Todd E. Barnhart

Iron Oxide Decorated MoS2 Nanosheets with Double PEGylation for Chelator-Free Radiolabeling and Multimodal Imaging Guided Photothermal Therapy

Theranostics for in vivo cancer diagnosis and treatment generally requires well-designed nanoscale platforms with multiple integrated functionalities. In this study, we uncover that functionalized iron oxide nanoparticles (IONPs) could be self-assembled on the surface of two-dimensional MoS2 nanosheets via sulfur chemistry, forming MoS2-IO nanocomposites, which are then modified with two types of polyethylene glycol (PEG) to acquire enhanced stability in physiological environments. Interestingly, (64)Cu, a commonly used positron-emitting radioisotope, could be firmly adsorbed on the surface of MoS2 without the need of chelating molecules, to enable in vivo positron emission tomography (PET) imaging. On the other hand, the strong near-infrared (NIR) and superparamagnetism of MoS2-IO-PEG could also be utilized for photoacoustic tomography (PAT) and magnetic resonance (MR) imaging, respectively. Under the guidance by such triple-modal imaging, which uncovers efficient tumor retention of MoS2-IO-(d)PEG upon intravenous injection, in vivo photothermal therapy is finally conducted, achieving effective tumor ablation in an animal tumor model. Our study highlights the promise of constructing multifunctional theranostic nanocomposites based on 2D transitional metal dichalcogenides for multimodal imaging-guided cancer therapy.

In Vivo Targeting and Imaging of Tumor Vasculature with Radiolabeled, Antibody-Conjugated Nanographene

Herein we demonstrate that nanographene can be specifically directed to the tumor neovasculature in vivo through targeting of CD105 (i.e., endoglin), a vascular marker for tumor angiogenesis. The covalently functionalized nanographene oxide (GO) exhibited excellent stability and target specificity. Pharmacokinetics and tumor targeting efficacy of the GO conjugates were investigated with serial noninvasive positron emission tomography imaging and biodistribution studies, which were validated by in vitro, in vivo, and ex vivo experiments. The incorporation of an active targeting ligand (TRC105, a monoclonal antibody that binds to CD105) led to significantly improved tumor uptake of functionalized GO, which was specific for the neovasculature with little extravasation, warranting future investigation of these GO conjugates for cancer-targeted drug delivery and/or photothermal therapy to enhance therapeutic efficacy. Since poor extravasation is a major hurdle for nanomaterial-based tumor targeting in vivo, this study also establishes CD105 as a promising vascular target for future cancer nanomedicine.

In Vivo Tumor Targeting and Image-Guided Drug Delivery with Antibody-Conjugated, Radiolabeled Mesoporous Silica Nanoparticles

Since the first use of biocompatible mesoporous silica (mSiO2) nanoparticles as drug delivery vehicles, in vivo tumor targeted imaging and enhanced anticancer drug delivery has remained a major challenge. In this work, we describe the development of functionalized mSiO2 nanoparticles for actively targeted positron emission tomography (PET) imaging and drug delivery in 4T1 murine breast tumor-bearing mice. Our structural design involves the synthesis, surface functionalization with thiol groups, PEGylation, TRC105 antibody (specific for CD105/endoglin) conjugation, and (64)Cu-labeling of uniform 80 nm sized mSiO2 nanoparticles. Systematic in vivo tumor targeting studies clearly demonstrated that (64)Cu-NOTA-mSiO2-PEG-TRC105 could accumulate prominently at the 4T1 tumor site via both the enhanced permeability and retention effect and TRC105-mediated binding to tumor vasculature CD105. As a proof-of-concept, we also demonstrated successful enhanced tumor targeted delivery of doxorubicin (DOX) in 4T1 tumor-bearing mice after intravenous injection of DOX-loaded NOTA-mSiO2-PEG-TRC105, which holds great potential for future image-guided drug delivery and targeted cancer therapy.

Non-invasive multimodal functional imaging of the intestine with frozen micellar naphthalocyanines

Overview There is a need for safer and improved methods for non-invasive imaging of the gastrointestinal tract. Modalities based on X-ray radiation, magnetic resonance and ultrasound suffer from limitations with respect to safety, accessibility or lack of adequate contrast. Functional intestinal imaging of dynamic gut processes has not been practical using existing approaches. Here, we report the development of a family of nanoparticles that can withstand the harsh conditions of the stomach and intestine, avoid systemic absorption, and give rise to good optical contrast for photoacoustic imaging. The hydrophobicity of naphthalocyanine dyes was exploited to generate purified ~20 nm frozen micelles, which we call nanonaps, with tunable and large near-infrared absorption values (>1000). Unlike conventional chromophores, nanonaps exhibited non-shifting spectra at ultrahigh optical densities and, following oral administration in mice, passed safely through the gastrointestinal tract. Non-invasive, non-ionizing photoacoustic techniques were used to visualize nanonap intestinal distribution with low background and remarkable resolution with 0.5 cm depth, and enabled real-time intestinal functional imaging with ultrasound co-registration. Positron emission tomography following seamless nanonap radiolabelling allowed complementary whole body imaging.

In Vivo Targeting and Positron Emission Tomography Imaging of Tumor Vasculature with 66Ga-Labeled Nano-Graphene

The goal of this study was to employ nano-graphene for tumor targeting in an animal tumor model, and quantitatively evaluate the pharmacokinetics and tumor targeting efficacy through positron emission tomography (PET) imaging using (66)Ga as the radiolabel. Nano-graphene oxide (GO) sheets with covalently linked, amino group-terminated six-arm branched polyethylene glycol (PEG; 10 kDa) chains were conjugated to NOTA (1,4,7-triazacyclononane-1,4,7-triacetic acid, for (66)Ga-labeling) and TRC105 (an antibody that binds to CD105). Flow cytometry analyses, size measurements, and serum stability studies were performed to characterize the GO conjugates before in vivo investigations in 4T1 murine breast tumor-bearing mice, which were further validated by histology. TRC105-conjugated GO was specific for CD105 in cell culture. (66)Ga-NOTA-GO-TRC105 and (66)Ga-NOTA-GO exhibited excellent stability in complete mouse serum. In 4T1 tumor-bearing mice, these GO conjugates were primarily cleared through the hepatobiliary pathway. (66)Ga-NOTA-GO-TRC105 accumulated quickly in the 4T1 tumors and tumor uptake remained stable over time (3.8 ± 0.4, 4.5 ± 0.4, 5.8 ± 0.3, and 4.5 ± 0.4 %ID/g at 0.5, 3, 7, and 24 h post-injection respectively; n = 4). Blocking studies with unconjugated TRC105 confirmed CD105 specificity of (66)Ga-NOTA-GO-TRC105, which was corroborated by biodistribution and histology studies. Furthermore, histological examination revealed that targeting of NOTA-GO-TRC105 is tumor vasculature CD105 specific with little extravasation. Successful demonstration of in vivo tumor targeting with GO, along with the versatile chemistry of graphene-based nanomaterials, makes them suitable nanoplatforms for future biomedical research such as cancer theranostics.

Tumor vasculature targeting and imaging in living mice with reduced graphene oxide.

Graphene-based nanomaterials have attracted tremendous attention in the field of biomedicine due to their intriguing properties. Herein, we report tumor vasculature targeting and imaging in living mice using reduced graphene oxide (RGO), which was conjugated to the anti-CD105 antibody TRC105. The RGO conjugate, (64)Cu-NOTA-RGO-TRC105, exhibited excellent stability in vitro and in vivo. Serial positron emission tomography (PET) imaging studies non-invasively assessed the pharmacokinetics and demonstrated specific targeting of (64)Cu-NOTA-RGO-TRC105 to 4T1 murine breast tumors in vivo, compared to non-targeted RGO conjugate ((64)Cu-NOTA-RGO). In vivo (e.g., blocking 4T1 tumor uptake with excess TRC105), in vitro (e.g., flow cytometry), and ex vivo (e.g., histology) experiments confirmed the specificity of (64)Cu-NOTA-RGO-TRC105 for tumor vascular CD105. Since RGO exhibits desirable properties for photothermal therapy, the tumor-specific RGO conjugate developed in this work may serve as a promising theranostic agent that integrates imaging and therapeutic components.

Engineering of Hollow Mesoporous Silica Nanoparticles for Remarkably Enhanced Tumor Active Targeting Efficacy

Hollow mesoporous silica nanoparticle (HMSN) has recently gained increasing interests due to their tremendous potential as an attractive nano-platform for cancer imaging and therapy. However, possibly due to the lack of efficient in vivo targeting strategy and well-developed surface engineering techniques, engineering of HMSN for in vivo active tumor targeting, quantitative tumor uptake assessment, multimodality imaging, biodistribution and enhanced drug delivery have not been achieved to date. Here, we report the in vivo tumor targeted positron emission tomography (PET)/near-infrared fluorescence (NIRF) dual-modality imaging and enhanced drug delivery of HMSN using a generally applicable surface engineering technique. Systematic in vitro and in vivo studies have been performed to investigate the stability, tumor targeting efficacy and specificity, biodistribution and drug delivery capability of well-functionalized HMSN nano-conjugates. The highest uptake of TRC105 (which binds to CD105 on tumor neovasculature) conjugated HMSN in the 4T1 murine breast cancer model was ~10%ID/g, 3 times higher than that of the non-targeted group, making surface engineered HMSN a highly attractive drug delivery nano-platform for future cancer theranostics.

Positron Emission Tomography Imaging of CD105 Expression with a 64Cu-Labeled Monoclonal Antibody: NOTA Is Superior to DOTA

Optimizing the in vivo stability of positron emission tomography (PET) tracers is of critical importance to cancer diagnosis. In the case of 64Cu-labeled monoclonal antibodies (mAb), in vivo behavior and biodistribution is critically dependent on the performance of the bifunctional chelator used to conjugate the mAb to the radiolabel. This study compared the in vivo characteristics of 64Cu-labeled TRC105 (a chimeric mAb that binds to both human and murine CD105), through two commonly used chelators: 1,4,7-triazacyclononane-1,4,7-triacetic acid (NOTA) and 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA). Flow cytometry analysis confirmed that chelator conjugation of TRC105 did not affect its CD105 binding affinity or specificity. PET imaging and biodistribution studies in 4T1 murine breast tumor-bearing mice revealed that 64Cu-NOTA-TRC105 exhibited better stability than 64Cu-DOTA-TRC105 in vivo, which resulted in significantly lower liver uptake without compromising the tumor targeting efficiency. In conclusion, this study confirmed that NOTA is a superior chelator to DOTA for PET imaging with 64Cu-labeled TRC105.

Amyloid burden and neural function in people at risk for Alzheimer's Disease

To determine the relationship between amyloid burden and neural function in healthy adults at risk for Alzheimers Disease (AD), we used multimodal imaging with [C-11]Pittsburgh compound B positron emission tomography, [F-18]fluorodeoxyglucose, positron emission tomography , and magnetic resonance imaging, together with cognitive measurement in 201 subjects (mean age, 60.1 years; range, 46-73 years) from the Wisconsin Registry for Alzheimers Prevention. Using a qualitative rating, 18% of the samples were strongly positive Beta-amyloid (Aβ+), 41% indeterminate (Aβi), and 41% negative (Aβ-). Aβ+ was associated with older age, female sex, and showed trends for maternal family history of AD and APOE4. Relative to the Aβ- group, Aβ+ and Aβi participants had increased glucose metabolism in the bilateral thalamus; Aβ+ participants also had increased metabolism in the bilateral superior temporal gyrus. Aβ+ participants exhibited increased gray matter in the lateral parietal lobe bilaterally relative to the Aβ- group, and no areas of significant atrophy. Cognitive performance and self report cognitive and affective symptoms did not differ between groups. Amyloid burden can be identified in adults at a mean age of 60 years and is accompanied by glucometabolic increases in specific areas, but not atrophy or cognitive loss. This asymptomatic stage may be an opportune window for intervention to prevent progression to symptomatic AD.

Chelator‐Free Synthesis of a Dual‐Modality PET/MRI Agent

Most of the radiometals with physical properties suitable for imaging and/or therapy applications (e.g. 64Cu, 89Zr, 99mTc, 111In, 177Lu, 90Y, etc.) require the coordination of certain chelators to form stable complexes.[1] Due to the uniqueness of each radionuclide, knowing the particular coordination chemistry and selecting the best chelator with sufficient in vivo stability are a vital, however, highly challenging task. Therefore, the development of a stable radiopharmaceutical that contains both diagnostic and therapeutic radioisotopes, labeled via a simple but effective chelator-free strategy, is highly desirable.