a new multifunctional theranostic nanotechnology platform for the clinic.
doi:10.1021/acs.nanolett.5b03370
PMCID: PMC4703344  PMID: 26540670
Lymph node resection; Cerenkov-guided surgery; combination therapy
5.  Broadly neutralizing human monoclonal JC polyomavirus VP1–specific antibodies as candidate therapeutics for progressive multifocal leukoencephalopathy 
Science translational medicine  2015;7(306):306ra150.
In immunocompromised individuals, JC polyomavirus (JCPyV) may mutate and gain access to the central nervous system resulting in progressive multifocal leukoencephalopathy (PML), an often fatal opportunistic infection for which no treatments are currently available. Despite recent progress, the contribution of JCPyV-specific humoral immunity to controlling asymptomatic infection throughout life and to eliminating JCPyV from the brain is poorly understood. We examined antibody responses against JCPyV major capsid protein VP1 (viral protein 1) variants in the serum and cerebrospinal fluid (CSF) of healthy donors (HDs), JCPyV-positive multiple sclerosis patients treated with the anti-VLA-4 monoclonal antibody natalizumab (NAT), and patients with NAT-associated PML. Before and during PML, CSF antibody responses against JCPyV VP1 variants show “recognition holes”; however, upon immune reconstitution, CSF antibody titers rise, then recognize PML-associated JCPyV VP1 variants, and may be involved in elimination of the virus. We therefore reasoned that the memory B cell repertoire of individuals who recovered from PML could be a source for the molecular cloning of broadly neutralizing antibodies for passive immunization. We generated a series of memory B cell-derived JCPyV VP1-specific human monoclonal antibodies from HDs and a patient with NAT-associated PML-immune reconstitution inflammatory syndrome (IRIS). These antibodies exhibited diverse binding affinity, cross-reactivity with the closely related BK polyomavirus, recognition of PML-causing VP1 variants, and JCPyV neutralization. Almost all antibodies with exquisite specificity for JCPyV, neutralizing activity, recognition of all tested JCPyV PML variants, and high affinity were derived from one patient who had recovered from PML. These antibodies are promising drug candidates for the development of a treatment of PML.
doi:10.1126/scitranslmed.aac8691
PMCID: PMC4820754  PMID: 26400911
6.  Silica Nanoparticles as Substrates for Chelator-free Labeling of Oxophilic Radioisotopes 
Nano letters  2015;15(2):864-868.
Chelator-free nanoparticles for intrinsic radiolabeling are highly desirable for whole-body imaging and therapeutic applications. Several reports have successfully demonstrated the principle of intrinsic radiolabeling. However, the work done to date has suffered from much of the same specificity issues as conventional molecular chelators, insofar as there is no singular nanoparticle substrate that has proven effective in binding a wide library of radiosotopes. Here we present amorphous silica nanoparticles as general substrates for chelator-free radiolabeling, and demonstrate their ability to bind six medically relevant isotopes of various oxidation states with high radiochemical yield. We provide strong evidence that the stability of the binding correlates with the hardness of the radioisotope, corroborating the proposed operating principle. Intrinsically labeled silica nanoparticles prepared by this approach demonstrate excellent in vivo stability and efficacy in lymph node tracking.
doi:10.1021/nl503522y
PMCID: PMC4412311  PMID: 25559467
intrinsic labeling; chelator-free; radionuclide; silica nanoparticle; nuclear imaging; lymph node
7.  Silica Nanoparticles as Substrates for Chelator-free Labeling of Oxophilic Radioisotopes 
Nano Letters  2015;15(2):864-868.
Chelator-free nanoparticles for intrinsic radiolabeling are highly desirable for whole-body imaging and therapeutic applications. Several reports have successfully demonstrated the principle of intrinsic radiolabeling. However, the work done to date has suffered from much of the same specificity issues as conventional molecular chelators, insofar as there is no singular nanoparticle substrate that has proven effective in binding a wide library of radiosotopes. Here we present amorphous silica nanoparticles as general substrates for chelator-free radiolabeling and demonstrate their ability to bind six medically relevant isotopes of various oxidation states with high radiochemical yield. We provide strong evidence that the stability of the binding correlates with the hardness of the radioisotope, corroborating the proposed operating principle. Intrinsically labeled silica nanoparticles prepared by this approach demonstrate excellent in vivo stability and efficacy in lymph node imaging.
doi:10.1021/nl503522y
PMCID: PMC4412311  PMID: 25559467
Intrinsic labeling; chelator-free; radionuclide; silica nanoparticle; nuclear imaging; lymph node
9.  Cerenkov Luminescence Imaging for Radiation Dose Calculation of a 90Y-Labeled Gastrin-Releasing Peptide Receptor Antagonist 
90Y has been used to label various new therapeutic radiopharmaceuticals. However, measuring the radiation dose delivered by 90Y is challenging because of the absence of suitable γ emissions and its low abundance of positron emissions. For the treatment of prostate cancer, radiolabeled gastrin-releasing peptide receptor (GRPr) antagonists have yielded promising results in mouse models. In this study, we evaluated whether Cerenkov luminescence imaging (CLI) could be used to determine radiation doses of a 90Y-labeled GRPr antagonist in nude mice.
Methods
Mice bearing subcutaneous prostate cancer xenografts were injected with 0.74–18.5 MBq of the 90Y-labeled GRPr antagonist DOTA-AR and underwent in vivo and ex vivo CLI at 1–48 h after injection. After imaging, animals were sacrificed, their tumors and organs were harvested, and the activity concentration was measured by liquid scintillation counting. In a second set of experiments, Cerenkov photon counts for tumor and kidney on in vivo CLI were converted to activity concentrations using conversion factors determined from the first set of experiments.
Results
90Y-DOTA-AR concentration in the 3 tumor models ranged from 0.5% to 4.8% of the injected activity per gram at 1 h after injection and decreased to 0.05%–0.15 injected activity per gram by 48 h after injection. A positive correlation was found between tumor activity concentrations and in vivo CLI signal (r2 = 0.94). A similar correlation was found for the renal activity concentration and in vivo Cerenkov luminescence (r2 = 0.98). Other organs were not distinctly visualized on the in vivo images, but ex vivo CLI was also correlated with the radioactivity concentration (r2 = 0.35–0.94). Using the time–activity curves from the second experiment, we calculated radiation doses to tumor and kidney of 0.33 ± 0.12 (range, 0.21–0.66) and 0.06 ± 0.01 (range, 0.05–0.08) Gy/MBq, respectively.
Conclusion
CLI is a promising, low-cost modality to measure individual radiation doses of 90Y-labeled compounds non-invasively. The use of Cerenkov imaging is expected to facilitate the development and comparison of 90Y-labeled compounds for targeted radiotherapy.
doi:10.2967/jnumed.114.149054
PMCID: PMC4470706  PMID: 25840974
gastrin-releasing peptide receptor; Cerenkov luminescence imaging; targeted radiotherapy; 90Y
10.  Molecular Imaging Using Nanoparticle Quenchers of Cerenkov Luminescence 
Cerenkov luminescence (CL) imaging is an emerging technique that collects the visible photons produced by radioisotopes. Here, we have investigated molecular imaging strategies by modulating CL signal off. Utilizing a combination of clinically approved agents, and their analogues, we demonstrate the noninvasive molecularly specific detection of cancer. CL was modulated in vitro in a dose dependent manner using approved small molecules (Lymphazurin), as well as the clinically approved Feraheme and other preclinical superparamagnetic iron oxide nanoparticles (SPIO). To evaluate the quenching of CL in vivo, two strategies were pursued. [18F]-FDG was imaged by PET and CL in tumors prior to and following accumulation of nanoparticles. Initially, non-targeted particles were administered to mice bearing tumors in order to attenuate CL. For targeted imaging, a dual tumor model (expressing the human somatostatin receptor subtype-2 (hSSTr2) and a control negative cell line) was used. Targeting hSSTr2 with octreotate-conjugated SPIO, we demonstrate quenched CL enabling non-invasive distinction between tumors’ molecular expression profiles. In this work, we demonstrate quenching of Cerenkov emissions in several proof of principle models using a combination of approved agents and nanoparticle platforms to provide disease relevant information including tumor vascularity and specific antigen expression.
doi:10.1002/smll.201400733
PMCID: PMC4167912  PMID: 24861843
molecular targeting; quenching nanoparticles; activatable imaging; Cerenkov luminescence; Activatable Cerenkov Luminescence
11.  Nanoparticles for Imaging: Top or Flop? 
Radiology  2014;273(1):10-28.
Diagnostic nano- and microparticles are favorably suited for labeling the mononuclear phagocytic system (eg, liver, spleen, lymph nodes), and the use of diagnostic nanoparticles is indicated for ex vivo labeling of cells, scaffolds, and other kinds of tissue-engineered implants that are to be visualized in vivo.
Nanoparticles are frequently suggested as diagnostic agents. However, except for iron oxide nanoparticles, diagnostic nanoparticles have been barely incorporated into clinical use so far. This is predominantly due to difficulties in achieving acceptable pharmacokinetic properties and reproducible particle uniformity as well as to concerns about toxicity, biodegradation, and elimination. Reasonable indications for the clinical utilization of nanoparticles should consider their biologic behavior. For example, many nanoparticles are taken up by macrophages and accumulate in macrophage-rich tissues. Thus, they can be used to provide contrast in liver, spleen, lymph nodes, and inflammatory lesions (eg, atherosclerotic plaques). Furthermore, cells can be efficiently labeled with nanoparticles, enabling the localization of implanted (stem) cells and tissue-engineered grafts as well as in vivo migration studies of cells. The potential of using nanoparticles for molecular imaging is compromised because their pharmacokinetic properties are difficult to control. Ideal targets for nanoparticles are localized on the endothelial luminal surface, whereas targeted nanoparticle delivery to extravascular structures is often limited and difficult to separate from an underlying enhanced permeability and retention (EPR) effect. The majority of clinically used nanoparticle-based drug delivery systems are based on the EPR effect, and, for their more personalized use, imaging markers can be incorporated to monitor biodistribution, target site accumulation, drug release, and treatment efficacy. In conclusion, although nanoparticles are not always the right choice for molecular imaging (because smaller or larger molecules might provide more specific information), there are other diagnostic and theranostic applications for which nanoparticles hold substantial clinical potential.
doi:10.1148/radiol.14131520
PMCID: PMC4186876  PMID: 25247562
12.  Cerenkov Imaging 
Advances in cancer research  2014;124:213-234.
Cerenkov luminescence (CL) has been used recently in a plethora of medical applications like imaging and therapy with clinically relevant medical isotopes. The range of medical isotopes used is fairly large and expanding. The generation of in vivo light is useful since it circumvents depth limitations for excitation light. Cerenkov luminescence imaging (CLI) is much cheaper in terms of infrastructure than positron emission tomography (PET) and is particularly useful for imaging of superficial structures. Imaging can basically be done using a sensitive camera optimized for low-light conditions, and it has a better resolution than any other nuclear imaging modality. CLI has been shown to effectively diagnose disease with regularly used PET isotope (18F-FDG) in clinical setting. Cerenkov luminescence tomography, Cerenkov luminescence endoscopy, and intraoperative Cerenkov imaging have also been explored with positive conclusions expanding the current range of applications. Cerenkov has also been used to improve PET imaging resolution since the source of both is the radioisotope being used. Smart imaging agents have been designed based on modulation of the Cerenkov signal using small molecules and nanoparticles giving better insight of the tumor biology.
doi:10.1016/B978-0-12-411638-2.00006-9
PMCID: PMC4329979  PMID: 25287690
13.  Dawn of Advanced Molecular Medicine: Nanotechnological Advancements in Cancer Imaging and Therapy 
Critical reviews in oncogenesis  2014;19(0):143-176.
Nanotechnology plays an increasingly important role not only in our everyday life (with all its benefits and dangers) but also in medicine. Nanoparticles are to date the most intriguing option to deliver high concentrations of agents specifically and directly to cancer cells; therefore, a wide variety of these nanomaterials has been developed and explored. These span the range from simple nanoagents to sophisticated smart devices for drug delivery or imaging. Nanomaterials usually provide a large surface area, allowing for decoration with a large amount of moieties on the surface for either additional functionalities or targeting. Besides using particles solely for imaging purposes, they can also carry as a payload a therapeutic agent. If both are combined within the same particle, a theranostic agent is created. The sophistication of highly developed nanotechnology targeting approaches provides a promising means for many clinical implementations and can provide improved applications for otherwise suboptimal formulations. In this review we will explore nanotechnology both for imaging and therapy to provide a general overview of the field and its impact on cancer imaging and therapy.
PMCID: PMC4183929  PMID: 25271430
nanoparticles; oncology; drug delivery; chemotherapy; targeted therapeutics
14.  Nanoparticles for Imaging: Top or Flop? 
Radiology  2014;273(1):10-28.
Nanoparticles are frequently suggested as diagnostic agents. However, except for iron oxide nanoparticles, diagnostic nanoparticles have been barely incorporated into clinical use so far. This is predominantly due to difficulties in achieving acceptable pharmacokinetic properties and reproducible particle uniformity as well as to concerns about toxicity, biodegradation, and elimination. Reasonable indications for the clinical utilization of nanoparticles should consider their biologic behavior. For example, many nanoparticles are taken up by macrophages and accumulate in macrophage-rich tissues. Thus, they can be used to provide contrast in liver, spleen, lymph nodes, and inflammatory lesions (eg, atherosclerotic plaques). Furthermore, cells can be efficiently labeled with nanoparticles, enabling the localization of implanted (stem) cells and tissue-engineered grafts as well as in vivo migration studies of cells. The potential of using nanoparticles for molecular imaging is compromised because their pharmacokinetic properties are difficult to control. Ideal targets for nanoparticles are localized on the endothelial luminal surface, whereas targeted nanoparticle delivery to extravascular structures is often limited and difficult to separate from an underlying enhanced permeability and retention (EPR) effect. The majority of clinically used nanoparticle-based drug delivery systems are based on the EPR effect, and, for their more personalized use, imaging markers can be incorporated to monitor biodistribution, target site accumulation, drug release, and treatment efficacy. In conclusion, although nanoparticles are not always the right choice for molecular imaging (because smaller or larger molecules might provide more specific information), there are other diagnostic and theranostic applications for which nanoparticles hold substantial clinical potential.
doi:10.1148/radiol.14131520
PMCID: PMC4186876  PMID: 25247562
nanoparticle; theranostics; molecular imaging; contrast agent; imaging
15.  Environment-responsive Nanophores for Therapy and Treatment Monitoring via Molecular MRI Quenching 
Nature communications  2014;5:3384.
The effective delivery of therapeutics to disease sites significantly contributes to drug efficacy, toxicity and clearance. Here we demonstrate that clinically approved iron oxide nanoparticles (Ferumoxytol) can be utilized to carry one or multiple drugs. These so called ‘nanophores’ retain their cargo within their polymeric coating through weak electrostatic interactions and release it in slightly acidic conditions (pH 6.8 and below). The loading of drugs increases the nanophores’ transverse T2 and longitudinal T1 NMR proton relaxation times, which is proportional to amount of carried cargo. Chemotherapy with translational nanophores is more effective than the free drug in vitro and in vivo, without subjecting the drugs or the carrier nanoparticle to any chemical modification. Evaluation of cargo incorporation and payload levels in vitro and in vivo can be assessed via benchtop magnetic relaxometers, common NMR instruments or MRI scanners.
doi:10.1038/ncomms4384
PMCID: PMC4108301  PMID: 24594970
16.  Non-invasive mapping of deep-tissue lymph nodes in live animals using a multimodal PET/MRI nanoparticle 
Nature communications  2014;5:3097.
The invasion status of tumour-draining lymph nodes (LNs) is a critical indicator of cancer stage and is important for treatment planning. Clinicians currently use planar scintigraphy and single-photon emission computed tomography (SPECT) with 99mTc-radiocolloid to guide biopsy and resection of LNs. However, emerging multimodality approaches such as positron emission tomography combined with magnetic resonance imaging (PET/MRI) detect sites of disease with higher sensitivity and accuracy. Here we present a multimodal nanoparticle, 89Zr-ferumoxytol, for the enhanced detection of LNs with PET/MRI. For genuine translational potential, we leverage a clinical iron oxide formulation, altered with minimal modification for radiolabelling. Axillary drainage in naive mice and from healthy and tumour-bearing prostates was investigated. We demonstrate that 89Zr-ferumoxytol can be used for high-resolution tomographic studies of lymphatic drainage in preclinical disease models. This nanoparticle platform has significant translational potential to improve preoperative planning for nodal resection and tumour staging.
doi:10.1038/ncomms4097
PMCID: PMC4080716  PMID: 24445347
17.  Quantitative imaging of disease signatures through radioactive decay signal conversion 
Nature medicine  2013;19(10):1345-1350.
In the era of personalized medicine there is an urgent need for in vivo techniques able to sensitively detect and quantify molecular activities. Sensitive imaging of gamma rays is widely used, but radioactive decay is a physical constant and signal is independent of biological interactions. Here we introduce a framework of novel targeted and activatable probes excited by a nuclear decay-derived signal to identify and measure molecular signatures of disease. This was accomplished utilizing Cerenkov luminescence (CL), the light produced by β-emitting radionuclides such as clinical positron emission tomography (PET) tracers. Disease markers were detected using nanoparticles to produce secondary Cerenkov-induced fluorescence. This approach reduces background signal compared to conventional fluorescence imaging. In addition to information from a PET scan, we demonstrate novel medical utility by quantitatively determining prognostically relevant enzymatic activity. This technique can be applied to monitor other markers and facilitates a shift towards activatable nuclear medicine agents.
doi:10.1038/nm.3323
PMCID: PMC3795968  PMID: 24013701
Activatable probes; Molecular imaging; Nanoparticles; Cerenkov luminescence
18.  Clinical Cerenkov Luminescence Imaging of 18F-FDG 
The aim of this study was to determine the feasibility of Cerenkov luminescence (CL) imaging of patients undergoing diagnostic 18F-FDG scans to detect nodal disease.
Methods
Patients undergoing routine 18F-FDG PET/CT for various malignancies consented to being scanned for CL. White-light and Cerenkov images (5-min acquisition) of the surface of the patient contralateral to and at the site of nodal 18F-FDG uptake were acquired using a cooled, intensified charge-coupled-device camera.
Results
The camera demonstrated linear correlation between activity and counts into the low nanocurie range using 18F-FDG. Imaging of patients revealed the presence of 18F-FDG uptake in nodes that demonstrated uptake on PET. A correlation between maximum standardized uptake value from PET and counting rate per area on the CL imaging was established.
Conclusion
CL imaging with diagnostic doses of 18F-FDG is feasible and can aid in detecting disease in the clinical setting.
doi:10.2967/jnumed.113.127266
PMCID: PMC3903390  PMID: 24078721
Cerenkov luminescence imaging; 18F-FDG; PET/CT; clinical
19.  Gadolinium-Encapsulating Iron Oxide Nanoprobe as Activatable NMR/MRI Contrast Agent 
ACS nano  2012;6(8):7281-7294.
Herein we report a novel gadolinium-encapsulating iron oxide nanoparticle-based activatable NMR/MRI nanoprobe. In our design, Gd-DTPA is encapsulated within the polyacrylic acid (PAA) polymer coating of a superparamagnetic iron oxide nanoparticle (IO-PAA) yielding a composite magnetic nanoprobe (IO-PAA-Gd-DTPA) with quenched longitudinal spin-lattice magnetic relaxation (T1). Upon release of the Gd-DTPA complex from the nanoprobe's polymeric coating in acidic media, an increase in the T1 relaxation rate (1/T1) of the composite magnetic nanoprobe was observed, indicating a dequenching of the nanoprobe with a corresponding increase in the T1-weighted MRI signal. When a folate-conjugated nanoprobe was incubated in HeLa cells, a cancer cell line overexpressing folate receptors, an increase in the 1/T1 signal was observed. This result suggests that upon receptor-mediated internalization, the composite magnetic nanoprobe degraded within the cell's lysosome acidic (pH = 5.0) environment, resulting in an intracellular release of Gd-DTPA complex with subsequent T1 activation. No change in T1 was observed when the Gd-DTPA complex was chemically conjugated on the surface of the nanoparticle's polymeric coating or when encapsulated in the polymeric coating of a non-magnetic nanoparticle. These results confirmed that the observed (T1) quenching of the composite magnetic nanoprobe is due to the encapsulation and close proximity of the Gd ion to the nanoparticles superparamagnetic iron oxide (IO) core. In addition, when an anticancer drug (Taxol) was co-encapsulated with the Gd-DTPA within the folate receptor targeting composite magnetic nanoprobe, the T1 activation of the probe coincide with the rate of drug release and corresponding cytotoxic effect in cell culture studies. Taken together, these results suggest that our activatable T1 nanoagent could be of great importance for the detection of acidic tumors and assessment of drug targeting and release by MRI.
doi:10.1021/nn302393e
PMCID: PMC3429787  PMID: 22809405
Activatable MRI imaging; magnetic relaxation; iron oxide nanoprobe; Gd-DTPA complex; theranostic application
20.  Positron Lymphography: Multimodal, High-Resolution, Dynamic Mapping and Resection of Lymph Nodes After Intradermal Injection of 18F-FDG 
The lymphatic system plays a critical role in the maintenance of healthy tissues. Its function is an important indicator of the presence and extent of disease. In oncology, metastatic spread to local lymph nodes (LNs) is a strong predictor of poor outcome. Clinical methods for the visualization of LNs involve regional injection and tracking of 99mTc-sulfur colloid (99mTc-SC) along with absorbent dyes. Intraoperatively, these techniques suffer from the requirement of administration of multiple contrast media (99mTc-SC and isosulfan blue), unwieldy γ-probes, and a short effective surgical window for dyes. Preclinically, imaging of transport through the lymphatics is further hindered by the resolution of lymphoscintigraphy and SPECT. We investigated multimodal imaging in animal models using intradermal administration of 18F-FDG for combined diagnostic and intraoperative use. PET visualizes LNs with high sensitivity and resolution and low background. Cerenkov radiation (CR) from 18F-FDG was evaluated to optically guide surgical resection of LNs.
Methods
Imaging of 18F-FDG uptake used PET and sensitive luminescent imaging equipment (for CR). Dynamic PET was performed in both sexes and multiple strains (NCr Nude, C57BL/6, and Nu/Nu) of mice. Biodistribution confirmed the uptake of 18F-FDG and was compared with that of 99mTc-SC. Verification of uptake and the ability to use 18F-FDG CR to guide nodal removal were confirmed histologically.
Results
Intradermal injection of 18F-FDG clearly revealed lymphatic vessels and LNs by PET. Dynamic imaging revealed rapid and sustained labeling of these structures. Biodistribution of the radiotracer confirmed the active transport of radioglucose in the lymphatics to the local LNs and over time into the general circulation. 18F-FDG also enabled visualization of LNs through CR, even before surgically revealing the site, and guided LN resection.
Conclusion
Intradermal 18F-FDG can enhance the preclinical investigation of the lymphatics through dynamic, high-resolution, and quantitative tomographic imaging. Clinically, combined PET/Cerenkov imaging has significant potential as a single-dose, dual-modality tracer for diagnostics (PET/CT) and guided resection of LNs (Cerenkov optical).
doi:10.2967/jnumed.112.104349
PMCID: PMC3537831  PMID: 22872741
lymph node mapping; PET/CT; Cerenkov; intraoperative
21.  Targeting the Internal Epitope of Prostate-Specific Membrane Antigen with 89Zr-7E11 Immuno-PET 
The potential of the positron-emitting 89Zr has been recently investigated for the design of radioimmunoconjugates for immuno-PET. In this study, we report the preparation and in vivo evaluation of 89Zr-desferrioxamine B (DFO)-7E11, a novel 89Zr-labeled monoclonal antibody (mAb) construct for targeted imaging of prostate-specific membrane antigen (PSMA), a prototypical cell surface marker highly overexpressed in prostate cancer. The ability of 89Zr-DFO-7E11 to delineate tumor response to therapy was also investigated, because it binds to the intracellular epitope of PSMA, which becomes available only on membrane disruption in dead or dying cells.
Methods
7E11 as a marker of dying cells was studied by flow cytometry and microscopy of cells after antiandrogen-, radio-, and chemotherapy in LNCaP and PC3 PSMA–positive cells. The in vivo behavior of 89Zr-DFO-7E11 was characterized in mice bearing subcutaneous LNCaP (PSMA-positive) tumors by biodistribution studies and immuno-PET. The potential of assessing tumor response was evaluated in vivo after radiotherapy.
Results
In vitro studies correlated 7E11 binding with markers of apoptosis (7–amino-actinomycin-D and caspase-3). In vivo biodistribution experiments revealed high, target-specific uptake of 89Zr-DFO-7E11 in LNCaP tumors after 24 h (20.35 ± 7.50 percentage injected dose per gram [%ID/g]), 48 h (22.82 ± 3.58 %ID/g), 96 h (36.94 ± 6.27 %ID/g), and 120 h (25.23 ± 4.82 %ID/g). Excellent image contrast was observed with immuno-PET. 7E11 uptake was statistically increased in irradiated versus control tumor as measured by immuno-PET and biodistribution studies. Binding specificity was assessed by effective blocking studies at 48 h.
Conclusion
These findings suggest that 89Zr-DFO-7E11 displays high tumor–to–background tissue contrast in immuno-PET and can be used as a tool to monitor and quantify, with high specificity, tumor response in PSMA-positive prostate cancer.
doi:10.2967/jnumed.111.092098
PMCID: PMC3537833  PMID: 21908391
PET; 89Zr; PSMA; 7E11; monoclonal antibodies; prostate cancer
22.  Will nanotechnology influence targeted cancer therapy? 
Seminars in radiation oncology  2011;21(2):80-87.
The rapid development of techniques that enable synthesis (and manipulation) of matter on the nanometer scale, as well as the development of new nano-materials, will play a large role in disease diagnosis and treatment, specifically in targeted cancer therapy. Targeted nanocarriers are an intriguing means to selectively deliver high concentrations of cytotoxic agents or imaging labels directly to the cancer site. Often solubility issues and an unfavorable biodistribution can result in a suboptimal response of novel agents even though they are very potent. New nanoparticulate formulations allow simultaneous imaging and therapy (“theranostics”), which can provide a realistic means for the clinical implementation of such otherwise suboptimal formulations. In this review we will not attempt to provide a complete overview of the rapidly enlarging field of nanotechnology in cancer; rather, we will present properties specific to nanoparticles, and examples of their uses, which demonstrate their importance for targeted cancer therapy.
doi:10.1016/j.semradonc.2010.10.003
PMCID: PMC3062202  PMID: 21356476
23.  Cerenkov imaging - a new modality for molecular imaging 
Cerenkov luminescence imaging (CLI) is an emerging hybrid modality that utilizes the light emission from many commonly used medical isotopes. Cerenkov radiation (CR) is produced when charged particles travel through a dielectric medium faster than the speed of light in that medium. First described in detail nearly 100 years ago, CR has only recently applied for biomedical imaging purposes. The modality is of considerable interest as it enables the use of widespread luminescence imaging equipment to visualize clinical diagnostic (all PET radioisotopes) and many therapeutic radionuclides. The amount of light detected in CLI applications is significantly lower than other that in other optical imaging techniques such as bioluminescence and fluorescence. However, significant advantages include the use of approved radiotracers and lack of an incident light source, resulting in high signal to background ratios. As well, multiple subjects may be imaged concurrently (up to 5 in common bioluminescent equipment), conferring both cost and time benefits. This review summarizes the field of Cerenkov luminescence imaging to date. Applications of CLI discussed include intraoperative radionuclide-guided surgery, monitoring of therapeutic efficacy, tomographic optical imaging capabilities, and the ability to perform multiplexed imaging using fluorophores excited by the Cerenkov radiation. While technical challenges still exist, Cerenkov imaging has materialized as an important molecular imaging modality.
PMCID: PMC3477724  PMID: 23133811
Cerenkov radiation; PET; optical imaging; fluorescence
24.  Intraoperative Imaging of Positron Emission Tomographic Radiotracers Using Cerenkov Luminescence Emissions 
Molecular imaging  2011;10(3):177-186.
Imaging the location and extent of cancer provides invaluable information before, during, and after surgery. The majority of “image-guided” methods that use, for example, positron emission tomography (PET) involve preoperative imaging and do not provide real-time information during surgery. It is now well established that the inherent optical emissions (Cerenkov radiation) from various β-emitting radionuclides can be visualized by Cerenkov luminescence imaging (CLI). Here we report the full characterization of CLI using the positron-emitting radiotracer 89Zr-DFO-trastuzumab for target-specific, quantitative imaging of HER2/neu-positive tumors in vivo. We also provide the first demonstration of the feasibility of using CLI for true image-guided, intraoperative surgical resection of tumors. Analysis of optical CLIs provided accurate, quantitative information on radiotracer biodistribution and tissue uptake that correlated well with the concordant PET images. CLI, PET, and biodistribution studies revealed target-specific uptake of 89Zr-DFO-trastuzumab in BT-474 (HER2/neu positive) versus MDA-MB-468 (HER2/neu negative) xenografts in the same mice. Competitive inhibition (blocking) studies followed by CLI also confirmed the in vivo immunoreactivity and specificity of 89Zr-DFO-trastuzumab for HER2/neu. Overall, these results strongly support the continued development of CLI as a preclinical and possible clinical tool for use in molecular imaging and surgical procedures for accurately defining tumor margins.
PMCID: PMC3083828  PMID: 21496448
25.  Cerenkov luminescence imaging of medical isotopes 
The development of novel multimodality imaging agents and techniques represents the current frontier of research in the field of medical imaging science. However, the combination of nuclear tomography with optical techniques has yet to be established. Here, we report the use of the inherent optical emissions from the decay of radiopharmaceuticals for Cerenkov luminescence imaging (CLI) of tumors in vivo and correlate the results with those obtained from concordant immuno-PET studies.
Methods
In vitro phantom studies were used to validate the visible light emission observed from a range of radionuclides including the positron emitters 18F, 64Cu, 89Zr, and 124I; β-emitter 131I; and α-particle emitter 225Ac for potential use in CLI. The novel radiolabeled monoclonal antibody 89Zr-desferrioxamine B-[DFO-J591 for immuno-PET of prostate-specific membrane antigen (PSMA) expression was used to coregister and correlate the CLI signal observed with the immuno-PET images and biodistribution studies.
Results
Phantom studies confirmed that Cerenkov radiation can be observed from a range of positron-,β-, and α-emitting radionuclides using standard optical imaging devices. The change in light emission intensity versus time was concordant with radionuclide decay and was also found to correlate linearly with both the activity concentration and the measured PET signal (percentage injected dose per gram). In vivo studies conducted in male severe combined immune deficient mice bearing PSMA-positive, subcutaneous LNCaP tumors demonstrated that tumor-specific uptake of 89Zr-DFO-J591 could be visualized by both immuno-PET and CLI. Optical and immuno-PET signal intensities were found to increase over time from 24 to 96 h, and biodistribution studies were found to correlate well with both imaging modalities.
Conclusion
These studies represent the first, to our knowledge, quantitative assessment of CLI for measuring radiotracer uptake in vivo. Many radionuclides common to both nuclear tomographic imaging and radiotherapy have the potential to be used in CLI. The value of CLI lies in its ability to image radionuclides that do not emit either positrons or γ-rays and are, thus, unsuitable for use with current nuclear imaging modalities. Optical imaging of Cerenkov radiation emission shows excellent promise as a potential new imaging modality for the rapid, high-throughput screening of radiopharmaceuticals
doi:10.2967/jnumed.110.076521
PMCID: PMC3068779  PMID: 20554722
Imaging technology; Cerenkov; PET; optical imaging; 89Zr; 124I; 131I; 64Cu; 225Ac; 18F; radioimmunoconjugate; prostate-specific membrane antigen (PSMA); J591; monoclonal antibodies

Results 1-25 (32)